PART I
TECHNICAL AND REVIEW PAPERS (Contd.)

RELATIONS ENTRE POLLUTION CHIMIQUE ET VALEUR ALIMENTAIRE ET HYGIÉNIQUE DU POISSON

Gérard Keck

École Nationale Vétérinaire de Lyon, Marcy L'Étoile, 69260 Charbonniers Les Bains, France

INTRODUCTION

La pollution chimique des milieux aquatiques pose non seulement le problème des répercussions à court et à long terme, au niveau des espèces et des biocénoses, mais également celui de la valeur hygiénique des animaux aquatiques en particulier des poissons qui peuvent renfermer des teneurs parfois importantes en résidus polluants. Du fait de la prépondérance sur le plan alimentaire des animaux marins, cette question est plus souvent étudiée chez les mollusques ou poissons de mer, d'autant que les milieux côtiers présentent fréquemment une pollution marquée, en particulier dans les mers fermées (Méditerrannée, Baltique). Néanmoins, les poissons d'eaux douces (cours d'eau, lacs, étangs) sont dans certaines zônes, gravement contaminés et peuvent présenter un risque potential non négligeable, lors d'une consommation régulière.

Les polluants les plus dangereux à cet égard sont bien entendu, les composés présentant une importante stabilité chimique (ou rémanence) aussi bien dans le milieu que dans les organismes vivants. Ce sont également les composés présentant une forte liposolubilité, qui permet un passage facile du milieu à l'intérieur des organismes vivants par voie branchiale ou digestive (phénomène de “bio-accumulation”). Rémanence et liposolubilité sont les 2 paramètres qui conditionnent la possibilité pour un agent chimique de subir une concentration le long des chaînes alimentaires (plus exactement des réseaux alimentaires), ce qui rend compte des teneurs particulièrement élevées chez les espèces prédatrices (Brochet, Lotte…) et finalement, chez l'espèce “super-prédatrice” de certaines chaînes alimentaires, l'Homme, chez qui pourront se manifester à long terme, certains effets néfastes des résidus. Parmi ces risques d'effets à long terme, les plus redoutés à l'heure actuelle sont les potentialités carcinogènes ou mutagènes de nombreux contaminants chimiques; les doses seuils non carcinogènes sont en effet très difficiles à définir (et pour certains auteurs inexistantes); en outre, l'exposition prolongée à un agent carcinogène même en concentrations très faibles, comme c'est le cas dans l'alimentation, favorise hautement l'apparition de cancers.

Les agents contaminants les plus importants, que nous envisagerons successivement, sont les suivants:

• composés organo-chlorés comprenant:

  • les pesticides organo-chlorés (DDT et dérivés, HCH α, β, γ, heptochlore, aldrine.…),

  • les polychlorobiphényles (PCB) contaminants organo-chlorés d'origine industrielle, que nous avons étudiés plus particulièrement dans certains cours d'eau français,

• métaux lourds, en particulier le mercure,

• divers dérivés organiques: hydrocarbures polycycliques cancérogènes, phénols…

Certains problèmes relatifs aux associations et interactions entre plusieurs contaminats chimiques seront également abordés. Pour les polluants les plus importants (organo-chlorés, mercure…) des normes de tolérance ou Concentrations Maximales Admissibles (CMA) ont été fixées dans les poissons et animaux aquatiques par des Comités d'experts nationaux ou internationaux (FAO/OMS) à partir d'une part, des Doses Journalières Admissibles (DJA) admises pour l'homme en fonction des données toxicologiques, d'autre part, de I'importance quantitative de la consommation moyenne de poisson dans un pays déterminé.

Nous envisagerons surtout pour ces principaux contaminants, les taux moyens (en milieu moyennement pollué) ou maxima (en milieu très pollué) dans le muscle des poissons, composante essentielle sur le plan de la valeur alimentaire et hygiénique.

LES COMPOSÉS ORGANO-CHLORÉS

Les composés organo-chlorés constituent, du fait de leur stabilité et de leur liposolubilité, des contaminants-types. De nombreux travaux ont été effectués sur la contamination des poissons d'eau dounce par les pesticides organo-chlorés, notamment le DDT, en particulier les célèbres études effectuées à partir de 1967 sur le Clea Lake en Californie qui démontrèrent le phénomène de concentration par les chaînes alimentaires et les dangers pouvant en résulter pour les espèces prédatrices (Oiseaux piscivores) et pour l'homme. Depuis une dizaine d'années, la réduction très importante de l'utilisation agricole des pesticides organo-chlorés (remplacés par des composés moins rémaments comme les organophosphorés) du moins dans les pays industrialisés a largement diminué la contamination par ces dérivés, qui est actuellement très faible dans les poissons.

Par contre, les polychlorobiphényles (PCB) composés organo-chlorés de structure proche de celle du DDT, de rémanence et de liposolubilité encore plus élevée, donnent lieu encore à une contamination importante qui ne fut évaluée à sa juste mesure qu'à partir de 1970. Les PCB, largement utilisés dans l'industrie pour de nombreux usages, isolants électriques, plastifiants etc., ont été également soumis à des restrictions d'emploi sévères depuis quelques années. La Dose Journalière Admissible (DJA) a été établie à 0,1 ppm dans la ration alimentaire totale; des normes de tolérance ont été fixées dans les poissons: 5 ppm en France (Keck 1977), 2 ppm au Canada.

Les contaminants organo-chlorés présentent en effet des effets à long terme préoccupants: ce sont des puissants inducteurs enzymatiques: ils entraînent au niveau foie une augmentation des enzymes de biotransformation, pouvant interférer dans le métabolisme des substances endogénes: hormones, notamment hormones sexuelles d'où leurs effets inhibiteurs de la reproduction. Ils possèdent en outre des potentialités cancérogènes non négligeables. Nous avons étudié de 1975 à 1979 la contamination par les PCB dans une petite rivière française: le Furans (Ain) située dans le massif du Jura, à l'écart de toute zône industrielle; la contamination provenait donc essentiellement de la pollution atmosphérique et hydrosphérique générale ainsi que de sources plus localisées (décharges, égoûts) comme le montre le fait que la contamination moyenne s'accroît d'amont en aval (Keck 1979).

Nous avons analysé en particulier, les taux de contamination dans les principaux organes des espèces piscicoles les plus représentatives et les plus pêchées, ainsi que chez les invertébrés qui constituent la base de leur régime alimentaire. Ces analyses ainsi que celles effectuées sur l'eau, les sédiments, les végétaux aquatiques nous ont permis de bien mettre en évidence les phénomènes de distribution et de concentration des PCB le long des réseaux trophiques, comme le montre la Figure 1 (Keck et Raffenot 1979).

En ce qui concerne les poissons, les teneurs moyennes dans les organes des principales espèces du cours inférieur du Furans figurent dans le Tableau 1 (prélèvements effectués en août 1975). Dans le Tableau 2 sont présentées des teneurs musculaires observées sur des poissons prélevés en août 1978. Ces deux tableaux montrent bien les différences existant en fonction de l'organe surtout en fonction des espèces.

En Fonction de l'Organe

En règle générale, l'ordre décroissant d'accumulation est le suivant: foie, (qui représente l'organe de concentration de nombreux polluants), branchies (qui constituent l'organe majeur d'échange avec le milieu); oeufs; l'accumulation dans le muscle varie en fonction des espèces mais est, en général, plus faible. On observe donc des teneurs plus importantes dans les tissus riches en lipides (foie, oeufs) que dans les tissus maigres (muscles).

En Fonction des Espèces

Les Salmonidés Truite fario (Salmo trutta fario) et Ombre de rivière (Thymallus thymallus) présentent en moyenne des taux de contamination relativement faibles, avec néanmoins une accumulation supérieure pour l'Ombre. Les teneurs observées chez certains Cyprinidés sont remarquablement plus élevées, en particulier pour le Chevaine (Leuciscus cephalus) et surtout le Barbeau (Barbarbus). Par contre, le Hotu (Chondrostoma masus) présente des teneurs faibles.

L'explication de cette différence d'accumulation n'est pas encore définitivement établie. Il est possible qu'interviennent des variations de régime alimentaire: notamment par la consommation d'algues et de périphyton qui contiennent des taux de PCB assez élevés (néanmoins le Hotu présente un régime typiquement algivore). Il est probable également qu'existent entre ces différentes espèces, des différences métaboliques intervenant dans l'accumulation de résidus; ce domaine est malheureusement encore très peu exploré. En fait, l'explication pourrait être simplement la différence d'âge existant entre les populations de Salmonidés et de Cyprinidés du fait de leur vitesse de croissance différente: à taille égale (par exemple 25 cm), les Salmonidés sont plus jeunes de 2 à 3 ans que le chevaine ou le barbeau, leur croissance étant beaucoup plus rapide.

Fig. 1. Diagramme des relations trophiques dans l'écosystème Furans. Les dimensions relatives des différents compartiments donnent une indication de la biomasse; la largeur des flèches est proportionnelle à l'importance relative supposée des échanges énergétiques (modifié de Hynes 1972). Les teneurs moyennes en PCB observées à chaque niveau sont exprimées en ppm/MF.

Tableau 1. Concentrations de PCB dans les poissons du Furans (ppm/MF) (prélèvements août 1975).

Tableau 2. Teneur en PCB dans le muscle des poissons du Furans (prélèvements août 1978).

