Fishing Ground Off Research Articles

Bycatch and discards of shrimp trawling in the Saudi waters of the Arabian Gulf: ecosystem impact assessment and implications for a sustainable fishery management

Shrimp trawl fishery has evoked serious concerns at both regional and global levels due to its strong association with the bycatch and its significant contribution to the total global discards. Using three data methods (examination of fishermen log-books, questionnaire survey and observer monitoring), the bycatch and discards associated with shrimp trawl fishery were studied, for two consecutive seasons (2013-2014 and 2014-2015), in the main shrimp fishing ground off Safaniya, along the Saudi coast in the Arabian Gulf. Safaniya fishing ground, with 37 large shrimp trawlers, was found to contribute a total shrimp catch of 500 to 755 t (up to 11% of the total national shrimp landings). Total bycatch (281-563 t) and discard (114-339 t) were substantial. A total of 104 fish and shellfish species were recorded in the bycatch, including 93 Osteichtyes, 3 Chondrichthyes, 6 Crustaceans and 3 Molluscs. The blue swimming crab, Portunus segnis, prevailed the bycatch (145-160 t), followed by the pharaoh cuttlefish Sepia pharaonis (2-16 t). Safaniya shrimp fishery was found to have high impacts on the shrimp (Penaeus semisulcatus; target species) juveniles and other commercial species. Estimations of total number of turtles captured in the catch ranged between 1492 and 2018, indicating a serious threat of shrimp fishery on local turtle populations. The results of this study emphasize the urgent need to adopt appropriate bycatch reduction devices in shrimp fishery, in addition to enforcement of fisheries management regulations in order to protect the non-target resources and ensure a sustainable shrimp production in the Arabian Gulf.

트롤조업에 의한 제주도 동부어장의 저서생물의 종조성 변동 특성

트롤조업에 의한 제주도 동부어장의 저서생물의 종조성 변동 특성

Comparative efficiency of fish trap with different funnel designs

The efficiency of four different funnel designs viz., rectangular, oval, heart-in and circular shaped funnels were tested in a serial collapsible fish trap through fishing trials conducted in a coastal fishing ground off Mandapam in Tamil Nadu, south-west coast of India. A total of 24 fishing operations were carried out. Significant difference in overall catch rate of experimental trap with respect to funnel designs could be observed (p<0.05). Among four types of funnels tested with the constant rear end funnel perimeter of 560 mm, traps with oval funnel caught more number of fishes (121 nos. in 24 soaking days) than those fitted with rectangular, heart-in shaped and circular type of funnels with 37; 82 and 70 nos. in 24 soaking days respectively. The study revealed that oval shaped funnel was superior to the other funnel designs with 560 mm circumference.

제주도 동부 먼바다 어장에서 겨울철에 어획된 저서생물의 분포특성

제주도 동부 먼바다 어장에서 겨울철에 어획된 저서생물의 분포특성

Nutrients and phytoplankton dynamics in the fishing grounds off Tiruchendur coastal waters, Gulf of Mannar, India.

Nutrients and phytoplankton dynamics in the traditional fishing grounds off Tiruchendur coast, Gulf of Mannar, India revealed a clear seasonal trend influenced by prevailing monsoon system in east coast of India. A total of 73 species of phytoplankton were identified from the fishing grounds, revealed higher abundance in summer months compared to other seasons. Among the three stations, maximum phytoplankton abundance was recorded in station 2 followed by stations 1 and 3. The phytoplankton abundance ranged from 2.85 × 104 to 6.34 × 104 cells/l, with higher and lower value observed during summer and post monsoon season respectively. Chl-a showed similar seasonal trend with phytoplankton abundance and fluctuated from 0.4 to 6.8 mg/m3 with high concentrates were recorded during summer. Primary productivity was ranged from 13.8 to 28.7 mg, C/m2/day with maximum and minimum during summer and monsoon respectively. It was understood from the study, ammonia could be acting as the limiting nutrient for phytoplankton growth, while the role of nitrate, nitrite, phosphate and silicate remained insignificant. At the time of diatom population proliferates there was a drop in the nutrient levels was observed during the study. The water current flowing from north to south during the northeast monsoon, nutrient rich fresh water discharged from Tamirabarani River influencing the nutrient dynamics in the fishing grounds that are ultimately increasing the nutrients concentration during northeast monsoon.

