La pêche artisanale en lagune Aby-Tendo-Ehy (Côte d'Ivoire): premières estimations de la production

This work is the result of one year of investigations on the artisanal fisheries of the Aby-Tendo-Ehy lagoon. The structure of fish catches varies with the fisheries zones and the fishing gears, but is relatively stable all year along, in the spite of the existence of some species with well worked seasonary cycle. The composition of beach seines catches, which are relatively unselective fishing gears, is: - in the Tendo lagoon (oligohaline) and Ehy lagoon (freshwater): Chrysichthys spp. 35.1%, Tilapia spp. 18.9%, Acentrogobius schlegelii 15.7%, Ethmalosa fimbriata 12% (those are two seasonary species), Tylochromis jentinki 8.8%, Elops lacerta 5.6%, other species 3.9%. - in the south of the Aby lagoon, under tide influence, Ethmalosa fimbriata 79%, Elops lacerta 12%, Chrysichthys spp. 6%, other species 3%. A preliminary estimation of 7900 tons for this lagoon artisanal fisheries total production is made for 1979 (from representative fishing villages) and can be shared as follows: - beach seines: 5300 tons; - purse seines and "syndicat" seines: 2600 tons; individual fishing: not estimated, it mostly concerns fill nets.

Statistiques de pêche en Lagune Aby (Côte d'Ivoire): évolution de l'effort et des captures de 1979 à 1990

Two kinds of fishing gears insure the exploitation in Aby lagoon: the individual gears are represented essentially by gill nets and collective gears by seines. The number of gill nets varies between 1500 in 1981 and 5600 in 1986. The beach seines, which number varies between 40 and 60, are regularly used. The purse seines (15-30) have been superseded by "syndicat" seines (15) in 1990.

Équation de production: adaptation du modèle de Ricker à un stock de poissons exploité par différents engins

The authors have developed the method used by Pianet and Le Hir (Doc.Sci.Cent. ORSTOM Pointe-Noire, 17, 1971) for the study of albacore (Thunnus albacares) in the Pointe-Noire region. The method is based on the fact that the ratio between unit of effort and number of fish for two fishing gears is equal to the ratio of their catchability coefficients.

Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia

The time series of abundance indices for many groundfish populations, as determined from trawl surveys, are often imprecise and short, causing stock assessment estimates of abundance to be imprecise. To improve precision, prior probability distributions (priors) have been developed for parameters in stock assessment models by using meta-analysis, expert judgment on catchability, and empirically based modeling. This article presents a synthetic approach for formulating priors for rockfish trawl survey catchability (qgross). A multivariate prior for qgross for different surveys is formulated by using 1) a correction factor for bias in estimating fish density between trawlable and untrawlable areas, 2) expert judgment on trawl net catchability, 3) observations from trawl survey experiments, and 4) data on the fraction of population biomass in each of the areas surveyed. The method is illustrated by using bocaccio (Sebastes paucipinis) in British Columbia. Results indicate that expert judgment can be updated markedly by observing the catch-rate ratio from different trawl gears in the same areas. The marginal priors for qgross are consistent with empirical estimates obtained by fitting a stock assessment model to the survey data under a noninformative prior for qgross. Despite high prior uncertainty (prior coefficients of variation ≥0.8) and high prior correlation between qgross, the prior for qgross still enhances the precision of key stock assessment quantities.