Le temps d'exposition moyen au milieu contaminé des Barbeaux et des Chevaines que nous avons analysés (tailles allant de 15 à 30 cm) serait donc bien supérieur aux Salmonidés dont les plus grands du fait de la pression de pêche mesuraient moins de 30 cm. Nous avons d'ailleurs retrouvé une certaine corrélation entre l'âge des truites et leur taux de contamination. Il est intéressant de signaler que ces différences inter-spécifiques d'accumulation ont été retrouvées dans les poissons du Furans pour le cas du mercure (cf plus loin).

Les poissons piscivores se situant au niveau le plus élevé de la chaîne alimentaire sont representés dans le Furans par le Brochet (Esox lucius) (rare, car éliminé par l'homme) et la Lotte (Lota lota) dans sa phase adulte. Les teneurs observées chez les Brochets ne sont que moyennement élevées (0,5 ppm dans le muscle; 3 à 5 ppm dans le foie) en relation probablement avec l'âge réduit des sujets analysés (taille inférieure à 30 cm). Des teneurs élevées (8 ppm) ont été notées dans le foie de lotte adulte (taille supérieure à 35 cm), qui constitue un plat très apprécié par certains pêcheurs.

L'analyse de la contamination par les PCB dans les poissons du Furans nous a permis de mettre en évidence une progression longitudinale de la contamination d'amont en aval et d'émettre des hypothèses sur les origines de la contamination par les PCB. Pour les organismes présents sur la totalité du cours d'eau, les variations longitudinales des taux de contamination ont été étudiées de la source jusqu'à l'embouchure du Furans. Cette étude a été réalisée pour des algues Cladophora, les mousses Fontinalis, les truites adultes, (Fig. 2), les truitelles et les chabots (Fig. 3). On observe, sur tous les profils, une nette augmentation des taux de contamination en aval de la confluence avec l'Arène (km 12). Cela permet de situer la source majeure des PCB le Furans: l'affluent Arène. Cet affluent est sévèrement pollué par des rejets organiques d'origine urbaine (égout de Virieu-le-Grand) et industrielle (salaison). Ces rejets organiques s'accompagnet de rejets très divers, en particulier de rejets de matières plastiques (récipients, sacs…) qui obstruent le ruisseau à certains endroits; cette situation durant depuis de nombreuses années, on peut supposer que, par relargage progressif de PCB, ces rejets constituent une source importante de contamination dans le bassin-versant du Furans (Mestres 1971 et Jensen 1972 dans Keck 1979). À cela s'ajoute, bien entendu, une contamination beaucoup plus générale d'origine atmosphérique ou phréatique. Au bilan, on voit que, même pour un milieu relativement éloigné de tout secteur industriel, les taux de contamination par les PCB sont relativement élevés, notamment dans les maillons supérieurs des réseaux trophiques.

Fig. 2. Progression longitudinale des teneurs en PCB dans les truites adultes du Furans (prélèvements août 1975).

Fig. 3. Progression longitudinale des teneurs en PCB dans les truitelles (▲) et les chabots(O).

Certaines espèces (Barbeau, Lotte…) présentent des taux approchant, voire dépassant la Concentration Maximale Tolérée (5 ppm). Fort heureusement, les PCB comme les autres organo-chlorés s'accumulent surtout dans le foie et les graisses et non dans le muscle poissons, ce qui réduit les risques de contamination humaine.

Autres Enquêtes Concernant les PCB

Certains milieux aquatiques exploités sur le plan piscicole présentent une contamination importante par les PCB, ce qui nécessite une surveillance des teneurs observées dans les poissons:

• Dans le lac Cayuga, aux États-Unis, les taux de PCB des “Lake trouts” (Salvelinus namaycush) dépassant 10 ppm pour les sujets de plus de 7 ans (Bache et al. 1972).

• Dans le lac Supérieur au Canada, les taux moyens de PCB dans les “Lake trouts” dépassaient en 3 localisations la norme de 2 ppm actuellement autorisée au Canada (Armstrong et Lutz 1977).

• les saumons coho des Grands Lacs américains ont été récemment retirés de la commercialisation du fait des taux particulièrement élevés de PCB (ainsi que d'autres contaminants) (Sonstegard 1977).

LA CONTAMINATION MERCURIELLE

La contamination mercurielle constitue un problème majeur à l'heure actuelle, notamment dans les milieux aquatiques. Le mercure provient de sources très diverses: naturelles (sols, volcanisme); industrielles: l'utilisation du mercure comme catalyseur en chimie de synthèse représente actuellement la source de pollution la plus importante; agricoles (fongicides organomercuriels sévèrement règlementés depuis quelques années). Par le biais des eaux de ruissellement ou des précipitations, le mercure, sous diverses formes, va se retrouver en majeure partie dans les milieux aquatiques, où s'effectue un phénomène capital: la méthylation bactérienne, c'est-à-dire la conversion de tous les dérivés mercuriels en méthyl-mercure CH₃Hg⁺, qui sera ensuite bio-accumulé par les organismes aquatiques et concentré le long des chaînes alimentaire. Le méthyl-mercure représente en outre la forme la plus redoutable du mercure, notamment par ses effets à long terme:

• toxicité nerveuse, comme l'a montré l'accident de Minamata;

• inhibition de la fonction reproductrice;

• effets génétiques anti-mitotiques et mutagènes.

La DJA de mercure total a été fixée à 0,03 mg/jour pour un homme de 70 kg (dont 0,02 mg au maximum sous forme de méthyl-mercure). Des concentrations maximales admissibles dans l'alimentation ont été fixées par divers pays. En France, la CMA dans les produits marins et d'eau douce est de 0,5 ppm de mercure total, sauf pour les poissons carnassiers (brochets, thons, squales): 0,7 ppm. Les autres pays (États-Unis, Scandinavie) ont édicté des normes voisines.

Les aliments du bétail (notamment les farines de poissons) doivent également faire l'objet de normes, les animaux d'élevage pouvant jouer un rôle de relais avec concentration dans les chaînes agro-alimentaires.

En France, la contamination mercurielle dans les poissons marins (notamment les Thons) et d'eaux douces est contrôlée notamment par le Laboratoire d'Hygiène Alimentaire de Paris (Dr Vét. G. Cumont) et par les Directions Départementales des Services Vétérinaires (Cumont et al. 1973). La majeure part de la pollution mercurielle des cours d'eau provient des rejets des industries chimiques fabriquant du chlore et de la soude par électrolyse du chlorure de sodium sur électrodes en mercure. Ainsi, dans certaines rivières comme le Doubs, en aval d'une usine de ce type, on observe dans les poissons des teneurs élevées en mercure largement supérieures en moyenne à 0,5 ppm, pouvant atteindre souvent 5 à 7 ppm.

Le phénomène de concentration des chaînes alimentaires est généralement bien observé: les teneurs maximales se retrouvent chez les poissons prédateurs: Perche, Brochet, Lotte. Les cours d'eau de la plaine alsacienne industrialisée (Rhin, Ill, Thur…) sont également contaminés de manière notable; les taux moyens dépassent largement la norme de 0,5 ppm, en particulier chez les Anguilles, du fait peut-être de leur comportement fouisseur, le mercure comme beaucoup de contaminants étant absorbé sur les sédiments. Même les cours d'eau situés à l'écart des zônes industrielles, comme le Furans, sont atteints par la contamination mercurielle: si les Salmonidés (Truite, Ombre) renferment des taux faibles (inférieurs à 0,1 ppm) certains Cyprinidés comme le Barbeau contiennent des teneurs pouvant dépasser la norme de 0,5 ppm. On retrouve ici, cette accumulation nettement supérieure chez certains Cyprinidés (mais non pour le Hotu qui présente là encore des taux faibles) par rapport aux Salmonidés (Keck, données non publieées).

D'une manière plus générale, on sait que la contamination mercurielle des eaux douces peut, comme pour les eaux marines, poser de réels problèmes sur le plan sanitaire (Keck 1979). En Suède, vers 1972, la pêche a été interdite dans près de 80 lacs du fait de l'importance de la contamination mercurielle provenant de l'utilisation de fongicides organo-mercuriels pour le traitement de la pâte à papier. Sur les bords de certains lacs canadiens, les populations indiennes vivant essentiellement du produit de leur pêche constitué par des poissons contaminés à des taux de 5 à 7 ppm en moyenne, présentent des troubles neuro-sensoriels (restriction du champs visuel, paresthésie) du même type que ceux observés à Minamata et des teneurs de 100 ppm de mercure dans les cheveux. Il est donc heureux que les pêcheurs alsaciens ou doubistes ne vivent pas du produit de leur pêche; il n'en reste pas moins que de telles contaminations dont l'origine est pour une grande part connue, doivent être résolues de façon urgente tant du fait de leurs risques pour la biologie des milieux aquatiques que pour ceux au niveau de la santé publique.

Bien d'autres métaux lourds, notamment le plomb, le cadmium, le nickel, le chrome, le cuivre… ou des métalloïdes comme l'arsenic, peuvent dans des secteurs pollués en particulier par des industries d'extraction de traitement ou de transformation métallurgique, se retrouver en teneurs non négligeables dans la chair des poissons; ceci peut poser localement des problèmes sanitaires et nécessiter une surveillance attentive, d'autant que certains métaux (arsenic, cadmium) présentent à long terme des potentialités carcinogènes.

