by Jordi Lleonart *
The Mediterranean (Figure B5.1) is a semi-enclosed sea with a surface of about 3.3 million km2, contributing 0.8 percent to the total world marine surface. Due to its geographical position, being placed at a relatively narrow range of latitudes (from 30°N to 46°N) in the temperate zone of the Northern Hemisphere, the Mediterranean Sea shows a marked seasonal cycle. Water masses are stratified in summer, but the deep-water (below 400 m) temperature is 13±0.3°C throughout the year. The low precipitation in the summer period is the main characteristic of the Mediterranean climate. The Mediterranean has a negative water budget: the loss of water through evaporation is greater than the inputs due to rain and river runoff, hence the contribution of about 1700km3/year of Atlantic water trough the Strait of Gibraltar balances these losses (Oliver, 2003).
Figure B5.1 - The Mediterranean and Black Sea (Area 37)
The system of basins includes water ranging from Atlantic origin in the Western Mediterranean to warm-temperate hypersaline water in the Levant basin, hyposaline waters in the Black Sea, and cold-temperate estuarine conditions in the boreal Azov Sea. Surface water entering from the Atlantic through the Strait of Gibraltar proceeds to the eastern Mediterranean progressively losing nutrients and increasing in salinity through evaporation. It eventually goes back out to the Atlantic to form the high saline component of the Atlantic circulation. This makes for a large number of habitats with many small local stocks and species whose stock trends cannot be individually described here but show up as dissimilarities between sub-areas (Garibaldi and Caddy, 1998).
Figure B5.2 - Annual nominal catches ('000t ) by ISSCAAP species groups in the Mediterranean and Black Sea (Area 37)
The Mediterranean has been globally considered as an oligotrophic sea (Margalef, 1985; Estrada, 1996; Stergiou et al,, 1997b). Normally, the gradual decrease in nutrient would result in a west to east decrease in productivity, but there are local exceptions resulting from a north-south productivity gradient evident also from satellite imagery of chlorophyll A, due to incoming nutrients from northern rivers (notably the Rhone, Po and Black Sea inflows into the Aegean). These anthropogenic effects on fisheries production have been described by Caddy, Refk and Do Chi (1995).
The continental shelf is mostly a narrow coastal fringe with the exceptions of the Adriatic Sea, Gulf of Gabès, northern Black Sea south of Sicily and gulf of Lions, and represents only 23 percent of the total area.
The fisheries of the Mediterranean have shown a surprising resilience to fishing compared with some areas of the Atlantic. This is especially noteworthy since formal and coordinated measures for fisheries management are largely absent in most Mediterranean countries, though more frequent activities and a revision of the terms of reference of the GFCM (General Fisheries Commission for the Mediterranean) and its Scientific Advisory Committee (SAC) is intended to remedy this from 2000. Farrugio et al. (1993), Farrugio (1996), Anon. (2001), Bas (2002), Oliver (2003) and Lleonart and Maynou (2003), among others, have reviewed Mediterranean fisheries.
PROFILE OF CATCHES
Nominal catches in Area 37 increased from slightly over 0.7 million tonnes in 1950, to near 2 million tonnes between 1982 and 1988 (Figure B5.2 and table D5). Catches subsequently declined steeply to 1.3 million tonnes as a result of the collapse of the sprat and anchovy fishery in the Black Sea (Figure B5.3). Total catches have subsequently increased to 1.5 million tonnes in 2001 and 2002, after some small fluctuations.
Figure B5.3 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 24 & 35, Mediterranean and Black Sea (Area 37)
Small pelagics account for approximately 50 percent of total Mediterranean catches. Anchovy (Engraulis encrasicolus) with 59 percent of small pelagics catch, and sardine (Sardina pilchardus) with 16 percent are the most abundant. Other small pelagics are sprat (Sprattus sprattus ), sardinella (Sardinella aurita ) and Azov sea sprat (Clupeonella cultriventris ).
The substantial increase in European anchovy catches from 1960 to the mid 1980s (Figure B5.3) partly reflects increased effort from Turkey in the Black Sea that was added to that of the former Soviet Union fleet previously dominating the fishery. As with sprat catches, it could reflect eutrophication of the Black Sea environment by incoming rivers (Mee, 1992; Zaitsev, 1993). The collapse of anchovy, sprat and Azov sea sprat in 1990 is the result of the introduced ctenophore species Mnemiopsis leidy in the Black Sea. A subsequent increase of catches did not reach the former levels. The sardine series shows a smooth increasing trend to late 1980s (282 000t in 1988) and a subsequent moderate decrease to about 187 000t in 2002.
Mixed bottom fisheries using small mesh trawls, gillnets, trammel nets, traps, pots and dredges capture a large suite of demersal fish and invertebrates of high value for the fresh fish market, with no single species making up more than 10 percent of the total demersals. However, in those areas where trawl fleets operate regularly, despite the inherent complexity of multispecies catches, there is an identifiable series of target species which in biomass or in economic terms, constitute an important basis of production. The species considered demersals (more than 100, although some of them show a pelagic behaviour) represent around 40 percent of total reported catches in the Mediterranean and Black Sea. Hake (Merluccius merluccius ), red mullets (Mullus spp.), blue whiting (Micromesistius poutassou ), whiting (Merlangius merlangus ), anglerfishes (Lophius spp.), Pagellus spp., bogue (Boops boops ), picarels (Spicara spp.) striped venus (Chamelea gallina ), Octopus spp., cuttlefish (Sepia officinalis ), red shrimp (Aristeus antennatus ), Norway lobster (Nephrops norvegicus) and deepwater rose shrimp (Parapenaeus longirostris ), are the main demersals.
By-catch species include species not registered individually in official catches or not always present but that together can represent a significant proportion of catches such as small sharks (Carbonell et al., 2003).
But there are also other local and/or well priced species caught in relatively small quantities like some species of flatfishes, Scorpaenidae, Sparidae, Triglidae, Mugilidae, Serranidae, and some invertebrates. The last by-catch group is from time to time also relatively abundant but not always high priced species such as some Scombridae and Carangidae, or from species with low market acceptability like bogueor picarels (Spicara spp.). Discards are also important, and the reasons for discarding diverse: illegal sizes, non-commercial species or sizes, or market reasons (Carbonell et al., 1998; Lleonart and Maynou, 2003).
It is worth noting the spectacular increase in catches of striped venus, Chamelea gallina, mainly in the Adriatic, reaching a maximum in 1993 (Figure B5.4). This could reflect the interaction of fishing with the transition from oligotrophic conditions in the early period to close to mesotrophic conditions.
Cephalopod catches (Figure B5.5) show a maximum around 1990 that could in part reflect reduced abundance of large predatory fish as speculated by Caddy and Rodhouse (1998), but in most cases these are components in a mixed groundfish fishery. The onset of deep water trawling off the slope areas in the mid-1980s appears to explain the sharp rise in deepwater rose shrimp catches, which are speculated to have benefited from a reduction in the biomass of large hake in slope areas.
Most of the gadoids, and other semi-pelagic species such as bogue and picarel (Spicara spp.), as well as red mullets (Mullus spp.), have shown steady increasing trends over the whole time period, except for declines of several species in the last few years. More remarkable is the case of hake which after reaching historic maxima in the mid 1990 (more than 52000 t), catches have dropped by more than half in 2002. The whiting, only present in the Eastern Mediterranean, shows also this general pattern with maximum around 1990 (Figure B5.6).
The prominent large pelagics are bluefin tuna (Thunnus thynnus) and swordfish (Xiphias gladius ). They represent 3 percent of total catches, but their economic value is far greater. Catches of bluefin tuna increased from the mid 1960s to the mid 1990s, but then significantly dropped (Figure B5.7). The bluefin tuna fishery in the Mediterranean is a matter of concern because of the marked expansion of the farming/fattening activities of wild specimens, which contributes to increase the fishing pressure on this resource by opening new markets, and it is possible that not all the catches are recorded. Swordfish catches increased steadily from 1950 to the early 1980s, more than doubling from 7 000t in 1983 to 18 000t in 1989, partially as a result of improved national statistics collection systems. Catches returned to between 12 000t and 16 000t since the 1990s. Albacore (Thunnus alalunga) catches follow a similar pattern but are smaller. In the case of bonito (Sarda sarda ), catches are highly variable from one year to the next, showing a slight decreasing trend in the long run.