Importance of shoreface sand ridges as habitat for fishes off the northeast coast of the United States

To determine if shoreface sand ridges provide unique habitats for fish on the inner continental shelf, two cross-shelf trawl surveys (23 km in length) were conducted in southern New Jersey (July and September 1991−95 with a beam trawl and July and September 1997−06 with an otter trawl) to assess whether species abundance, richness, and assemblages differed on and away from the ridge. The dominant species collected with both gears were from the families Paralichthyidae, Triglidae, Gobiidae, Serranidae, Engraulidae, Stromateidae, and Sciaenidae. Overall abundance (n=41,451 individuals) and species richness (n=61 species) were distributed bimodally across the nearshore to offshore transect, and the highest values were found on either side of the sand ridge regardless of gear type. Canonical correspondence analysis revealed three species assemblages: inshore (<5 meters depth), near-ridge (9−14 meters depth), and offshore (>14 meters depth), and variation in species composition between gear types. Environmental factors that corresponded with the assemblage changes included depth, temperature, distance from the top of the ridge, and habitat complexity. The most abundant near-ridge assemblages were distinct and included economically important species. Sand ridges of the inner continental shelf appear to be important habitat for a number of fish species and therefore may not be a suitable area for sand and gravel mining.

Using the empirical Bayes method to estimate and evaluate bycatch rates of seabirds from individual fishing vessels

Minimizing bycatch of seabirds is a major goal of the U.S. National Marine Fisheries Service. In Alaska waters, the bycatch (i.e., inadvertent catches) of seabirds has been an incidental result of demersal groundfish longline fishery operations. Notably, the endangered short-tailed albatross (Phoebastria albatrus) has been taken in this groundfish fishery. Bycatch rates of seabirds from individual vessels may be of particular interest because vessels with high bycatch rates may not be functioning effectively with seabird avoidance gears, and there may be a need for suggestions on how to use these avoidance gears more effectively. Therefore, bycatch estimates are usually made on an individual vessel basis and then summed to obtain the total estimate for the entire fleet.

Incidental catch and estimated discards of pelagic sharks from the swordfish and tuna fisheries in the Mediterranean Sea

Large pelagic sharks are caught incidentally in the swordfish and tuna fisheries of the Mediterranean Sea. In our study, twelve shark species were documented as bycatch over three years from 1998 to 2000. Blue shark (Prionace glauca) was the predominant species in all gears and areas examined. Shortfin mako (Isurus oxyrinchus), common thresher shark (Alopias vulpinus), and tope shark (Galeorhinus galeus) were the next most abundant shark species—found in more than half of the areas sampled. Catch composition varied both in the areas and gears investigated. Sharks represented 34.3% in weight of total catches sampled in the Alboran Sea and 0.9% in the Straits of Sicily. Higher shark catches were observed in the swordfish longline fishery, where a nominal CPUE value reached 3.8 sharks/1000 hooks in the Alboran Sea. Size distribution by fishing gear varied significantly. Albacore longline catches consisted mainly of juveniles, whereas subadult and adult specimens were more frequent in the swordfish longline and driftnet fishery. The percentage of sharks brought onboard alive was exceptionally high; only 5.1% of the specimens died. Few discards (seven blue shark) were recorded in the Greek longline fleet during onboard sampling in the Aegean Se

Length-weight relationships of commercially important marine fishes and shellfishes of the southern coast of Karnataka, India

The parameters of the length-weight relationship of the form W = aLb are presented for 51 species of commercially important marine fishes and shellfishes caught along the southern coast of Karnataka, India. Samples from commercial (trawl, purse seines, gill nets) and artisanal gears were taken during August 1999 to May 2001. The ‘b’ value ranged between 1.942 and 3.616 with a mean of 2.80, standard deviation of 0.32, and mode of 3.

A comparison of monofilament gillnet and small hook longline selectivity in a multispecies artisanal fishery in the Algarve, southern Portugal

As part of the ongoing studies concerned with the small-scale fisheries of the South of Portugal, experimental fishing was carried out with monofilament gillnets and small hook longlines within the same area. Sixty-two species were caught, of which 20 were common to both gears. Pronounced differences in terms of the relative importance of different species in the catches were observed. Size selection patterns also differed, with highly overlapped hook catch distributions and few species showing evidence for size selectivity. In contrast, strong selectivity was characteristic of species which tend to be wedged in gillnets. Whereas smaller stretched mesh sizes (particularly 40 and 50 mm) caught significant numbers of illegal sized fish, this was mininmal in the longlines. Some implications for management are discussed.