DIVERS DÉRIVÉS ORGANIQUES

Ces peuvent déprécier la valeur alimentaire ou hygiènique du poisson; les phénols (provenant des industries chimiques, des teintureries…) et surtout les chlorophénols, provenant également de la dégradation de certains herbicides très utilisés de type phénoxyalcanoïques (2,4D; 2,4,5T…) s'accumulent dans les organismes aquatiques ce qui leur confère même à des taux faibles, un goût très désagréable et caractéristique du “mazout.” Certains dérivés organiques carcinogènes peuvent également contaminer les organismes aquatiques, c'est le cas des hydrocarbures polycycliques, notamment le benzo-pyrène, qui comptent parmi les agents cancérigènes environnementaux les plus puissants, ces dérivés en provenance de la transformation des énergies fossiles (charbon, pétrole) ont été détectés dans les Mollusques côtiers, dans les poissons des Grands lacs américains (Armstrong et Lutz 1977), dans les poissons des cours d'eau en URSS (Griciute comm pers.). La fréquence des tumeurs cancéreuses observées chez les poissons augmente d'ailleurs de façon inquiétante (Sonstegard 1977). On a mis en évidence récemment la possibilité de formation de nitrosamines, agents carcinogènes très actifs, dans les milieux aquatiques par combinaison entre des nitrites (provenant des pollutions organiques) et d'amines secondaires d'origine naturelle ou artificielle (herbicides azotés par exemple). Ces nitrosamines pourraient ensuite être bio-accumulés par les organismes aquatiques. Avec le perfectionnement croissant des méthodes analytiques, de nombreux agents polluants nouveaux sont régulièrement détectés dans les milieux aquatiques, et les poissons: dérivés organo-chlorés d'origine industrielle (styrènes polychlorés, naphtalènes polychlorés…) plastifiants notamment les phtalates etc…

Il faut souligner, pour terminer, un fait important: dans de nombreux cas, les poissons vivants dans un secteur pollué présentent des teneurs élevées en divers agents contaminants: organo-chlorés, métaux lourds, hydrocarbures. En outre, certaines espèces du fait de leur position trophique (prédateurs) ou de leur longévité et probablement d'autres facteurs, notamment d'ordre métabolique, concentrent de nombreux agents chimiques rémanents. Ceci pose le problème de l'association de divers contaminants et des effets qui résultent de cette association pouvant conduire à une synergie d'action, comme pour les effets sur la reproduction des PCB et du méthyl-mercure (dont l'action probablement combinée est responsable de la stérilité de nombreuses espèces de rapaces piscivores) ou pour l'activité cancérigène de divers agents chimiques (hydrocarbures polycycliques et nitrosamines). Dans d'autres cas néanmoins, l'association de 2 agents contaminants peut aboutir à un antagonisme: ainsi les PCB qui eux-mêmes sont cancérogènes, diminuent les effets carcinogènes de divers agents biologiques (virus oncogènes) ou chimiques (aflatoxine B1, hydrocarbures polycycliques) (Keck 1978).

AU TOTAL

La contamination chimique des milieux aquatiques dont nous avons analysé quelques exemples majeurs, menace sérieusement la qualité hygiénique des poissons provenant de certains milieux, non seulement ceux exposés directement à des rejets polluants, mais également ceux situés à l'écart des zônes industrialisées. Elle peut en outre, modifier de façon non négligeable, la biologie des espèces aquatiques (reproduction, résistance aux maladies…) et donc la productivité piscicole des milieux.

RÉFÉRENCES BIBLIOGRAPHIQUES

Armstrong, F.A.J. et A. Lutz. 1977 Lake Superieur 1974: PCB chlorinated insecticides, heavy metals and radio-activity in offshore fish. Tech.Rep.Fish.Mar.Serv.Canada, No. 693.

Bache, C.A., J.W. Serun, W.D. Youngs, et D.J. Lisk. 1972 PCB residues: accumulation in Cayuga lake trout with age. Science, 177:1191–1192.

Cumont, G., C. Gilles, M.B. Dagorn, et G. Stephan. 1973 État de la contamination par le mercure des poissons de mer et d'eau douce. C.R. Colloque C.E.E. Luxembourg 3–5 juillet, 296–307.

Keck, G. 1977 Étude écologique et toxicologique d'un micro-polluant type: les biphényles polychlorés (PCB). Revue Méd. Vét., 128:25–49.

Keck, G. 1979 Étude des effets immunologiques des PCB chez la souris. Effets de la contamination par les PCB sur le développement de la tumeur d'Ehrlich chez la souris. Rapport technique convention recherche Ministère Environ. Décembre.

Keck, G. 1979 Toxicologie actuelle du mercure et de ses dérivés. La pollution mercurielle. Revue Méd. Vét., 130:7–47.

Keck, G., et J. Raffenot. 1979 Chemical contamination by PCBs in the fishes of a French river: the Furans (Jura). Bull. Environm.Contam. Toxicol., 21:689–696.

Keck, G., et J. Raffenot. 1979 Étude éco-toxicologique de la contamination chimique par les PCB dans la rivière du Furans (Ain). Revue Méd. Vét., 130:339–358.

Sonstegard, R.A. 1977 Feral aquatic organisms on indicators of waterborne environmental carcinogens. Proc. 2nd int. symposium on aquatic pollutants, Amsterdam Sept. 26–28, 1977, Pergamon Press.

CAPACITY-PLANNING AND SPORTFISHERY IN THE NETHERLANDS

A. P. C. Kerstens

Netherlands Governmental Service for Land and Water Use, Ministry of Agriculture and Fisheries, Griffioenlaan 2, 3502 La Utrecht, The Netherlands

ABSTRACT

In the Netherlands there is growing need for a dynamic system of policy-making and goal formulation—with feedback system—to realize a well balanced (optimal) demand-supply situation for sport fishing facilities. The progress made in this context in the Netherlands is discussed in the light of the conceptualization of the idea of capacity planning and the need for it. Capacity-planning can lead to an overall and comprehensive planning in the concept of landscape, which is a dynamic complex of biotic, abiotic and socio-cultural factors. Unbalanced use of the landscape can be approached for the suitability of the landscape as a living and outdoor recreational environment as well as for its overall appearance, experience value and psychological contents. To improve and correct the procedure of planning and management of sport fishing facilities different types of behavioral research to be started are indicated in the broader context of the overall outdoor recreational planning.

RÉSUMÉ

Les Pays-Bas ont de plus en plus besoin d'un système dynamique de prise de décisions et de formulation d'objectifs—avec élément rétroactif—pour parvenir à un bon équilibre (situation optimale) de la demande et de l'offre d'installations de pêche sportive. Les progrès réalisés à cet égard aux Pays-Bas sont envisagés à la lueur de la conceptualisation de l'idée de planification du rendement et du besoin de celle-ci. La planification du rendement peut déboucher sur une planification globale et complète du concept de paysage qui est le résultat d'une combinaison dynamique d'éléments biologiques, anthropiques et socio-culturels. L'étude de l'utilisation du paysage peut être conduite à différents niveaux: utilité du paysage en tant que milieu ambiant de vie et de loisirs extérieurs, apparence générale, valeur pratique et contenu psychologique. Pour améliorer et corriger les procédures de planification et d'aménagement des installations de pêche sportive, il convient d'entreprendre différents types de recherche comportementale qui sont indiqués dans le contexte plus vaste de la planification globale des loisirs de plein air.

INTRODUCTION

In my paper for the Gothenburg E.I.F.A.C. conference (Kerstens 1975) “Some remarks about research and inquiries into angling in the Netherlands (demand side),” I proposed to develop a dynamic system of policy making and management goal formulation where, by building into it a feedback system, one may manage to guide the development of angling possibilities and facilities to a well balanced demand-supply equilibrium, which means that the differentiation in angling can become optimal. Can this purpose be reached? “Perhaps”, Dill (1977) remarks in his paper, “initial concepts of angling from fishing for food to the contemplative man's recreation and somewhat beyond” in Oxford.

In this paper I shall give an idea of the advancements made in Holland to reach the ideal situation. I'll do this by giving a conceptualization of the idea of “capacity-planning” and by going into the need for capacity-planning. After that I'll give an idea of the procedure in Holland to come to a strategy for the planning and management of the fishery possibilities and facilities, often in situations where several kinds of land and water uses including recreational fisheries, are conflicting. To improve this strategy different types of behavioral research are necessary. I'll end this paper with some final remarks about the need for research in the future.

CAPACITY-PLANNING

The overall goal of this meeting is to study and evaluate alternatives for the conservation and management of fishery resources so as to optimize the overall benefits to society. The opinions about the overall benefits to society are going through an evolution. The very broad differentiation in opinions and values at the base of these opinions there is a more or less clear trend from consumption ethics to ecological ethics. This evolution meant here can be illustrated by several “social facts.”

In the reports “Sport Fishery Economics, the Final Report to the National Marine Fisheries Service” and “Workshop on Fishery Economics” at Moscow, Idaho, and Madison, Wisconsin (1973), attention is paid to the values, which may not come out of the demand evaluation studies in recreation and for recreational fisheries. These values are, for instance, the price that non-users would pay to maintain the fishery for the future generations, the value that can be assigned to those who would pay the preservation of the genetic pool in a threatened fishery, the value that can be assumed for those who do not even plan to use the fishery but wish to have it preserved as a biological resource.

In this report the next conclusive statement is: “A very significant component of social benefits of preservation may be ignored if decision makers rely only upon user-oriented values assessed by travel cost of willingness-to-pay questionnaires. Studies should be designed to develop the methodology for estimation of preservation values.” Capacity-planning is directed to the preservation of ecosystems. This, for instance, is the main goal of the development of a very important water in Holland called Ooster-Schelde. The idea of capacity-planning is not only relevant for the regions in Holland with a very high level of urbanization, but also for regions with no pressure of urbanization.

