Trawl Nets Research Articles

Assessment of the impact of broadband acoustic backscattering techniques for understanding the abundance, biomass, and distribution of the Ocean Twilight Zone

Mesopelagic fishes, which inhabit the Ocean Twilight Zone spanning ocean depths from 200-1000 m, are some of the most abundant vertebrates on earth, and are thought to play an important role in global ocean biogeochemical cycles. And yet there remain large uncertainties in their abundance, biomass, distribution, and behavior. Mesopelagic fishes are difficult to sample, or harvest for the purpose of commercial fisheries, due to their often remote and inhospitable habitats, and their ability to efficiently avoid trawl nets and cameras. As a result, there has been increased interest in using shipboard sonar systems to survey mesopelagic fishes, though little is known about their acoustic properties and target strengths. Recent advances in broadband acoustic scattering systems, post-processing analysis and approaches, and in situ platforms are being used to fill the technology gap and infer in situ target strengths of these elusive mesopelagic fishes. This talk presents an overview of the work done in this area to date, discusses the key challenges that still remain, and assesses the impact of broadband acoustic techniques in advancing our knowledge of the abundance, biomass, and distribution of mesopelagic fishes in the Ocean Twilight Zone. [Work supported by NSF and the WHOI OTZ Project.]

Testicular development and reproductive references of Glossogobius giuris in Mekong Delta, Vietnam

The present study contributes information to the testicular development and reproductive aspects of Glossogobius giuris (Hamilton 1822), one of the target fishes in the Mekong Delta. Trawl nets were used to monthly collect fish specimens from January to December 2020 in four sites along Bassac River, from Cai Rang, Can Tho (CRCT) to Long Phu, Soc Trang (LPST), Hoa Binh, Bac Lieu (HBBL) and Dam Doi, Ca Mau (DDCM). Data analysis of 632 Glossogobius giuris individuals showed that five-stage of sperm development was found in testis histological slides. At stage IV of the testis, different phases of the sperm were observed, indicating that it is a multi-spawner, releasing sperms many times during the breeding season. Further analyses of the testis about apparent frequency and gonadosomatic index showed that this goby can release sperms monthly with a peak in the main wet season. The length at first maturity was observed at 7.24, 7.18, 7.43, and 6.57 cm of TL in CRCT, LPST, HBBL, and DDCM, respectively. The findings contribute essential information to fish population management and sustainable exploitation.

Biological and Ecological Aspects of the Blackmouth Catshark (Galeus melastomus Rafinesque, 1810) in the Southern Tyrrhenian Sea

Data on the biology and ecology of Galeus melastomus are old/absent for the Southern Tyrrhenian Sea, despite there being numerous studies in the wider area. A total of 127 specimens of G. melastomus from the southern Tyrrhenian Sea, collected in 2018–2019 using trawling nets, were analyzed to investigate size at sexual maturity, sex ratio, length–weight relationships, and feeding habits. To our best knowledge, this is the first time in which all these features were investigated in the Southern Tyrrhenian Sea for G. melastomus. The stomach content analysis showed that G. melastomus had intermediate feeding habits, preying on a great variety of species, especially Cephalopoda, Osteichthyes, and Crustacea. The Levin’s index value (Bi) was 0.53. Sex ratio was 0.92:1, with females slightly more abundant and bigger than males. The results also showed a decrease (33.7 cm for females, 31.1 cm for males) in length at 50% maturity (L50). This could be a result of anthropogenic stressors, such as overfishing and/or and environmental changes, which can induce physiological responses in several species. Our results highlighted the differences related to sexual maturity, growth, and feeding habits of the blackmouth catshark in the studied area, providing reference data to allow comparison with future studies on this species adaptations to this and other deep-sea areas in the Mediterranean Sea.

Status of the hammerhead shark (Carcharhiniformes: Sphyrnidae) fishery in Indian waters with observations on the biology of scalloped hammerheadSphyrna lewini(Griffith & Smith, 1834)

