Demersal Fish Caught Research Articles

An assessment of demersal fisheries by trawling in less than 50 m of water off Egypt’s Mediterranean coast

Trawl fishing is identified as one of the most significant factors that could affect the diversity of demersal fish groups but not for all depth strata. Since the increased exploitation of Non-Indigenous Species (NIS) has caused the trawl fishing grounds to shift towards shallower seas where their biomass density is maximum, this study aimed to assess demersal fisheries by bottom trawls in the Mediterranean water off Egypt at depths less than 50 m. In this study, data from eight bottom-trawl hauls were used to describe the diversity of the demersal fish catch. The hauls varied in their species composition and both in the number and the weight of individuals. The length frequency distribution of the most occurred species was studied. A total of 87 species were identified in the catch, out of which 32 were recognized as NIS. The percentages of most of the NIS decreased from the east to the west of the surveyed area. There are always changes in fish diversity because of increasing fishing efforts on demersal fish communities, but not for all depth strata, therefore, a monitoring program has to be designed for better assessment of fisheries resources in the Mediterranean water off Egypt.

Fishing Ground Mapping of Demersal Fish in The Riau Islands Province Waters Related to the Oceanographic Factors

Research on the potential fishing ground for demersal fishing is a way to determine the areas that have the potential for fishing activities. Potential fishing ground mapping can be done by observing the dynamics of oceanographic parameters. The use of satellite imagery helps in providing oceanographic data in order to study the variability of oceanographic parameter. The aim of the study was to analyse the relationship between oceanographic parameter and demersal fish catch in order to validate potential fishing grounds for demersal fish. This research has been conducted in the waters of the Riau islands. Field observations and data collection including surveys of fishing grounds and identification of fish catches were carried out during March to August 2020. To support the analysis, Aqua-Modis Level-3 satellite data was used to observe the oceanographic variations. The data used in the analysis consisted of fishing grounds coordinate information, catches, sea surface temperature, chlorophyll-a, water depth, and salinity. The results showed that during the period 2010-2020, oceanographic dynamics did not experience significant changes or tended to be stable. Most of the research areas indicated appropriate categories for fishing activities based on the research parameters analysis. The correlation of the research parameters described a significant effect on fishing activities.

Isotopic niche and niche overlap in benthic crustacean and demersal fish associated to the bottom trawl fishing in south-central Chile

In habitats impacted by bottom trawling that influences the resilience of few and widely distributed abundant species, it is relevant to analyze how populations are structured according to their niche and niche overlap, and hence contributing to the ecosystem-based management approach. We evaluated and compared the isotopic niche width and determined the isotopic niche overlap for target and bycatch species of crustaceans and demersal fish caught with bottom trawling on the continental shelf and upper slope of the central-southern zone of Chile. Stable isotope analysis relied on carbon and nitrogen isotopes (13C and 15N) and Bayesian statistics of niche size and community metrics. Crustaceans and fish species are structured in three clusters according to the stable isotope values and the Chilean hake Merluccius gayi, which was probably clustered isolated due to its pelagic stable isotope values due to diel vertical migrations associated with feeding on euphausiids in the water column. The first group was constituted by demersal fish, that showed higher δ15N (19‰) and narrower δ13C (−16‰). The two other groups constituted a mix of crustaceans and fish, with access to different carbon sources. There were degrees of specialization for most species within the groups and overlap in the isotopic niche between populations. The benthic and demersal macrofauna species are structured by sharing resources in the habitat, probably on available sources supported by the productive pelagic system.

The demersal fish composition and catch per unit effort of mini bottom trawl at the coast of Demak Regency Central Java

Demak is a coastal area on the North Coast of Java with a large enough potential for demersal fish resources. This research aimed to determine the composition, the length and weight distribution, and catch per unit effort (CPUE) of demersal fish caught using mini bottom trawl at the north coast of Demak Regency. The research was carried out in October-December 2020 by observation of ten trips of mini bottom trawl fishing. Each fish captured was then grouped by type, identified, and measured its length and weight. The result showed that 38 species consist of 31 fishes, four mollusks, and three crustaceans. The fish captured dominated by pony fish (Leiognathus equulus) as much as 31.23% and largehead hairtail (Trichiurus lepturus) of 23.52%. The catch per unit effort (CPUE) average of mini bottom trawl was 44.77 kg/trip. Mainly fish (more than 95%) caught in small size compared it’s the maximum attainable length (L-max), with all the weight ranges from 0.3 to 520 g and more than 98% sized 0.3-80 g. Mini bottom trawl catches many types of fish and small size; therefore, mini bottom trawl is classified as a type of fishing gear with a very low selectivity level.