This evolution in thinking has very important implications. The implication is not only that more attention is paid to the development of functions like living, traffic and communication, outdoor recreation and agriculture but also that more aspects are brought into the planning processes like the long term consequences of interactions of these spatial functions. This means that these developments and interactions are placed in the broad approach of a total ecosystem landscape.

This idea of capacity-planning is very important for the development of the possibilities and facilities for sport fishing. Capacity-planning can lead to an overall comprehensive planning based on a well defined concept of landscape.

In Fig. 1 the global definition of the landscape is an integrating, holistic concept for the configuration resulting from the interactions between the components I, II and III. For all those components capacity-concepts are defined already. Philips (1970) uses, for instance, the concepts of ecological and economic capacity and also the concepts of physical and perceptual capacity. Also a concept as used by Houghton-Evans and Miles (1979) i.e. “environmental capacity”, is very interesting. You can divide all capacity-concepts into two main categories; concepts from the point of view of the human being and concepts from the point of view of the environment. On the base of Fig. 1 you can formulate the concepts of physical capacity, bio-ecological-capacity, the infrastructural-capacity, the accommodation-capacity, the social-economical-capacity, the cultural-capacity and the overall concept of the landscape-ecological-capacity or the environmental-capacity conceived in a very broad sense.

The need for the use of the concept of the environmental-capacity is decended from the consciousness of the ecological crisis and from the idea that a lot of developments have on the long run unforeseen consequences, which are very negative in the perspective that the society is evolving to a situation where higher requirements are put on the socio-cultural and physical environment (think for instance of the hierarchy of desires of Maslow). Not using the idea of capacity-planning endangers the conditions for a better life and more well-being.

Fig. 1. Conceptual structure of landscape.

Fig. 2. Subjective reduction of the objective socio-physical structure.

Landscape

As you see here, landscape is defined as the objective socio-physical structure. This is the working concern of the manager of outdoor recreation-space, infrastructure and facilities.

To go to the approach of the behavioral scientist a reduction must be introduced because of the selective perception and the selective use by the recreationist of the socio-physical structure which presents the system of what is called the landscape. In a diagram I can explain this relation very quickly. The subjective reduction of the objective socio-physical structure is imaginable as is presented in Fig. 2. Only a part of the objective socio-physical structure is the activity-space of an outdoor recreationist.

In Fig. 3 the relationship between the objective socio-physical structure and the activity-space of a recreationist is further elaborated. The behavioral scientist is trying to describe and understand the behavior of the recreationist, i.e., the fisherman.

LEISURE BEHAVIOR

For a scientific approach of leisure behavior there is a need for a paradigm (Levy 1979). In this paradigm the basic structure of the explanation of the behavior is represented (Fig. 4).

In Fig. 5 there is a further elaboration of the idea. In the “pattern of activities” only the so called manifest demand is actualized. To get a good idea of the total demand you must pay attention to the so called not realized needs and latent needs, which are components of the latent demand. This is visualized in Fig. 6.

Fig. 3. The relation between landscape and activity-space.

Fig. 4. A conceptual paradigm for the study of leisure behavior.

Recreation demand is the resultant interaction of persons and environment. Some kind of behavior is stimulated, other kinds are frustrated. In the concept of the recreation-experience-continuum this idea is expressed. A recreation-engagement can be divided in three phases. In Fig. 7 this idea or conception is elaborated. You see that in this diagram two categories of research are mentioned. This brings us to the question of the types of research necessary to construct an adequate system to cover the whole field of the approaches from the point of view of the behavioral sciences.

TYPES OF RESEARCH

In Fig. 7 the concept of the recreation-experience-continuum is visualized. As you see there are two main types of research to approach the demand-use of sport fishing. The dividing criterium is where the information is gathered.

To realize an adequate approach of the demand-side it is better to make a classification in four types of research:

1. A general market-exploration. This is mostly done by a household survey. Often it is not possible to build in objective indications for aspects of the physical and environmental structure of possibilities and facilities.

2. Research to formulate standards for the dimensions and qualities of possibilities and facilities for fishermen. In this type of research, which can be carried out by household interviews and also by doing on-site research, objective indications of elements and aspects of the physical structure and the environment are built in the model.

3. Research for the proper management of a certain sport fishery-object. Questions must be answered like: how do people use the object, how much fish do they catch?, etc.

4. Research to formulate an empirical basic structure for the policy for management of the supply-structure for sport fishing in a certain region. Both sides of the matter, demand and supply, must be investigated.

Fig. 5. The pattern of activities as resultant of PERSON × ENVIRONMENT.

An example of type I as mentioned here is the research-object that is published in the report “De Nederlandse Sportvisser” (Prinssen and Kropman 1975) (“The Dutch Angler.” An abstract of this report was presented on the Gothenburg E.I.F.A.C. Conference in 1975).

A type of research of type II is reported in the publication “De betekenis van de Grevelingen voor de sportvisserij; visserijkundige waarnemingen in de jaren 1971-1977” (The meaning of the Grevelingen for sport fishing; observations in the years 1971-1977) by Steinmetz and Slothouwer (1979).

An example of type III research is the research on “The meaning of the Biesbosch for Sport fisheries” (De betekenis van de Biesbosch voor de Sportvisserij) by Steinmetz and Bakker (1976).

Fig. 6. The componenets of empirical basic of the demand-side.

F E E D B A C K

Fig. 7. The concept of recreation experience-continuum.

Also, “The use of special sport fishery waters in Limburg,” by Muyres (1977) is a research project of type III.

An example of a type IV research project is the determination of the present demand for fishing places in a region. An outline of this determination is given by Van Alderwegen. One element of this determination is the counting of the number of sport fishermen per municipality (Steinmetz 1974 and 1979). In Holland good advancement in the research-based planning of possibilities and facilities for sport fishing has been made. It is a kind of type IV research.

PLANNING FACILITIES

In April of 1979 the so called "provinciale informatienota's (Provincial information reports sport fishing) were presented to the provincial daily government boards. This means that in every province in Holland there is now a good well-structured survey of the demand-side and a well-structured survey of the supply (De Groot and Van Haasteren 1979). The supply-side is surveyed from two points of view: the possibilities and the obstructions. These obstructions can be:

• no right to fish

• no right to walk

• no entrance

• no good slope (water not deep enough)

• too many weeds

• bad water quality

• other uses

• other obstructions.

This instrument of the provincial information report on sport fisheries can help make progress to reach a better demand-supply balance. The idea of the demand-supply balance has a formal basis in an arrangement of the Minister of Agriculture and Fisheries; measures to improve the facilities or to make new facilities must be necessary in relation to the facilities for sport fisheries in the neighborhood.

RESEARCH IN THE FUTURE

There are a lot of theories of leisure behavior patterns. Witt and Bishop (1970) have presented a number of these theories. Each of the theories suggests that people favor different activities after having been in certain antecedent situations. This is also the basic idea of the conceptual paradigm in Fig. 4. These situations can be the general setting in which people live, for instance a noisy urban center, or the situation just before the recreation engagement starts.

In my opinion you can say that in general too little is known about the relation of these antecedent situations to an outdoor recreation engagement like sport fishing. So I propose to do research into the motives of why people go fishing in general and why they go fishing at a specific spot. This is the first subject that needs attention of analytical behavioral research, i.e. psychological research.

In relation to these items I ask your attention for the problem of what you can call the “push aside” question and the question of frictions and conflicts between sport fishing and other types of outdoor recreation. About the “push aside” question in relation to a sport fishery not much is known. There are some general indications that this problem is real. From the results of research done in 1973 it appears that of those who have fished longer than 4 years and who have lived longer than 4 years in the same town 44% say that there are no longer fish in some of the waters they visited earlier. The reasons for not returning to these waters were:

Sixty-two percent of those who did not go back to a water in question is the same as 28% of those who have fished longer than 4 years. When people fish less frequently than in the past many give as the reasons water pollution, less catch and crowding. As a reason for less frequent fishing in the future 20% mention water quality and catch. The question of “push aside” is real. The question of the frictions and conflicts between sport fishing and other kinds of outdoor recreation is important. Research indicating this importance has been done several places. In the polder Achttienhoven, 92% of the fishermen present said motorboating should not be allowed (Steinmetz 1973). About 60% of these fishermen have objections against swimming and sailing. These 141 interviewed fishermen fished from the shoreline of the rather narrow waters in this polder. About 25% of them have no objections against rowing, but 50% did object. Of the rest, 25% like to see rowboats but at a distance of 10–100 m.

Most fishermen attach importance to undisturbed fishing. For sport fishing perhaps the restoration-relaxation theory and the diversionary-relaxation theory are valid. It may be that sometimes social and physical compensation plays a significant role. This appears from the fact that the motive of being outdoors in a quiet place is accepted. You see not only “on site” research is necessary but also household surveys to detect unrealized needs and to know how many fishermen are frustrated. In the conceptual paradigm for the study of leisure behavior you see that elements of this paradigm are the consequences of leisure behavior for the social system and the consequences for the human system. I think that very little is known about the psychic restoration and other possible consequences for the psycho-somatic functioning of human beings. So I suggest to do more research in this medical-sociological field.

The next subject is very closely related to the research done for our provincial information reports. I think it is necessary to do a survey in Holland to investigate the possible discrepances between demand for facilities and the supply-structure. The demand for facilities must be differentiated on personal and social characteristics. The relation must be surveyed between the objective socio-physical structure, the subjective image of the socio-physical structure and the activity-space (see Fig. 3 and 4). The supply-structure must be analyzed from the point of view of attainability, attractiveness, and the like. So in the model for this research subject, situational variables must be built in from two points of view: as objective structures and from the point of view of the perception of these same aspects and elements of facilities and the environment.

