Commercial Fish Landings Research Articles

Characterization of commercial fish landings of Chandragiri estuary, Kerala, India

Characterization of commercial fish landings of Chandragiri estuary, Kerala, India

New observations of the endangered giant freshwater whipray, Urogymnus polylepis, provide further evidence for its distribution and breeding in the north-east coast of India.

The present study reports observations of 13 giant freshwater whipray (Urogymnus polylepis) from commercial fish landings along the north-east coast of India and updates existing records based on field observations and local social media reports. The disc width of the landed specimens ranged from 120 to 223 cm and they weighed 95-300 kg. All 13 specimens observed were mature (nine females and four males) and three females were pregnant, with embryo numbers ranging between 4 and 15. Globally, U. polylepis is listed as 'Endangered', and greater protection measures are needed in India to assist in reversing current population declines.

Quantifying fish catches and fish consumption in the Amazon Basin

Abstract The Amazon Basin is the largest in the world and for many of its inhabitants fishing is a crucially important source of food and income. However, the benefits derived from mostly informal, part time, seasonal, and subsistence-based activities such as fishing are largely invisible to policy-makers, and addressing the threats to aquatic habitats, ecosystem functioning, and fisheries is frequently given low priority in national development agendas. To estimate the total extraction of fish in the Amazon Basin, we reviewed various publications and databases with quantitative data related to the landings, trade, and consumption of fish. We estimated the total landings to be between 422,000 and 473,000 t yr-1 in live weight, near to previous estimates. Almost 75%, however, represented landings in the Brazilian part of the basin, and there is a very large margin of uncertainty given that, among other issues, there are no recent official statistics on commercial landings. Conversely, landings in Bolivia, Colombia, and Ecuador seem to be considerably higher than previously thought. In all Amazonian countries, from 50% up to almost 100% of the fishing takes place for personal consumption, implying that it is not recorded in official landing statistics. Available time series data indicate that fish consumption in Brazil, as well as commercial fish landings in Peru and Colombia, have declined in recent years. Local case studies, national household consumption and expenditure surveys (HCES), and market surveys, all have their benefits and drawbacks. Some minor modifications of HCES procedures could considerably improve their usefulness for estimating fish landings in the Amazon Basin. To improve such estimates, we propose that local case studies be used to calibrate HCES data, thus combining the high precision of local case studies with the wide coverage and representativity of HCES data

Morphometric variations associated with breeding season in obtuse barracuda, Sphyraena obtusata Cuvier, 1829 observed from the commercial fish landings at Vizhinjam, Kerala, India

Marine biology,marine ecology,Phytoplankton, marine algae, zooplankton, nekton, benthos, corals and coral reefs, ecology, zoogeography and systematics, primary production and experimental work on ecosystem including energy flow at different trophic levels, population dynamics and theoretical models, recycling of matter, influence of environmental factors on metabolic activity, marine microbiology, mariculture and experimental work on propagation of cultivable species, biology of fishes, marine reptiles, sea birds and mammals, physical, chemical, geological and meteorological features of the environments related to marine biology, marine environmental damage caused by pollution and engineering works, underwater observations, conservation of living resources, modifications in methodology and techniques and development of new apparatus related to marine sciences

Trace elements in muscle tissue of three commercial shark species: Prionace glauca, Carcharhinus falciformis, and Alopias pelagicus off the Manzanillo, Colima coast, Mexico.

Given their predatory characteristics, long life, and high trophic levels, sharks can have a remarkable ability to bioaccumulate and/or biomagnify trace elements (TE). In the present study, 13 TE (Hg, Pb, Cd, Cu, As, Se, Zn, Cr, V, Fe, Ni, Co, and Mn) were analyzed in the muscle tissue of three shark species (Prionace glauca, Carcharhinus falciformis, and Alopias pelagicus) using high-resolution mass spectrometry inductively coupled to a plasma generator (HR-ICP-MS); 30 shark specimens of each specie were obtained during commercial fish landings in the port of Manzanillo, Mexico. The morphometric characteristics and sex of the sharks were recorded. Shark A. pelagicus accumulated higher concentrations of TE, especially for Hg and Cd, than the other species. Significant differences in the TE levels were detected between sexes in P. glauca and A. pelagicus; in all cases, the highest concentrations were found in female muscle tissue. The ability of sharks to bioaccumulate ETs depends of the metals (essentials higher than non-essential) but is explained mainly by feeding habits associated to sexes (population segregation) and size (ontogeny). The association between TE in shark specimens was related to the essentiality, their antagonistic action, and origin. The Se/Hg ratio was significantly higher than 1, evidence of the protective role of dietary Se against Hg uptake and toxicity in all specimens of the three shark species. Also, the elevate inverse correlation of As and Cd versus Se could indicate a protective action of Se against these toxic metals, but the mechanism must be investigated.

