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2.1 Basic Concepts

These concepts can be described by taking the simple example of a single fishery consisting of only one species exploited by one group of fishermen using the same fishing method. This rather oversimplified situation does not allow adequately for the diversity of cases encountered in practice; on the other hand, it affords a firm grasp of the internal dynamic of fisheries and the bases underlying the importance and problems of their management. The concepts that emerge are classic. They can therefore be reviewed quickly. Nevertheless, consideration of them, especially in formulating development plans, is by no means the rule; that is one of the reasons why all too often these programmes do not achieve the expected results.

2.1.1 Biological aspects

The classic stock assessment models (Schaefer, 1954 and 1957; Beverton and Holt, 1957; Ricker, 1958) describe the evolution, in a fishery of this type, of the total catch and yield (catch per unit of effort) in terms of fishing effort (Figure 1). The value of analysis of responses of the fishery to variations of fishing effort lies in the fact that this factor is the chief parameter of exploitation which can be directly controlled by man, and through it the latter can have the best expectation of influencing the state of the stock and its productivity.

When the rate of exploitation increases in a fishery, we see that at first there is an almost proportionate increase in total catches. Then this growth rate drops in steadily and the curve finally shows a maximum level (maximum sustainable yield or MSY)2 which marks the upper limit of the stock's production. Beyond this maximum the average yield tends to drop fairly quickly.

Maximum production, in this definition, was for a long time the sole objective for fisheries management. Its success can be explained by the simplicity of the model on which it is based, which did much to convince administrators of the need to limit fishing if they wished to maintain yields at a high level. In international fisheries where the various national authorities each had to defend the rival interests if their fishermen and their respective fishing industries, and tried to obtain for them the most advantageous catch quotas (or in any case, the least reduced), the MSY was the option involving the least reduction in catches and catch methods in a fishery that was already being overexploited.

The yield curve (catch per unit of effort or cpue), for its part, drops steadily when a stock starts to be exploited. If this characteristic is not duly considered when a resource is being developed it inevitably leads to an overoptimistic forecast of the productivity, and therefore of the profitability, of the new catch methods contemplated.

1 This section is based on a course already published (Troadec, 1980)

2 Maximum Sustainable Yield

Figure 1

Figure 1 Fishery consisting of one species, a single method of fishing and a single community of fishermen: yield (a) on the one hand, catch and size of stock (b) on the other hand, in relation to fishing rate (or fishing effort)

The two curves (a and b, Figure 1) can be shifted within moderate limits, towards higher or lower values by changing the age structure of the catch (Figure 8). Thus one can get higher yields for greater fishing efforts by increasing the average age of the first catch. This can be achieved, for example, by increasing the size of the mesh of the trawl; in this way, by letting young individuals escape one can later capture a part whose total weight will be greater than the total weight of those that were allowed to escape by enlarging the mesh. This is the second and the only other factor on which man can act directly to improve the exploitation rate of natural fish stocks (see Section 3.1).

The yield curve also respresents the evolution of the stock's biomass when fishing is intensified, since the cpue, insofar as they have been measured accurately, are in proportion to that biomass. At moderate fishing levels, it has been found that the reduction of the biomass resulting from intensification of fishing does not substantially affect the stock's capacity to reproduce. The theory shows, and it is confirmed by the history of fisheries, that fish stocks are capable of supporting sizable removals during long periods. At moderate levels of exploitation, one can even see a rise of average recruitment as a reaction by which the stock tends to compensate the drop in abundance resulting from its exploitation. This compensatory mechanism operates mainly at the egg and larvae stage. Every year fish spawn a large number of eggs. The number of these which will survive until the beginning of the exploitation phase is minimal and will depend much more on the environmental conditions they will experience during their larva phase and the environment's biotic capacity than on the number of eggs originally spawned, and therefore on the size of the producer stock. In fact, contrary to what laymen believe, for a long time it was thought that in most species the recruitment level was largely independent of the size of the parent stock, and that therefore it was useless to try to improve their recruitment, and hence the production it occasioned, by protecting the breeders or their spawn.

This observation, which is a fundamental of the dynamics of fish populations, explains why it is important to preserve recruits after they have passed the critical phase of their lives as larvae. Since they are no longer protected by any compensatory mechanism, the average age of first catch and the exploitation rate to which all the recruits spawned by the stock each year are suspected, should then be adjusted so as to derive from them the optimum of what they can produce throughout their fished phase.

In fact, it has been noted that with high intensification in the exploitation of various stocks there is a chronic and sometimes sharp drop in recruitment, even if it is difficult to establish the ratio between the parent stock and recruitment because of the dispersal of data (caused by the variability of the environment and its effects on recruitment) and the shortness of the data series available for most fisheries. This chronic drop in recruitment is felt particularly when the fishing exceeds the MSY. Indeed, it has been demonstrated that beyond this maximum the speed of the decline in catches reflects to a great extent the form of the stock recruitment curve for the lower stock levels, i.e., the chronic drop in recruitment following overfishing of the parent stock (Laurec, 1977). In practice, conservation of a sufficient parent stock to maintain recruitment at a high level will be achieved by control of the fishing rate to which the whole stock is subject rather than by temporary, and therefore too brief, protection of spawners immediately before and during spawning.

The models on which the production and yield curves are based take as their initial hypothesis that the environment is invariable. Actually, each yearly observation deviates more or less markedly from these averages curves depending in particular, on the changes in the environment and their effects on recruitment. When these natural variations are random they do not affect either the height nor the shape of the curves. But this is not the case when the environment shows long-term evolutions. Several fisheries have been established (haddock of Bank George, for example) thanks to natural but temporary increases of the stock, which can occur side by side with colonization or expansion of the stock's distribution area (extension of Moroccan sardine to the south). Consequently, as long as stock assessments are based on short historical data series, the longer the term of the forecasts the higher will be the risk of error.