There is now a growing recognition by a number of behavioral scientists of the behavioral impact of such environmental variables as form, shape, noise, crowding, climate, etc. Also total global environments as rural, rural-urban and urban settings can be used as environmental variables. There is as yet no comprehensive behavioral typology or taxonomy of man-made and natural environments, which could be used to formulate empirical hypotheses on the impact of these antecedents on leisure behavior. A better detailed special differentiation of the relations between demand and supply must enable the planners to construct a better empirically based framework for planning activities. Special attention must be paid to distances people must travel to a spot where they can realize their needs. This type of research can help to realize a well-balanced demand-supply equilibrium.

FINAL REMARKS

Coming to the end of my explanation remember that I started by observing that there is an evolution in our culture in the direction of ecological ethics. Nevertheless, you still can ask where the consciousness of an ecocrises will lead? Will a lot of people indulge in dissipation? Or will they try to clean, for instance, the waters in our dirty cities and in our rivers and canals? This is not only important from the point of view of milieu hygiëne, which is so important from the point of view of capacity-planning, but also from the point of view of outdoor recreation in general and the sport fishery especially. The fight against environmental pollution can be better directed using adequate capacity-concepts.

As I explained, capacity-planning can lead to an overall and comprehensive planning in the concept of landspace, which is a dynamic complex of biotic, abiotic and socio-cultural factors. Capacity-planning is a necessary condition for the development of facilities and environments for sport fishing. With my plea for planning and research activities to reach a well balanced demand-supply equilibrium I hope to have focussed your attention on the danger that the research of the behavior of the sport fisherman will be directed too much on the status quo and the manifest needs. Potential supply and latent need and the consequences of sport fishing for the person and the social system are important research items.

The aim of the sport fishing policy is to create such a diversity of assortment of facilities and provisions that the quantity and quality of the supply makes optimal differentiation in angling possible. This is a dynamic option not a static goal. In the strategy of planning there must be a dynamic integration of findings of research and fishery management goals formulation. As I explained, we have made a step in that direction. In 1979 the “Provincial information reports for sport fishing” were sent to the provincial governments to integrate the goals of sport fishing in the systems of goals of the total provincial planning system. These activities can be localized on the strategic planning level. As a complementary activity on a higher planning level, the normative research and planning level, there will be a national survey through household questionnaires to investigate the possible discrepancies between demand and supply, as I suggested. Also “on site” research will be done of type III mentioned above.

LITERATURE CITED

Alderwegen, H.A., B. Steinmetz and A.T. de Groot. 1978 Rekenschema voor bepaling huidige vraag naar visplaatsen in een regio. Recreatievoorzieningen 1978, no. 2:60–62.

Brown, K.S. 1979 Authority. Resolution of conflicts in the United Kingdom. Recreational freshwater fisheries. Their conservation, management and development. Paper 6. Session 2. A Water Research Centre Conference. Stevenage 1977.

Dill, W.A. 1977 Patterns of change in recreational fisheries. Their determinants. Recreational freshwater fisheries. Paper 1, Session 1. A Water Research Centre Conference, Stevenage.

Ginkel, C.J. van. 1979 Resultaten sportvisserijtellingen en enquêtes op het Ijsselmeer. Visserij; voorlichtingsblad voor de Nederlandse Visserij, 6; 32:441–449.

Groot, A.T. de and L.M. van Haasteren. 1979 Provinciale samenvatting. Informatienota's, sportvis-serij; een samenvatting van de provinciale analyses van de vraag naar en het aanbod van mogelijkheden voor de sportvisserij. Ministerie van Landbouw en Visserij. Directie van de Visserij, 's-Gravenhage.

Houghton-Evans, W. and I.C. Miles. 1970 Environmental capacity in rural recreation areas. Journal of the Town Planning Institute, December 1970, 36:423–427.

Jaarverslag Visserij. 1979 Annual Report 1978. Directie van de Visserijen; Ministerie van Landbouw en Visserij. Directorate of Fisheries Ministry of Agriculture and Fishery. Visserij 32 September, 1979.

Kerstens, A.P.C. 1976 Evaluatie sportvisserij, Utrecht, 53p.

Kerstens, A.P.C. 1979 Some remarks about inquiries into angling in the Netherlands. E.I.F.A.C. Tech. Pap. (26):149–154.

Levy, J.A. 1979 A paradigm for conceptualizing leisure behaviour. Towards a person-environment interaction analyses. Journal of Leisure Research, 11(1):48–60.

Muyres, W.J.M. 1979 Het gebruik van voor de sportvisserij aangelegde viswateren in Limburg. Documentatierapport nummer 10. Directie van de Visserijen. 's-Gravenhage.

Owens, P.L. 1977 Recreational conflict: the interaction between Norfolk Broads coarse anglers and boatusers. Support Paper A. Recreational freshwater fisheries. Their conservation, management and development. Stevenage.

O'Riordan, 1977 T. Angling and boating. Recreational freshwater fisheries. Their conservation, management and development. A Water Research Centre Conference, Paper 9. Session 2. Stevenage.

Phillips, A.C.C. 1970 Research into planning for recreation. Countryside Commission. London.

Prinssen, J.C.C. and J.A. Kropman. 1975 De Nederlandse sportvisser; een onderzoek naar kenmerken, gedrag en wensen van de sportvisser. Instituut voor Toegepaste Sociologie. Nijmegen.

Steinmetz, B. 1973 De sportvisserij in het polder- en plassengebied “Nieuwkoop-Noorden” (angling in the “Nieuwkoop-Noorden” polder and ponds area). Visserij 26(2):81–83.

Steinmetz, B. 1979 De in de visseizoenen 1973/1974 en 1974/1975 per gemeente uitgereikte publiek-rechtelijke visdocumenten. Directie van de Visserijen. Hoofdafdeling Sportvisserij en Beroepsbinnenvisserij, 's-Gravenhage.

Steinmetz, B. 1979 De in de visseizoenen 1975/1976, 1976/1977 en 1977/1978 per gemeente uitgereikte publiekrechtelijke visdocumenten. Directie van de Visserijen, hoofdafdeling Sport-visserij en Beroepsbinnenvisserij. Documentatierapport number 22. 's-Gravenhage.

Steinmetz, B. and J.G. Bakker. 1976 De betekenis van de Biesbosch voor de sportvisserij. Documentatierapport number 18. Directie van de Visserijen, Den Haag.

Witt, P.A. and D. W. Bishop. 1970 Situational antecedents to leisure behaviour. Journal of Leisure Research, 2(1):64–77.

INTEGRATING FISHERY RESOURCE ALLOCATION INTO TROPICAL RIVER BASIN DEVELOPMENT AND WATER MANAGEMENT SCHEMES

Karl F. Lagler

School of Natural Resources, The University of Michigan, Ann Arbor, Michigan 48109 USA

ABSTRACT

In river basin development and in irrigation and flood control schemes, as in all forms of water use that impinge on fisheries, a vast array of actors with different perceptions of the problem take roles in fishery resource allocation. Only by improved information flow—by communication—can the misallocation of fishery resources and their potential as “costs” of river basin development be slowed, arrested, or reversed. Such costs range from 10% of production in the well-planned scheme for the Lower Mekong Basin to 30% in the Chandpur project in Bangladesh where fishery considerations arrived ex post facto. By careful thought, with an ecosystem perspective, timely inputs to the planning of many, many projects otherwise allocatively costly to fisheries will be found to have in them the potential for gain in fishery production, especially when rigorous management inputs are made or when aquaculture is vigorously promulgated in the new opportunities provided.

RÉSUMÉ

En matière de développement de bassin hydrographique, de même que d'irrigation et de système de contrôle des crues, ainsi que dans toutes les formes d'usage de l'eau qui empiétent sur les pêcheries, un vaste déploiement d'acteurs avec des perception différentes des problèmes joue un rôle dans l'allocation des ressources des pêches. C'est seulement par une meilleure circulation de l'information—par la communication—que la mauvaise allocation des ressources des pêches, ainsi que sa valeur potentielle ou compte “débit” du développement de bassin hydrographique, peuvent être ralenties, arrêtées, ou inversées. De tel coûts s'échelonnent depuis 10% de la production, dans le projet bien plannijié du bassin du bas-mékong, jusqu'à 30%, dans le projet Chandpur au Bangladesh, où les considérations concernant la pêche sont arrivées ex post facto. Par un jugement prudent, dans une perspective de type “écosystèmique,” des investissements opportuns dans la plannification de nombreux, nombreux projets, qui autrement auraient été couteux pour la pêche par l'allocation des ressources, seront trouvés ayant en eux le potential d'augmenter la production de la pêche, specialement lorsque de rigoureux investissements dans la gestion sont effectués, ou lorsque l'aquaculture est promulguée vigoureusement dans le cadre de l'ouverture des nouvelles possibilités.

BACKGROUND

In the context of this seminar, fishery resources are the managed or unmanaged supplies of living aquatic organisms, plants and animals, which exist on earth. These resources typically have a harvestable “surplus” not required by the species for their perpetuation. We are here concerned with the optimum allocation of this surplus among the possible users or harvesters, but in an ecosystem framework we must also have concerns over the users of the ecosystem that impact upon quality and quantity of water—the production medium of the fishery stocks to be allocated. Our concern thus spreads from fishery resource users, to water resource users, and to users of the land that drains into the water. Many non-fishery uses, such as consumptive or water-quality-destructive uses, limit fishery production and in this sense subtract an allotment of the fishery resource from fishers. Still other land and water uses may enhance fishery production, such as enriching (but not over-enriching) nutrient inflows from fertilized agricultural land or from domestic sewage systems. Still others directly destroy aquatic organisms, such as the growing losses due to water intake for cooling in thermoelectric plants and the multiplying losses due to toxic pollutants.

