Shrimp Trawl Fishery Research Articles

Length-Weight Relationships of Four Fish Species Associated to Shrimp Trawl Fishery as by-Catch in the Persian Gulf, Iran

Length-length relationships (LLRs) and length-weight relationships (LWRs) were determined for four marine fish from Iranian waters of the Strait of Hormuz: Pseudotriacanthus strigilifer, Rhinobatos annandalei, Muraenesox cinereus, Nematalosa nasus belonging to four families Triacanthidae, Rhinobatidae, Muraenesocidae, Clupeidae. Specimens were collected monthly between October to December 2018 from artisanal shrimp vessels equipped with non-selective bottom trawl net (with mesh size of 20 and 40 mm, respectively at cod-end and body of trawl net). Trawling operation carried out in a depth range of 2 to 20 m. Total length (TL) (nearest to 0.1 cm) and body weights (nearest 0.1 g) were taken each individual. The result of this research provides first length-weight relationship references for R. annandalei and P. strigilifer and first LLR for R. annandalei and new maximum total length for M. cinereus. Estimated parameters of the LLR and LWR models (a and b value) of the equation WB = a(TL)b and TL = a + b(SL) were highly significant (P < 0.01) with a reliable coefficient of determination (R2) ranged from 0.967 to 0.99.

Simple gear modifications for achieving greater than 40% bycatch reduction in an estuarine shrimp trawl fishery

Simple gear modifications for achieving greater than 40% bycatch reduction in an estuarine shrimp trawl fishery

Population structure, size at first sexual maturity, and feeding ecology of Conodon nobilis (Actinopterygii: Perciformes: Haemulidae) from the coasts of Pernambuco, north-eastern Brazil

Background. Although the information on fish ecology and population dynamic are fundamental for fisheries assessment and the development of sustainable management practices, there is still a gap for bycatch species, mainly in tropical coastal areas. The aim of the presently reported study was to describe the feeding habitats, mean length of maturation, and the population structure of Conodon nobilis (Linnaeus, 1758) caught as bycatch of the shrimp trawl fisheries in the south of Pernambuco, north-eastern Brazil. Materials and methods. Specimens of C. nobilis were collected monthly from August 2011 through July 2012, using an artisanal shrimp outrigger trawler from the local fleet. The population structure was analysed by sex, length, and seasons. Stomachs and gonads were removed and examined to define the length at first maturity (L50) and the feeding habits of C. nobilis in north-eastern Brazil. Results. A total of 272 specimens were caught. The sex ratio was similar among females and males in the area. The mean size at first maturity (L50) was estimated as 14.3 &plusmn; 0.65 cm. The diet of the species was mainly based on crustaceans (Penaeidae) and fish, however, it was not observed differences in the diet between juvenile and adults, and climate seasons. Conclusion. Conodon nobilis was classified as a zoobenthivore species, and showed a higher proportion of individuals caught above the L50. The information here provided, combined with other studies in the region, may contribute to the development of improved management strategies to species conservation and exploited marine habitats in northeast Brazil, which is still mostly unknown.

Dose-response relationship between shrimp trawl fishery and the macrobenthic fauna community in the coastal zone and Wadden Sea

The potential environmental effect of the brown shrimp fishery in the shallow shelf of the North Sea and Wadden Sea is debated because the fishery operates for a large part in designated Natura2000 sites. In this fishery a beam trawl is pulled along the seafloor, potentially affecting organisms living on and in the seabed. Because the effect by the trawl used in the shrimp fishery is unclear, has long been debated, and hardly studied to date, we carried out an experimental study to test short to medium term effects of the fishery on the benthic community in an area with a decadal long fishery. The study consisted of two complementing parts: one experiment focussed on the effect of a single fishing event in 15 different areas throughout the distribution area of shrimp fishery along the coast and in the Wadden Sea; in another experiment we measured the dose-response relationship between fishing intensity and the benthic community in one area in the Wadden Sea. Unfortunately, the first experiment was severely hampered by unplanned fishing by fishermen.Instead of the originally planned BACI design with 15 replicates, the first experiment was analysed by correlating actual fishing intensity and benthos community parameters. We found a negative relationship between fishing pressure and the change in number of species from pre- (T0) and post-fishing (T1, eight weeks later), but not in total density or Pielou's evenness. In the second experiment the change between T0 and T1, ten weeks later and T2, eight months later) in Pielou's evenness was negatively related to fishing pressure. The change in total density and the number of species were unrelated to fishing intensity. The pattern in evenness was primarily due to the positive relationship of the change of Ensis leei with fishing pressure. For eight of the ten most common individual macrofauna species, there was no relationship between their development and fishing pressure, while for two species the change in density showed a negative relationship with fishing pressure in the T0-T1 (Ascidia sp.) or T0-T2 comparison (Cerastoderma edule). We interpret the observed response in Ensis leei as their ability to relocate and quickly colonise space, that became vacant because the original inhabitants were disturbed, removed or died. Especially this last finding, that an apparently mobile opportunistic species is able to colonise vacant space is a fishery-related mechanism that adds to the understanding of the potential effect of shrimp fisheries.