Long-Term Seasonal and Interannual Patterns of Marine Mammal Strandings in Subtropical Western South Atlantic.

Understanding temporal patterns of marine mammal occurrence is useful for establishing conservation strategies. We used a 38 yr-long dataset spanning 1976 to 2013 to describe temporal patterns and trends in marine mammal strandings along a subtropical stretch of the east coast of South America. This region is influenced by a transitional zone between tropical and temperate waters and is considered an important fishing ground off Brazil. Generalized Additive Models were used to evaluate the temporal stranding patterns of the most frequently stranded species. Forty species were documented in 12,540 stranding events. Franciscana (n = 4,574), South American fur seal, (n = 3,419), South American sea lion (n = 2,049), bottlenose dolphins (n = 293) and subantarctic fur seal (n = 219) were the most frequently stranded marine mammals. The seasonality of strandings of franciscana and bottlenose dolphin coincided with periods of higher fishing effort and strandings of South American and subantarctic fur seals with post-reproductive dispersal. For South American sea lion the seasonality of strandings is associated with both fishing effort and post-reproductive dispersal. Some clear seasonal patterns were associated with occurrence of cold- (e.g. subantarctic fur seal) and warm-water (e.g. rough-toothed dolphin) species in winter and summer, respectively. Inter-annual increases in stranding rate were observed for franciscana and South American fur seal and these are likely related to increased fishing effort and population growth, respectively. For subantarctic fur seal the stranding rate showed a slight decline while for bottlenose dolphin it remained steady. No significant year to year variation in stranding rate was observed for South American sea lion. The slight decrease in frequency of temperate/polar marine mammals and the increased occurrence of subtropical/tropical species since the late 1990s might be associated with environmental changes linked to climate change. This long-term study indicates that temporal stranding patterns of marine mammals might be explained by either fishing-related or environmental factors.

Trends and composition of trawl bycatch and its implications on tropical fishing grounds off Goa, India

Trawl bycatch is a globally recognized issue with intensified effects in tropical waters affecting both the ecosystem function and biodiversity, as well as causing physical damage and habitat loss. The present study envisages temporal variations of bycatch with regard to the species and their biological interactions based on data obtained from commercial single-day bottom trawlers operating off Goa, west coast of India. The data revealed that bycatch constituted about 68% of the trawl catch, the remaining being target species (shrimp, flat fishes, sciaenids, squids and crabs). Approximately 89% of the species discarded into the sea comprised of juveniles of target and trash species, suggesting a major share of non-target species, leading to species loss. Out of 196 taxa observed in the trawl catch, 174 constituted bycatch with a significantly high percentage of biomass. Abundance of discarded bycatch species (crustaceans, echinoderms, teleosts) displayed distinct peaks during pre-monsoon whereas molluscs, crustaceans and teleosts dominated during post-monsoon. A conspicuous increase in abundance of molluscs during post-monsoon (October, 2012) and echinoderms during pre-monsoon (April, 2011 and April, 2013) is largely attributed to the recruitment process. Cluster analysis identified different clusters during pre-monsoon and post-monsoon season corresponding to their recruitment patterns and diverse species assemblages. Principal Component Analysis performed using three environmental parameters accounted for 84% (five components) and 86% (four components) of variance during pre-monsoon and post-monsoon, respectively. Regression analysis indicated a significant linear relationship between total catch and bycatch (R2=0.89), and between bycatch and discarded catch (R2=0.94).