It has also been frequently observed that the interannual variability in the biomass of the stock, and hence of yields, increases with intensification of the fishing rate. This can be explained by a lowering of the average life expectancy of cohorts and, therefore, a reduction in the number of those which actually contribute most each year to the catches. Thus, the same variability and recruitment will be felt all the more when it affects a stock composed of a small number of age classes.

It is difficult to determine the influence of the various factors, both natural and those caused by fishing, which could have operated in the collapse of many fisheries in recent years. Such factors include the effects of long term climatic fluctuations on the geographic distribution of resources and the biotic capacity of the environment, the natural variability of stocks which is often higher with coastal pelagic species, a drop in recruitment due to overfishing of parent stock, an increase of natural variability due to fishing, etc. (Saville, 1980). Even though fishing probably played only a minor role in the collapse of some fisheries (Plymouth herring, Cushing, 1981), the fact remains that the collapse of many fisheries occurred during periods of intensive exploitation which clearly exceeded the level corresponding to MSY (Peruvian anchovy, Atlantic-Scandinavian herring, North Sea herring, Ivory Coast Ghana sardinella, Namibian pilchard, California sardine, etc.) (Troadec, Clark and Gulland, 1980).

Although the hypothesis of the average invariability of the environment and recruitment has proved practical in order to define and analyse the effects of intensification of fishing, the natural variability of stocks must be considered as a basic characteristic of fisheries. This variability, which is different according to the stocks and environments, must be recognized in management schemes, especially when catch methods (fleets) and processing (plants) show a sluggishness that prevents their immediate adjustment to stock fluctuations or when, because of a concern to stabilize employment, it is necessary to cut down bottlenecks and reduce off-seasons to the maximum.

In order to eliminate the negative effects of overintensive fishing on recruitment and average productivity of stocks, as well as the risks of collapse which they entail, and in order not to increase the natural interannual variability of stocks and incur sizable excess costs for the industry, and, lastly, for protection against the consequences of assessments which are overoptimistic since they are based on the analysis of fisheries performances which may have been established at the time of temporary natural increases of stocks (Doubleday, 1976), biologists (e.g. Sissenwine, 1974) have come to the conclusion that the MSY is often an overly ambitious strategic objective for fishing. They have therefore, recommended the adjustment of exploitation rates and catch levels below MSY (Gulland and Boerema, 1973). Even though such objectives involve a certain drop of maximum MSY in the short term, these losses are modest compared to the substantial economies in research and continuous stock surveillance programmes afforded by the reduction in variability which they encourage.

The meaning of the word “sustainable”, which appears in the concept of maximum sustainable yield (MSY) is important and needs to be explained. The two curves representing production and yield in Figure 1 had been established after the fishing effort, for each exploitation level, had been kept constant for enough time to allow the size and structure of the stock to become re-established after any modifications made in the fishing regime (global fishing effort and age structure of the catches). In fact, when this fishing regime is altered, the size of the stock and the volume of the catch do not reach their final balance until all the age classes subjected to the previous fishing regime have disappeared from the stock fished (a similar effect is observed, for example, in the age pyramids of human populations where the effect of wars on the age groups which fought is observed until the final disappearance of all the age groups decimated by the conflict). This inertia, which will obviously depend on the lifespan of the species, means that it is always possible by suddenly increasing the fishing effort to immediately, but only temporarily, capture more than is indicated by the sustainable production and yield curves.

2.1.2 Economic aspects

If there are statistics available on the value of catches and estimates on the various items making up production costs (capital, labour,fuel, etc.), it is easy to transform the curves in Figure 1 into economic equivalents (Figure 2). The total cost of production will be proportionate to a large extent to fishing effort while the value of landings, as a first estimate, will be proportionate to their weight. Gains in productivity can undoubtedly be achieved by an increase in the volume of fishing operations, and the average unit value of the catches is likely to drop with the quantity of the supply or the decrease in the average size of the individuals captured which always accompanies intensification of fishing. These secondary effects could slightly shift the position of the maximums and other significant points of curves (a) and (b) of Figure 1 expressed in economic equivalents. However, these distortions would still not be enough to substantially change the shape of the curves and, in particular, the conclusions that could be drawn from them concerning the position of the different objectives in relation to the axis of the fishing effort.

Figure 2 shows, in relation to total fishing effort:

An examination of these last two indices is particularly interesting. A marginal yield curve (c') passes through the value 1 - i.e. the unit growth in total costs will then be just covered by the corresponding increase in the value of the resulting total production (V = ∑C - for fishing effort decidedly less than that leading to MSY. It is also with this effort that the total economic yield, or total net profit1 is at the maximum. This point is called MEY (maximum net economic yield).