Figure B5.4 - Annual nominal catches ('000t) of selected species in ISSCAAP Group 56, Mediterranean and Black Sea (Area 37)
Figure B5.5 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 45 & 57, Mediterranean and Black Sea (Area 37)
Figure B5.6 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 32 & 33, Mediterranean and Black Sea (Area 37)
The medium sized pelagics catches corresponds to the 7 percent of total catches, and includes jack and horse mackerels (Trachurus spp.), Mediterranean horse mackerel (Trachurus mediterraneus ), Atlantic horse mackerel (Trachurus trachurus ), chub mackerel (Scomber japonicus ), and Atlantic mackerel (Scomber scombrus ). Catches of horse mackerel are also highly variable, without clear trend. Chub mackerel shows maxima from mid 1980's to mid 1990's. Lagoon and coastal species such as grey mullet and silversides show similar trends, although in smaller quantities (Figure B5.8).
Figure B5.7 - Annual nominal catches ('000t) of selected species in ISSCAAP Group 36, Mediterranean and Black Sea (Area 37)
Figure B5.8 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 33 & 37, Mediterranean and Black Sea (Area 37)
The decrease of catches in the last 5 years is a general trend for the non-pelagic species. After 25 years of steady increase they reached the maximum, around 700 000t, in 1994, and have smoothly declined since then to less than 400 000t in 2002.
The pelagics show a different pattern, dominated by the dramatic Black Sea events. After a sharp increase from 700 000t to 1300 000t in 6 years, they keep this figure from 1983 to 1988 and since then they have oscillated, in a declining trend to 990 000t in 2002.
The Black Sea accounts for 39 percent of total catches in the area in 2002 and for 57 percent of the total catches of small pelagics.
RESOURCE STATUS AND FISHERY MANAGEMENT
The reliability of historical data series of catches in the Mediterranean is variable, but data on effort are almost absent. However, given the complexity and diversity of Mediterranean fisheries the available data is probably not sufficient for regular and trustworthy assessments for most species. The very structure of Mediterranean fisheries (atomized fleets, a huge number of landing points, multi-species catches and the lack of large industries as it exists in other seas) make it difficult and expensive to obtain data for stock assessment purposes.
The biological parameters of the main target species (hake, anchovy, sardine, red mullets, some sparids and flatfish, bluefin tuna, swordfish, some high priced crustaceans) are quite well known. However most of this knowledge has been obtained by specific scientific projects, without continuity in time. It is difficult to maintain and update series of biological data, size frequency distributions, etc. without long-term monitoring projects.
Assessment suffers from the same shortcomings, few formal stock and fisheries assessments have been carried out in the Mediterranean, largely because most of the stocks are not shared between countries. As consequence there is no pressure for assessing the resources and no adaptive management has been implemented. With the exception of large pelagics and some very particular fisheries (as striped venus in the Adriatic) fishery management does not involve quotas but is based on effort limitation.
Information has been steadily increasing on aspects of the population dynamics of key species, and population parameters have been accumulated within FAO's data bases and information systems, such as POPDYN (Coppola, Garibaldi and Die 1994) or FIGIS (http://www.fao.org/fi/figis/). There are numerous papers on parameter estimation and assessments, but most of them in grey literature or not presented in a formal way (Lleonart and Maynou, 2003). A bibliographic list of papers related to Mediterranean fish stock assessment (in the broad sense) recently gathered by the Subcommittee on Stock Assessment of the SAC-GFCM, collected more than 700 titles (ftp://cucafera.icm.csic.es/pub/scsa/biblio_MED.pdf).
The multispecies nature of most trawl fisheries with a high diversity of species in the catch, as well as the geographic diversity of environments, suggests that stock units in many cases may be small and local (GFCM, 1998), but also that multispecific and ecological approaches to the assessment and management should be envisaged.
Drastic ecological changes have occurred in the Black Sea from the introduction of a number of harmful exotic species, both phytoplankton and animals, through ship ballast water. Similarly a growing number of Red Sea species are entering the eastern Mediterranean through the Suez Canal (Lessepsian migrants), and subsequently moving northwards and westwards. In fact, species coming from the North Atlantic are mainly found in the northern areas of the Mediterranean. Saharan and subtropical species are mostly found in the eastern sector, while the ponto-caspic species occur in the Aegean Sea and North-Adriatic Sea (Quignard and Tomasini, 2000). The dramatic accidental introduction and spread of a species of seaweed (Caulerpa taxifolia) into the western Mediterranean is also likely to affect demersal food chains in that area in a manner which is not easily predicted (Zaitsev and Öztürk, 2001; Galil et al., 2002; Golani et al., 2002).
In general, evidence for trends in fishing effort and mortality is based on fragmentary data on fleet size and catch per unit effort. In the western Mediterranean (e.g. Baino, Auteri and Serena, 1985; Abella, Caddy and Serena, 1997) high exploitation rates have probably been applied to demersal stocks over the last few decades, judging from reports of the Subcommittee on Stock Assessment of the GFCM. At the same time, comparison of local populations (e.g. Abella et al., 1999) show a wide range of exploitation rates, depending on local fleets and local fishing opportunities. Thus, a broad classification of demersal resources status in Table D-5 as Fully exploited to Overexploited (F–O), not only reflects the uncertainty of the assessment, but also the range of exploitation rates applied to local stocks of a species throughout the Mediterranean.
In the Gulf of Lions, a multispecies production model showed that already by the late 1980s the fishery was fully developed, and similar studies show this to be the case for southern Tunisian waters (GFCM, 1995), although in rocky north Tunisian waters there seems to be some room for further exploitation. In the Aegean, and probably also the eastern and southern Mediterranean, effort and catch seem to have increased steadily at least since the early 1970s (Stergiou et al., 1997a). Aldebert et al. (1993) and reports to the Subcommittee on Stock Assessment of the GFCM in 2001 and 2002, by means a VPA (Virtual Population Analysis), plus a Y/R (Yield-per-Recruit analysis) assuming constant recruitment, estimate the interaction between types of gear (two trawls, gillnet and longline) exploiting the hake stock of Gulf of Lions and concluded that the stock is certainly overexploited and that the trawlers, fishing mainly small individuals, have a great influence on the catches of the other gears (gillnets and longlines). This analysis confirm those from other areas, showing that the fishing pattern of trawl fleets catches the youngest age-classes and can therefore intercept fish before they become available to the other gears.
Shelf demersal resources
At the 2004 SAC meeting 22 assessments, involving seven geographical subareas, nine species and two shared stocks were presented. The SAMED (Stock Assessment in the MEDiterranean, EU project No 99/047), based on MEDITS Trawl Surveys (1994–1999) (Bertrand et al., 1998; Bertrand and Relini, 1998) presented to the Subcommittee on Stock Assessment in 2002 the evaluation of three species: Merluccius merluccius, Mullus barbatus and Nephrops norvegicus . These assessments correspond to the EU countries (not including neither Balearic islands and Alboran Sea) plus Malta.
This is the most widely studied species, Lleonart and Maynou (2003) account for more than 20 references regarding hake assessments. It is a main target species for many trawl (with small mesh aimed at juveniles), longline and gillnet fleets, operating over rocky bottom or further offshore for larger individuals. Although high juvenile mortality rates have led to the suspicion of an overexploited status, no obvious decline in recruitment has been observed (Oliver, 1993), and in fact catches have increased in both east and west Mediterranean until 1995 (Fiorentini, Caddy and De Leiva, 1997). But from 1995 to 2002 the reported catches have abruptly declined to less than the half (52 000t to 21 000t) being at present similar to 1980's level (Figure B5.6). This suggests the probable reduction of the spawning stock surviving in some less exploited areas (the so-called spawning refugia, Caddy 1990) responsible for the recruitment. In any case, the assessments presented at the Subcommittee on Stock Assessment of the GFCM demonstrate a clear overexploitation of this species. Two assessments on hake (Gulf of Lions and Ligurian and Northern Tyrrhenian Sea), based in analytical methods showed an evident status of overexploitation and recommended a decrease of effort. In the case of the Gulf of Lions also an increase of the length of the trawl catches was also recommended. The SAMED project (based on the MEDITS trawl surveys) detected an intense exploitation, with decreasing trends in many Geographical Subareas. Globally growth-overfishing can be assumed. Temporal closures of the nursery areas and effort limitation were recommended.