Population characteristics of five major commercial fish species of the Tono Reservoir in northern Ghana

AbstractFive major commercial fish species, comprising Sarotherodon galilaeus, Oreochromis niloticus, Coptodon zillii, Clarias gariepinus and Auchenoglanis occidentalis of the Tono Reservoir fishery, were studied from January, 2015 to December, 2016 using length‐based models to establish the state of the stocks. Routines in the FAO‐ICLARM Stock Assessment Tools II (FISAT II) were used to determine the growth and mortality parameters, exploitation rates (E) and recruitment patterns of the length–frequency data generated from commercial fish landings and experimental catches. The growth coefficients (K) of the five fish species ranged 0.48–4.89 per year; asymptotic lengths (L∞) ranged from 18.38 to 76.16 cm; and hypothetical ages (t0) ranged between 0.03 and 0.28 years. All five fish species were exploited above the optimal exploitation rate (Eopt = 0.5), indicating overfishing of the species. There was a year‐round recruitment, with major and minor peaks corresponding with the major and minor spawning seasons. Fishing gear regulation and community‐based co‐management system were some management options recommended to enhance sustainable exploitation and management of the fishery.

Ecological Dynamics in the Kinneret Littoral Ecosystem

A study of the Kinneret Littoral ecosystem is presented. Environmental parameters were integrated, aimed at evaluation of the Littoral ecosystem functioning: Water Level Fluctuations Index (WLFI), commercial fish landings with respect to stock assessment, fingerling food sources and density distribution, the beach vegetation impact, spawning intensity of nest builder-mouth breeder tilapias. It is concluded that WLFI is not affecting reproduction whilst long-term low WL altitude reduces the intensity of nesting by Sarotherodon galilaeus and Tristramella simonis simonis. Low WL did not affect reproduction of Coptodon zillii (Syn. Tilapia zillii). Density of fingerlings was not correlated with Inundated Beach vegetation during WL decline. Nevertheless, submerged macrophytes and shadowing Tamarix trees were preferably utilized by fingerling shoals as documented in the north-eastern half open lagoons of the lake shallows (Beteicha).

Recent changes in fish communities of the equatorial Lake Naivasha, Kenya

Changes in fish species composition and abundance in Lake Naivasha were investigated monthly for a period of 12 months. Data were obtained both from experimental surveys as well as commercial fish landings. The structure metrics considered included species abundance and composition, length- frequency and physico-chemical attributes. Results of the study showed that the fishery is currently dominated by the recently introduced common carp,Cyprinus carpio accounting for over 95% of the total fish landings, with the naturalized fish populations performing dismally both in terms of abundance as well as health conditions. The entry of the common carp into Lake Naivasha may have completely transformed the lake’s ecosystem integrity, driving the initially abundant tilapiine species to near local extinction. The study also confirms a restricted distribution of Micropterus salmoides to rocky-bottomed habitats of Hippo Point and Crescent Lake. Conversely, the long-fin barb, Barbus paludinosus,initially confined to the north swamp and the mouth of River Malewa, currently exhibits a lake-wide distribution. The changing climatic conditions as manifested in the lake level recessions may be a real threat to the fish stocks in the lake. Human activities in the catchment areas may also have contributed to the recent ecological changes witnessed in Lake Naivasha. This study proposes a number of recommendations with a view to ensuring ecosystem integrity and consequent sustainable fisheries of Lake Naivasha. Key words: Ecosystem integrity, habitat preference, species introductions, sustainable fisheries, fish population, equatorial lake.