Figure 2

Figure 2 Economic model of a fishery consisting of a single species, a single fishing method and a single community of fishermen:

  1. = total value of catches (∑V)
  2. = gross economic yield (∑V/∑C)
  3. = gross marginal yield (ΔV)
  4. = net total economic yield (∑V - ∑C)
  5. = total cost of production (∑C)
    in terms of fishing effort

N.B. The different curves are not all shown on the same scale (vertical): this does not affect the position of the points of these curves seen in relation to the axis of variation of fishing effort, the only aspect which concerns us here

1 The total costs, in their meaning here, include a return for the capital and labour corresponding to their opportunity costs. The net economic yield, calculated between the total costs and the total value of the production, therefore, excludes the normal exploitation profits. It corresponds to the added value which attaches only to the intrinsic value of the resource

It is this objective which one can suppose that a single operator, for example the State, whose sole aim will be to maximize the economic yield produced by fishing the stocks in its zone of jurisdiction, will try to reach and maintain for its fishery. But there are few fisheries owned by a single operator. Because of the mobility of the individuals making up the large majority of fish stocks, it is usually impossible to allocate a particular part of the resource to each fisherman. Therefore, he is unable to take the responsibility of minimizing the fishing costs corresponding to the share of the resource belonging to him, and so extracting the economic yield attached to that resource. For him the problem is simple: each fish that he does not succeed in catching is most likely to be lost to him, whether it be captured by another fisherman or dies a natural death. On the contrary, he can hope to increase his share of the total yield by increasing his means of capture (see Section 2.3.1). In fact he will do so as long as his average returns exceed his average costs, i.e. as long as curve b' in Figure 2 will be higher than 1. Unfortunately, placed in the same position, all operators will be inclined to do the same. Moreover, potential new arrivals will join their predecessors as long as the fishery provides them with an income at least equal to that provided by other job alternatives outside the fishing sector, in other words until the whole of the economic benefit will be dissipated by mobilization of unnecessary capital and labour. Since the opportunity costs of excess labour and capital are included in the global costs of the catch - and therefore excluded from the calculation of the yield - these excess material and human resources will by definition be used better in other sectors of the nation's economy.

At present fisheries represent one of the best examples of the exploitation of natural resources where neither the number of operators - even if there are some exclusive clauses, e.g. regarding foreigners nor the volume of their respective activity are themselves limited before the zero profitability threshold is reached. Once this threshold is reached, the productivity increases of the more efficient competitors lead to the failure and withdrawal of the less efficient or less fortunate ones. The dynamics governing the exploitation of shared resources are well known; without the intervention of a central authority is doomed to economic stagnation (Gordon, 1954; Scott, 1955). In national as well as international fisheries this development may not even stop at the threshold where the average individual and global profitabilities cancel each other out. There are several reasons for this:

The economic return, the amount of which depends apart from fishing levels, on the unit value of the catches as well as on the total cost of production can, however, be quite high. Thus, allowing for a reasonable return on the capital invested in the fleets (Griffin, Warren and Grant (1979) and christy (1979)) have estimated that the North West African cephalopod fishery could provide the States owning the resource with a hypothetical resource yield of an order of US$ 200 million, i.e. about US$ 1 500 per t of catch if a system to control the fishing effort were to be applied effectively. This yield is termed “hypothetical” because it can only be totally extracted if the other coastal countries controlling the other world cephalopod stocks apply the same system. In fact, the competition between the countries owning this resource is very likely to force them to leave part of the economic yield to the fishing countries. Another example is that of the Maldives where the revenues which the State derives from the country's tuna production are about twice those it pays to the fishermen (Christy, et al., 1981).

In reality, the phenomenon of overfishing breaks down into three distinct aspects:

These three phenomena appear fairly consecutively according to the intensification of the fishing rate. The fact that maximum economic production (MEY) is placed, in terms of effort, beyond maximum gross weighted production (MSY) is the result of the concavity of the total economic production curve, whereas the increase of the costs themselves is almost linear. The concavity of the total value curve is due first of all to overfishing of young individuals (growth overfishing) to which one can later add the decline of recruitment through too great reduction of the parent stock (recruitment overfishing). This sequence shows that, contrary to the anxieties currently expressed, the need to preserve stocks does not generally become apparent before the economic interest of their management. To be convinced of this one need only consider the case of low density and/or unit market value stocks whose exploitation reaches the zero profitability threshold (point of theoretical bio-economic balance toward which an uncontrolled fishery aims) before maximum production (MSY) is reached (Figure 3). Although temporarily preserved from biological over-exploitation, in economic terms such fisheries would benefit from regulation of fishing effort just as much as the ones mentioned previously.

The gap between the MEY and MSY is often even further accentuated by the relatively quicker depletion of the larger individuals and therefore, by a drop in the unit market value of catches which takes place when fishing is intensified. In the same way, the drop in abundance which occurs in the development of the fishery of the most valuable species often found in multispecies fisheries (see Section 2.2.2), is likely to accentuate this difference still further.

On the other hand there is another factor which operates conversely. Until now it had been accepted that the changes of equilibrium in the fishery occurred instantly. This is clearly not true. We have seen that the stock possessed an inertia equal to the duration of the fishing phase of the species composing it and that operators could enter the fishery more easily, i.e. more quickly, than they could leave it. This inertia has consequences for the fishery's economy insofar as both the future profits and costs must be reduced according to the respective discount rates. Dynamic models have been worked out to take account of this time effect. Unfortunately they are mathematically complex and demanding in terms of information. But they show that, depending on the value of the discount rate, the dynamic economic optimum lies between the static MEY (in which case the discount rate would be zero) and the bio-economic equilibrium point of an unregulated fishery (undetermined discount rate). In practice one will deduce from this that the economic optimum is less far (below) from the MSY than the static model suggests.

2.1.3 Social aspects

One can assume that at any given moment the amount of employment in the actual fishing industry will be approximately in proportion to the fishing effort1. The need to limit or even reduce fishing of a particular stock will thus have a direct effect on the number of jobs available. On the other hand, the average individual income 1 of the fishermen will be a function of the catch per unit effort (curves b and b' on Figures 1 and 2), that is to say, their average individual incomes will be all the higher as the fishing rate is lower.