Elucidating the relative importance of increased escapement of juveniles and spawners remains an important focus for this and other Mediterranean demersal species, especially if the introduction of nursery areas and marine parks is to be considered.
Red (Mullus surmuletus) and striped (Mullus barbatus) mullets
These species are caught by trawlers and a various other small scale fishing vessels with a range of gears practically in all Mediterranean areas. The fishery begins on age group 0, in many areas the small individuals (caught in summer and early autumn) reach higher prices. In the Adriatic, survivors later migrate to the east and largely remain there as adults, hence this constitutes a shared stock. Very high exploitation rates have been recorded in Italian waters (GFCM 1995; Baino, Auteri and Serena 1985; Abella et al., 1999) except for Sardinia and other areas of the Tyrrhenian Sea, the species is overexploited, as in the Adriatic (Ungaro, Rizzi and Marzano, 1994) or Western Mediterranean (Martin et al., 1999). While the red mullet is fully exploited in southern Tunisian waters and in the Ionian Sea (Tursi et al., 1995), the striped mullet is apparently underexploited on the Northern Tunisian shelf (GFCM, 1995) and overexploited in Cyprus (Hadjistephanou, 1992). Seasonal closures on trawling in Italian waters have been aimed at protecting fast-growing juveniles of this and other species during restricted periods of recruitment to the bottom. The results have been very positive increases in survival to age 1+, although seasonal declines in prices have ensued from gluts during the open season (Froglia 1989). At the same time, fishing in nursery areas within 3 miles of shore have led to high capture of juveniles (Baino, Auteri and Serena 1985). The historical series (Figure B5.6) show a slightly decreasing trend in the last 10 years. The assessments presented to the Subcommittee on Stock Assessment concern mainly Mullus barbatus, which is the main species. In the Ligurian and Northern Tyrrhenian Sea the species appears to be fully exploited or overexploited. Seasonal and area closures were recommended in order to protect juveniles. According to the SAMED project full exploitation and growth overfishing can be assumed in most Geographical Subareas, and it was recommended to close shallow waters to fishing to protect recruitment.
Sparids, seabreams and pandoras
Sparids and sea breams play an important role in Mediterranean demersal fisheries and are generally heavily exploited, with peak mortality rates for Tunisian waters generally at or beyond the fishing mortality generating the maximum sustainable yield (FMSY). Analysis of data for Sparus aurata in the Gulf of Lions (Farrugio and Le Corre, 1994) suggested that it is fished above FMSY, and a high proportion of production of this species now comes from aquaculture. Pandoras (Pagellus spp.), as for groupers, appear to be one of the demersal species least resistant to heavy exploitation, and catch rates have declined in a number of areas. They are considered underexploited off rocky areas of Northern Tunisia (Ben Meriem, Garbi and Ezzedine-Najai, 1996) but overexploited in the Gulf of Gabès. Pandoras stocks are heavily overfished in Greek waters (Papaconstantinou et al.,1988b), and depleted in Cyprus, as are bogue and red mullet stocks (Hadjistephanou, 1992), though picarels (Spicara spp.) are considered to be exploited close to MSY (maximum sustainable yield).
Analysis of data for the Gulf of Lions (Farrugio and Le Corre, 1994) suggested that sole is exploited at FMSY, but although evidence was found that exploitation rates had been rising in the early 1990s, there was not yet a clear indication that recruitment had declined. In Tunisian waters sole seems to be exploited close to optimally.
These are important incidental catches in trawl fisheries and there is a directed fishery for octopus in some areas. A high proportion of short-lived species (squids, cuttlefish and octopus) in demersal catches from heavily fished areas such as the Adriatic (GFCM, 1995) tends to suggest that exploitation is high, where low catch rates are in part compensated by high unit prices. Available analyses, though fragmentary (e.g. Baino, Auteri and Serena 1985 for the Tyrrhenian Sea), support a close to optimal exploitation for these cephalopod resources, while fish species are somewhat overexploited. No assessment of cephalopods has been presented to the Subcommittee on Stock Assessment.
While little data exists for (Trachurus trachurus and T. mediterraneus ), they are apparently not heavily fished, and their biomass appears to be variable, presumably responding to environmental changes.
Grey mullets (Mugilidae)
They are principally plant and detritus feeders and have presumably found favourable conditions in eutrophic estuaries. A move to the exploitation of small inshore fish such as silversides (Atherinidae) reflects the search for alternatives to heavily exploited nearshore resources.
Thisis a quite well studied species. In 1998 a monographic volume on this species (Sardà, 1998) was published. This volume focuses on biological knowledge of the species including fisheries and exploitation, distribution, population dynamics and selectivity. The SAMED project presented an assessment to the SCSA concluding that this species is slightly overexploited or fully exploited in most Geographical Subareas, technical improvement of the gear to avoid the capture of small individuals was recommended. The known behavioural characteristics of this species (large periods of time inside the burrows, from which it emerges periodically giving rise to diurnal and seasonal fluctuations in the catches) makes it less vulnerable than other species to the fishing pressure. Notwithstanding patchiness in population structure and density dependence phenomena could be related with cases of “local” stocks or “stocklet” overexploitation. Due to the burrowing behaviour it was considered important to reduce the impact of the otter trawl doors on the bottom to protect the burrows.
Continental slope resources
The increase in slope fisheries, especially for the blue and red shrimp and hake over the last few decades should be viewed with a certain apprehension. The traditional fisheries for hake have used small mesh trawls in inshore areas and targeted 0+ to 2 year-old age groups. The fisheries for hake by other gear in deeper waters are now targeting concentrations of mature fish. Increased offshore fisheries on mature fish is a cause for concern because the continued productivity of demersal stocks is possibly due to the fact that a small proportion of the 0+ to 2 year-old age groups escape from the inshore areas and find a ‘refugium’ for spawning escapement in offshore waters. This hypothesis appears to receive support from selectivity studies, which suggest that larger fish such as big hake are less available to capture in small mesh trawls than small fish.
Red shrimp (Aristeus antennatus )
It is intensely exploited in the Western Mediterranean by bottom trawlers fishing the continental slope together with significant catches of giant red shrimp (Aristeomorpha foliacea ). The two species are probably not always well separated in the statistics, suggesting total catches of around 5000 t a year (Oliver, 1996). Assessments applying length cohort analysis (LCA) and yield-per-recruit (Y/R) analysis conclude that the current fishing mortality (F) is very close to that giving the maximum yield-per-recruit (FMAX), but the values of the natural mortality (M) remain uncertain (Demestre and Lleonart, 1993; Fiorentino et al., 1998; Ragonese and Bianchini, 1996). Current exploitation seems to be sustainable but the steady increase in fishing effort should be controlled. In Balearic islands a LCA, Y/R, and Fox production model under the steady-state assumption show the same state of over-exploitation and the need to reduce the current effort (Carbonell and Lauronce, 2000). For Greece and Italy, significant catches of deep-water shrimp are probably reported to FAO as Natantia decapods nei (20000–32 000t), and likely includes a significant amount of Aristeus and Aristeomorfa . According to an assessment presented to the SCSA, the red shrimp appears to be overfished in the Western Mediterranean and a reduction of effort is recommended.
Small pelagic resources
Sardine and anchovy
Monitoring of sardine and anchovy stocks over more than a decade in areas such as the Alboran Sea and North-western area, Adriatic, Aegean and Black Seas, has been done based on acoustic surveys (Abad et al., 1996; Abad and Giraldez, 2000; Azzali and Luna, 1988; Patti et al., 2000; Guennegan et al., 2000). Daily Egg Production Methods (DEPM) have been used in the Mediterranean several times but they are not employed routinely on a year by year basis. These methods have been applied mainly to anchovy but also to the sardine in some instances (Chavance, 1980; Regner, 1990; Palomera and Pertierra, 1993; Garcia and Palomera, 1996; Somarakis and Tsimenides, 1997; Casavola et al., 1998; Casavola, 1999; Quintanilla et al., 2000). A comparison between the results of DEPM, acoustic surveys and population dynamics models showed that the results were quite similar (Pertierra and Lleonart, 1996).