AbstractHammerhead sharks are represented by four species in India's marine fishery –Sphyrna lewini,Sphyrna mokarran,Sphyrna zygaenaandEusphyra blochii. This paper describes the hammerhead shark fishery in India during 2007–2018 and summarizes observations on the biology ofS. lewiniexploited along the Indian coast.Hammerhead sharks are caught by trawl nets, gillnets, seines and line gear, mostly as bycatch. Annual average landing of hammerhead sharks during 2007–18 was 639 t, with a low of 290 t in 2018, of whichS, lewiniwas the dominant species, comprising 95% of landings. Hammerhead sharks formed nearly 1.31% of the total elasmobranch landings. About 54% of hammerhead sharks were landed by trawlers.Length range ofS. lewiniin regular landings was 36–300 cm total length (TL). The dominant size class was 30–100 cm TL; 79.5% of males and 83.2% of females measured between 40 and 100 cm TL. Length–weight relationship was derived as W = 0.0218*(L)2.634and W = 0.0131*(L)2.769for males and females, respectively.Overall sex ratio (F: M) was 1.3:1; below 100 cm TL, the sex ratio was skewed in favour of females. The length at first maturity of males was estimated as 168 cm. The length at first maturity of females was estimated at 239.6 cm. Fecundity ranged from 12–40, size at birth was 36–45 cm TL. Bony fishes were the preferred prey, followed by cephalopods.TheS. lewinilandings in India are dominated by juveniles and threatens sustainability of the stock. Capture of juvenile sharks can be excluded to a considerable extent through strict implementation of minimum legal size of capture, and a conservative minimum legal size of 220 cm is suggested for this species in Indian waters. Identification of recurring juvenile aggregation grounds, their spatio‐temporal closures, gear restrictions and greater stakeholder awareness could lead to conservation of the resource and a sustainable fishery.

Bioeconomic impacts of two simple modifications to trawl nets in the NW Mediterranean

A bioeconomic model was built to assess the contribution of more selective trawl nets to the objectives of the European Multi-Annual Plan for demersal fisheries in the Western Mediterranean (WM MAP). The biological submodel was parameterized with age-structured population parameters for the five target stocks in the WM MAP (European hake, red mullet, deep-water rose shrimp, Nephrops and red shrimp) with a sixth stock combining the remaining commercial by catch and following a biomass dynamics model. The trawl fleet was composed of three fleet segments, according to Vessel Length class (VL1218, VL1824, VL2440), practicing two métiers: coastal mixed demersal fishery and deep-water crustacean fishery. The technological solutions analyzed are two simple technical modifications to the otter bottom trawl and based on i) using a panel of meshes turned 90° (T90) in the extension of the trawl net, and ii) inserting a selective grid built from 40 mm square mesh (SM40) netting into the extension of the trawl net. The Results show that, in terms of policy objectives, the reduction in the values of fishing mortality achieved with these selectivity modifications would be insufficient to reach the target fishing mortality at maximum sustainable yield (Fmsy) prescribed in the WM MAP by 2025. However, model results project a substantial recovery of hake and red mullet stock biomass. The recovery of these two important stocks would help improve the evolution of the economic indicators, resulting generally in higher income, profits and salaries in the short (2025) and mid term (2030).

Distribution, abundance and spatial variability of microplastic pollution on the surface of Lake Superior

In 2014, 94 paired neuston net samples (0.5 mm mesh) were collected from the surface waters of Lake Superior. These samples comprise the most comprehensive surface water survey for microplastics of any of the Great Lakes to date, and the first to employ double net trawls. Microplastic abundance estimates showed wide variability, ranging between 4000 to more than 100,000 particles/km2 with most locations having abundances between 20,000 to 50,000 particles/km2. The average abundance in Lake Superior was ~30,000 particles/km2 which was similar to previous estimates within this Laurentian Great Lake and suggests a total count of more than 2.4 billion (1.7 to 3.3 billion, 95% confidence interval) particles across the lake’s surface. Distributions of plastic particles, characterized by size fraction and type, differed between nearshore and offshore samples, and between samples collected in the eastern versus western portion of the lake. Most of the particles found were fibers (67%), and most (62%) were contained in the smallest classified size fraction (0.50–1 mm). The most common type of polymer found was polyethylene (51%), followed by polypropylene (19%). This is consistent with global plastics production and results obtained from other studies. No statistically significant difference was detected between the paired net samples, indicating that single net sampling should produce a representative estimate of microplastic particle abundance and distribution within a body of water.