Legacy and Emerging Contaminants in Demersal Fish Species from Southern Norway and Implications for Food Safety.

The present study aimed at measuring the levels of legacy and emerging contaminants in fillet samples from four demersal fish caught in two fishing sites from Southern Norway, in order to assess possible implications for food safety. Levels of organochlorine compounds (OCs), organophosphate pesticides (OPs), polychlorinated biphenyls (PCBs), polybromodiphenyl ethers (PBDE), per- and polyfluoroalkyl substances (PFASs), and polycyclic aromatic hydrocarbons (PAHs) were measured in fillet from Atlantic cod (Gadus morhua), European plaice (Pleuronectes platessa), lemon sole (Microstomus kitt), and European flounder (Platichthys flesus) specimens. A negligible contamination by all the investigated chemicals was noted in both the fishing sites, as very low levels of OCs, PCBs, and PFASs were noted in a limited number of individuals for each species. Considering the levels of contaminants measured in fillets of the four demersal fish species, negligible risk for human health for Norwegian consumers can be supposed.

The relationship between total suspended matter and sea current for the spread of Chlorophyll-a and fishing area in Jakarta Bay

Jakarta bay is a water with high input load due to activities from the surrounding river estuaries comes from Jabodetabek regions. This activity impacts the availability of Total Suspended Matter (TSM) in Jakarta Bay. The problem comes when the concentration of TSM exceeds the carrying capacity of the water thus encouraging plankton to grow and breed rapidly which has caused eutrophication. This research has three objectives: (1) Analyzing the relationship of TSM and Chlorophyll-a Case 2 (CHL2), (2) Analyzing impacts between sea current with CHL2 distribution, and (3) Analyzing correlation CHL2 distribution with fish catch data. Data collection was conducted on January 2018 until December 2018. Monthly TSM and CHL2 data were obtained through GlobColour data, monthly data on sea currents were obtained through Marine Copernicus data. TSM and CHL2 data were processed using the GIS and time series method to determine distribution area. Furthermore, a regression analysis is used to determine the relationship of TSM and CHL2. The result: Relationship of TSM and CHL2 obtained R = 0,8508 so that there is a strong association between TSM and CHL2; the current pattern in the Jakarta bay strongly affected by monsoon wind, the highest distribution occurs in the NWM, evenly distribution occurs in the transition 1, and SEM, the lowest distribution occurs in the transition 2; the demersal and pelagic fish catch period occurs in the end of transition 2 period where high CHL2 concentration and low sea current velocity make it easier for fishermen to catch the fish.

Markov chain model for demersal fish catch analysis in Indonesia

As an archipelagic country, Indonesia has considerable potential fishery resources. One of the fish resources that has high economic value is demersal fish. Demersal fish is a fish with a habitat in the muddy seabed. Demersal fish scattered throughout the Indonesian seas. Demersal fish production in each Indonesia’s Fisheries Management Area (FMA) varies each year. In this paper we have discussed the Markov chain model for demersal fish yield analysis throughout all Indonesia’s Fisheries Management Area. Data of demersal fish catch in every FMA in 2005-2014 was obtained from Directorate of Capture Fisheries. From this data a transition probability matrix is determined by the number of transitions from the catch that lie below the median or above the median. The Markov chain model of demersal fish catch data was an ergodic Markov chain model, so that the limiting probability of the Markov chain model can be determined. The predictive value of demersal fishing yields was obtained by calculating the combination of limiting probability with average catch results below the median and above the median. The results showed that for 2018 and long-term demersal fishing results in most of FMA were below the median value.