Quantification of bell-shaped size selectivity in shrimp trawl fisheries using square mesh panels and a sorting cone after a Nordmøre grid.

Shrimp trawlers in the Barents Sea use a Nordmøre sorting grid ahead of a small-mesh codend to avoid bycatch while catching shrimps efficiently. However, small fish can still pass through the grid to enter the codend, which increases their risk of being retained. In this study, we quantified the selectivity of a standard Nordmøre grid used together with one of two different codend designs, namely a diamond mesh codend with square mesh panels and a codend with a square mesh sorting cone section, for deep-water shrimp (Pandalus borealis), redfish (Sebastes spp.), and American plaice (Hippoglossoides platessoides). For the first time, the selective properties of these two alternative designs were estimated and compared to those of a Nordmøre grid used together with a 35-mm diamond mesh codend, which is the compulsory gear used in the fishery today. With this traditional codend, the size selectivity of both bycatch species showed the expected characteristic bell-shaped size selection pattern, with low retention probability of very small fish and bigger fish but with high retention probability of certain sizes of juveniles. Using the square mesh sorting cone significantly reduced the maximum retention risk of redfish. The maximum retention with the diamond mesh codend with square mesh panels was estimated to be 14% lower than that of the traditional codend, but the difference was not statistically significant. The two alternative codend designs did not result in any significant reduction in bycatch of American plaice.

Shorter trawls improve size selection of northern shrimp

Discards of small northern shrimp (Pandalus borealis) are a problem in the Skagerrak northern shrimp trawl fishery. To reduce catches of small shrimp, we studied the effect of trawl belly length on size selectivity in November 2017 and June 2018 onboard 15 and 27 m double-rigged shrimp trawlers. The selectivity of the vessels’ standard trawl was compared with a trawl differing only in the belly length, being 37% shorter. The trawls had 40 mm bottom panels and cod ends of 35 mm mesh sizes. Eleven and 14 hauls were made, respectively, in 2017 aboard the 15 m vessel and in 2018 aboard the 27 m vessel. The trawls fished shrimp above 19 mm carapace length equally, while catch rates of shrimp below 15.5–16 mm carapace length in the shorter trawl were more than halved. The results were consistent between the two vessels. In short, modifying trawl length is a simple design modification that can reduce catches of small shrimp. Bycatch of Norway pout (Trisopterus esmarkii) was slightly reduced in the shorter trawl, unrelated to fish length.

Mollusk bycatch in trawl fisheries targeting the Atlantic seabob shrimp Xiphopenaeus kroyeri on the coast of Sergipe, northeastern Brazil