Marine fisheries of Karnataka State, India

This contribution provides an overview of the marine capture fisheries off the coast of Karnataka State, India. It covers the main fisheries and fishing gears, production trends (by main species /groups and gears), assessment results and fisheries management. Marine fisheries production in the State increased from about 57,000 t/year during the 1950s to a peak of about 250,000 in 1989, declining to about 150,000 t/year by 1995. Substantive changes have been noted in dominant gears and species groups contributing to the catch between 1980-84 and 1990-95. Results of assessments indicate that many commercially important stocks are overfished, thus requiring a reduction in fishing effort.

The fisheries of St. Lucia, West Indies

An overview of the fisheries of St. Lucia using currently available information is presented. The fisheries are entirely artisanal, characterized by relatively simple and inexpensive gears and boats. The 2,100 fishers (who land roughly 750 t per year of fish) appear socially and economically marginalized and beset by low occupational mobility. The status of the major species groups they exploit are briefly discussed, and initial indications of overfishing are noted. Consideration on both resource and resource-user situations in management of the island's fisheries is emphasized.

An analysis of the multigear, multispecies fishery in the Kenyan waters of Lake Victoria

Catch rates for both Nile perch (Lates niloticus) and dagaa (Rastrineobola argentea) from Kenyan waters of Lake Victoria have steadily increased through the 1980s, even though the fishing effort also increased during the same period. However, analysis of catch and effort data within and outside the Nyanza Gulf suggests an increase in catch rates due to a shift in effort from the inshore Gulf region to higher catch rates in the offshore region, rather than an increase in abundance. Analysis of catch rates by gear type both in and outside the Nyanza Gulf show that 1991 catch rates are lower than 1989 levels by 60-80% in some instances. Since the fishing power of these gears has increased during this period, it is likely that fish abundance declined more than catch rates. A dynamic population model is used to stimulate Nile perch dynamics. It indicates that a decline in catches should be anticipated.

Conservation and management of marine fishery resources of Kerala State, India

The highly productive fisheries of Kerala, India, are suffering from overexploitation. Use of unsuitable fishing gears that result in a high level of wasteful bycatch and destruction of egg bearing and juvenile fish should be controlled. This paper makes some suggestions for monitoring and conservation of the fisheries in Kerala.

Socioeconomic characteristics of payang seine (lampara) and driftnet fisheries in West Sumatra, Indonesia

A proportionate random sample survey of 10 percent of the driftnet and Payang seine fishers in West Sumatra was carried out in 1998. A total of 45 driftnet and 66 lampara fishers were interviewed to obtain socioeconomic data on the fisheries. About 40 percent of the driftnet and 76 percent of the lampara fishers owned and operated their fishing vessels and gears indicating a high level of ownership of fishing assets by these small scale fishers. The lampara catches consisted mainly of eastern little tuna, skipjack tuna, yellow fin tuna and mackerel, while the driftnets caught mainly Spanish mackerel, Indian mackerel, eastern little tuna and scad.

Effects of current speed and turbidity on stationary light-trap catches of larval and juvenile fishes

Light traps are one of a number of different gears used to sample pelagic larval and juvenile fishes. In contrast to conventional towed nets, light traps primarily collect larger size classes, including settlement-size larvae (Choat et al., 1993; Hickford and Schiel, 1999 ; Hernandez and Shaw, 2003), and, therefore, have become important tools for discerning recruitment dynamics (Sponaugle and Cowen, 1996; Wilson, 2001). The relative ease with which multiple synoptic light trap samples can be taken means that larval distribution patterns can be mapped with greater spatial resolution (Doherty, 1987). Light traps are also useful for sampling shallow or structurally complex habitats where towed nets are ineffective or prohibited (Gregory and Powles, 1985; Brogan, 1994; Hernandez and Shaw, 2003).