1 Excluding possible replacements of manpower through change of the equilibriums between the production factors, e.g., through mechanization of fishing operations

Figure 3

Figure 3 Evolution of the total value (∑V) of catches (a) and total costs (∑C) of production (b) in terms of fishing effort in a simple fishery where the value of catches is low compared to their fishing costs; the economic profitability disappears before the stock is fully exploited; nevertheless a regulation of fishing effort is necessary in order to obtain an economic return from the fishery

That is why maximization of employment and improvement of average individual incomes are in direct conflict. In all fisheries, the level of fishing is influenced by the minimum acceptable individual income in the light of the alternative employment opportunities which exist outside the fishery sector. In the developing countries subject to a high unemployment rate, fishing is one of the last remaining job opportunities for a labour force lacking training and capital (land). In areas where resources accessible to artisanal fishing are limited they are often reduced by the development of commercial fishery, which has been the beneficiary of fishery promotion plans in the past, or where there are few prospects of employment outside the fishing sector and where there is a potential mass of people already to enter fishery (Panayotou, in preparation), overpopulation seems to be the major constraint and the opportunity cost of labour (fishermen) the dominant factor in determining the exploitation level: the best, and possibly the only, way of improving the fishermen's individual income appears to lie in the creation of employment opportunities outside the fishing sector (Smith, 1979) in an attempt to reverse the flow of manpower between fishery and the other national economic sectors.

Another example of the conflict between employment and individual income is provided by the situation of some developing countries like Mauritania for example, which have abundant fishery resources but whose national fisheries are still small. To encourage their nationals to take part in exploiting the stocks which they now fish with foreign partners, such countries could consider it preferable to block foreign fishery (and the royalties they derive from it) at a level where the stock density can remain sufficiently high to compensate for the lower efficiency of their fishermen (see Section 2.3.1), at least at the start. Furthermore, countries such as Canada and Norway, which have resources exceeding the needs of their domestic consumption, might wish to block the fishing of certain stocks at sufficiently high levels to guarantee adequate incomes to their fishermen in order to maintain a certain distribution of their populations on their national territory.

1 Sizeable differences can be seen between the individual yields of different fishermen; but these differences in efficiency and the returns attaching to them do not directly concern the authority in charge of management who must deal mainly with average situations for the profession as a whole

In countries where the opportunity costs of labour are low, particularly because of the effect of unemployment, total exploitation costs will be comparatively small. Consequently there will be a shift of the MEY toward the MSY: in economic terms the employment of relatively more abundant labour and the exercise of a relatively higher fishing effort will therefore be justified. But the socio-economic optimum will not be able to reach the MSY for that would mean accepting that the total costs of production, including the opportunity costs of labour, might be nil.

The frequently-held opinion that the total volume of employment increases with the fishing rate is no longer valid if, at the same time, one considers the effects on employment in related industries (processing, distribution and marketing) as well as the repercussions on the gross national product. Although activity in shipbuilding is still based largely on fishing effort, this is no longer true in the industry's secondary activities. The volume of the latter's activities will depend mainly on the tonnage of catch landed. Employment in this sector should therefore, be at its maximum around the MSY. Now, the number of jobs in the secondary and tertiary downstream sectors could be several times greater than that of the primary sector. There are very few estimates of the multiplier effect: coefficient of 2 to 3 are mentioned for the artisanal fisheries sector; possibly they can reach 7 or 8 in some industries fisheries. In fact, the higher the net economic and social benefits in processing and marketing compared to those obtained, at equal weight, in fishing, the more worthwhile it will be to obtain a catch higher than the MEY and close to the MSY. Moreover, the effects of rationalization of fishery on economic growth must be considered. We have seen (Section 2.1.2) that the fishing effort is now controlled at a level close to MEY and could produce substantial economic returns: they could be used:

The fishing rate leading to maximum employment in the fishing sector as a whole will therefore depend only partly on the labour force engaged in fishing activities. It will also depend on factors such as labour opportunity cost, the slope of the production curve, the share of labour costs in total production costs, the multiplier effect in complementary activities and the net economic income produced by the fishery. In many fisheries maximum employment may not be as far from the MSY as is commonly accepted and can even be below it. A fishing policy having social benefits as its major objective would therefore, have to be based on an appropriate analysis of the relevant factors involved.

2.2 More Complex Situations

2.2.1 Sequential fisheries

The homogeneous and clearly defined fisheries examined in the previous section are hardly ever encountered in real life. If within the same fishery there are separate groups of fishermen distinguished by the fishing methods they employ or by their social and professional backgrounds, they are likely to concentrate their activities on fish of different ages. The terms of their competition will therefore be altered in the sense that the respective capacity of different groups of fishermen to mutually harm each other will no longer be equally distributed. The Penaeid shrimp fishery (Penaeus duorarum) in the Gulf of Guinea provides a good example of the complexity of the problems which can arise when different gear or specialized fishing methods for the capture of individuals of different ages are used by separate social groups in different fishing areas or seasons.

Spawning takes place at sea, and the larva quickly reach nurseries located in lagoons and river mouths. There they spend several months before migrating to sea, where they colonize relatively defined bottoms. Sexual maturity takes place after this migration. Shrimp die naturally after about a year and a half. During this cycle they are first fished at the time of their migration from the lagoon to the sea. This fishing is mainly done with fixed gear which the artisanal fishermen place across river mouths and passages. Out at sea the shrimp are fished by specialized trawlers and, incidentally, by trawlers seeking fish.

Stock assessments show that if there is an attempt to maximize production, artisanal fishery harvests individuals which are too young. By delaying their capture one can expect to increase the overall lagoon + sea yield considerably (Garcia, 1976). The advantage is even more obvious if it is expressed in monetary terms, since the unit market value of shrimp increases with their size. Were it not for the fact that tropical penaeid shrimp have generally shown good resistance to exploitation, there might also be cause to fear that an intensification of lagoon fishing could affect the survival of the stock, since lagoon fishing involves individuals which have not had an opportunity to spawn; this danger could be all the more serious inasmuch as those individuals are much more vulnerable because of their concentration during migration.