The malacofauna bycatch of sea-bob shrimp Xiphopenaeus kroyeri (Heller, 1862) trawl fisheries on the coast of Sergipe was studied for 5 years. The malacofauna bycatch considered was obtained in nine oceanographic sampling campaigns carried out between May 1999 and June 2003 in 18 stations distributed in six transects along depths of 10, 20 and 30 m. A total of 2,669 individuals of mollusk belonging to 54 species were captured on the 18 sea-bob shrimp trawl stations carried out along the coast of Sergipe. The considerable richness of mollusks was composed by 19 families and 31 species of gastropods, 12 families and 19 species of bivalves and 2 families and 4 species of cephalopods. The highest abundance were observed at stations 13 (373 individuals) and 16 (685 individuals) that represents the lowest depth (10 m) and the richness was higher at stations 15 and 12 (17 and 11 species, respectively) both located at the highest depth (30 m). Cephalopods had high frequency of occurrence being collected in all the stations and by far the most abundant group with a total of 2,488 individuals captured. On the other hand, gastropods (with 142 individuals found in 83.3% of stations) and bivalves (about 1% of the individuals collected) contribute with a much smaller percentage of individuals captured. Lolliguncula brevis (Blainville, 1823) was most representative cephalopod in number and frequency of occurrence. Arcidae, Conidae, Muricidae and Strombidae were the families with the higher number of species in the trawl-fishery. Among bivalves, Pitar arestus (Dall &amp; Simpson, 1901) and Spathochlamys benedicti (Verrill &amp; Bush [in Verrill], 1897) were the species with higher frequency of occurrence. Although the considerable sample effort and a number of mollusks captured as bycath, the richness estimators indicated that the species richness could increase with additional sampling effort in the study area. The present study expands the taxonomic alpha knowledge on the mollusk bycatch of sea-bob shrimp trawl fisheries on the northeastern coast of Brazil. However, it is of crucial importance to assess urgently the negative impacts of the sea-bob shrimp trawl fisheries on the benthic community of the entire coast of Brazil.

Modelling the spatio-temporal bycatch dynamics in an estuarine small-scale shrimp trawl fishery

The Patos Lagoon estuary in Southern Brazil is an important nursery ground for many commercially important fish and invertebrate species, with shrimp fisheries sustaining most of the surrounding small-scale fishermen. Although they are illegal, trawl gears are widely used by small-scale fishermen in order to catch shrimp. Shrimp trawl fisheries in tropical waters have high bycatch rates and cause a variety of problems, spanning from conflicts with other fisheries to changes in ecosystem trophic dynamics. A better understanding of the factors driving the bycatch process is therefore needed to establish reliable management measures. Here we used hierarchical Bayesian spatio-temporal models (HBSMs) to describe the bycatch of a small-scale shrimp trawl fishery in the Patos Lagoon estuary relative to a set of environmental and spatio-temporal predictors. Two different models were used to estimate bycatch trends: an effort-based method (BPUE) and a ratio-based method (BR, bycatch rate). A third model was used to evaluate the dynamics of shrimp catch per unit of effort (CPUE) as this measure is equally important to describe the underlying bycatch process. Overall, the bycatch consisted of 61 species of which 45 have market value. The mean bycatch rate was 86.2% for the entire period, which represents 6 kg of bycatch for every 1 kg of shrimp caught. Although the contribution of environmental variables differed among the models, the yearly spatial effect was identified as a common that explained bycatch dynamics. Moreover, the predictive maps revealed consistent hot and cold-spots from year-to-year, which varied in intensity for BR, BPUE and CPUE, and, therefore, represent a valuable benchmark for stakeholders and managers.

Effect of three different codend designs on the size selectivity of juvenile cod in the Barents Sea shrimp trawl fishery

Shrimp trawlers often use a Nordmøre sorting grid ahead of a small mesh codend to avoid bycatch of juvenile fish while allowing shrimps to be efficiently caught. However, small fish can pass through the grid to enter the codend and risk being retained. The risk of retention for fish of different sizes depends the size selection in the Nordmøre grid and the size selection in the subsequent codend, which makes the process complex and often results in a bell-shaped size selection curve. In the Barents Sea shrimp fishery, cod (Gadus morhua) is one of the species of concern because of its great commercial value. We studied the size selection of juvenile cod when the trawl was equipped with the compulsory gear in the fishery: a 19 mm Nordmøre grid followed by a 35 mm diamond mesh codend. As expected, the size selection curve showed a bell-shaped signature, with a certain size range of juveniles having high retention risk, while the risk for smaller and bigger cod was smaller. The retention risk was highest for cod between 12 and 20 cm in length. We also tested two alternative designs in the aft section of the gear: a codend with 35 mm square mesh panels and a square mesh sorting cone section. Neither of these designs affected the size selection in the trawl significantly.