These analysis reveal a pattern of fluctuations that is not obviously related to fishing intensity. In the Adriatic, anchovy catches peaked in 1980 and subsequently declined while local sardine stocks peaked in the mid 1980s. Anchovy stock biomass increased from 18 000t in 1989 to about 340 000t in 1991 which is, however, lower than earlier stock sizes in the 1970s and 1980s (Arneri, 1994). Cingolani et al. (2004a, 2004b) analysed the dynamics of anchovy and sardine in the Adriatic Sea using VPA (time series 1975–2003) showing a persistent sardine decline. In the Alboran Sea catches peaked in 1982 with 27 878t to subsequently decline to 1 016t in 1988 (Abad and Giráldez, 1990). In the Gulf of Lions and northern part of Spain catches increased in 1989, probably because fleets moved from the southern part of Spain, where the anchovy catch had fallen off.
In the Aegean, as for most resources, mean catch rates for small pelagics declined until the mid-1970s before stabilizing, while total catches, especially in the eastern Mediterranean, have continued to increase, suggesting increasing productivity of formerly very low-nutrient waters. This suggestion gains credibility from the parallel increase in phytoplankton and zooplankton abundance as well as acoustic estimates of small pelagic biomass along a line from the northern Aegean to the south-eastern Mediterranean Sea (Stergiou et al., 1997b). Pelagic biomasses are also generally low in Libyan waters (GFCM, 1995) except for a local seasonal upwelling in the Gulf of Sirte. A sharp decline in pelagic catches of the Levant region was also observed following construction of the Aswan dam (Halim et al., 1995). In Tunisian waters, some 40 percent of the sardine stock is estimated to be exploited annually, probably above optimum, and sardine and anchovy biomasses tend to fluctuate out of phase with one another.
In the 2004 SCSA meeting anchovy and sardine assessments for the Western Mediterranean, Alboran Sea, and Adriatic Sea were presented, detecting no trend in the estimates except in the case of the Adriatic sardine, with decreasing biomass and increasing fishing mortality trends in the last 15 years. The general conclusions were: abundance is heavily dependent on recruitment and stock biomass shows high inter-annual variability, when risk of recruitment overfishing is detected, it is advisable to avoid the catch of fish smaller than their first maturity size, and biomass estimations should be given sufficiently in time to allow the managers to adapt in real time the exploitation.
Sardinellas and silversides
Similar long-term fluctuations are shown elsewhere in the Mediterranean where small pelagic stocks are harvested, suggesting long-term periodic fluctuations may be occurring in environmental conditions superimposed on the anthropogenic effects. The recovery of pelagic production off the Nile delta following the decline mentioned above seems to be largely of Sardinella spp., the dominant small pelagic fish in the south-eastern Mediterranean. Sardinella show a clear increasing trend in the catches. This continuous increase of Sardinellas (tropical) and the apparent decrease of sprat (boreal) can indicate a global warming process. In other parts of the eastern Mediterranean, new inshore fisheries have developed for very small pelagic species, such as the silversides.
Mackerels, jack and horse mackerels
Mackerels show high variability in catches. No specific assessments have been carried out on these species, and although mackerel catches from Greek waters have increased, there is also indirect evidence that it has ceased to enter the Black Sea in large numbers in recent years.
Large pelagic resources
World wide information on large pelagics is provided in section C1. However a few specific comments related to Area 37 follow:
Bluefin tuna and swordfish
Bluefin tunaand swordfish are the most important large pelagic species in the Mediterranean. They represent around 3 percent of the total reported catches, but their economic importance is far greater. ICCAT (International Commission for the Conservation of Atlantic Tunas) considers a single stock of bluefin tuna for the Eastern Atlantic and the Mediterranean, and the Mediterranean holds the main spawning area. Driftnets, longlines and seines exploiting bluefin tuna represent the only real industrial fleet in the Mediterranean. After reaching a landing of 39 000t in 1994, the value has declined to 22 000t in 2002. Concern has rightly been expressed about the status of both species. In both cases the (apparently unrestrained) growth of fisheries over the last decade has increased vulnerability of these stocks as has regular fishing by non-coastal States on bluefin stocks. For this species, the GFCM has adopted the regulations on bluefin fisheries from the ICCAT, to apply to all member countries of GFCM. Recently the number of coastal cages to fatten the bluefin tuna caught in the open sea in order to increase quality and to make the market independent of the catch season has increased substantially. They are believed to also increased the fishing pressure, by opening new markets and because all catches may not be reported. These activities have an effect on many aspects of the assessment-management process as data collection and consequently the stock assessment. They have actual effects (statistical, biological, management) as well as potential ones (environmental, socio-economical, management) (Anon., 2002; Oray and Karakulak, 2003). The concern created by the fast development of this activity, based on capture fisheries, has generated the organization of a crosscutting working group on sustainable tuna farming/fattening practices in the Mediterranean to provide common guidelines to make this activity a sustainable practice.
Swordfish is the second large pelagic species in importance. ICCAT considers the existence of a distinct single Mediterranean stock. Swordfish is fished with longlines and driftnets. In the case of swordfish, the high exploitation rate is also reflected in progressive decreases in mean size and mean age at capture.
Bonito and albacore
Fisheries for these species have not been specifically assessed, but there is indirect evidence that bonito has decreased its range, now rarely entering the Black Sea in large numbers. Bonito show no long-term trends but a high variability catches. Albacore catches have increased from 1980 showing fluctuations.
The Azov and Black Seas
The slight improvement of environmental conditions recorded in the last decade in the Black and Azov Seas creates a favourable background for recovery of biodiversity and marine living resources. In spite of this improvement in the case of demersal fisheries the over-fishing, degradation of vital habitats, including spawning and nursery grounds, and disturbance of structural balance in biota still continue.
Unlike the rest of the Mediterranean, in the Black and Azov Seas EEZs have been declared by all riparian countries. The legislative and regulatory framework that have been established permits the management of living resources at the national level, but more harmonization is required.
According to the conclusions in a recent workshop on Responsible Fisheries and conservation of the Black Sea ecosystem (http://www.blacksea–environment.org/text/default.htm), the fish stock assessment and monitoringactivities are fragmented and irregular while illegal fishing remains one of the most important unresolved issue for all Black Sea coastal states
In the Azov Sea several stock collapses of freshwater fish stocks occurred in the 1960s, such as pike, bream, roach (Ivanov and Beverton, 1985). These collapses were associated with progressive salination due to damming of, and water extraction from, major inflowing rivers resulting in increased salinity by several parts per thousand. This, plus impacts on spawning routes and spawning areas in the main rivers, has seriously affected natural sturgeon populations, whose catches are now in part maintained by hatchery production. Declines occurred in demersal fish stocks, most importantly turbot, benthic crustaceans, and zoo- and phyto-benthos. These latter formerly played a major role, e.g. mussels in filtering and red algae in oxygenation of shelf water, in the Northwest Black Sea. Their disappearance were largely due to anoxic events caused by a greatly increased planktonic production, which, in turn, was linked to increased nutrient inputs from the large Black Sea catchment basin. Collapses of stocks of the Azov Sea sprat, and in the Black Sea, the anchovy, and declines in Mediterranean horse mackerel, and sprat stocks in the late 1980s, were almost certainly linked to the introduction to the Black Sea and Azov of the west Atlantic ctenophore Mnemiopsis leidyi (Zaitsev, 1993). Meanwhile, a species of grey mullet (the haarder, Mugil soiuy, introduced from the Pacific coast of Russia), a detritus feeder which breeds in shallow water, appears immune to M. leidyi predation on its larval stages, and has increased in stock size. Several other introduced species appear pre-adapted to eutrophic conditions, such as the Mya clam and Rapana sea snail, the latter now being a major export item in some countries, and can be considered fully exploited.