Thus, in fishery resource allocation, we are obliged to consider not only the division of the harvestable resource among the fisherpersons—subsistence, commercial, artisanal, and recreational, but also the amounts that are allocable as production losses to other users and uses of water—householders, farmers, shippers, flood controllers, power generators, industrialists, etc. In this entire context we must recognize that to allocate means to apportion for specific purposes and/or to particular persons or things. Finally, we must not lose sight of the opportunities and challenges to ameliorative management that exist in, or are engendered by “misallocations.”

Perhaps we should have entitled this symposium, “Allocation of Residual Living Aquatic Resources,” with the recognition that what we have to allocate continues to shrink. However, we must also recognize that the potential exists for augmenting inland fishery resources by creating new bodies of water, such as man-made lakes, by increasing derivable crops through intensified management of aquatic production potential, and by seizing the manifold opportunities in aquaculture, we could amend our seminar title further to read, “Allocation of Residual and Emergent Living Aquatic Resources” (Fig. 1).

Within the concept that we are here considering, the allocation of residual and emergent fishery resources, I leave to others the explication of allocational problems in temperate water systems and focus upon inland (continental) tropical systems with river basins and their integrated, multidisciplinary development as the pinpoint. These tropical systems are concentrated in less developed countries, and existing socio-industrial impacts upon aquatic production are generally less limiting than in Western Europe, much of North America, and parts of the Middle East. These fisheries are prosecuted mostly for food or to gain foreign exchange; there is little if any recreational fishing in the Western sense. The systems contrast further with most of those in the temperate zones by having: (1) warmer temperatures; (2) longer annual growing seasons; (3) greater rainfall; (4) important dependency of aquatic production on riverine systems with annual inundation of flood plains of both mainstreams and tributaries, but generally without primary dependence on anadromous fish stocks; (5) an extremely low level of management inputs to protect living aquatic resources or to maximize their production and use; (6) vast deficiency in statistics on catch, effort, and economics; (7) all that is harvested is used, nothing is wasted intentionally; and (8) prevailing are unrestricted resource use and unmanaged fisheries in which anyone can fish at any time and take all of anything that can be gotten. There is very little or no enforcement of even such fishing regulations as may exist. The basic fisheries in such waters are essentially free and laissez-faire. They have continued for centuries, mostly in traditional fashion, without benefit of national policies or management programs, and with but few legal constraints, among which are only such gross actions as government allocation of major weir or culture sites by tradition, lottery, or competitive bidding, or as outlawing (but poorly policing) the use of destructive methods of fishing such as explosives or toxicants. Although vastly irregular and only slightly effective, government support to allocatees has taken the forms of loans and of extension or other training services to improve methods of catching, aquafarming, handling, preserving, marketing, and forming cooperatives.

Fig. 1. Hypothetical allocation of fishery production among some uses (and users) of tropical river systems.

Planners (mostly expatriate) of tropical river basin and water management schemes have been so handicapped by lack of baseline data on the fisheries that it is little wonder the resource losses allocated against fisheries as a cost of other resource development schemes have seldom emerged in benefit/cost analyses or feasibility studies. It is almost axiomatic that such losses are not considered in terms of resource allocation. Even when gains in fishery resources were certain to result from projects (such as from man-made Lake Volta in Ghana, Lake Kossou in Ivory Coast, Nam Pong reservoir in Thailand, and Nam Ngum reservoir in Laos P.D.R.) allocation of the gains was inadequately considered by the planners. The possibility that reservoir gains in fish production may lessen the gross impact of losses downstream was not included in the planning of the high dam at Aswan and Lake Nasser, even though the some 20 000-ton annual gain in catch from the lake after 15 years may still not have offset the dam-attributable losses in production in the Nile estuary and eastern Mediterranean. In examples like the foregoing, the result of such deficiencies in adopting an ecosystemic viewpoint in planning results in an inadequate shift in the allocation of a major segment of the national fishery resource away from downstream and/or coastal fishermen. Early on, the questions should have been asked: “If the dam is built, will there be more or fewer national fishery resources to allocate? Where will they be, and how shall they be allocated?” Carrying this view of planning deficiency a step further, allocation of the fishery resource in a new man-made lake has never really been achieved from a combined crop-potential and fisherman socioeconomic viewpoint. For example, 15-year-old Nam Ngum reservoir in Thailand has a carrying capacity of some 2 000 fishermen; yet in the absence of resource allocation more than 4 000 fishermen are doing poorly on the resource base that economically could support well only perhaps half the number.

Quite early in allocation we need to consider the share of fishery resources or their potential claimed by non-fishery land and water use. We need also to address the perceptions of allocations among the many human actors involved in decision-making in the fisheries. Adapting from Brewer (1979), these can be grouped (Table 1) into: (1) Analysts; (2) Managers; (3) Politicians; (4) Fishers (subsistence, artisanal, commercial, and recreational) and Aquaculturists (public and private); (5) Environmentalists; (6) Consumers of fish and fishery products; and (7) Society at large.

(1) The analysts include earth, biological, and social scientists, along with appliers of scientific knowledge such as lawyers, operations specialists, planners, public or private administrators, nutritionists, and public health persons. This group classicially adopts tunnel vision in data collection, in development of theories, and in application of methodologies for problem solving. The analysts are constrained by disciplinary outlooks and personal imperatives and incentives. Consequently, there is little study of comprehensive societal problems, including fishery resource allocation in the broadest sense.

Table 1. Complex of some of the actors (participants) in fishery resource allocation with implicit differences in perception of the problem.

(2) The resource managers operate in the local, national, regional, or international arenas. They are constrained by budgets and the fostering of institutional growth and survival, along with concerns over individual fulfillment and advancement. The information they generate and the management strategies they propose generally lack and ecosystem point of view; the strategies tend to be of short-term, narrow, “fire-fighting” nature. Managers consistently fail to direct the attention of analysts, whose information they use for making management proposals, in such ways as to encourage adequately broad-range, multidisciplinary approachs in the design of needed studies.

(3) Politicians, operating in the local, national, and international arenas, are constrained in their perceptions of allocation problems by concerns over elections, ego-satisfaction, political power structure, constituents' interest, and inflation.

(4) Fishers (including aquaculturists) view the resources selfishly for gain—pleasure, food (even survival), income, or profit. All look upon each other as competitors and look to government for support and resource allocation. Those in the industries ancillary to fishing, such as producers of fishing gear, boats, motors, machinery, and supplies, or of fish food and other items for aquaculture, also have a primarily selfish viewpoint, like the fisherpersons themselves. The common concern of both groups is a steady supply of fish of a desired quality or kind. In the commercial area the merchantable quality of the product is also of concern, as is the price structure. In free economies, there is pressure to keep or expand the share of the market and the profit. Where the different kinds of fisheries—sport, subsistence, artisanal, commercial—compete for a common resource, allocational problems emerge and are sometimes even violent. Communication between resource managers and users is ever a problem. All fishers want perpetually to increase the catch or production, preferably with less effort.

(5) Environmentalists are primarily for preservation and against fishery expansion.

(6) Consumers who use fishery products as food or for other purposes perceive the resource as a steady supply of desired material of good quality at the lowest possible price. Subsistence consumer/fishers view the product for survival. Commercial consumers desire to retain or expand the market and, in free economies, to increase the profit.

(7) Society at large compounds the allocational problems because of geographical, political, economic, and ethnic subgroups, each with different views of the position of fisheries in the total socioeconomic structure. The issue perceptions differ among the groups, but most often relate to inequality, inequity, interdependence, and conflict of perceptions.

Thus, the allocator of fishery resources must understand not only the size and dynamics of the resource to be allocated, but the complexity of the socio-economic system with which he must deal in his apportionment procedures.

CASE HISTORY: THE LOWER MEKONG RIVER BASIN

Now let us see how fishery resource allocation has fared in the most magnificently planned river basin development plan and program the world has ever known—that for the Lower Mekong Basin. Then, in contrast, let us examine the allocation considerations in an irrigation and flood control scheme between Chandpur and Chittagong in Bangladesh.

The Mekong is the twelfth largest river in the world. Its Lower Basin, south from the China border, has an area of 620 000 km² (larger than France) and a population of some 40 million.

In its 1970 Indicative Basin Plan, the Mekong Committee¹ presented an ambitious and farreaching scenario for development of the Lower Mekong River Basin (Table 2). In order that the ultimate objective of improving the lives of the people in the Basin can be fully achieved, the impacts of Basin development on the fisheries and their allocation are integrated into the plan (Fig. 2). In this Basin the fisheries have unusual importance to the nutritional and economic wellbeing of the population of some 40 million people in Laos P.D.R., Thailand, Cambodia, and S.R. Vietnam.

In terms of allocational problems the potential impacts on the fisheries of the Basin development will consist of: (1) direct impacts on the standing crop and catch of fish, and therefore on the value of the fishery resources; and of (2) indirect impacts on the commodities, processes, and factors important to the production of the fisheries, as identified in the macrosystem model (Fig. 3) of our 1974–76 Mekong Basinwide Fishery Studies (Lagler 1976). From the fishery perspective, the actual direct impact mechanism of Basin resource development is action on the vitality of individual fish species. Some species may be hard pressed to overcome new survival difficulties; other kinds may experience little change; and still others will benefit from an increase of their preferred habitat, food supply, spawning sites, etc.