Assessing the changes in international trade of marine fishes under CITES regulations – A case study of seahorses

Trade regulations may be useful for conserving marine species that are suffering from overexploitation. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has emerged as an instrument to help tighten fisheries management. However, the impacts of CITES regulations have not been examined for the trade in fully marine fishes. This study used seahorses (Hippocampus spp.), the first fully marine fishes listed in CITES Appendix II since treaty inception, as a case study. Drawing on Customs data from Taiwan and Hong Kong SAR (which cover pre-CITES periods), iterative-segmented regressions were applied to investigate changes in seahorse trade corresponding to CITES interventions. Principal component analyses were conducted to understand characteristics of seahorse source countries, and a gravity model of trade was applied to identify predictors of seahorse trade volumes. This study found that the total weight of seahorses in documented trade decreased significantly after CITES implementation, recorded trade became concentrated in fewer countries, and prices increased. Seahorse source countries were found having more fishers, demersal fish catch and general trade with China, compared to other range states. However, countries that reported no exports, unchanged export volumes or declining volumes after CITES were similar. In addition, volumes traded between two countries were found significantly higher when the two countries were closer together or when the source country had a lower per capita GDP or higher demersal catch. This study can help guide targeted actions to maximize CITES effectiveness for marine species.

Can changes in fishery landings explain long-term population trends in gulls?

ABSTRACTCapsule: Long-term population trends of gulls on the Isle of Canna, Scotland, showed a correlation to fish tonnage landed in a nearby port.Aims: To assess whether gull numbers and breeding success at Canna have been influenced by the amount of fish discarded in the area.Methods: We examined data on gull breeding numbers, breeding success and diet studied at Canna from 1969 to 2014, and data on fish landings at the nearby port of Mallaig for 1985 to 2014. We examined correlations between gull and fishery data, and performed a detrended analysis of Herring Gull Larus argentatus numbers in relation to demersal fish catch (the latter as a proxy for discard volumes).Results: Gulls fed extensively on discards. Gull breeding numbers declined at Canna, especially between 2000 and 2006, the decline being more pronounced than seen in national totals. Gull breeding numbers correlated with demersal landings, even after detrending for long-term decreases in both.Conclusions: Correlation between detrended Herring Gull breeding numbers and detrended demersal fish landings provided strong evidence for a causal link between fishery discarding and gull breeding numbers.

동해구외끌이중형저인망에 의한 동해 중남부 해역 저어류의 종조성 및 군집구조

동해는 동아시아와 일본에 둘러싸인 반폐쇄구조의 대륙 주변 해로서, 총 면적이 1.01×106 km2이고 수심은 평균 1,350 m, 최 대 3,700 m이다. 동해의 북쪽은 폭이 좁은 대륙붕에서 급경사 대륙사면이 형성되어 심해저로 연결되지만, 남쪽은 북쪽에 비 해 넓은 대륙붕이 형성되어 있으며 대한해협을 지나 동쪽으로 평균 수심 120 m 정도의 평탄한 지형으로 이루어져 있다(Lee and Kim, 2007). 동해는 북한한류가 대륙붕 연안을 따라 남하 하다가 대한해협을 통해 유입되는 고온고염의 대마난류와 약 37°N 부근에서 강한 수온전선을 형성하는데, 이 해역은 기초생 산력이 높고 다양한 먹이 생물이 번식하여 동해 수산자원의 중 요한 어장과 성육장의 역할을 한다(Choi et al., 2008; Gong et al., 2010). 또한 수온에 따라 다양한 한류성, 난류성, 온대성 어 종들이 서식하고 회유나 생활사에 따라 연안 정착성, 심해성, 회 유성 어종들이 함께 출현하고 있어, 생물다양성의 측면에서도 매우 중요한 곳이다(Kim and Nam, 2003). 우리나라에 서식하는 전체 해산어류는 약 947종이고, 이 중 동해구외끌이중형저인망에 의한 동해 중남부 해역 저어류의 종조성 및 군집구조 손명호·박정호*·윤병선·최영민·김진구

Simulation Model for Evaluating the Response of Management Options on the Demersal Resources of Tamil Nadu Coast

The response of different management options on demersal fish catch in Tamil Nadu was examined using simulation model and time series data on catch and effort of demersal resources in Tamil Nadu during 1989-2005. For the simulation study surplus, production model and spectral models were used to simulate effort, yield and biomass. Genetic algorithm was used to estimate parameters of surplus production model. Effort, biomass and yield were simulated for the period 2006 to 2015 under different levels of effort such as reducing by 25%, 50%, and 75% of present level increasing by 25%, 50%, 75% and 100% of present level and also for the present level. The simulation results revealed that when the level of exploitation is kept at 25%, 50%, 75%, and 100% of the present level, the yield falls below the maximum sustainable yield (MSY) level and the biomass is kept above its MSY level. When the exploitation level is increased by 25% of the present level of exploitation, the yield falls below the MSY level in the years up to 2013 and the biomass remains above that at MSY level. But at this level of exploitation, the yield falls above the MSY level and the biomass falls below its MSY level for the years 2014 and 2015. The optimum exploitation level was worked out as 91.25% of the present level of exploitation.