Mercury in the Gulf of Mexico: Sources to receptors

Gulf of Mexico (Gulf) fisheries account for 41% of the U.S. marine recreational fish catch and 16% of the nation's marine commercial fish landings. Mercury (Hg) concentrations are elevated in some fish species in the Gulf, including king mackerel, sharks, and tilefish. All five Gulf states have fish consumption advisories based on Hg. Per-capita fish consumption in the Gulf region is elevated compared to the U.S. national average, and recreational fishers in the region have a potential for greater MeHg exposure due to higher levels of fish consumption. Atmospheric wet Hg deposition is estimated to be higher in the Gulf region compared to most other areas in the U.S., but the largest source of Hg to the Gulf as a whole is the Atlantic Ocean (>90%) via large flows associated with the Loop Current. Redistribution of atmospheric, Atlantic and terrestrial Hg inputs to the Gulf occurs via large scale water circulation patterns, and further work is needed to refine estimates of the relative importance of these Hg sources in terms of contributing to fish Hg levels in different regions of the Gulf. Measurements are needed to better quantify external loads, in-situ concentrations, and fluxes of total Hg and methylmercury in the water column, sediments, and food web.

Bootstrapping Your Fish or Fishing for Bootstraps? Precision of Welfare Loss Estimates from a Globally Concave Inverse Demand Model of Commercial Fish Landings in the U.S. Great Lakes

We extend Holt and Bishop's (2002) normalized quadratic inverse demand function by obtaining measures of precision of elasticities and consumer welfare loss estimates due to reductions in commercial landings in the U.S. Great Lakes. Even with curvature constraints imposed, confidence intervals are obtained by using the bootstrap, subsample bootstrap, and subsample jackknife.

Piscivorous birds as top predators and fishery competitors in the lagoon ecosystem

Piscivorous birds have received much attention with respect to competition with fisheries for resources. The majority of studies have been focused on cormorants Phalacrocoracidae, while predation by other piscivorous bird species has often been overlooked. This study was designed to supplement sociological research (Bell, 2004), which revealed that the fishermen community at the Lithuanian section of the Curonian Lagoon considers great cormorants Phalacrocorax carbo, but not other fish-eating birds, to be significant competitors of fish resources. In this paper, we estimate fish consumption by cormorants and other abundant piscivorous birds, and attempt to interpret this level of predation in relation to fish resources and commercial fishery landings. We estimate that four piscivorous bird species consumed nearly 700 tonnes of fish during the breeding season of 2001 and winter 2001/2002, which corresponds to ~9% of the total fish resources in our study area. Bird consumption equalled two-thirds of the amount of fish landed by commercial fishermen. However, we argue that direct competition between birds and humans for fish resources is low, because there is a size segregation of exploited fish stock segments and abundant fish species that dominate the diet of birds. Fish monitoring and commercial fish landings indicated no apparent changes in fish stock size and composition, which could be attributed to a recent increase in piscivorous birds. Great cormorants consumed the largest biomass of fish compared to other piscivorous bird species. However, total fish intake by grey herons Ardea cinerea, great-crested grebes Podiceps cristatus, and goosanders Mergus merganser combined, equalled that of cormorants. Our results do not support the common public perception that cormorant predation greatly exceeds that of other piscivorous birds, and is detrimental to commercial fisheries.

Patterns of commercial fish landings in the Loreto region (Peruvian Amazon) between 1984 and 2006

Patterns of commercial fish catches over the period from 1984 to 2006 were studied in the Loreto region and in Iquitos, which is the most important town of the region and the principal fish marketplace of the Peruvian Amazon. Despite important inter-annual variations, the overall fish landings have significantly increased in the region during this period. The same three species dominated the catches during the whole period (Prochilodus nigricans, Potamorhina altamazonica and Psectrogaster amazonica), making up about 62% of the catches. However, the number of species exploited by commercial fisheries increased considerably during the 22 years of this study (from about 21 species in 1984 to over 65 in 2006), although part of the difference may be accounted for by a better identification of individual species nowadays. At the same time, the large high-valued species, such as Arapaima gigas, Colossoma macropomum and Brachyplatystoma rousseauxii, declined significantly and were replaced by smaller, short-lived and lower-valued species. Catches of the silver Arahuana (Osteoglossum bicirrhosum) also declined significantly during the studied period, strengthening recent warnings about the species' conservation status (Moreau and Coomes, Oryx 40:152-160, 2006). The relative proportions of the trophic groups (detritivores, omnivores and piscivores) remained relatively constant over the study period, but there were significant changes in the relative abundances of the species groups. The proportion of the dominant group, the Characiformes, which averaged about 81% of the catches, increased between 1984 and 2006, whereas the proportion of the Siluriformes and Perciformes remained constant. On the other hand, the proportion of Osteoglossiformes, represented only by two well known species (Arapaima gigas and Osteoglossum bicirrhosum), declined sharply during the same period. Important differences were observed between the landings of Iquitos and the landing of the whole Loreto region, indicating that conclusions drawn from the study of the Iquitos landings cannot be extrapolated to the whole landings of the Loreto region. The most important difference was the decreasing fish landings in Iquitos, whereas the total landings increased in the Loreto region at the same time. Potential causes of this phenomenon are discussed. Decreasing fish abundance around Iquitos (because of a higher fishing pressure) and a behavioural adaptation of fishermen to better law enforcement in Iquitos are likely explanations to be further investigated.