Can a large-mesh sieve panel replace or supplement the Nordmøre grid for bycatch mitigation in the northeast Atlantic deep-water shrimp fishery?

The Nordmøre grid is the principle bycatch mitigation device in many shrimp trawl fisheries. However, in several of these fisheries, bycatch is a problem because small sized fish can pass through the grid and enter the codend together with the targeted shrimp. One such fishery is the Northeast Atlantic deep-water shrimp (Pandalus borealis) fishery, where the use of a Nordmøre grid is mandatory. In this fishery, redfish (Sebastes spp.) and polar cod (Boreogadus saida) are two common bycatch species. Redfish is a commercially important species that at times is captured in great numbers, whereas polar cod is a threatened species that can also be caught in high numbers. Sieve panels are bycatch reduction devices commonly used in shrimp fisheries and their potential to replace or supplement the Nordmøre grid in the Northeast Atlantic deep-water shrimp fishery is of interest. We investigated the size selectivity of redfish, polar cod and deep-water shrimp for the Nordmøre grid and four sieve panel configurations differing in mesh size (182 and 286 mm) and inclination angle (10 and 20°). The sieve panels were unable to replace the Nordmøre grid as a stand-alone device due to greater catches of the bycatch species. However, combining the two devices provided promising results. Specifically, when a large-mesh sieve panel was placed in front of the Nordmøre grid, 20–40% fewer small redfish and polar cod in a specific size range entered the codend, while the loss of targeted shrimp was less than 5%.

The effect of Nordmøre grid length and angle on codend entry of bycatch fish species and shrimp catches

The Nordmøre grid is regarded as an efficient bycatch-reducing device and is used in various shrimp trawl fisheries globally. However, in some shrimp fisheries, bycatch remains a problem that seriously impacts commercial trawl activities. This study tested and compared the performance of two versions of the Nordmøre grid in the northeast Arctic deepwater (northern) shrimp (Pandalus borealis) fishery, a standard version with an operating angle of approximately 45° and a longer version of the grid (40% longer) with an operating angle of approximately 30°. The grid passage probability for the bycatch of juvenile cod (Gadus morhua), haddock (Melanogrammus aeglefinus), American plaice (Hippoglossoides platessoides), and redfish (Sebastes spp.) increased significantly for certain size ranges of fish when using the longer grid. The longer grid also resulted in a significant increase in grid passage probability for large shrimp. Previous studies have reported that a reduced operating angle can lead to a lower grid passage probability for bycatch fish species and shrimp; however, the results of the current study demonstrate that a longer Nordmøre grid more than compensates for the reduced operational angle.

ICHTHYOFAUNA BYCATCH OF THE ARTISANAL FISHERY OF PENAEID SHRIMPS IN PERNAMBUCO, NORTHEASTERN BRAZIL

The shrimp trawl fisheries are highly efficient in capturing target species but is an unselective gear that commonly catches untargeted organisms, which are usually discarded due to their small size or no commercial value. To understand and, eventually, mitigate the impacts of trawling on bycatch species, the whole capture should be addressed. The present study has the objective of determining the seasonal importance of the fish bycatch within shrimp trawling fishery in south Pernambuco, Sirinhaém. It also quantifies the importance of each fish caught within this fishery. Samples were collected monthly, between August 2011 and July 2012. Fish bycatch was described as % in number (%N) and weight (%W), while the seasonal abundance of the shrimp and fish bycatch was assessed based on the monthly catch rate given as the Capture Per Unit of Area (CPUA) in weight (CPUAb) and in number of individuals (CPUAn). Considering the fish bycatch, a total of 608 kg of organisms were sampled: 9,723 fish specimens from 17 families, 38 genera and 51 species. The largest CPUAb value of bycatch was observed in the months of June (488 kg.km-2), February (285 kg.km-2) and April (276 kg.km-2). The proportion target species: bycatch in weight was of 1:0.39. A clear annual cyclic pattern of the species composition of the bycatch based both CPUAn and CPUEb could be observed, following the rainfall patterns, possibly related to a higher productivity associated to river runoffs. Impacts on bycatch have been extensively reported in Brazil and around the world, with most of this bycatch being a relevant additional food source for the local community. However, basic information on bycatch from small-scale fisheries is still missing in many areas, making it difficult to identify and evaluate the management recommendations needed to sustain the resources and ecosystems.