​An Annotated Checklist of Elasmobranchs Along the Coromandel Coast of Tamil Nadu, Southeast Coast of India

Background: Elasmobranch is one of the largest marine fish resources, consisting of sharks, sawfishes, rays and skates. A worldwide estimate of elasmobranch diversity reveals 815 species coming under 9 orders, 42 families and 164 genera, of which 359 species are sharks and 456 are skates and rays. Hence, it has been planned to investigate the biodiversity and fishery of elasmobranchs along the Coromandel Coast of Tamil Nadu, Southeast India. Methods: Elasmobranch specimens were collected during June 2019 to March 2020 from three main landing centres of Coromandel Coast of Tamil Nadu viz Royapuram (Chennai), Cuddalore and Nagapattinam Fishing Harbours. Sampling was done fortnightly in the above three landing centres. The specimens were collected from the catches of trawl nets, bottom set gillnets and hook and lines. The specimens were identified morphologically in the landing centres itself based on the valid taxonomic keys. Result: In the present study, 67 species of elasmobranch belonging to 7 orders, 21 families and 46 genera were recorded. Of the 7 orders, Carcharhiniformes had the largest number of species (27). Among the 25 families, Carcharhinidae (21) had the largest representation.

Global Causes, Drivers, and Prevention Measures for Lost Fishing Gear

Abandoned, Lost or otherwise discarded fishing gear (ALDFG) comprises a significant part of global marine plastic pollution, with adverse consequences for fishers, the seafood industry, and marine wildlife and habitats. To effectively prevent and reduce ALDFG at source, an understanding of the major causes of and drivers behind fishing gear losses is required. We interviewed 451 fishers from seven countries around the world (Belize, Iceland, Indonesia, Morocco, New Zealand, Peru, and the United States of America) representing five key fishing gear types (gillnets, purse seine nets, trawl nets, longlines, and pots and traps) about why and under what circumstances they lose their gear. We also asked them their views on the most effective interventions to reduce gear losses. Across all major gear types and countries where interviews were undertaken, bad weather was the most common cause of gear loss, followed by interactions with wildlife (identified as a cause for loss by 81% and 65% of all fishers interviewed, respectively). Snagging gear on a bottom obstruction was a major cause of loss for gears that contact the seafloor, along with conflicts with other fishers, often via gear and vessel interactions, for gillnet and pot and trap fishers. Operational and behavioral characteristics such as gear type, trip length, and the party responsible to pay for gear repairs and replacements all significantly influenced gear losses. Gear maintenance was the most effective gear loss prevention measure across all gear types and countries reported by fishers, followed by training crew in gear management (identified as an effective prevention measure by 95% and 82% of all fishers interviewed, respectively). Actions available to fishers, managers and port operators to effectively prevent fishing gear losses include: gear maintenance; reducing active gear interactions with wildlife; reducing financial and administrative burdens for port reception facilities; reducing trip lengths; and targeting education and gear stewardship programs to fishers with limited ALDFG awareness, particularly those in low income fisheries and countries.

Fisheries induced shift in sea snake community assemblages along the Konkan coast, India

Abstract The impacts of fisheries on several charismatic marine fauna have been a subject of global concern. Sea snakes share the same habitats as many commercially important fish species and often end up as fisheries bycatch. Previous studies of bycatch from India have been limited to individual reports of mortality, with little information on the regional community structure of sea snakes. This study was carried out along the Konkan coast, off the central west coast of India, between 2016 and 2018, to determine trends in the bycatch of sea snakes in coastal fisheries. In this study, 922 sea snakes were encountered in 916.57 gillnet haul hours and 449.16 trawlers haul hours of fishing, comprising largely of two species: beaked sea snake (Hydrophis schistosus) and spine‐bellied sea snake (Hydrophis curtus) (83.05 and 16.94% respectively) which was in stark contrast to a similar study conducted in 2002–03, which recorded a dominance of H. curtus (84%) followed by H. schistosus (14%) in the same region. Both studies, however, indicated higher mortality in H. curtus than in H. schistosus in trawl nets. This study highlights the significant impact of non‐selective fishing practices on regional assemblages of other marine organisms such as sea snakes from South Asia, which has been relatively understudied, and the potential consequences for local ecosystems.