Seasonal variation of zooplankton and pelagic fish catch in the fishing grounds off Tiruchendur coast, Gulf of Mannar, India

The present study on zooplankton species diversity, abundance and water quality parameters with special emphasis on pelagic fish catches in three fishing grounds off Tiruchendur coast was conducted from January 2009 to December 2010. As zooplankton are playing important roles in transfer of energy to the pelagic food webs, an attempt was made to understand the role of zooplankton on pelagic fish catch in the potential fishing grounds. Stations 1–3 are located about 3.7km, 14.1km and 17.3km from the Tiruchendur coast respectively. Sea surface temperature (SST) in three stations varied from 25.0 to 31.7°C and minimum and maximum SST recorded unifromly in monsoon and summer seasons. Dissolved oxygen and salinity varied from 4.15 to 6.2mg/l and from 33 to 36.3 PSU respectively. Total of 49 species of zooplankton have been documented during the study. Zooplankton diversity was significantly differed from seasons to seasons. Calanoid and larvae of crustacean's crabs were dominant group in three stations and significantly contributing to the pelagic fishery. High and low population density recorded during summer months and monsoon season respectively. The statistical analyses showed that, physical parameters significantly (positive) correlated with zooplankton abundance; however, chemical parameters exhibited significant negative correlation with zooplankton density in stations 1 and 2. Among the pelagic fishes, Sardinella longiceps and Scomberomorus commerson are the dominant species in the study. The high rate of zooplankton population density and maximum pelagic fish catch were inconsistent due to lacking period between spawning and fish catch.

Influence of the hydrodynamic conditions on the accessibility of Aristeus antennatus and other demersal species to the deep water trawl fishery off the Balearic Islands (western Mediterranean)

Monthly catches per unit of effort (CPUE) of adult red shrimp (Aristeus antennatus), reported in the deep water bottom trawl fishery developed on the Sóller fishing ground off northern Mallorca (Western Mediterranean), and the mean ocean surface vorticity in the surrounding areas are compared between 2000 and 2010. A good correlation is found between the rises in the surrounding surface vorticity and the drops in the CPUE of the adult red shrimp. This correlation could be explained by assuming that most of the surface vorticity episodes could reach the bottom, increasing the seabed velocities and producing sediment resuspension, which could affect the near bottom water turbidity. A. antennatus would respond to this increased turbidity disappearing from the fishing grounds, probably moving downwards to the deeper waters. This massive displacement of red shrimp specimens away from the fishing grounds would consequently decrease their accessibility to fishing exploitation. Similar although more intense responses have been observed during the downslope shelf dense water current episodes that occurred in a submarine canyon, northeast of the Iberian peninsula. The proposed mechanism suggesting how the surface vorticity observed can affect the bottom sediments is investigated using a year-long moored near-bottom current meter and a sediment trap moored near the fishing grounds.The relationship between vorticity and catches is also explored for fish species (Galeus melastomus, Micromesistius poutassou, Phycis blennoides) and other crustacean (Geryon longipes and Nephrops norvegicus), considered as by-catch of the deep water fishery in the area. Results appear to support the suggestion that the water turbidity generated by the vorticity episodes is significant enough to affect the dynamics of the demersal species.

Diversity and Community Structure of Decapod Crustaceans at Hydrothermal Vents and Nearby Deep-Water Fishing Grounds Off Kueishan Island, Taiwan: A High Biodiversity Deep-Sea Area in the NW Pacific

Kueishan island (northeastern taiwan) is an important deep-water fishing ground and is world famous for its unique hydrothermal vents that extend from shallow to deep waters. The global scale community structure of deep-sea fauna has received scant attention, thus the present study investigated the biodiversity and community structure of decapod crustaceans in these unique vent and non-vent regions of Kueishan island. The fauna was sampled with 24 quantitative benthic trawls and with additional monthly surveys of bycatch and commercially important species collected over a year by commercial trawlers. We recorded a total of 51 families, 119 genera, and 202 species of decapod crustaceans. Brachyura was the most diverse group, representing 34% of the species, followed by Caridea (20%), Dendrobranchiata (20%), and Anomura (18%), while Astacidea, Achelata, Polychelida, and Axiidea had lower abundances (8% combined). Multivariate analyses revealed significant differences in species composition between the vent and non-vent regions. Some species were recorded at both regions but differed in abundance between the two habitats. The vent crab, Xenograpsus testudinatus Ng, huang and Ho, 2000, had high abundance on vents but was not recorded in non-vent regions. Comparisons between the community structure of Kueishan island with Tosa Bay, Sagami Bay, and Suruga Bay, Japan, indicated that Kueishan island has the highest average taxonomic distinctness and variation in taxonomic distinctness among these deep-water regions. Our results suggest that Kueishan island is a species-rich, deep-water ecosystem not dominated by a specific taxonomic group.