Performance of Bycatch Reduction Devices in the Small-Scale Shrimp Trawl Fishery of the Persian Gulf

High rates of discards have been noted for shrimp fisheries worldwide and especially for the small-scale shrimp trawl fisheries of the Persian Gulf. Bycatch reduction devices (BRDs) can significantly decrease discards in shrimp trawl fisheries. We tested the performance of a square mesh panel BRD (SMP) and a juvenile and trash fish excluder device (JTED) in the small-scale shrimp trawl fishery of the Persian Gulf. Efficiency of the BRDs was determined in terms of shrimp loss, by-product loss, the reduction in discards by weight and differences in size selectivity of commercial fishes. Where a JTED was used, reductions in catch, by weight, were (mean ± 95% CI) 12% ± 2.35 for shrimp, 31.9% ± 5.22 for by-product fish and 49% ± 7.52 for discards. Similar reductions were observed when a SMP was used: 16% ± 4.19, 38.3% ± 6.41 and 45% ± 6.15 for shrimp, by-product and discards, respectively. There was no significant difference in the exclusion rate of discards between the JTED and SMP. Significant difference was found for loss of shrimp between JTED and SMP. The mean escapement rate for by-product species in trawl net with JTED and SMP were 35% and 40%, respectively. Selectivity curves of both BRDs indicated, that for each species, the length of 50% retention probability (L50) were smaller than the length at maturity (LM) and an increase in bar spacing in JTED and mesh opening in SMP would be required to delay capture until fish had reached Lm. The results indicated that SMP allows a higher proportion of sub-legal by-product species to escape the trawl, compared to the JTED used in the study. Implementing BRD requirements for the Persian Gulf small-scale shrimp fisheries would contribute to meeting strict sustainability criteria, a good outcome for this small-scale fishery.

Spatio temporal distribution of four commercial shrimp species in the southeastern Gulf of California, Mexico

The shrimp trawl fishery in the southeastern Gulf of California is one of the most important in Mexico due to the high economic value of the resource in the national and international market. The management of this fishery is based on permits, a no-trawling zone, a no-fishing season and regulations of fishing gears. In order to analyze the efficiency of the no-fishing season and the viability of a spatial closure, we analyzed the distribution and size structure of four species targeted by the commercial fishery during the 2005-2006 shrimpfishing season, the white shrimp ( Penaeus vannamei ), blue shrimp ( P. stylirostris ), brown shrimp ( P. californiensis ) and crystal shrimp ( P. brevirostris ). We found that the size distribution of four shrimp species was wide and with variable frequency during the fishing season. The average biomass for each species was different throughout the fishing season, and the white and brown shrimps were the most abundant species. However, the spatial distribution of the biomass was similar for the four species. Our results suggest that the nofishing season is more effective for brown shrimp because the individuals caught by the fishing gear have already reproduced at least once.

Effects on the bycatch of eulachon and juvenile groundfish by altering the level of artificial illumination along an ocean shrimp trawl fishing line

Abstract We examined how catches of ocean shrimp (Pandalus jordani), eulachon (Thaleichthys pacificus), and juvenile groundfish could be affected by altering the level of artificial illumination along the fishing line of an ocean shrimp trawl. In the ocean shrimp trawl fishery, catches of eulachon are of special concern, as the species’ southern Distinct Population Segment is listed as “threatened” under the US Endangered Species Act. Using a double-rigged trawl vessel, with one trawl illuminated and the other unilluminated, we compared the catch efficiencies for ocean shrimp, eulachon, and juvenile groundfish between an unilluminated trawl and trawls illuminated with 5, 10, and 20 LED fishing lights along their fishing line. The addition of artificial illumination along the trawl fishing line significantly affected the average catch efficiency for eulachon, rockfish (Sebastes spp.), and flatfish, with the three LED configurations each catching significantly fewer individuals than the unilluminated trawl without impacting ocean shrimp catches. For Pacific hake (Merluccius productus), the ten LED-configured trawl caught significantly more fish than the unilluminated trawl. For the five and 20 LED configurations, mean Pacific hake catches did not differ from the unilluminated trawl. This study contributes new data on how artificial illumination can affect eulachon catches (and other fish) and contribute to their conservation.