The influence of selected environmental parameters on the distribution of the dominant demersal fishes in the Kariega Estuary channel, South Africa

The Kariega Estuary channel was sampled using an otter trawl and the demersal fish catch analysed using the PRIMER statistical package. A biological-environmental (BIOENV) analysis was undertaken using the catch per unit effort ichthyofaunal data from the spring/summer period of 1996/97 and concurrent water temperature, salinity and turbidity data. No strong correlations between the ichthyofauna and recorded physico-chemical parameters were documented, although temperature did show a weak correlation to demersal fish distributions. A second sampling programme undertaken in 2004 was specifically designed to test the influence of sedimentary characteristics on the distribution patterns of the dominant demersal species. Analyses showed that sediment size composition and organic content was strongly correlated (r = 0.70) to the distribution of the soles Solea bleekeri and Heteromycteris capensis, as well as the goby Glossogobius callidus. S. bleekeri and G. callidus showed a preference for the muddier middle and upper reaches of the Kariega Estuary channel, whereas H. capensis and Psammogobius knysnaensis were more abundant in the sandier lower reaches and mouth region of the estuary. The exact reasons for these preferences are unknown but are likely to be related to preferred prey availability, foraging success and predator avoidance in the different types of sediment. Other species caught in the otter trawl were not significantly correlated to sedimentary characteristics.

The influence of selected environmental parameters on the distribution of the dominant demersal fishes in the Kariega Estuary channel, South Africa

ABSTRACT The Kariega Estuary channel was sampled using an otter trawl and the demersal fish catch analysed using the PRIMER statistical package. A biological-environmental (BIOENV) analysis was undertaken using the catch per unit effort ichthyofaunal data from the spring/summer period of 1996/97 and concurrent water temperature, salinity and turbidity data. No strong correlations between the ichthyofauna and recorded physicochemical parameters were documented, although temperature did show a weak correlation to demersal fish distributions. A second sampling programme undertaken in 2004 was specifically designed to test the influence of sedimentary characteristics on the distribution patterns of the dominant demersal species. Analyses showed that sediment size composition and organic content was strongly correlated (r = 0.70) to the distribution of the soles Solea bleekeri and Heteromycteris capensis, as well as the goby Glossogobius callidus. S. bleekeri and G. callidus showed a preference for the muddier...

Fishing gear associated with global marine catches: II. Trends in trawling and dredging

A new method for associating global marine catch statistics with fishing gears has allowed the creation of maps which detail the changing use of fishing gears such as trawls and dredges from the 1950s to the present. These gears, often associated with high impacts on benthic communities, are associated with a wide range of demersal fish, molluscan and crustacean catch. The use of these gears has increased globally since the 1950s when it accounted for more than 40% of reported catches to a peak in most areas such as North America and Europe in the 1980s. This increase extended into the 1990s along the coast of Argentina particularly for squid. Dredging, usually associated with the catch of bivalves, often peaked later than trawling but had begun to decline in most areas by the 1990s.

Catch analysis on demersal fish caught by the RV. Stella Maris in Lampung Bay

Catch analysis on demersal fish caught by the RV. Stella Maris in Lampung Bay

Influence of Velocity and Types of Beam Trawl Towing on Deep-Sea Demersal Fish and Decapod Crustacean Samples