All these observations argue in favour of sea fishery and a reduction in lagoon fishery. However, research over a wider field would probably show that lagoon fishery is not necessarily as irrational as this consideration of its biological aspects alone suggests. The following table summarizes the specific characteristics which distinguish the two fisheries.

In fact, it has been demonstrated in the Ivory Coast fishery that every net increase of one dollar in lagoon fishing led to a drop of 4 to 6 dollars of net yields in trawl fishery; on the other hand, the first used nearly ten times more fishermen than the second. Lastly, the development of lagoon fishery, by directly reducing its recruitment, may have caused the economic collapse of trawl fishery (Griffin et al., in preparation).

FactorsLagoon fisherySea fishery
Total productionlowhigh
Stock availabilityconcentrated phasedispersed phase
Fishing groundslittoralopen sea
Cost of fishing gearlow (pirogues)high (trawlers)
In foreign currencynoneoften considerable
Fuel consumptionlow (passive fishing)high (active fishing)
Processing costslower (on land)higher (partly at sea)
Foreign expertise requirednoneconsiderable at first

In order to make an objective judgement of the relative and absolute importance to be attached to both types of fishing, we would need to have assessments enabling us to compare the respective performances of the two sectors on the economic and social levels, particularly in terms of:

This simple example shows that identification of suitable management in development objectives is not so easy when one considers fisheries having a heterogeneous structure, and that the field of research necessary to the formulation of rational fishing strategies goes far beyond the framework of a simple assessment of the effects of intensification of fishery on production and stocks. Fishing is an activity whose objective is to obtain a maximum of net economic and social benefits. The conservation of the resource and its maintenance at a level which can produce the desired profits is a condition of that objective. Unfortunately until now there have been assessments aimed at analysing the economic and social terms of management. That is why there is an urgent need for carefully chosen simulation studies covering the whole range of biological, economic and social factors.

2.2.2 Multispecies fisheries

There are few fisheries dealing mainly with only one species. The importance acquired by multispecies fisheries (FAO, 1976) in the past few years has two main causes:

Moreover, the small administrative capacities of many countries force them to undertake the management of their fisheries through large, necessarily heterogeneous groups.

Trawl fishing, in particular, simultaneously captures species with different catchability, demographic parameters and commercial value. In this case, what will be their combined maximum production? What fishing rate will provide the maximum net economic yield when the fact that the species are fished simultaneously makes it impossible, in practice, to apply to each stock any specific fraction of the overall effort?

Globally the response of multispecies stocks to an intensification of fishery is similar to that already described for single species fisheries (Section 2.1.1): a steady decrease of total yields corresponds to a diminishing increase of total catches until a maximum or threshold is reached. In fact, one can approximately assess the multispecies stocks and the situation, in terms of optimum fishing effort, of different management objectives by applying a global model similar to that described in Section 2.1.1 (Pope, in press).

However, there is a fundamental difference: the species composition of catches is bound to change, either as a result of differences in the selectivity with which the different existing species are captured or due to the effects of an intensification of fishing on the specie composition of the stock. These changes are the result of interactions of a technological (fishing method) and biological order.

So far as the first of these is concerned, one can try, applying various available methods, (mesh size and gear selectivity, use of new gear like the vertical wide opening trawl, regulation of the distribution of fishing operations in space and time) to find ways to improve the selectivity with which the fleet “filters” the multispecies resource accessible to it in a given space and time. As in single species fisheries where one tries to improve the value of yields by exerting action on size composition, here one will try, by the selectivity of the fishing, to lift the yield curve more (in value). But the possibilities are few because species are captured simultaneously, which prevents distributing nominal fishing effort at will among the different species, and because of the freedom enjoyed by fishermen to change the time space distribution of their fishing operations.

Concerning exploitation of species or stocks accessible to the same fleet but in part caught separately during separate fishing operations (e.g. different shrimp fishing grounds, different tuna species in surface fishing), the ships will tend to spread the economic returns obtained equally over the different components of the multispecies stock. This practice, which is generally acceptable in economic terms, in principle reduces the problem of the rationalization of the exploitation of multispecies stocks. There is a risk, however, that it may lead to the extinction of the most valued species when the fishery remains economically viable with species of less immediate economic interest, and that the former are encountered during operations aimed at the latter. For example, this scenario has progressively endangered the main large Antarctic whale species (Gulland, 1974).

The changes in the species composition of stock under the effect of intensified fishing result from differences in their catchability and their demographic parameters especially of natural mortality as well as some biological interactions between the different species (Pauly, 1979). When the nominal total effort increases one can see that the yield maximums of the principal species composing the stock are reached and exceeded sequentially: this inevitably leads to biological overfishing of certain species while others continue to be underexploited. A complex, and irregular, network of relations of predation and competition links the various species to one another. Thus the abundance of a species, over and above the direct effects of its own exploitation, will also depend on the natural fluctuations and on the fishery exercised on other species to which it is linked trophically or otherwise. These relations are complex, since they change with the size (and age) of predators; thus a predator's prey (small pelagic species, for example) could quite probably eat that same predator's eggs and larvae.