¹ Committee for the Coordination of Investgations of the Lower Mekong Basin (c/o UN/ESCAP, Bangkok). Coordinating support for nearly 25 years has been provided to the Committee via its UNDP-funded Secretariat and by donations from more than 25 non-basin countries.

Table 2. Official goals, objectives, and means of the Indicative Basin Plan^a

^a From Lagler (1976).

Impact analysis and resource allocation consist of two principal elements in integrated river basin development. First, the specific actions planned for the development of the basin are identified. These are the potential cause of changes in the allocable fish productivity. Second, the linkages between these causative actions and their consequences are traced systematically for each of the natural fisheries of the Basin. An “impact” is conceived as any change in an existing commodity, process, or factor, whether beneficial or detrimental.

In the lower Mekong River Basin, development will result from implementation of the Indicative Basin Plan at different levels. Some of the impacts of the Plan are inherent in the basic goals, such as the goal of increasing fish production by the year 2000 (Table 2). Other impacts are inherent in the means proposed to achieve those goals, and could be either lessened or enhanced by adoption of alternative means. For example, agricultural development could be achieved by intensification of rice culture or by cultivation of other crops, with each alternative having significantly different potential impacts on the allocable resources. At an instrumental level, further impacts upon fisheries will depend upon the design and operation of each water management action, such as the height of the penstock opening in a dam and amount and timing of water passed through it or through the flood gates of the dam. Finally, significant impacts of such development projects may result from the ancillary actions necessary to achieve a goal, such as the discharge of chemical wastes from new industries.

Fig. 2. Macrosystem view of relationships among Lower Mekong Basin resources and their integrated development; all of which involve fishery resource allocation decisions. (Diagrammed from “Report on Indicative Basin Plan,” Mekong Committee, Bangkok, 1970.)

The Indicative Basin Plan established several basic goals (Table 2) for integrated socio-economic development of the Lower Mekong River Basin:

Agricultural Development (including irrigation)
Industrial Development (including hydroelectricity)
Flood Control
Navigation Improvement
Freshwater Fishery Development

Of these various goals, agricultural and industrial development are identified as primary goals, and have been used as the basis for estimates of the Plan's expected benefits.

For each of these two primary goals, the Plan defines a specific objective for resource development. The objective for agriculture development is to increase field crop production by 3,6% per year throughout the Basin. The objective for industrial development is to initiate or increase the electro-process, agriculture-related, and river-transportation-dependent industries. These objectives are to be achieved by a combination of water management and ancillary actions (Table 2). The impacts of the water resource management actions, therefore, will result from the direct effects of dams and other physical structures for water management as well as from the impacts of related development actions. For agricultural development, these include: putting new lands into production; double cropping; the introduction of new seed stock, equipment, chemical fertilizers, and pesticides; and soil moisture control by irrigation, drainage, flood control, and salinity control. For industrial development, these include installation of generating capacity to produce large amounts of hydroelectric power, and installation of major barge navigation facilities as far upriver as Vientiane.

From the goals, objectives, and means presented in the Indicative Basin Plan and subsequent documents, six major clusters of activities are identifiable that could significantly affect allocable fishery productivity: (1) dam emplacement and operation; (2) agricultural development; (3) industrial development; (4) flood control; (5) navigation improvement; and (6) freshwater fishery development. Each cluster includes both construction activities and ongoing management operations, and each cluster of activities will generate its own set of direct impacts upon the fisheries and will generate allocation problems.

Fig. 3. Conceptual macromodel of impacts and allocation problems of river basin development on the human component of the fishery system. (Circles are pools of net accumulation of a product; rectangles indicate flows between pools; ovals indicate factors or action sources; solid lines indicate an influence.) A = Total fishery participants; 1 = government fishery management and regulation; 2 = fish processors; 3 = fish handlers; 4 and 5 = the fishers, with self taught skills and low capital investment (4), or with high technical skills and high technical skills and high capital investment (5). (Adapted from Patterson, R.L., in Lagler, 1976.)

Dam Construction and Emplacement

The Indicative Basin Plan proposes construction of a system of six major mainstream dams on the Mekong, a series of lesser dams on upstream tributaries, and indicates the possibility of a barrage on the Tonlé Sap River to regulate the Great Lake in Cambodia. The emplacement of dams involves the creation of concrete or earth barriers across flowing water courses, allowing the water to pass only through man-made channels: spillways, powerplant pen-stocks and turbines, diversion canals, and navigation locks. Mainstream dams, which store water for flood control and irrigation in addition to directing it through power plant turbines, will create permanent man-made lakes that will replace long stretches of flowing mainstream.

Construction activities require large-scale earthmoving to create earth-fill dams and to provide new port facilities, the recruitment or importation of a construction labor force, the creation of at least temporary communities for this labor force, and temporary diversion and disruption of river flows to permit construction. Related activities include the clearing of vegetation from some or all of the lands to be flooded above the dams, the resettlement elsewhere of populations presently living in those lands, and the actual flooding lands above the dams up to the maximum water levels. Subsequent activities involve the construction of new communities, industries, roadways, and port facilities.

Agricultural Development

A principle objective of Mekong River development is to increase field crop production from 12,7 to 37 million tons in the Basin by the implementation of intensive agricultural techniques. This will require the control of downstream flooding of potentially productive land, a total of 5,8 million ha (97% located in the deltaic lowlands), by the upstream Pa Mong and the Stung Treng dams, and the irrigation of land presently too dry for year-round or “double-cropping” cultivation. The mainstream dam projects alone should irrigate 5,6 million ha of agricultural land, most in Northeast Thailand by Pa Mong, but some in the Delta areas of Cambodia and Vietnam by Stung Treng, Sambor, and diversion canals in the Vietnam Delta.

Development of irrigation agriculture will require the construction of at least 237 km of irrigation canals (assuming a canal along one side of each hectare to be irrigated), and the diversion through these canals of a maximum of 2 848 m³/sec per month of water from the reservoirs. To realize the potential of irrigation agriculture will require ancillary actions such as application of some 30 kg/ha of fertilizer annually, or 69 480 tons a year in the Basin; application of some 5 kg/ha of pesticide annually, or 11 580 tons a year; increase in tractor cultivation from 4% to 40% of the cultivated land; a major increase in livestock production; diversification of field crops; and, probably, drainage of large areas of natural fish-producing ponds, pools, and puddles.

Agricultural development plans also include action to control the salinity of agricultural lands in the Delta region of Vietnam in order to increase their potential for agricultural field crops. This would include diking of both sea and river banks to prevent inundation drainage of brackish waters into stream courses by gravity ditches and pumping, augmentation of seasonal low flows in the river to prevent upstream intrusion of brackish waters, and irrigation of pouldered lands by freshwater canals from upstream. Ancillary activities include intensive production of field crops in presently underdeveloped land, which will require additional fertilizer, pesticide, etc.

Industrial Development

The dams will contain 108 hydropower generating units to produce 14 709 megawatts of firm power per year and 23 958 megawatts of peak capacity, with some of the dams primarily designed to produce hydroelectric power. This involves penstocks and turbines for electric power generation, transmission lines to major urban centers, and management of river flows to insure at least year-round minimum “heads” at all downriver hydropower dams.

The Plan calls for development of three major types of industries. Electro-processing industries will use the river's hydroelectric power potential to produce iron and steel, calcium carbide, caustic soda, chlorides, ferro-alloys, copper, phosphoric acid, tin, and particularly aluminum. Agriculture-related industries will accompany the planned agricultural development and will include input industries to produce pesticides, fertilizers and other chemicals, livestock and fish feed, veterinary medicines, and farming implements, and output industries for food processing and extraction. River-transport-oriented industries will use the navigation improvements to exploit the Basin's mineral and timber resources and for mineral processing (copper, iron ore, coal, rock salt, and tin concentrate) and wood processing (lumber, plywood, pulp and paper, and shipyards).

Primary activities associated with the industrial development will include the construction of industrial plants, and then formation of urban communities with related urban public health services, the consumptive use of water resources, and increased riverine commercial vessel traffic. Ancillary activities will include the production of industrial waste materials, both airborne and waterborne; the generation of increased concentrations of urban and municipal wastes; and accelerated development of land resources, both directly for industries and their related services and indirectly for the use of urban industrial populations. Use of water for urban and industrial supplies could increase to 2 227 million m³ a year by 2000.

Flood Control

As a corollary to agricultural development, downstream seasonal flooding will be controlled. The intention is to reduce or eliminate seasonal inundation of alluvial lands, particularly in the Delta areas of Cambodia and Vietnam, so that these lands might be developed more intensively. The current maximum downstream flood levels will be lowered by redistributing the flow pattern more evenly between the wet and dry seasons, with the excess wet season water stored in the reservoirs.

Downstream flood control includes both primary and ancillary activities that may affect allocable fishery productivity. Primary actions include the construction of dikes to reduce overbank flooding and the seasonal storage of water in various types of impoundments. Ancillary actions include the substitution of single-transplant for floating rice, and other agricultural and industrial development.

Navigational Improvement

Navigational facilities are to be improved to permit commercial shipping as far upriver as Vientiane, which will need a minimum river depth of 3 meters. The required primary activities to do this include the construction of navigation locks in all mainstream dams downstream from Vientiane, Laos, excavation of stream channels to the required depth, inundation of existing waterfalls and rapids, regular dredging of river channels and of sea channels at the river mouth, and augmentation of seasonal low flows from upstream impoundments to maintain navigable depths. Ancillary activities include increases in riverine port facilities and vessel traffic, and development of facilities to handle the new industrial production along with future maintenance dredging and disposition of the dredged spoil.