The partial recovery of the anchovy stock, which was formerly targeted in the Northern Black Sea, but is now predominantly fished in the southern Black Sea, is probably the most important fishery event in this area. It has recently been aided by the appearance of a species of Beroid ctenophores (Beroe cucumis or B. ovata, depending on the sources), a predator on M. leidyi, which was largely responsible for collapse of the anchovy stock (Zaitsev and Öztürk, 2001). Despite its collapse and partial recovery, it would be misleading to consider the anchovy stock underexploited. Except for the fleets of the former socialist countries, which are undergoing reconstruction, hampered by shortage of funds for repair and investment, the former over-capitalization of the fishing industry mentioned in the last review still continues in the southern Black Sea. By contrast, the stocks of sprat and several other species in the Northern Black Sea may not now be overexploited. The remaining demersal resources should be allowed to rebuild (Prodanov et al., 1997), where environmental conditions permit.
Top Black Sea predators such as dolphins have seriously declined in abundance. Predatory fish, including mackerel (Scomber scombrus ), blue fish (Pomatomus saltatrix) and bonito which used to seasonally enter from the Sea of Marmara (also subject to heavy pollution and fishing), now rarely penetrate into the waters to the north and west of the Black Sea. Stocks of these species can be considered depleted, although not necessarily by fishing alone.
Five species provide useful indices of recent drastic changes in fisheries ecosystems for the Black Sea (Prodanov et al., 1997; Daskalov, 1998 and 1999).
Biomasses of these anadromous species (like the more important sturgeon) have declined by some 75 percent or more compared to the 1970s. Exploitation rates have been high, but have not shown consistent upward trends, and the deterioration of conditions within incoming rivers over recent decades probably played a major part in stock depletion.
Azov Sea sprat
With a highly variable biomass, the sprat stock shows wide fluctuations but supported intensive fishing by the former Soviet Union in the 1950s and 1970s. More recent increases in exploitation rate are associated with declines in catches, that are linked to the explosion of the predatory ctenophore Mnemiopsis leydei which has been dominant in the pelagic ecosystem since the late 1980s.
The single largest resource in the Black Sea, its biomass increased in the late 1970s and early 1980s at a time when catches were also increasing; apparently in response to nutrient inputs to the Black Sea. It collapsed in the late 1980s largely due to predation and feeding competition with the ctenophore Mnemiopsis leydei . Effort subsequently decreased, allowing the species to recover somewhat but anchovy biomass and catches have not reached the previous values.
A main predator on Black Sea sprat, this species has been affected by the decline in sprat stocks due to the Mnemiopsis plague. Whiting is largely taken as a bycatch to the sprat stock which is heavily exploited, with consequences in reducing the stock size of this predator (Prodanov et al., 1997).
According to the conclusions of the workshop on Demersal Resources in the Black Sea and Azov Sea (Öztürk and Karakulak [Eds], 2003) demersal fisheries continue to represent an important economic activity having a very significant impact on the coastal population and on marine ecosystem. Although the problems of over-fishing, degradation of vital habitats, the demersal resources still have potential for recovery. The most important species besides whiting, are turbot (Psetta maxima maeotica ), dogfish (Squalus acanthias ), Raja clavata, and mullets (mugilidae). Most of them have declining catches in recent years.
For the most common species: Acipenser gueldenstaedtii, Acipenser stellatus and Huso huso, figures show a decreasing trend during the last years (with different oscillations and slopes for different species and countries). Acipenser sturio and Acipenser nudiventris have almost disappeared. A.sturio and A.brevirostrum are in the CITES appendix I (threatened with extinction), the rest of Acipenseridae in appendix II (may become threatened with extinction unless trade is closely controlled) A. guendelstaedtii, A. nudiventris, A. persicus, A. stellatus, A.sturio and Huso huso are included in the IUCN Red List.
The Scientific Advisory Committee (SAC) of the General Fisheries Commission for the Mediterranean (GFCM) analysed, in May 2000, the available scientific information for 1985–1999 on the eight most important shared demersal and small pelagic species: hake, red mullet, striped red mullet, blue whiting, red shrimp, anchovy, sardine and sardinella (Fiorentino, 2000). More than 100 evaluations were identified and analysed (GFCM, 2000a). Three species of large pelagics (bluefin tuna, swordfish and albacore) were also taken into consideration (ICCAT, 1999).
Most of the evaluations correspond to stocks of the Northern and Western part of the region. The assessments were based on the application of Virtual Population Analysis or Length Cohort Analysis together with a Yield-per-Recruit Analyses and sometimes surplus production methods, based on short series of data and on the results of scientific surveys. Unfortunately, some existing, but non-published, information were not available at the meeting.
The assessments presented to the SAC in 2001 to 2004 (including SAMED) are summarized in the Table B5.1 (no assessments were presented for large pelagics).
A substantial effort is urgently needed in the Mediterranean to improve the scientific advice provided as well as its application by management. The current investment in stock assessment and, more generally, in fishery research for assessment purposes is not enough or not appropriate for the elaboration of proper and efficient advice to fishery managers and industry. In order to encourage the efforts to produce the needed scientific advice, the SAC, recommended in 2000, inter alia, to update and improve the quality and coverage of fishery data and statistics, to increase the number of assessments in the southern and eastern areas and to ensure that all the assessments be carried out on a regular basis. SAC also drew the attention on the importance of the role of the relationship between the environment and resources. Additionally the SAC indicated that the definition of geographical management units to report the indicators is essential and that homogenous socio-economic indicators in each of these management units had to be developed.
The continental shelf and slope, especially of the Northern Mediterranean, are exploited down to 800m by a variety of gears aimed at a suite of demersal fish and invertebrates, dominated by hake, blue whiting, red mullet, whitings, cephalopods, Norway lobster and shrimps. The mix varies geographically, with the majority of catches made up of fish in the age range 0+ to 2+ (GFCM, 1995). With respect to size at first capture, the use of cod end mesh sizes of 40 mm stretched mesh or smaller continues. This means that the trawl fishery for larger species such as hake is mainly a fishery for juveniles, but as noted by Dremière (1979) and Bertrand (1990) the optimal size at first capture of economically important smaller species in the multispecies catch (shrimps and small cephalopods) has made it difficult to increase mesh size. In addition, the survival of specimens filtered through meshes has not been evaluated. In Cyprus the slim-bodied picarels form a majority of the catch, and catches would apparently be seriously affected by increased mesh size (Hadjistephanou 1992). Reliance has been placed in some areas on seasonal closures during the period of recruitment to the bottom, and regulations requiring permanent closures of shallow waters and marine parks to trawling exist in some countries.
Table B5.1 Assessments presented at the SAC meeting (2001–2004)
|Species||Assessments||Comments and recommendations|
|Merlucciusmerluccius||4||2||3||3||O, growth-overfishing, risk of recruitment overfishing. Reduce effort. Improve trawl selectivity. Temporary nursery areas closures.|
|Mullus barbatus||3||1||2||4||O-F, Coastal zone closure for protection of juveniles. Use of artificial reefs. Seasonal closure. Reduce effort. Enforce current management measures.|
|Nephrops norvegicus||1||1||F, Technical improvement of gear to avoid capture of small individuals. Reduce trawl doors effect on bottom.|
|Sardina pilchardus||3||5||4||5||O-F, not to increase the effort|
|Engraulis encrasicolus||3||6||3||3||Risk of recruitment-overfishing. Set minimum legal size to that of 1st maturity.|
|Trachurus trachurus||1||1||F, Keep fishing effort at current level.|
|Boops boops||1||F, Keep fishing effort at current level.|
O - Overexploited,
F - Fully exploited,
U - Underexploited
It is difficult to evaluate Mediterranean fishing effort trends, especially by trawling, but new fleets have been acquired in e.g. Croatia and Libya, and fleet replacement schemes have operated in other areas suggesting that effective fishing effort may have increased. Overall, there are few management measures restricting fishing effort or overall catch in most countries. At the same time, there are surprisingly few indicators of stock collapses, with more species showing increasing catches than declines (Fiorentini et al., 1997). In recent years, regular standard trawl surveys for demersal resources have operated under European Commission funding in waters off its member countries, and this data set is beginning to allow some stock assessments (e.g. Papaconstantinou et al., 1988a,b; Farrugio, 1994; Oliver, 1996).