The sampling efficiency of two types of beam trawl towed at different velocities was compared when sampling deep-sea demersal fish and decapod crustaceans. The trawls were a Sigsbee-Agassiz type of 2 m span, and an Oregon type of 3 m span. The different hauls caught by the Oregon type beam trawl of 3 m span towed at 1.5 knot (3m 1.5 kt), the Oregon type towed at 0.8 knot (3m 0.8 kt) and the Sigsbee-Agassiz type towed at 1.5 knot (2m 1.5 kt) were compared by analysis of variance (ANOVA), the Tukey test, cluster analysis based on Morisita-Horn index, and correspondence analysis. The minimum viable sample size was determined by a randomization test. For demersal fish, the type of gear used had more influenced on the samples obtained than the towing velocity. For decapod crustaceans, no significant difference was detected between different trawls towed at different velocities. The common idea that if these types of trawl are towed at 1 knot or more, they cannot efficiently sample epifauna, but demersal fish can be well sampled, should be abandoned. The samples of demersal fish caught by 3m 1.5 kt revealed the greatest consistency and lowest variation than the others. We recommend using an Oregon type beam trawl of 3 m span towed at 1.5 knot as an ordinary deep-sea sampling device. Only a single successful haul or a sample size of 52 individuals was sufficient for estimating demersal fish diversity, but at least two successful hauls or a sample size of 54 individuals were needed for decapod crustaceans. If possible, seven successful hauls or a sample size of 189 individuals of decapod crustaceans are recommended for community study.

Estimates of fishery potentials of the EEZ of India

An attempt has been made to estimate the fishery potentials of the EEZ of India on the basis of data on primary and secondary production. The total column primary production and zooplankton production have been calculated to be 265·9 and 9 million tonnes of carbon per year, respectively. From these values the fishery potential has been estimated as 2·5 million tonnes per year. To this, if we add the estimated demersal fish catch, being 1·2 million tonnes per year, the total potential yield comes to 3·7 million tonnes per year. Since the present average total catch is about 1·6 million tonnes in a year, the fish catch could be doubled.

Comparison of the Performance of Two Bottom-Sampling Trawls

The performance of two bottom-sampling trawls was evaluated under various rigging configurations and operating conditions. The trawls examined were a semiballoon shrimp trawl usually towed from a single warp and a high-rise trawl towed from two warps. The geometric performance (i.e., configuration of the trawl while in operation) of the full-scale nets was measured hydroacoustically in the field, and scale models were tested in a tow tank. For the shrimp trawl, wingspread increased significantly with increased bridle length but was not significantly affected by increased speed or current direction. Headrope opening decreased with increased towing speed and bridle length. For the high-rise trawl net, wingspread and headrope opening both decreased with increased speed. In contrast to the clear differences in geometric performance related to net design, rig, and operation, the analyses of catch data from Narragansett Bay, Rhode Island, were not definitive. The high-rise trawl captured significantly more total demersal fishes and winter flounder Pseudopleuronectes americanus by weight than the shrimp trawl, but the two nets caught similar sizes of winter flounder. Catches of winter flounder in the shrimp trawl were significantly affected by towing speed and current direction; however, bridle length of the shrimp trawl did not affect these catches demonstrably. Towing speed and current direction did not significantly affect total catch, demersal fish catch, or pelagic fish catch.

Fisheries in the Orkney area

SynopsisFishing has long played an important part in the economy of Orkney. Local vessels are all small, and fish predominantly inshore for shellfish. Demersal and pelagic fish are abundant in the offshore waters around Orkney, but these exposed waters can be fished only by large vessels from more distant ports, so that few fish are landed in the islands.Gadoids, especially haddock, cod and whiting, form the bulk of the demersal fish caught at Orkney. Stocks of all three are giving cause for concern, with declining spawning stock biomass and reduced recruitment. With the coming of processing, more local landing of demersal fish might occur. The closure of the herring fishery in 1977 was followed by a great expansion of mackerel fishing, but with the lifting of the ban west of 4CW in 1981, herring catches have once again become valuable. Because of fishing pressure, landings of both species are subject to quota restrictions.In recent years, the traditional fisheries for lobsters and crabs have been supplemented by a new fishery for scallops. Lobster stocks are now under some pressure. Conditions around Orkney appear suited to farming filter-feeding bivalve molluscs, and culture and marketing of Pacific oysters has started.

The predation of mysids by fish of the Rockall Trough, northeastern Atlantic Ocean

The stomach contents of representatives of approximately 100 species of pelagic and demersal fish caught in the Rockall Trough, northeastern Atlantic ocean, have been examined for the occurrence of mysids. More than 40 species of fish included mysids in their diets. The majority of the 21 species of mysids identified in the stomachs live in close association with the sediment and are rarely caught in pelagic nets. Mysids contributed significantly to the diets of many demersal fish but were not apparently important constituents of the food of pelagic fish.