Macrozoobenthic fauna associated with benthic marine litter (Northern Tyrrhenian Sea, Italy) and first report of two bryozoan species in Italian waters

Marine litter is a serious global environmental threat that has received increasing attention in the last decades from the academic world, intergovernmental organizations and agencies due to its impact on ecosystems, fisheries and, ultimately, human health. The Mediterranean Sea is characterized by one of the highest densities of marine litter in the world: although much research has been conducted on floating litter, little data exist on benthic litter and its associated macrozoobenthic fauna and only one study has investigated the matter in Italian waters. In the present work, marine litter was collected through demersal trawl nets in the coastal sector of Civitavecchia (northern Tyrrhenian sea, GSA 9) at 50–120 m of depth with the aim of (i) describing the marine litter-associated macrozoobenthic community, (ii) identifying the associations between macrozoobenthic species and litter categories and (iii) evaluating the presence of unrecorded and/or non-indigenous species (NIS) associated with marine litter. Marine litter was recovered from all hauls, confirming its ubiquity and global dispersion in coastal areas, with plastic materials being the most frequently retrieved category. The highest and lowest litter items density were 2125 and 312.50 items/km2. A total of 656 litter items weighing 15.8 kg were classified according to the MSFD Technical Group on Marine Litter categories and analyzed. Their associated fauna consisted of 1536 benthic organisms belonging to 62 species. Species abundance-wise, Bryozoans were the dominant taxon followed by Polychaeta, Bivalvia, Ascidiacea and Anthozoa. Six non-indigenous species (NIS) were retrieved on anthropogenic substrates and, among them, two bryozoans species previously unreported in Italian waters were herein recorded. At last, our results highlight the possible selective association between some sessile species and specific marine litter categories, even though further validation is needed.

The mesh size effect: counting long thin fish in seagrass

Seagrass meadows and the often poorly described ichthyofauna that reside within this habitat are threatened globally. Small-bodied fish in seagrass habitats are often of conservation concern due to their vulnerable life-history characteristics, depauperate distribution and abundance data and importance to artisanal fisheries. We employ a novel approach simultaneously deploying concentric trawl nets comparing mesh sizes that capture cryptic within-canopy species from Posidonia spp. meadows in Shark Bay and Ngari Capes Marine Parks, Western Australia. A discrete species assemblage passed through the 10 mm trawl net and were retained on the 2 mm net at both locations without effecting species richness estimates. Fish size distributions within net fractions differed between locations; fish retained by the 2 mm net at NCMP were much longer than those in the >10 mm net-fraction at that location, and the 2−10 mm portion of the SBMP catch. Of pipefish species globally, 30 % are identified as data-deficient by the IUCN. In NCMP 46 % of fish in the 2−10 mm fraction were pipefish and only 4 % of the >10 mm fraction, whereas pipefish were just 0.4% of individuals recorded in the smaller mesh size in SBMP. In both locations, seahorse species were only captured in the larger net size. These results demonstrate that small differences in net mesh-size can drastically alter catch compositions in seagrass habitat. Accurately surveying syngnathids of conservation interest will require the use of a net mesh that selects fish based on body shape rather than length, an important consideration regarding data-deficient pipefish species. Furthermore, fisheries and research by-catch may be minimised by using mesh sizes that avoid prominent syngnathids when net-fishing in seagrass.

Reproductive traits of Goby Glossogobius sparsipapillus Akihito and Meguro, 1976 in Tra Vinh Province, Vietnam

Aim: This study was conducted to contribute data on the reproductive biology such as sex proportion, spawning season and pattern, fecundity and its relation to fish size, and length at first mature of the commercial fish Glossogobius sparsipapillus in Tra Vinh province, Vietnam. Methodology: Fish was collected monthly using trawling nets at four sampling sites during dry and wet seasons between July 2019 to June 2020. Next, fish was stored in ice before transporting to the laboratory. In laboratory, total length, body weight, and sex before removing gonads were examined histologically. Results: Female G. sparsipapillus (806 individuals) out numbered males (591 individuals). This goby was a multi-spawner as different developmental stages of oocytes and spermatocytes were present in the cross-section of testes and ovaries. A combined analysis of frequency of mature ovaries and GSI showed that this goby could spawn throughout the study period with the mean peak from July to October. The batch fecundity was 17,537 SE and related positively to fish length and weight, indicating it increased as fish grew Interpretation: This study results in an enhanced understanding of this species' reproductive biology for better sustainable management and brood stock study in studied regions.