The relations are also changeable according to the availability of targets, since opportunism appears to be a major characteristic of the trophic relations in fish (Le Guen and Chevalier, 1982). Consequently, although these questions are now receiving increasing attention, an understanding of the reactions of multispecies stocks (both in their abundance as a whole and in their species composition) to intensification of fishing is still far from giving rise to even approximative management rules. For example, Régier (1973) suggested that the intensification of fishing and the degradation of the environment (pollution) in the North American Great Lakes were accompanied by a progressive scarcity of the species occupying the upper trophic levels which were generally the most valuable. On the other hand, Pauly (1979) maintains that in the Gulf of Thailand demersal fishery, on the whole the prey species caught have declined more rapidly than their predators. Furthermore in many regions (North West African coasts, Thailand), large cephalopod stocks of very high commercial value appeared after the intensification of trawl fishery.

Until we have a better understanding of the evolution of the exploited ecosystems their management must remain empirical. Briefly, the strategy could be the following:

  1. to follow the evolution, in weight and composition (age and species), of catches in terms of the intensification of exploitation and changes in the selectivity of the fishery;

  2. to transpose this evolution in economic and social terms (value of catches, costs of production factors);

  3. to attempt experimentally to raise the production curve in value by operating on the selectivity of the fishery taken as a whole (mesh size, gear used, time-space distribution of fishing operations); and

  4. at the same time, to determine the fishing rate corresponding to the exploitation objective chosen.

Nevertheless, these complexities do not in any way change the fundamental characteristics of the problem of fisheries management as described in the case of a single species fishery (Section 2.1): the resources available in each national exclusive economic zone are limited. For any given exploitation method (global selectivity of all national fisheries, costs and earnings structure) an overall production limit will be reached; during this development the marginal cost will be increasing steadily until it reaches the value of the gross marginal profit.

2.3 Application of These Concepts and Examples of Conflicts Between Various Possible Development and Management Objectives

2.3.1 Increase of fishing effort

In section 2.1.1 the immediate and long term consequences of changes in the exploitation rate were described. Gulland (1968) has studied the relative error involved in planning which fails to take into account the decline in yields following a contemplated increase of fishing effort. Figure 4 outlines these effects for a Δf growth of fishing effort f already being exerted.

Before this increase is achieved it is assumed that the stock had been in equilibrium; its density, represented by the angle θA, was then proportional to the catch per unit of effort AEA/OEA corresponding to the fishing rate A. Once the increase of effort (f) has been made, the stock gradually becomes stabilized at a new equilibrium corresponding to fishing rate B; its density will then be represented by the angle θB, and production will be equal to BEB.

Because of the slope of the production curve, the actual marginal gain BC obtained in the long term will always be less than the growth DC expected beforehand. The BC/DC ratio is called the marginal efficiency of the additional effort Δf. It is cancelled out at MSY and then becomes negative.

The marginal efficiency is not the same if the increase in catch methods affects only a part of sector of the fishery. In that case one can demonstrate that the difference between sectorial marginal efficiency and global marginal efficiency is greater - always in favour of the former as the sector is small in relation to the fishery as a whole. Should it be small enough, the marginal efficiency could remain positive even if that for the fishery as a whole is negative. In simple terms this means that a fisherman or a crew can always expect to increase their catches, even if the stock is already being fished beyond maximum sustainable yield. This is another manifestation of the conflict between immediate individual interest and long-term collective interest which leads to economic stagnation of fisheries.

An illustration of this concept is provided by the study of the effects of sectorial increases of fishing effort on the schemes for allocation of resources. This will be the case, for example, of canoe mechanization programmes or of any other plan for increasing catch capacity concerning only one segment of an artisanal fleet, or the assignment, for example to foreign ships, of licenses for fishing of stocks already exploited by national operators or, again, of development of an industrial fishery on stocks already exploited by artisanal fishery. If the segment exercising the effort Δf is responsible for a production increase equal to BC, its total production BG will be achieved in part (which will vary according to the respective positions of EA and EB) at the expense of fleet EA which is already operating (Figure 4). In other words, the growth in means of capture (f) in one section causes a drop in yields (θB θA) and production (AF) in the fleet already operating.

2.3.2 The consequences of innovations, subsidies and changes in fishing costs and the value of yields

It is interesting to analyse the probable effects of the different factors liable to change the equilibrium of a fishery in which:

This is the situation, in particular, of many artisanal fisheries in developing countries (Panayotou, 1980). In these conditions, the fishery tends to stabilize at a point where total costs equal total earnings, the latter being established at the minimum wage level acceptable to the fishermen, bearing in mind the possibilities of outside employment and of the mobility of the fishermen and the unemployed who are likely to join them. The acceptable minimum income, excluding operating costs, will be equal, in principle, to the opportunity costs of capital and labour. But if mobility is low, the net income can fall below the opportunity cost (Panayotou, in preparation).

Figure 4

Figure 4   Effects of growth of fishing effort (Δf) on a fleet already in operation (f) and on a fishery as a whole
AEA - total catch under fishing regime A
BEB - total catch under fishing regime B
BC - increase of actual catch following increased effort Δf
AF - loss of catch for the fleet (f) already in operation
BG - catch obtained by additional catch capacity Δf; it should be noted that BG = BC + CG, in other words the additional catch made through additional means of capture, is obtained partly (CG) at the expense of catches already made by the pre-existing fleet (CG = AF)

Figure 5 shows the effects of changes in the cost of catch. It may go up, particularly under the influence of a rise in the cost of fuel, or go down, thanks to increased efficiency resulting from the introduction of technological innovations or the granting of subsidies. Likewise, Figure 6 shows the effects on the fishery of changes in the value of the catch due to other causes. In both cases, once the fishery has attained an equilibrium, the major effect is on the fishing rate and on the amount of employment and the degree of capitalization of the fishery. Conversely, one may say that in a fishery to which access remains free, any government intervention (subsidies for purchase of diesel fuel, technical assistance to artisanal fishery, etc.) the main consequence in the long term will be to change the amount of employment and the degree of overcapitalization, but not the individual income of the fishermen inasmuch as the latter is mainly determined by the employment opportunities outside the fishery sector. Subsidies for purchase of diesel fuel, in particular, will not bring about any lasting effect on the economic state of the fishery (FAO, 1981b). If the authorities responsible for management intend to maintain the level of employment and individual remuneration by this means alone, we must expect all future increases of the price of fuel to be covered in the subsidies. In the long term such a policy is liable to cause a biological overexploitation of the stock with a drop in total production and, therefore, in employment.