Could green artificial light reduce bycatch during Barents Sea Deep-water shrimp trawling?

The Nordmøre grid is widely used in shrimp trawls to reduce the bycatch of fish species. However, small-sized fish species and juveniles still pass through the grid and enter the codend, along with the targeted shrimp. This bycatch of small fish has a negative impact on the ecosystem due to increased fish mortality, and leads to additional sorting work onboard. Some small-sized fish that enter the trawl avoid entering the codend by escaping through the outlet above the grid, without making contact with the grid itself. Design changes that promote this behavior could potentially reduce bycatch in shrimp trawl fisheries. Light-emitting diodes (LEDs) mounted around the escape outlet have previously been found to have either a negative effect, or no effect at all, on fish bycatch species. This study investigates the effect of mounting green LEDs on the lower part of a Nordmøre grid, to determine if their presence would encourage bycatch fish to rise towards the escape outlet prior to contacting the grid. Experimental fishing trials were conducted to assess the size selective properties of a 19 mm bar spaced Nordmøre grid with and without LEDs, mounted on a bottom trawl targeting Deep-water shrimp (Pandalus borealis). For the four bycatch species investigated, 51–100% of small fish passed through the Nordmøre grid. The addition of green LEDs to the Nordmøre grid did not significantly affect the escape probability or the size selectivity of any of the investigated species. Very few Deep-water shrimp were found to escape through the escape outlet independent of the presence of the LEDs mounted on the grid.

New Strategy toward Sustainable Livelihoods in Coastal Fisheries How Japanese Experiences Could Be Applied to Southeast Asia

Coastal resource management, community empowerment and socio economic development are the cornerstones for uplifting the lives of coastal area inhabitants. Japan is one of country who succeed to empowered economy of coastal community by diversify coastal and fisheries livelihoods. This study aims; to explore Japanese experiences on coastal resources management, to assess the fishing activity in case study area of Hiroshima, and to describe livelihood strategy in coastal fishery of case study area of Hiroshima. Primary data were collected from representatives of shrimp-trawl fishermen, and key informants using structured and semi-structured questionnaires. Secondary data such as statistical data and reports and books from previous studies were used as preliminary information. The data were analyzed by using descriptive analysis and qualitative contents analysis. The results of the study showed that Japan has many years’ experiences to manage coastal fishery in effective and sustainable ways using community-based coastal fishery management and co-management approach. Meanwhile, Fisheries Cooperative Associations (FCAs) and Fisheries Management Organization (FMOs) are as institutional tools. In case study of coastal fishery activity, shrimp-trawl fishery in Akitsu has been manage by FCA, even the number of fishermen and their activity gradually decrease. However, the problems faced related to the sustainability of fishing activities in Akitsu is related to catch decreased, initial investment, regeneration of the fishing activities itself, and upwelling in the past. Increased a number of aging fishermen and no successors are another problems in sustainability of fisheries livelihoods. In fact, young people escape from the fishery communities to work in the cities and aging people remain in fishery community. This is occurred in shrimp-trawl fishery ( Sokobikiami ) in Akitsu. Therefore, local government as well as central government can expand the oyster culture by providing incentives or subsidies to attract young generation back to the area to pursue this business.

Size Composition of Fish By-Catch Species from Industrial Shrimp Trawl Fishery in Nigerian Coastal Waters