A PESCA DA ALBACORA-LAGE (Thunnus albacares) REALIZADA PELA FROTA BRASILEIRA DE VARA E ISCAVIVA NO SUDOESTE DO OCEANO ATLÂNTICO

In the southwest Atlantic Ocean, the catches of yellowfin tuna (Thunnus albacares) are relatively high, but skipjack tuna (Katsuwonus pelamis) is the target species. However, due to the high market value, fishermen have been interested in trying to increase the yellowfin catches and yields in the southeast and south Brazil. In order to gather information to improve yellowfin fishery we analyzed the spatio-temporal variations of the fishing patterns (effort, catch and CPUE) off Brazil. The preliminary results obtained suggest that the vulnerability of yellowfin tuna is large all over the traditional baitboat fishing ground off Brazil. However, the profits are especially high in the second quarter and in south (southward of 30°S). Furthermore, aggregating devices (e.g. oilrig platforms and drifting or anchored buoys) proved to enhance yellowfin tuna yields.

The Yellow Croaker War: Fishery Disputes between China and Japan, 1925–1935

Beginning in the 1920s, the convergence of ecological transformations that originated in China and Japan gave rise to protracted disputes over yellow croaker fishing grounds off of China's southeast coast. These conflicts highlight the importance of transnational perspectives in marine environmental history. Geopolitics influenced patterns of marine resource exploitation, as Japan's diplomatic and military advantage prevented the Chinese government from excluding the Japanese fleet from yellow croaker fishing grounds. Motivated by a mutual understanding of fishery expansion as a way to strengthen the nation-state, Chinese and Japanese exploitation hastened the decline of yellow croaker resources by the late 1930s.

Feeding ecology of the grooved tiger shrimp Penaeus semisulcatus De Haan (Decapoda: Penaeidae) in inshore waters of Qatar, Arabian Gulf

The feeding ecology of the green tiger shrimp Penaeus semisulcatus was studied in inshore fishing grounds off Doha, Qatar, using a combination of stable isotope (δ13C and δ15N) analysis and gut contents examination. Samples of post-larvae, juvenile and adult shrimp and other organisms were collected from intertidal and subtidal zones during the spawning season (January–June). Shrimp collected from shallow water seagrass beds were mostly post-larvae and juveniles and were significantly smaller than the older juveniles and adults caught in deeper macroalgal beds. Gut content examination indicated that post-larvae and juvenile shrimp in seagrass beds fed mainly on benthos such as Foraminifera, polychaetes, benthic diatoms and small benthic crustaceans (amphipods, isopods and ostracoda), whereas larger shrimp in the macroalgal beds fed mainly on bivalve molluscs and to a lesser extent polychaetes. In shrimp from both seagrass and algal beds, unidentifiable detritus was also present in the gut (18, 32%). δ13C values for shrimp muscle tissue ranged from −9.5 ± 0.26 to −12.7 ± 0.05‰, and δ15N values increased with increasing shrimp size, ranging from 4.1 ± 0.03 to 7.7 ± 0.11‰. Both δ15N values and δ13C values for shrimp tissue were consistent with the dietary sources indicated by gut contents and the δ13C and δ15N values for primary producers and prey species. The combination of gut content and stable isotope data demonstrates that seagrass beds are important habitats for post-larvae and juvenile P. semisulcatus, while the transition to deeper water habitats in older shrimp involves a change in diet and source of carbon and nitrogen that is reflected in shrimp tissue stable isotope ratios. The results of the study confirm the linkage between sensitive shallow water habitats and the key life stages of an important commercially-exploited species and indicate the need for suitable assessment of the potential indirect impacts of coastal developments involving dredging and land reclamation.