Abella et al. (1999) have attributed the resilience of Mediterranean hake despite highly intense fishing on juveniles to the net result of the uneven distribution of trawl effort spatially, notably the distribution of mature fish outside the main trawling grounds and the relatively low vulnerability of large fish to fine mesh trawls (Caddy, 1990). These effects were not planned in the past but should be taken into account in planning future management measures. In particular, the effect of potential increases in fishing effort in deep waters on hake recruitment should be evaluated.
The GFCM at his twenty-fifth session in September 2000, after consideration of the advice provided by SAC, recommended inter alia: “to develop and apply management measures necessary to correct these problems of overfishing”. The GFCM also recommended: “That efforts should be made to increase the number of assessments carried out in the southern and eastern areas” and “that active participation of member countries in providing the Working Groups with all the existing information at their disposal was essential”.
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* FAO, Marine Resources Service, Fishery Resources Division
by Jorge Csirke *
This Area covers a total surface of 17.65 million km2off the eastern South American coast, between latitudes 05°00'N off northern Brazil and 60°00'S off southern Argentina and includes a total shelf area of 1.96 million km2(Figure B6.1). In the north, in the Amazon River area the continental shelf may extend as far as 160 nm (320 km) offshore where the bottom is mostly river deposits and debris. As one moves south away from the influence of the Amazon River the shelf becomes narrow, coraline and mostly unsuitable for trawling. The shelf is also narrow and mostly rocky further south, off central and southern Brazil, becoming wider and more suitable for trawling only as higher latitudes are approached. The best and largest trawling areas are found in the River Plate area and over the Patagonian shelf and the Falkland-Malvinas area, where the shelf extends well beyond the 200 nm limit (more than 370km) off the coastline, turning this into the largest shelf area in the southern hemisphere.
Figure B6.1 - The Southwest Atlantic (Area 41)
The variety and abundance of fishery resources and types of fisheries in this area are determined by the topography and other physical characteristics, including the environmental conditions that range from typically tropical in the north to sub-Antarctic in the south. Towards the northern part of this area, the marine environmental conditions are dominated by the South Equatorial Current that flows from the coast of Africa and encounters the South American coast branching into the North Brazil Current that flows along the north Brazilian coast and the Brazil Current that flows south, along the central and southern Brazilian coast. The northern part of the area is further influenced by the great flow of fresh water from the Amazon River. Further south, the marine environment is dominated by the warmer south-flowing Brazil Current and then by the colder northern-flowing Falkland-Malvinas current, which merge into an offshore flow of subtropical convergence just off the River Plate area where there is also a great flow of freshwater in to the coastal areas (Emílsson, 1959; Hempel, 1971; Dias Neto and Mesquita, 1988; Bakun and Parrish, 1991; Bakun, 1993; Castro and Miranda, 1998).
Figure B6.2 - Annual nominal catches ('000 t) by ISSCAAP species groups in the Southwest Atlantic (Area 41)
Shrimps and lobsters, and to a lesser extent reef fishes and other tropical demersals tend to be of particular relevance towards the northern part of the area. Further south, in nutrient-rich coastal areas where water masses mix off central Brazil and off Uruguay-northern Argentina, the area sustains important populations of small pelagics, particularly in the River Plate area. Coastal demersals are particularly important off southern Brazil and in the River Plate area, while mid- and deepwater demersals tend to dominate over most of the River Plate, the Patagonian and Falklands-Malvinas shelf area, where there is also an important squid fishery. Large pelagics are mostly caught off central Brazil and the River Plate area.
PROFILE OF CATCHES
Total capture fish production from the southwest Atlantic area comes mostly from demersals, and more recently from squids mainly caught in the southern Patagonian shelf and slope area. This is one of the FAO Statistical Areas were capture fisheries have seen a rapid development in terms of total production, with a more or less sustained rate of increase until recent years. In 1950 the total catch for the whole area was only 172 000t, and by then most of the known fish stocks in the area were only lightly or moderately exploited with several important stocks still virtually unexploited. Several new fisheries have developed since and except for the burst in catches between 1966 and 1968, with a peak catch of 599 000t in 1967 caused by an intense pulse fishing of hake and probably other demersals by the ex-USSR fleet, total annual catches increased almost steadily at an average rate of 7.4 percent per year, to reach a maximum of 2.4 million tonnes in 1987. This was followed by a decline, with some year-to-year fluctuations, to a low 2.0 million tonnes in 1990 and 2.1 million tonnes in 1994. A new maximum was reached in 1997 at 2.8 million tonnes. Catches have declined since, with approximately 2.0 million t landed in 2002 (Figure B6.2 and Table D6). Worth mentioning is that total marine aquaculture production has increased in this area at a rate of almost 42 percent per year over the last five years, from 8 000t in 1996 to 72 000t in 2002, but contributing only 3 percent of the total production in this area.
Demersal species in ISSCAAP Group 32 (cods, hakes, etc.) and molluscs in Group 57 (squids, etc.), are the major contributors to the catches from this area, followed by the coastal species in Group 33 (croakers, weak fishes, etc.), the small pelagics in Group 35 (herrings, sardines, anchovies, etc.), and other demersals in Group 34 (toothfish, cusk-eel, etc.) and Group 38 (sharks, rays, chimaeras, etc.). The dominant species in terms of volume are the Argentine hake (Merluccius hubsii ), the Patagonian grenadier (Macruronus magellanicus ), and the southern blue whiting (Micromesistius australis) in the demersals Group 32, the Argentine shortfin squid (Illex argentinus) in Group 57, and the Brazilian sardinella (Sardinella brasiliensis) in the small pelagics Group 35.
The Argentine hake sustains one of the most important fisheries in the River Plate area and over most of the Patagonian shelf. From 1950 total catches of this species, at first all taken by the coastal states, Argentina, Brazil and Uruguay, increased steadily to 102 000t in 1965. Following the exceptionally high catches of hake reported by the USSR in 1966 (56 000t), 1967 (513 000t) and 1968 (100 000t), catches by the same coastal states and then total catch for the area declined to 70 000t in 1969 to then increase steadily to 462 000t in 1979. Total catch of hake declined to a low 255 000t in 1984, and increased again to a record high of 682 000t in 1996. Since then, total catches of this species have steadily declined to a record low in the last 25 years of 243 000t in 2000, with an increase to slightly over 400 000t in 2002 (Figure B6.3).
The Argentine hake is now mostly exploited by Argentine and Uruguayan fleets. Both fleets increased in the 1980s to the early 1990s, and the fleet of Argentina continued to increase in the 1990s. Other deepwater demersals in the Group 32 which make a significant contribution to the total fish production in the area are the Patagonian grenadier and the southern blue whiting (Figure B6.3) that produced 116 000t and 64 000t respectively in 2002. These are particularly abundant in the southern Patagonian shelf and slope area, where they are exploited by long-range fleets from the region as well as from distant areas.
The miscellaneous demersals in Group 34 (Figure B6.4) that mostly contribute to the total fish production in this area are the pink cusk eel (Genypterus blacodes) and Patagonian toothfish (Dissostichus eleginoides) with 20 000t and 11 000t respectively in 2002. These species are exploited by both coastal and long-range fleets from the region and from other areas. Coastal demersal species within Group 33 also produce significant catches within the area, particularly the Argentine croaker (Umbrina canosai ), the stripped weak fish (Cynoscium striatus ), the whitemouth croaker (Micropogonias furnieri ), and the weakfishes (Cynoscion spp.), which have reported relatively high and stable catches over the past few years, with a total of 113 000t for the four species group and 247 000t for the whole species group in 2002. These species are all exploited by coastal fleets.