Fish species composition of by-catch in the industrial shrimp trawl fishery in Nigeria was investigated with the Sciaenidae family being the most prevalent by-catch fish species. In order of prevalence Pseudolithus elongatus with a mean weight and length of 15.28g and 86.39mm, respectively and Pseudolithus typus (n= 102) having an average weight of 18.76g and mean length of 88.01mm. Other fish by-catch species include Pseudolithus senegalensis (n= 99, mean weigh = 15.49g, mean length= 88.60mm); Galeoides decadactylus (n= 59, mean weight= 15.26g, mean length= 87.66mm); Pteroscion peli (n= 48, mean weight= 16.05g, mean length = 88.23mm); Drepane africana (n= 33, mean weight= 13.29g, mean length= 45.73mm) and Cynoglossus senegalensis (n= 11, mean weight= 21.78g, mean length = 86.45mm). Despite the small number of Cynoglossus senegalensis, it had the highest weight contribution to the by-catch. Significant (P&lt;0.01) relationship exists between weight and length of fish species. The adjusted R2 of the parameters indicated that 19.4% of the weight gained is accounted for by increase in length of Pseudolithus elongatus; 1.7% in Pseudolithus typus; 31.7% in Pseudolithus senegalensis; 13.7% in Galeoides decadactylus; 7.8% in Pteroscion peli; 57.4% in Drepane Africana; and 48.9% in Cynoglossus senegalensis. The by-catch associated with shrimp trawls should be properly monitored and controlled to reduce the quantity of non-target fish species in their catch. Also, the use of diamond-shaped 44mm mesh size for shrimp should be encouraged or made mandatory for fishers to reduce fish by-catch. Keywords: Shrimp, by-catch, fishery, weight

Assessing the vulnerability of demersal elasmobranchs to a data-poor shrimp trawl fishery in Costa Rica, Eastern Tropical Pacific

The impact of shrimp trawl fisheries on slow-growing demersal sharks, skates and rays has been widely documented. Yet, a lack of catch records and biological information has hindered improvements in elasmobranch bycatch management, particularly in tropical regions. When information is scarce, data–poor methods can be valuable tools to guide the management and conservation of vulnerable marine taxa. Here we combined an Ecological Risk Assessment commonly used in data-deficient fisheries (Productivity Susceptibility Analysis or PSA) with a spatial analysis (Hotspot Analysis) to (i) identify which elasmobranch species are most vulnerable to the Costa Rican shrimp trawl fishery, and (ii) locate areas and seasons with high concentrations of vulnerable elasmobranchs. According to the results of our PSA, the scalloped hammerhead (Sphyrna lewini), prickly shark (Echinorhinus cookei), and long–tail stingray (Hypanus longus) were the most vulnerable species, while the least vulnerable species were small batoids of the Urotrygonidae family. We identified large information gaps, namely demographic parameter estimates and long–term bycatch trends. Spatial aggregations of vulnerable elasmobranchs occurred near highly productive estuaries and coastal habitats, especially at depths of 50–100m. Based on our findings, PSA and Hotspot analyses can be powerful tools to identify spatial areas where trawl fishing grounds overlap with the habitat of vulnerable bycatch species, and thus can be used to design spatial trawling closures that protect species at risk. We therefore conclude that our methodological approach may aid in the implementation of ecosystem–based fisheries management in data–poor situations.

Turtles and other marine megafauna bycatch in artisanal fisheries in the Saudi waters of the Arabian Gulf

Fisheries impacts on marine megafauna have received global attention and are recognized as a serious problem. In Saudi waters of the Arabian Gulf, the artisanal fishery is responsible for 99.6% of landings. It uses a range of boat sizes and various types of fishing gears and operates in all accessible areas from shallow coastal bays to deep offshore waters. The objective of this work is to assess the captures and the impact of all fishing gear types used by the Saudi artisanal fishery on four marine megafauna groups: turtles, birds, dolphins, and dugongs (Dugong dugon). Nine questionnaire surveys were carried out from May 2013 to November 2014, covering a two-month period each. Ten main gear types were found to be used by 25 directed fisheries, including shrimp trawl, wire trap, hand line, troll, pelagic and demersal longline, and drift, surrounding, fixed, and set gillnets. Turtles were captured in relatively high numbers (4726 captures year−1) in nine directed fisheries, among which shrimp trawl fishery was responsible for 86.3% of the captures. The lowest capture rates were found with birds (13.1 captures year−1) and dolphins (7.4 captures year−1), related mainly with the Spanish mackerel longline and Indian mackerel surrounding gillnet fisheries. No dugong captures were recorded. In all, the Saudi artisanal fishery operating in the Arabian Gulf has a high impact on turtles and low impact on birds and dolphins. No impact on dugongs was reported during this study.