The medium term effects of certain technicological improvement programmes aimed at increasing the fishing strength of the existing catch capacities can be studied on the same model. In Figure 7 the effects of a programme to mechanize canoes have been compared for two different levels of development of the fishery: one which is still moderate (1) and one which is high (2) but does not as yet correspond to full utilization of the resource. It is assumed, arbitrarily but optimistically, that mechanization will lead to an average rise of 10 percent in the total costs of the catch and an increase of 50 percent in fishing power. In both cases the point of departure is a balanced regime where the gross costs and total earnings are equal (bio-economic balance). We find that while in the case of fisheries which are still little developed, the mechanization programme is likely to result in a net gain in the medium term, and thus to promote the development of the resource - such action can lead to a net lose in the long term in a case where the resources are fished more heavily, even if it is applied to a fishery not yet fully exploiting the resource at its disposal. Yet the littoral zones where artisanal fishery operations are concentrated are generally very intensively exploited already. There is therefore, a real danger of impoverishing the fishermen or reducing employment when such programmes are adopted without having given due attention to the exploitation rate of the available resource.

If the mechanization of canoes aims at increasing the volume of the resource accessible to the fleet by extending the latter's range of action, it is possible to push down the point to the level at which the net gains are cancelled out. Unfortunately, even further out to sea resources not yet fully exploited do not always exist (mainly as a result of competition with commercial fleets), and mechanization plans combined with measures which can ensure that mechanized canoes will really fish further offshore and will not add to the overexploitation of an already crowded coastal strip are exceptional. Such mechanization programmes, far from postponing the regulation of effort directly, pose the problem of control of its distribution in time and space which, in reality, implies that the effort can already be controlled.

Figure 5

Figure 5 Effects of changes in the total cost of production in a simple uncontrolled fishery:

  1. An increase in production costs (e.g. fuel or labour) results in a drop in the fishing rate and, consequently, in total employment;

  2. A drop in the costs of catch (e.g. increased efficiency through the adoption of technological innovations, subsidies) results in an increase in the fishing effort and, consequently, in total employment, and intensifies overcapitalization. In both cases individual income is unchanged

Figure 6

Figure 6 Effects of changes in the total value of catches in a simple uncontrolled fishery:

  1. The increase in value (e.g. by an increase in the price of fish, the adoption of controls on mesh size, changes of the pattern of rejects and marketing of fish sizes previously rejected, expansion of the range of action of fleet and a growth of the accessible stock, etc.) brings about a rise in the fishing rate, and consequently in employment, and increases overcapitalization;

  2. A drop in the total value of the catches (e.g. through a fall in the selling price, natural decline of a stock, reduction of accessible stock due to greater participation of a competing fleet, etc.) brings about a drop in the fishing rate and, as a result, in employment.

In both cases, net individual income is unchanged

Figure 7

Figure 7 Example of the medium-term effects of mechanization for two different levels of fishing. Hypothesis: in both cases mechanization is supposed to bring about an increase of 10 percent in the total cost of capture and an increase of 50 percent in the fishing effort. If the effort is low (case 1) mechanization leads to a net gain in the medium term and can thereby contribute to the development of the fishery in the long term. If the effort is already high without, however, yet having reached the level of full exploitation (case 2), mechanization can cause a net loss in the medium term and therefore impoverishment of the fishermen or the departure of the least competitive among them.

2.4 Clarification of Objectives

This brief review of the dynamics of fisheries shows that every country has the possibility of using the fishery resources available to it in different ways: to increase production - in value (economic returns) or in weight (protein supply) - exports (foreign exchange), employment either in the fishery as a whole or primarily in certain socioprofessional sectors (to slow down the rural exodus), etc. The balance which will be ultimately accepted will depend on the specific needs of each country as well as its advantages and handicaps. Thus the profound divergences which one can see in the philosophy of the different geo-political blocks, such as the countries of North America, those of Eastern or Western Europe, Japan, and the different groups of developing countries, etc., concerning the development and management of fisheries are largely explained by the weight represented in their respective economies by key constraints or prospects such as the need to ensure the protein supply of their populations, the chronic difficulties of ensuring full employment or the possibility of drawing substantial economic yields from abundant resources (Royce, 1965).

The choice and establishment of development and management targets should not take into account only the gross value of production or incomes. In fact, only the strategies which at the same time consider the corresponding costs and compare them to the potential profits deserve consideration since, whatever the unit in which they are expressed, they are the only ones that can maximize the net benefits.

This review has also shown that most of the targets which can be contemplated (economic, social, food) are reached through different exploitation levels. This characteristic of fisheries makes these different targets partly incompatible. Nevertheless this disparity should not be exaggerated. In a great many contexts the long-term objectives of management ultimately prove to be fairly close and on the average often below maximum weighted production compared to the point of bio-economic balance at which fisheries whose exploitation level and selectivity are uncontrolled tend to stabilize. Therefore, the identification of the objectives that can be considered and a comparision of the conditions of their execution will be followed by their hierarchization and integration in a long-term fishing policy. The formulation of such a policy will be facilitated by analysing the longterm perspectives of the contribution that the fisheries sector can make to the national economy. The final choice of an overall guiding plan will require decisions of an essentially political character inasmuch as any intervention, as well as any lack of it, will have effects on the distribution of wealth among the different socio-professional groups. But the assessment of the various biological, economic and social aspects of fisheries should contribute to a better appreciation of the long-term advantages of management and the implications of the various options open and, finally, encourage the adoption of decisions.