The main small pelagic species within Group 35 are the Brazilian sardinella (S. brasiliensis) and the Argentine anchovy (Engraulis anchoita ). After the record catches of 228 000t of Brazilian sardinella reported in 1973, total catches of this species have been declining, although with some marked year-to-year fluctuations, to hit a lowest level of 17 000t in the year 2000, with a slight increase to 35 000t in 2001 and catches of 28 000t in 2002 (Figure B6.5). Catches of Argentine anchovy have been between 10 000t and 25 000t per year in recent years. Catches of tunas and other large pelagics in Group 36 have been more or less stable at 50000–60 000t per year, after reaching a maximum of 74 000t in 1996.
Figure B6.3 - Annual nominal catches ('000t) of selected species in ISSCAAP Group 32, Southwest Atlantic (Area 41)
Figure B6.4 - Annual nominal catches ('000t) of selected species in ISSCAAP Group 33 and 34 Southwest Atlantic (Area 41)
Figure B6.5 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 35, 36, Southwest Atlantic (Area 41)
Another very important fishery in this area is that for squids (Group 57). The main dominant species is the Argentine shortfin squid (Illex argentinus) which represents 94 percent of the squid catches and 24 percent of total marine catches in this area in 2002. The overall abundance and actual catches of Argentine shortfin squid have been very variable since the fisheries started in the late 1970s. After reaching 638 000t in 1993, total catches of this species declined to 506 000t in 1994, to increase again to a record high of 1.1 million tonnes in 1999 and decline to 930 000t in 2000 and to a further 511 000t in 2002 (Figure B6.6). Although less abundant, total catches of Patagonian squid (Loligo gahi) have also been fluctuating between a maximum of 89 000t reached in 1989 and a low 22 000t in 1997. In 2002, the total catch of this species was 25 000t. Other squid species caught occasionally are the sevenstar flying squid (Martialia hyadesi ), that except for a record high catch of 24 000t in 1995, followed by 3 800t and 8 300t in 1996 and 1997, respectively, had relatively low catches in other years, ranging from 0 and 1 000t per year. Catches of non-identified squids has declined sharply in recent years, suggesting great improvements in the identification at species level of squid catches from the area.
Shrimps, prawns, lobsters, crabs and other crustaceans in Groups 42, 43 and 45, also sustain important local fisheries in the area, from the tropical to the sub-Antarctic zone. Altogether these species groups have yielded total catches of over 100 000t since 2000 (Figure B6.7) which are important volumes considering their relatively high market value. The single crustacean species yielding the highest catches is the Argentine red shrimp (Pleoticus muelleri ), with highly variable catches ranging from 3000 to almost 40 000t per year since the fishery started in the 1980s, with record high catches of 79 000t reported in 2001.
Figure B6.6 - Annual nominal catches ('000t) of selected species in ISSCAAP Group 57, Southwest Atlantic (Area 41)
Figure B6.7 - Annual nominal catches ('000t) of selected species in ISSCAAP Groups 42, 43 & 45, Southwest Atlantic (Area 41)
Around 8 percent of the total catches in this area (176 000t in 2002) are reported as not identified marine fishes in the official FAO statistics grouped under ISSCAAP Group 39 (marine fishes not identified). These mostly come from small-scale fisheries, particularly in Brazil, where the variety of species and landing sites makes the recording of catches by species a rather difficult task.
RESOURCES STATUS AND MANAGEMENT
Until the late 1970s and early 1980s, this area was amongst the few major fishing areas of the world still having a large potential for expansion and where abundant and potentially valuable fish resources were still reported as underexploited or lightly exploited (FAO, 1979, 1981, 1983; Otero et al., 1982, 1983; Csirke, 1987; Dias Neto and Mesquita, 1988). Several coastal and mostly industrialized long-range fisheries have developed since and most of the fish stocks are now considered to be fully exploited, while some are, or have been, overexploited, even severely, in recent years (Bezzi, Akselman and Boschi, 2000; Dias Neto, Saccardo and Bernardino, 2001; FAO, 1997, 2002).
International fisheries research, stock assessment and fisheries management activities in the area are mostly dealt through bilateral arrangements. The Joint Technical Commission for the River Plate Maritime Front, based in Montevideo, Uruguay, was established in 1973. One of of its main objectives is the promotion of bilateral cooperation between neighbouring Argentina and Uruguay regarding the assessment and management of shared stocks in the River Plate Maritime Front (“Frente Marítimo del Río de la Plata”, http://www.cofremar.org), taking management action when required. In so doing, this Commission has been organizing or coordinating joint research surveys and other research activities in the area under its competence. It has also actively promoted scientific meetings and publications of regional and international relevance, where various stock assessment and fisheries management issues of interest to the two member countries but also to other countries in Latin America and countries fishing in the area are or were addressed and discussed. While very active in the 1980s and 1990s, the activities of this regional Commission have decreased somehow, particularly with regards to their scientific activities having a wider regional or international coverage.
Argentina and the United Kingdom are also cooperating in the assessment of fish stocks and management of fisheries in the Falklands-Malvinas area. In November 1990 the Governments of Argentina and the United Kingdom signed a joint statement on the conservation of fisheries that established a South Atlantic Fisheries Commission, composed of delegations from both States (http://www. oceanlaw.net./docs/ficz4.htm, last visited 26/10/03). The South Atlantic Fisheries Commission meets regularly and provides a forum for the exchange of information on marine living resources and the discussion and implementation of measures to improve the conservation of commercially important fish stocks and the management of fisheries exploiting them in the southwest Atlantic with particular reference to the Falklands-Malvinas area.
Brazil has some ten informal permanent working groups (Grupos Permanentes do Estudos, GPE), which over the years have had variable degrees of activity and in certain circumstances have been instrumental in coordinating research work and in providing technical advice on the assessment and management of important fisheries in Brazil, such as tunas, shrimps, lobsters, sardines and coastal demersals. Through some of these working groups covering the northernmost part of Area 41, there is an active cooperation with the Western Central Atlantic Fisheries Commission (WECAFC) covering Area 31 regarding the study and assessment of fish stocks in the Guyana-Brazil area.
Most of the reported expansion in production in Area 41 over the last two decades is due to the increased catches of hake and more recently of other demersals as well as squids, particularly in the Patagonian shelf and slope area. There are two well known species of hake in this area, the Argentine hake (Merluccius hubsii) and the Patagonian or southern hake (M. australis) and a third one (M.patagonicus, sp. nov, Lloris and Matalallanas, 2003), has recently been described. But by far the Argentine hake is the most conspicuous and abundant, while its area of distribution and fishing grounds tend to overlap in the outer Patagonian shelf and slope with that of the southern hake and the new described one, from which it can hardly be distinguished from simple observation. Given the higher abundance and relative importance of the Argentine hake, it is likely that at least some proportion of the actual catches of southern hake are reported as Argentine hake. Reported catches of southern hake have been well under the 10 000t per year in recent years, while those of Argentine hake have been in the range of 243000 to 682 000t per year.
There seem to be at least two stock units of Argentine hake (M. hubbsi ), with some authors proposing the existence of three-four and up to five stock units (Otero and Kawai, 1981; Bezzi and Perrotta, 1983; Otero, Giangiobbe and Renzi,1986; Perrotta and Sanchez, 1992; Bezzi, Verazay and Dato, 1995). However, this possible distinction into two or more stock units are not taken into account in the official annual catch statistics and are not always taken into account in the assessment and management of the hake fishery within the common Argentine-Uruguayan fishing zone and in the remaining Patagonian shelf area.
The assessments available indicate that until the 1980s and early 1990s the stocks of Argentine hake were fully exploited, but this soon developed into a state of overexploitation by the mid-1990s and stock depletion later on (FAO, 1983; Csirke, 1987; Bezzi, Verazay and Dato, 1995; Consejo Federal Pesquero, 1998; Aubone et al., 1998; Bezzi, Aubone and Irusta, 1999; Aubone, 2000; Bezzi, 2000; Bezzi, Akselman and Boschi, 2000; INIDEP, 2001; Tringali and Bezzi, 2001; Arena and Rey, 2003). At first the overexploitation of the hake stocks was mainly caused by growth overfishing, soon evolving into recruitment overfishing with a serious depletion of the spawning stock biomass. This resulted in the hake resource to be declared in a state of emergency and called for severe restrictive measures by both main fishing countries, Argentina and Uruguay, since 1998. The restrictive measures are still in force and include reduced Total Allowable Catch quotas (TACs) and extensive seasonal and zonal closures to protect juveniles and spawners. While some signs of increased recruitment are being reported, the restrictive measures adopted so far do not seem to have caused the drastic reduction in fishing pressure which would have allowed a more rapid long-lasting recovery of the Argentine hake stocks in the area.