Freshwater Fishery Development

Finally, freshwater fisheries of the Mekong Basin are to be developed by management of reservoir fisheries to increase production to 152 000 tons per year from the 1970 production of some 13 000 tons. Supplemental activities to further increase fish production include fish farming on non-arable lands in irrigation service areas, improvement in fishing gear and in technical training, encouragement of aquaculture, some forest clearance in impounded areas, development of fish seed farms and rearing facilities, and intensification of other management inputs.

The total impact of the Mekong basinwide development will consist of the differential effects of the foregoing specific development activities on the various natural fisheries of the Basin—the upstream fisheries, the downstream freshwater and brackishwater fisheries, and the reservoir fisheries. The effects on the distribution, abundance, and survival of various fishery species are primary concerns.

Basinwide development along the Mekong following the Indicative Plan could conceivably allocate to the fisheries a loss in total catch of some 50 000 metric tons annually, enough to meet the basic fish demand of half a million people. The loss in landed value of catch thus would be about 6 million US dollars a year (Table 3). Estimates of such a potential loss take into account the significant increase in fishery production expected to come from reservoirs. These estimates, however, do not take into account the social costs of reallocating the center of natural fish production in the Basin from the deltaic lowlands to the uplands upstream from kratié. Nor do the estimates take into account the dramatic potential of aquaculture, the emergent potential of fish culture in irrigation systems such as ponds and canals, and improvements in fishing technology that can be expected. Given the awareness of these potentials by the Mekong Committee, effective management in these areas could increase crop and catch so significantly that these possible losses should not be taken as plausible losses.

Table 3. Estimated allocational “costs” to fisheries of river basin development in the lower Mekong of Lao P.D.R., Thailand, Cambodia, and Vietnam. (Data from Lagler 1976; subsistence fisheries and aquacultural production not included.)

The Upstream Basin Fisheries

The losses allocated to the upstream Basin will be primarily through the reduction of riverine and localized inundation zone fisheries along the mainstream Mekong.

The catch loss allocated to the deltaic low-lands will include a reduction in annual commercial catch of 700 tons from the Kratié fishery, but primarily will consist of the elimination of the majority of mainstream inundation zone catch and some of the Great Lake and Tonlé Sap catch. The loss of catch could easily approach 100 000 tons a year. But this loss will be offset by upstream reservoir catches estimated minimally at 49 628 tons, and at 89 330 or more tons with improvements in catch efficiency. The net loss in catch, therefore, assuming minimum and maximum losses and increments respectively, will be from 11 370 to 51 072 tons annually. Any such loss could very easily be compensated for by realization of some of the significant potential of aquaculture, particularly of river cage culture with controlled and augmented low flow of the river.

Brackishwater, Estuarine, and Coastal Zone Fisheries

Augmented low-water flow of the Lower Mekong River will have the effect of moving the limit of brackishwater intrusion farther downstream, i.e., nearer to the South China Sea than at present. Many breeding grounds will be contracted in longitude and latitude. Pouldering in the Delta will further affect the availability of breeding grounds. The ultimate result of development will be a reduction in the natural fisheries of the zone.

With a potential of a significant reduction in brackishwater habitats, the annual catch could decrease by 15 500 tons of inland fish and 33 335 tons of shellfish, perhaps a total loss of 48 855 tons annually. Hypothetically the change to a freshwater habitat could provide a replacement fishery, but the promise of intensive agriculture is likely to inhibit its development to the same degree the freshwater inundation zone will be impacted.

Aquaculture is currently practiced as an alternative source of production of brackish and estuarine fish and shellfish, but with the gross reduction or elimination of natural seed stocks due to habitat dislocation in much of the zone it could become difficult to obtain natural seed for aquaculture practices. Fish and shellfish hatcheries and farms can greatly alleviate this future condition, and possibly offset the losses in natural production, but present development of aquaculture will need to be augmented to do so.

The fishery of the Mekong plume in the South China Sea also will be subject to impacts of the controlled and augmented low-flow regime. Whereas the characteristics of the fishery are anticipated to change, little is known scientifically of the migratory patterns of fish to and from the plume or of the relationship of river discharge to these patterns. Without further studies, only the direction of change can be postulated as negative.

Economic Impacts

Without accounting for the potential of aquaculture, including irrigation-system culture, and of improvements in yield in the natural fisheries due to inputs in management and in fishing and product technologies, as mentioned above, the total net change in annual landed value of fish could range around 6 million 1976 US dollars. This loss would accrue despite the gain in landed value from the reservoir fisheries in the upstream Basin zone, where the mainstream impoundments should increase the estimated landed value of the catch from about US$4,4 million to US$8 million.

In the downstream freshwater zone the loss in the annual landed value of fish could result in a net deficit between US$1 410 000 and US$6 330 000. Most of the loss, of course, is expected to be in the inundation and Great Lake fisheries, where a loss of about US$12,5 million could be expected if intensive agriculture is instituted as planned. Although the agriculture development will provide some incremental value to offset the loss from fisheries, the potential for aquaculture needs still to be explored thoroughly.

In the brackishwater and estuarine zone the losses could approximate US$8 million, unless they are offset by extensive aquacultural development.

In sum, the economic impacts on the fisheries of the entire Lower Mekong River Basin could be significant in the absence of effective aquacultural development including the intensively developed use of irrigation systems to provide for fish culture, and of strong management inputs including applications of modern techniques of fishery management and technology. We must note, however, that this analysis includes the fishery potential of mainstream reservoirs only. The proposals for tributary reservoirs are numerous, with the overwhelming majority of the existing and proposed reservoirs being on tributaries above Khone Falls. Implementation of the remaining tributary programs will further increase standing crops and annual catch in the Mekong Basin, and expand the potential for aquaculture especially upstream. They may also serve, however, to accentuate the undesirable aspects of reductions in freshwater supplies and transported nutrients for the inundation and riverine fisheries of the lowland Delta and of the estuarine and adjacent coastal fisheries. In view of the potential economic impacts and recognition of the allocational problems of development on basinwide fisheries, great needs for further study persist for the natural fisheries and the aquacultural potential.

CASE HISTORY: IRRIGATION AND FISHERY DEVELOPMENT IN BANGLADESH

In contrast to the multidisciplinary planning for Mekong River Basin development that has allocated to fisheries a 10 percent “cost” in reduced catch, in the Chandpur Irrigation and Flood Control project of Bangladesh “cost” of 30% was allocated to the fisheries (Lagler, et al. 1978). The Bangladesh Chandpur project is only a 517-km² pygmy, less than 1/1 000 the size of the giant Mekong scheme, but with a thousand people per km² the population density is perhaps 15 times that for the lower Mekong Basin (some 65 people per km²). Inasmuch as most of Chandpur population is emaciated from malnutrition, and inasmuch as fish is the principal source of protein, there was already a great inadequacy of fish production within the project area. In the Chandpur Unit, the estimated total catch in 1977 of 3 403 tons (commercial, 1 769 tons; artisanal, 89 tons; and subsistence, 1545 tons) provided only 6,5 kg per person per year (averaging 18 g per day, yet the irrigation project required an allocation of about 6-g reduction of this to leave an average amount of something like one spoonful of fish per person per day)!

The Chandpur project is surrounded by a hand-built dike, 96 km long, with a 382-ha continuous ring of borrowpit inside it. This levee is large—large enough to have a road on top—and surrounds low, flat, flood-plain land, adjacent to the Bay of Bengal, formerly transected by the South Dakatia River. Near its northerly and southerly extremities, the dike now transects the river. At the north a massive pumping station brings irrigation water into the project during the dry season, and carries it out during the wet season. A simple water-level control structure at the south shares regulation of high water with the pumping station. Although the pumping station has a navigation lock alongside it, as operated the S. Dakatia River in the project unit is now effectively cut at both the north and south from its former connections which afforded migratory routes for fish, the giant river prawn (Macrobrachium), etc. The barriers and water control are particularly serious in their fishery impacts not only in having eliminated both access by spawning carps and other fishes and by growing prawns, but also in eliminating most of the traditional inundation-zone spawning and nursery grounds of the fish.

Different from the Mekong Committee's inclusion of fishery considerations from the beginning, the real fishery considerations came into the Chandpur project only after the fact. With help from the World Bank, the country is now working to offset the allocated fishery losses by studies to influence the timing of certain water management actions to help fish migration and by building a major fish seed farm backed with strengthened extension services to help the affected fishermen and aquaculturists (domestic, village, and artisanal-commercial). But the cost is high and the benefit-cost ratio has not been calculated. Clearly, however, as in the Mekong a major allocation has been made away from a natural production system toward the artificial system of aquaculture.

LITERATURE CITED

Brewer, G.D. 1980. An international institute of fishery management. Pages 75–99 in Report of the ACMMR working party on the scientific basis of management measures. FAO Fisheries Report No. 236.

Chowdhury, A.Q., and K.F. Laglar. 1978. Fishery development in irrigation and flood control systems. First Annual Report. Irrigation Fishery Development Project, Directorate of Fisheries, Dacca, Bangladesh. Variously paged.

Lagler, K.F. 1976. Fisheries and integrated Mekong River Basin development. Committee for Coordination of Investigations of the Lower Mekong Basin, UN/ESCAP, Bangkok, 3 vols., variously paged.