The selection of the various objectives assigned to each fishery will at the same time give rise to objective criteria for evaluation of the benefits and sacrifices which justify development and management. In particular, these criteria will make it possible to judge the importance of decisions concerning the distribution or redistribution of catches and the wealth they can produce and the political difficulties to be overcome, the costs of research, administration, control and monitoring, etc., to be undertaken, which justify the fishery. Such costs must all be considered together in the quantitative evaluation of each fishery and the establishment of the optimum fishing rate. If they are very high one could be led to renounce managing those fisheries, at least temporarily. Lastly, these criteria will make it possible to evaluate the performances of development and management plans later on.

2.5 Development and Management

At first sight it is surprising to see how few fishery development plans are based on an overall evaluation of the national fisheries and their long-term prospects. Many of them are set in a sectorial approach whose limits we have seen in section 2.1 and 2.3.1, particularly with regard to the prevention of overfishing. Perhaps there are even fewer feasibility studies which consider the possibility of changing fishing effort (particularly to reduce it) to reach the objectives chosen. Yet this variable is the essential chain of transmission in the improvement of fisheries. Such practices of the past can doubtless be explained by the fishery regime existing before the extension of national jurisdictions, which placed national administrations, and indirectly also, the planning agencies they employed, in a position similar to that of an isolated fisherman in an open fishery. Although world fishery production was globally limited, this limit was not individualized at the country level since each country could always increase its activities to the detriment of those conducted by the others. In the case of national fisheries operating on stocks also exploited by long-range fleets or by neighbouring countries this observation is obvious. For each country, the only strategy that could be considered was to increase its catch capacities in the hope of increasing its participation more rapidly and more efficiently than that of its rivals. Even in the case of stocks exploited solely by national operators, it was difficult for national administrations to impose limits to national expansion in view of the ever present prospect of increasing the national fisheries through expansion of their activities beyond the territorial waters. That is why even in purely national fisheries an indiscriminate expansion strategy was able to prevail; because of the competition, any other would have led to a decline of the national share. The new law of the sea makes it possible to escape from these conditions and warrants new practices. The theory of fishery shows that national natural, financial and human resources can be utilized appropriately now that a central authority may intervene to maintain the rate of exploitation in the national fisheries at the level corresponding to the selected development objective.

The theoretical analysis of fisheries has shown that development occurred by itself as soon and as long as a fishery produced net profits. Figure 3 shows that development consists basically of widening the distance between the value curve and the curve for total production costs. The choice of strategies to achieve this must be based on an overall analysis of each fishery in order to identify and give a sequence to the fundamental constraints (amount of resources available and the potential that can be caught, value of the products, cost price of catches and structure of capital costs, labour, energy) which limit the space it is likely to occupy.

Thus, in the case where resources allow for a substantial increase in production,a comparison will be made between the prospects offered by reducing the production costs and increasing the value of the catch. In general terms, assistance to financing of fleets or improving fishing methods will be reserved for situations where the cost price of the catch or of processing is too high and constitutes the major constraint - compared to the prospects for increasing the value of production and where lowering them depends on introducing new techniques and equipment which it is difficult for the fishermen to obtain for themselves. On the other hand, this kind of intervention is scarcely justified when it is aimed simply at quantitively increasing the volume of current operations. In fact, if the fishery produces net profits the latter is most likely to occur without outside intervention.

So far development programmes have often taken too little account of the consequences of the limited nature of resources and free accessibility to their exploitation. This is especially the case of artisanal fisheries in Third World countries (Smith, 1979). Moreover in these countries the development model of industrial fishery in the advanced countries has often been directly transposed, thereby applying exploitation systems (costly in capital, foreign exchange, energy and technology) unsuited to local conditions (abundant labour, limited infrastructures and human capacities). In this effort at promotion the emphasis has been placed mostly on increasing the means of capture, whereas the constraints often come afterward, in the placement of the products or in the fisheries environment. The choice of unsuitable exploitation methods and an incorrect identification of priorities in development programmes could only lower the profitability of the operations and, therefore, reduce the competitivity of countries already handicapped by their lower level of technological and economic development in their competition for participation in the exploitation of international stocks (Troadec, in preparation).

Bearing in mind the specific dynamic of fisheries, state intervention plans should deal with the factors over which the profession itself has less or no control, i.e.:

In both development and management it will be necessary to optimize the structure of production costs so as to maximize net profits. In this respect both functions are identical, as are the research studies and analyses enabling us to identify them. On the other hand, development will be attained by increasing one or several production inputs (capital, labour, energy), while management will mean simultaneously maintaining fishing effort at the level corresponding to the selected objective. It is from this point of view, and from it alone, that the two functions can be regarded as distinct and sequential. Even in a developing fishery, expansion could be promoted by control of the fishing effort and of access to the resource by operators so as to maintain its profitability and stimulate investments. Likewise, in a fishery where the resource is already fully exploited, it will still be necessary to try to increase the economic return by improving the value of the raw material while reducing the production costs. Development and management should thus be seen as two complementary functions operating (to different degrees, of course) at all the stages of a fishery's expansion.

1 This last aspect is particularly important in artisanal fisheries: if the mobility of the fishermen is slight, their incomes will be lower than their opportunity costs. This manpower will therefore no longer be used rationally; by definition, there are more remunerative possibilities elsewhere

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