In comparison to the Argentine hake, the southern hake (M. australis) stock is much smaller and is distributed further south in the southern region of the Patagonian shelf and slope with possible connection with a larger stock of the same species in Area 87, off the southern coast of Chile (Tingley et al.,1995). The stock of southern hake is considered to be fully exploited and current catches are within the recommended TAC for this species. However, as suggested by Bezzi and Dato (1995), the situation could easily deteriorate if only a small fraction of the large fleet fishing for Argentine hake switches its effort to southern hake.
The Patagonian grenadier (Macruronus magellanicus) is usually found in deeper waters in the southern Patagonian Shelf and according to recent estimates is considered to be moderately exploited, with current catches being well under the estimated TACs. The other main fish stock in Group 32 is the southern blue whiting (Micromesistius australis ), that is also found in deeper waters in the southern Patagonian Shelf and slope, particularly around the Falkland Islands (Malvinas). While this stock was considered to be moderately to fully exploited until the mid-1990s, more recent studies suggest that at current catches the stock of southern blue whiting is being overexploited (Bezzi, Akselman and Boschi, 2000; Cordo and Wöhler 2000; Wöhler, 2000; Consejo Federal Pesquero, 2002).
Other demersal fish stocks in Group 34, such as the Patagonian toothfish (Dissostichus eleginoides) and the pink cusk eel (Genypterus blacodes) are considered as moderately to most likely fully exploited in this area, although there is the general perception that at least the Patagonian toothfish is in a much critical situation due to high non reported catches in international waters. There are several stocks of coastal demersal species of Group 33 throughout the region. The main species in this ISSCAAP Group are the Atlantic croaker (Umbrina canosai ), stripped whitefish (C. striatus ), various species of weakfishes (Cynoscium spp.) and the whitemouth croaker (Micropogonias furnieri ). Most of these stocks are fully exploited, while some local stocks are still being moderately exploited and others are giving clear signs of overexploitation (Otero and Ibañez, 1986; Haimovici, 1988; Arena, 1990; Dias Neto and Dornelles, 1996; Arena and Rey, 1999; Bezzi, 2000; Bezzi, Akselman and Boschi, 2000).
The Brazilian sardinella (Sardinella brasiliensis) is one of the main small pelagics in ISSCAAP Group 35 being exploited in this area. It is found over the shallower continental shelf off Central Brazil between 22° and 29°S. After the record high catches of 228 000t obtained in 1973, catches of this species dropped to then fluctuate in the range of 100 000t and 250 000t until 1986, when another period of decline occurred. The total biomass of Brazilian sardinella declined from an estimated 350 000t in 1977 to 80 000t in 1997, and since then there have been no signs of stock recovery (Saccardo and Rossi-Wongtschowski, 1991; Rossi-Wongtschowski, Saccardo and Cergole, 1995, 1996; Matsuura, 1998; Vasconcellos, 2001). The causes of the severe decline and lack of recovery of this sardine stock is a source of great interest and active debate among fisheries scientists and administrators (Saccardo 1983; Saccardo and Rossi-Wongtschowski, 1991; Rossi-Wongtschowski, Saccardo and Cergole, 1996; Dias Neto, Saccardo and Bernardino, 2001; Vasconcellos, 2003). All seems to indicate that as with other stocks of sardines in other parts of the world, the Brazilian sardine is also exposed to decadal cycles of favourable and unfavourable environmental conditions that could drive the population size up and down more or less independently of fishing pressure. This comes in addition to the effects of heavy fishing, which seems to have maintained this sardine stock under a state of overexploitation almost continuously since its first recorded outburst more than three decades ago. In this respect, it has already been suggested that excessive fishing pressure could contribute to making declining biomass abundance trends steeper and delay or compromize possible natural increasing trends.
Another small pelagic fish stock particularly abundant in the Southwest Atlantic is the Argentine anchovy (Engraulis anchoita) that usually is found off southern Brazil, Uruguay and northern Argentina, although in some years it has been reported as far north as Central Brazil, in areas usually inhabited by Brazilian sardine (Lima and Castello, 1994). This is one of the few cases of highly abundant, well-known commercial fish stocks of the world that still remains underexploited. Total catches are in the lower tens of thousands tonnes per year, while the potential for the whole distribution area is more in the order of one or more hundred thousand tonnes. The total estimated biomass of Argentine anchovy, while highly variable, has mostly been well over one million tonnes, with maximum estimates close to 10 million tonnes in some years (Ciechomski and Sánchez, 1988; Hansen and Madirolas, 1999). This is a stock that clearly could support a much higher fishing pressure. However, it is clear that, as the species is close to the base of the food web of the northern Patagonian and River Plate system, any significant increase in the fishing pressure on this stock could have negative impacts on other fish stocks feeding on it.
Catches of tunas and other large pelagics have been more or less stable in recent years and most stocks seem to be fully exploited although some room for limited expansion exists in some cases. Total catches of sharks, rays and chimaeras have remained more or less stable or increased slightly over the last decade or so, with 57 000t reported for this species group in 2002. Although some stocks are not subject to direct fishing, they might still be moderately or fully exploited as by-catch in other more intensive demersal fisheries in the area. Due to their low fecundity and other life history characteristic there is some concern that through this indirect fishing individual populations of sharks, rays and chimaeras be exposed to undesirably high fishing mortality, become overexploited and in extreme cases depleted, even if not targeted by any particular direct fishery. More studies are needed in this respect, particularly in the context of the IPOA on sharks.
Amongst the crustaceans, the most abundant single species producing the highest yield is the Argentine red shrimp (Pleoticus muelieri) in the central Patagonian Shelf area (Boschi, 1989; Bezzi, Akselman and Boschi, 2000). This stock is considered to be fully exploited.
Another main stock is the Argentine shortfin squid (Illex argentinus ), which is distributed along the shelf and slope from 22° to 54°S and is exploited by long range fleets from the area as well as from distant areas. Several studies have been conducted on the shortfin squid stock in the Patagonian Shelf and slope area (Koronkiewicz, 1980, 1986; Brunetti, 1981; Otero et al., 1982; Hatanaka, 1986, 1988; Csirke, 1987; Haimovici and Perez, 1990; Haimovici et al., 1998; Bakun and Csirke, 1998). Some work has been done to distinguish possible population groups or stocks units in the area by analysing differences in reproductive seasonality and distribution of early and older life stages. At least three main spawning stocks are described, the summer-spawning stock, the south Patagonic stock and a Bonaerensis-north Patagonic stock, with a possible fourth one, the southern Brazil stock, that could well be an extension of the Bonaerensis-north Patagonic stock.
During the first years of rapid development of this fishery there was great uncertainty and concern regarding the state of this stock and the risk of overexploitation. However, the various research and management efforts made and in particular the joint or coordinated actions by Argentina and the United Kingdom in the context of the South Atlantic Fisheries Commission have contributed to improve the assessment, monitoring and control of fishing operations of local and particularly of long-range fleets. Regardless of the high year to year variability in abundance and resulting catches, the Argentine shortfin squid as well as the Patagonian squid are considered fully exploited.
Most of these fisheries are under some kind of management scheme with specific management measures varying from one country to another and from one fishery to another. Enforcement, however, is not always as effective as desirable. Only a few fisheries are under an open access regime and these are mostly coastal small-scale fisheries. In most cases there is a limited access scheme for which a fishing licence is required, which is usually combined with other nominal fishing effort and total catch limitations to keep fishing mortality under control. Also size at first capture regulations and seasonal and area closures are used to protect juveniles and spawners. In particular, Argentina and Uruguay and their sub-regional organization, the Frente Marítimo, have been compelled to adopt more severe restrictive regulations, combining TAC limits, size at first capture limits and seasonal and area closures to face the critical situation of the Argentine hake stock.
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* FAO, Marine Resources Service, Fishery Resources Division