On the characteristics of invertebrate community structure of bottom trawl and its relationship with environmental factors in coastal waters of Tianjin

In order to study the relationship between the structural characteristics of invertebrate communities in Tianjin coastal waters and environmental factors, bottom trawl nets were used to conduct a monthly survey of Tianjin coastal waters in April and from June to November of 2019, and the invertebrate species in Tianjin coastal waters were analyzed. The relationships between composition, dominant species, community structure changes and abundance distribution and environmental factors were studied. Results showed that: 34 species of invertebrates were monitored in 2019, of which Arthropods and Molluscs were the most (16 species), followed by Echinoderms (1 species) and Moths (1 species); the dominant species of invertebrates in 2019 were 4 species: <italic>Arcuatula senhousia</italic>, <italic>Loligo beka</italic>, <italic>Charybdis japonica</italic>, <italic>Oratosquilla oratoria</italic>; the average abundance of invertebrates in 2019 was 1 267.9 ind·h^-1, and the average biomass was 9.58 kg·h^-1, and invertebrate abundance and biomass were significantly different between months (<italic>P</italic><0.05), and there was no significant difference between stations (<italic>P</italic>>0.05), and there were characteristics of changes over time. Based on the analysis of the generalized additive model, temperature, oxidation reduction potential and dissolved oxygen were the main environmental factors affecting invertebrate abundance (<italic>P</italic><0.05). Results of this study can provide a systematic reference for the investigation of fishery resources in the coastal waters of Tianjin.

Length–weight relationships of seven fish species in the Yangtze River Estuary and its adjacent waters, Eastern China

The length–weight relationships (LWRs) for seven fish species belonging to five families in the Yangtze River Estuary and its adjacent waters are presented. Cynoglossus gracilis, Cynoglossus macrolepidotus, Ctenotrypauchen chinensis, Collichthys niveatus, Ophichthus apicalis and Erisphex potti were collected monthly in 2009 using trammel nets (the size of smaller mesh net was 1.5 m × 15 m × 4 panels with mesh sizes of 2.5, 3.4, 4.3 and 5.8 cm; the size of larger-mesh net was 2.4 m × 30 m × 4 panels with mesh sizes of 5.0, 6.0, 7.0 and 8.0 cm; soaking overnight). Lophiogobius ocellicauda were collected December in 2020 using shrimp trawl nets (mesh size 2.0 cm). The precision of measurement for the fish specimens is 0.1 cm total length and 0.1 g total weight. The estimated ranges of the parameters a and b for the seven fish species were from 0.0001 to 0.0289 and 2.718 to 3.541, respectively. Two new maximum total length were recorded for Ctenotrypauchen chinensis and Ophichthus apicalis.

Microplastics in sea surface waters around Scotland

This is the first regional, multi-annual assessment of floating microplastics in Scotland's seas. Sea surface samples were collected from 2014 to 2020, using a catamaran swimmer body/neuston net trawl and evaluated for the presence of microplastics. Microplastics were present in the surface waters of all Scottish Marine Regions (SMR) and Offshore Marine Regions (OMR) though almost 35% of sample sites contained no microplastics. Concentrations ranged from 0 to 91,128 microplastics km−2 sea surface. Potential hotspots were identified in the Clyde (0–77,168 microplastics km−2), Forth & Tay (0–83,729 microplastics km−2) and the Solway (607–91,128 microplastics km−2). Fragmented plastics accounted for almost 50% of the microplastics recovered and this may suggest that the microplastics in Scotland's seas are predominantly from the breakdown of larger items. Due to the variable geographic and temporal extents of the data it was not possible to carry out a trend assessment.

Catch efficiency of trawl nets used in surveys of the yellow squat lobster (Cervimunida johni) estimated by underwater filming records

Catch efficiency is an important index to relate observed density to the size of a population in the context of bottom trawl surveys. The estimation of catch efficiency is challenging because it involves independent measures of animals in the path of the bottom trawl. We estimated catch efficiency using an underwater camera system on three trawl fishing vessels used for estimating the density of the yellow squat lobster (Cervimunida johni) off central Chile. During 2015 and 2018, 54 hauls were analyzed, and a total of 20 h of filming were recorded. A total of 4,155 yellow squat lobster individuals were analyzed approaching the net in the path of the trawl, of which 2,330 (56%) were captured and 1,825 escaped underneath the groundrope. The median estimated ranges of catch efficiency varied between 0.81–0.90 for vessel 1, 0.15–0.72 for vessel 2 and 0–0.58 for vessel 3. According to a hierarchical generalized linear model (HGML), fishing vessels and mean depth of hauls showed significant differences in catch efficiency (p<0.05). The results were comparable with estimates available for other crustacean species, and differences among vessels can be associated with differences in rigging configurations. Discussion was focused on the processes affecting catch efficiency and how differential catchability among sampling vessels may bias the construction of spatially explicit density maps and further abundance estimates of yellow squat lobsters in Chile.