제주도 함덕 연안의 정치망 어획량 변동

Fish catch by a set net in Hamdeuk fishing ground off Jeju Island were studied to determine seasonal variation of species composition and catch from 1998 to 2000. A total 72,022.9 kg was caught during the survey period, including Scomber japonicus and Trachurus japonicus of <TEX>$76.4\%$</TEX> in the total. The other dominant species were Siganus fuscescens, Loligo chinesis, Seriola dumerili, Sepioteuthis lessoniana, Sardinops melanostictus, and Seriola lalandi accounting to <TEX>$20.0\%$</TEX> of the total. The fishing period conducted by a set net in Hamdeuk fishing ground were from May to November. The catch by a set net were higher in summer than in spring and autumn and closely related with the seasonal variation of sea water temperature. The catch was higher in 1998 than In 1999 and 2000, which was related to the sea water temperature in fishing ground.

Shrimp trawl catches and stomach contents of redfish, Greenland halibut and starry ray from West Greenland during a 24-hour cycle

A total of 179 redfish (Sebastes spp.), 495 Greenland halibut (Reinhardtius hippoglossoides) and 133 starry ray (Raja radiata) stomachs were collected from the catch in four bottom trawl hauls carried out at 6-hour intervals on a shrimp fishing ground off West Greenland in September 1991. Between 90 and 96% of the total catch in each of the four trawl hauls consisted of northern shrimp (Pandalus borealis). The fish catches were small and dominated by redfish, Greenland halibut, starry ray and polar cod (Boreogadus saida). The stomach contents of redfish consisted of crustaceans (mysiids, hyperiids and copepods) followed by cephalopods, northern shrimp and redfish. Fish (mainly redfish), cephalopods and northern shrimp were the most important stomach content of Greenland halibut. The stomach content of starry ray consisted mainly of northern shrimp and redfish. Plots of redfish and shrimp sizes found in the stomachs of Greenland halibut and starry ray versus predator size showed only weak associations indicating that availability overruled the importance of size-dependent prey preference. The present study indicates that redfish, Greenland halibut and starry ray feed throughout the 24-hour cycle with no clear diel feeding rhythms.

Shrimp trawl catches and stomach contents of redfish, Greenland halibut and starry ray from West Greenland during a 24-hour cycle

A total of 179 redfish (Sebastes spp.), 495 Greenland halibut (Reinhardtius hippoglossoides) and 133 starry ray (Raja radiata) stomachs were collected from the catch in four bottom trawl hauls carried out at 6-hour intervals on a shrimp fishing ground off West Greenland in September 1991. Between 90 and 96% of the total catch in each of the four trawl hauls consisted of northern shrimp (Pandalus borealis). The fish catches were small and dominated by redfish, Greenland halibut, starry ray and polar cod (Boreogadus saida). The stomach contents of redfish consisted of crustaceans (mysiids, hyperiids and copepods) followed by cephalopods, northern shrimp and redfish. Fish (mainly redfish), cephalopods and northern shrimp were the most important stomach content of Greenland halibut. The stomach content of starry ray consisted mainly of northern shrimp and redfish. Plots of redfish and shrimp sizes found in the stomachs of Greenland halibut and starry ray versus predator size showed only weak associations indicating that availability overruled the importance of size-dependent prey preference. The present study indicates that redfish, Greenland halibut and starry ray feed throughout the 24-hour cycle with no clear diel feeding rhythms.