Uncertainty in ocean‐dumping health risks: Influence of bioconcentration, commercial fish landings and seafood consumption

AbstractHuman consumption of marine organisms that have been contaminated by ocean disposal of municipal sewage sludges may pose significant health risks. Previous models of ocean dumping health risk, however, have failed to assess uncertainties associated with model parameters. This failure has resulted in risk assessments that may be misleading to policymakers. Uncertainties regarding contaminant bioaccumulation, commercial fish landings and seafood consumption were incorporated into a model of carcinogenic health risk for two materials found in municipal sewage sludges, dichlorodiphenyltrichloroethane and metabolites (DDT‐R) and polychlorinated biphenyls (PCBs). Iterative Latin hypercube simulation was employed to generate probability distributions of health risks. Results indicate that parameter variability and uncertainty, particularly in bioaccumulation models, can lead to a several‐orders‐of‐magnitude range in estimated risk values. This distributional range straddles current risk‐management thresholds, suggesting that ocean disposal of municipal sludges may, indeed, pose substantial health risks to seafood consumers under certain sets of conditions and assumptions. Moreover, if not explicitly considered in risk models, uncertainty can lead to errors in risk‐based decision making.

Distribution, abundance and food of commercial fish in the Black Volta and the Volta Man-made Lake in Ghana during the filling period (1964–1968). II. Characidae.

The characids Alestes and Hydrocynus are common fish of the Black Volta River in Ghana. In Lake Volta, which formed in 1964 after damming the Volta River, Alestes formed a large percentage of commercial fish landings since the beginning of impoundment. However, this genus has been gradually changing its areas of distribution in the lake, and from the third year on it has been occupying mainly the upper end of the new lake. This area with large inflowing rivers has been found to favour Alestes baremose, which has been congregating there in large numbers. The strictly lacustrine environment of the south was poor in Alestes for some time. This was evidently due to overfishing, natural mortality, emigration of the fish from this area, and possibly to small recruitment because of the poorly oxygenated waters during the first two years of impoundment. With time, however, the numbers of Alestes baremose, Alestes dentex senthente, and especially Alestes macrolepidotus have increased in commercial landings in the south.

Californian Fisheries

THE report on the commercial fish catches of California for the year 1940 (State of California Department of Natural Resources. Division of Fish and Game. Bureau of Marine Fisheries. Fish Bulletin No. 58 ; 1942) makes available the summaries of commercial fish landings in each region of the State and also includes tables of numbers and nationality of the commercial fishermen and the number of boats of each type engaged in the fishery. A rapid development of the shark fishery is outstanding and is caused by the high price offered for liver oils of high vitamin A potency. This increase in the shark fishery, with intensive mackerel fishing and the large amount of sport fishing, has resulted in an increase of 350 boats fn 1940-41 registrations over the previous year and is most noticeable in the group between 25 ft. and 39 ft. Jong. There has been a steady development of sport fishing in the ocean waters of Southern California, and the amount of small fish required as bait nuist be considered together with its effect on the several species used as bait. The statistical records include not only the sport catch itself but also the harvesting of the small-sized fishes used by the anglers for bait. Sardines and anchovies are the most important in the bait catch,, comprising 98 per cent of the total, the fishes being 2½-6 in. long. A useful list of the common and scientific names of fishes, crustaceans and molluscs involved in the fisheries is given at the end of the report.