Catch difference of groundfishes between two survey trawl nets having differing headrope and groundrope configurations in the East China Sea

We compared the shapes and catches of two trawl nets having differing headrope and groundrope configurations based on paired tow data collected by two research vessels (Yoko Maru and Kumamoto Maru) in the East China Sea. According to the paired data, the vertical opening of the net was significantly higher on the Yoko Maru, which employed a headrope kite, than the Kumamoto Maru, which uses floats on the headrope, while the horizontal opening of the net was significantly wider on the Kumamoto Maru than Yoko Maru (p < 0.01). According to generalized linear model (GLM) analysis of paired data, the capture of Dentex hypselosomus and Photololigo edulis increased when either or both the vertical and horizontal openings of the net of Yoko Maru increased or the horizontal opening of the net of Kumamoto Maru decreased. The catch of these fishes was estimated to be 0.9–4.0 times greater for Yoko Maru compared with Kumamoto Maru, depending on the vertical opening of the net of Yoko Maru. The catch of Champsodon snyderi was only influenced by the horizontal opening of the net, while for two Carangidae species, Trachurus japonicus and Kaiwarinus equula, no influence of the net shape was detected.

Space-time variations of megazoobenthos subject to natural and anthropogenic impacts in two Cuban bays: evidence of recovery?

The spatiotemporal variations of megazoobenthos on soft bottoms in Buena Vista (BV) and San Juan de Los Remedios (SJR) bays, Cuba, were assessed to infer the effects of the elimination of bottom trawl fisheries and the creation of protected areas. Data were collected at 11 sites in 2010-2013 (six routines and five exploratories) and 11 sites in 2014-2017 (four routines and seven exploratories). Samples were obtained by dredging. Mollusks were the most frequent and diverse group, followed by echinoderms and crustaceans. Total density (7.60 ind m-2) and biomass (15.82 g m-2) of the benthic community were highest in SJR in 2015. Although total biomass was lower at BV (t = 2.21; P = 0.032), there were no significant differences in density between bays (t = 0.77; P = 0.444). The site with a lower total density and biomass was located at BV. There were no differences between years except at one site, where density increased between 2010 and 2017. Total density and biomass were not significantly different inside and outside of the Zone Under Special Regime of Use and Protection (ZUSRUP) at the beginning of the sampled period. However, both density and biomass were significantly higher within the ZUSRUP at the end (2017), which suggests this protected area’s effectivity. The progressive increase in density at one site and greater density and biomass values at SJR, where bottom trawl fisheries were more intensive, suggest eliminating bottom trawl nets may have contributed to the benthic fauna recovery.

Production Performance and hematological analysis of Zapteryx brevirostris in a Closed System / Desempenho Produtivo e Hemograma da Zapteryx brevirostris em Sistema Fechado

The shortnose guitarfish ray, Zapteryx brevirostris , is constantly hauled by seven-beard-shrimp trawl nets are currently within the endangered species category. One means of preserving some aquatic species is to maintain them in a captive system such as tanks and aquariums, where it is possible to know their behaviors, as well as hematology and their well-being. The objective of this study was to analyze the productive performance and hematological analysis of Zapteryx brevirostris when submitted to different sediments in a captive system of water recirculation. For this, four treatments were used: Treatment 1 (gravel), treatment 2 (coarse sand), treatment 3 (medium sand) and treatment 4 (control) without sediment. At the end of the experiment, growth and weight data were taken for calculations of productive performance. Further, the hematological analysis was performed. The results showed that the species showed no significant difference for productive performance and hematological analysis in all treatments. However, treatment 3 (medium sand) was the only one to demonstrate weight gain, but the hematological analysis proved that the rays of all treatments were with hypochromic microcytic anemia. Thus, none of the treatments contributed to the productive performance and well-being of the rays.

Study the present trawl fishery of Penaeus monodon (Fabricius, 1798) in coastal waters off digha coast, West Bengal, India

During the present study the average annual catch of Penaeus monodon during 2011 - 2013 was 281.29±9.67 ton, which contributed 0.41 % to the total trawl net catches at Digha coast. The average catch rate was 43.41 kg/h. The percentage of P. monodon to total shrimp catch was 1.91% in trawl landings at Digha coast. Monthly mean landings were 28.13±0.97 t from the trawl nets. Peak landings were observed from June to November with a maximum of 56.46±1.97 t in September and lean landings were observed from December to March with a minimum of 6.12±0.21 t.