定置網漁場における天然礁に関連する魚群の行動

定置網漁場における天然礁に関連する魚群の行動

東北海域における南下期のカツオ漁場形成とその判別分析

The formation of southbound skipjack fishing grounds off Touhoku sea area was studied through the use of satellite imageries and satellite-aided issues by JAFIC covering the recent six years. It was verified that the two conditions of “to be close to the warm core ring off Sanriku or the SST (sea surface temperature) boundaries” were essential to the formation. Then, by quantifying those conditions, the method to discriminate and predict the formation of fishing grounds was studies.The discriminant variables were 1, the spatial and 2, the temporal SST gradients of a sample mesh and 3, the proximity to the current path within a warm core ring or to the SST boundary, respectively, divided by the deviation of the present SST from the favourable water temperature. On meshes sampled from the sea areas, data of variables were obtained and subjected to discriminant analysis.Within the discriminant model thus obtained, plus sign of composite variable of a mesh discriminates and indicates that a fishing ground for skipjack is formed in the sea area represented by the mesh. The mean correct discrimination rate reached 88% for used data and 82% for new data and proved its usefulness.

カタクチイワシシラスの主要餌料生物であるＯｉｔｈｏｎａ属かいあし類のシラス漁場内における分布特性

Distribution pattern and abundance of cyclopoid copepods belonging to the genus Oithona were studied on the basis of 648 samples collected every 3 or 4 days from July to October, 1984 at 18 stations in Shirasu fishing ground off Hiratsuka in Sagami Bay. Samplings were made in both surface and bottom layers at each station. O. davisae is the most dominant species, comprising 90-100 percent of a total catch of Oithona in number from late July to the middle of September and 70-90 percent from late September to October. The density of Oithona in the bottom layer was about 4 times as high as that at the surface. The bottom densities showed a seasonal change, highest in late July, 425 inds/l ont he average (range 104-1073), at a level of 100-250 inds/l through August, below 100 inds/l in September, and below 50 inds/l in October. O. davisae is abundantly distributed in the bottom waters of the salinity range, 30-33% in the area shallower than 10m deep whose surface layer is usually affected by the water from Sagami River. It is suggested that its habitat overlaps with that of Shirasu and that O. davisae is important as a food of Shirasu.

REARING THE PENAEID SHRIMP Artemesia longinaris FROM EGG TO JUVENILE IN THE LABORATORY

ABSTRACTThe brown shrimp (Artemesia longinaris) has been reared in laboratory conditions from eggs to juveniles of 60 mm in total length.The ripe females are obtained from the coastal fishing grounds off Mar del Plata City (latitude of 38°S) in the spring from September to December. The depth in this zone is between 3 and 10 m. The shrimps are caught with a beam trawl commonly used by the small boats in this region. The size of the adult females reaches about 145 mm of the total length.The ripe females brought to the laboratory are put in special spawning aquaria. The spawning generally occurs within 24–48 hours. In some cases some females spawn after 4–5 days. Generally if the spawning does not take place immediately the ovary is reabsorbed.At the temperature of 17–20 C the hatching of the naupli takes place after 24–36 hours. This species has six stages of nauplius which are accomplished after 4–5 days. Afterwards the nauplius is transformed in a protozoea with its three characteristic substages. These stages last during 11–12 days. These larvae were fed on the Alga Skeletonema costatum, especially reared for this purpose. Its concentration in the aquarium with shrimp larvae was of 25,000 and 60,000 cells/ml of Skeletonema.After the stage of protozoea appears the stage of Mysis with its typical four substages appear. This stage lasts during 12–14 days. The mysis were fed on the just hatched naupli of Artemia. After the moult the mysis are transformed in postlarvae of 5.0 – 5.7 mm in length.The growth of postlarvae is relatively fast if one considers that Artemesia longinaris belongs to the species of temperate waters. According to the results obtained in the summer 1972–73 and at the end of 1973 the average growth rate was 0.3–1.0 mm/day. The shrimps reared in aquaria during 90 days from the first postlarvae reached the size of 40–60 mm total length. These animals were fed first on Artemia naupli and afterwards on minced meat of shrimp and special diet with vitamins, proteins, vegetables, etc.