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  • 1
    Publication Date: 2021-05-19
    Description: The occurrence of gurnard Prionotus stephanophrys was studied in the course of a series of fisheries research cruises on the Ecuadorian continental shelf between 1980 and 1985. The species is common in coastal waters south of 1°S . Its abundance is very variable, possibly associated with sea temperatures. Normally densities are between 0.8 and 1.6 t.km-2. The standing stock varies between 13,000 and 150,000 t wich it is estimated can sustain catches of around 4,000 t pet year, and up to 40,000 t in times of great abundance. P. stephanophyrs is found in large shoals on the bottom during the day but a night moves up into mid-water to feed on euphausids. The fish caught had size range of 12 cm to 37 cm, but the majority were between 16 cm and 21 cm in total length. The growth parameters and natural mortality were calculated. The present fisheries catch large quantities of these gurnards, but most is discarded at sea and the small amounts landed are only used for fish meal production. However, the flesh is of good quality and could easily be used for human consumption.
    Description: Published
    Keywords: Biomass ; Catch composition ; Biomass ; Abundance ; Catch composition ; Natural mortality
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 2
    Publication Date: 2021-05-19
    Description: A survey of demersal fish resources of the Continental Shelf of Ecuador was carried out between October 1980 an July 1985 by the National Fisheries Institute of Ecuador, with British Technical Cooperation. This report deals with the stock assessment part of the work. In the course of seven cruises, 366 valid diurnal hauls were made with a high-opening bottom trawl. The demersal fish resources were estimated by swept area methods and the results are presented. The overall average standing stock of demersal fish was 78 000 t of which 22 000 t was good fish, but 36 000 t were gurnards (Triglidae) and 3 000 t of unusable fish. The main stocks were gurnards, grunts and croakers, sharks and corvinas Cynoscion spp. The southern areas especially the Gulf of Guayaquil had the highest densities of fish (9,6 t.Km-2 or 4,0 t.Km-2 excluding gurnards). There was a massive abundance of the gurnard, Prionotus stephanophys in 1984 and 1985. There was a general decrease and other changes in the demersal stocks due to the effects of the ”El Niño” in 1983.
    Description: Published
    Keywords: Demersal fisheries ; Geographical distribution ; Biomass ; Demersal fisheries ; Geographical distribution ; Abundance ; Biomass
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 3
    Publication Date: 2021-05-19
    Description: The seasonal variation of diversity, density and biomass of the main species of the bentho-demersal fauna present in the 'prawn-shrimp' fishing grounds in the coastal sector between Cabo Corrientes and Torreon del Monje, Mar del Plata (38 degree S-57 degree W), Argentina, was studied. The quali-quantitative information obtained allowed to know the fluctuations of the bentho-demersal components of the community. The study included the annual cycle between April 1998-April 1999. Monthly samples at different depths (4-10 m) and distance from the coast (500 and 1,000 m) were obtained in two stations using a bottom net. Sampling in each station lasted 15 minutes and covered 2,400 m super(2). Number of specimens and weight for each species were recorded. Abundance of species, density (individuals 100 m super(-2)), biomass (g 100 m super(-2)) were registered. The number of captured species, density and biomass fluctuated throughout the year. A total of 28,437 individuals corresponding to 8 taxa at Phylum or Class level were captured. A total of 66 different taxa at specific level (22 crustaceans, 19 fishes, 14 mollusks, 5 cnidarians, 3 polychaetes, one pygnogonid, one urochordate and one sponge) were caught. The bentho-demersal community studied is typical of a temperate marine environment where few taxa are dominant over a large number of occasional species. The prawn Artemesia longinaris (Penaeidae) was considered the dominant species (62% in number). Three other species were considered subdominant: juveniles of stripped weakfish Cynoscion guatucupa (Sciaenidae) accounting for 12.5%, sergestid Peisos petrunkevitchi (Sergestidae) for 10.1% and red prawn Pleoticus muelleri (Solenoceridae) for 3.5%. The remaining 11.8% corresponded to sixty-four occasional species that were 〈 2% in abundance each. Density ranged from 14 to 129 specimens 100 m super(-2) and biomass between 192-638 g 100 m super(-2). The Shannon-Wiener diversity index was statistically different between sampled stations and during the annual cycle. Mean annual diversity value for both stations was H'=2,151 bit/ind. Species diversity and variation in richness were found to be directly related to sea water temperatures during the annual cycle. This quali-quantitative information will be considered as base line to assess the environmental impact of different human activities (tourism, artisanal and commercial fisheries, discharge of agricultural, urban and industrial effluents, etc.) on the coastal ecosystem.
    Description: Published
    Description: Artemesia longinaris, Peisos petrunkevitchi, Pleoticus muelleri, Cynoscion guatucupa, camarón, langostino, pescadilla, zoobentos, abundancia, zona litoral, zonas de pesca, diversidad de especies, captura incidental,
    Keywords: Biomass ; Zoobenthos ; Fishing grounds ; Species diversity ; Zoobenthos ; Fishing grounds ; Biomass ; Abundance ; Littoral zone ; Species diversity ; By catch
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: 911554 bytes
    Format: application/pdf
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  • 4
    Publication Date: 2021-05-19
    Description: The stock estimates obtained during the demersal fish resources survey in 1980-1985 were used to estimate the potential yields of demersal stocks of the Ecuadorian Continental Shelf. The difficulties of predicting yields for multispecies fisheries are discussed and modified version of the Gulland model was adopted. The potential realizable yields for multispecies fisheries are discussed and a modified version of the Gulland model was adopted. The potential realizable yield was calculated to be between 15,000 t and 20,000 t per year, of which 2,000 t is good quality fish, 5,000 t per year of small and medium fish and 8,000 t of gurnards. The majority of these resources are at present being fished at around their optimum levels and any further developments that would increase the fishing effort on demersal resources which are at present being exploited should be approached with caution. The national fisheries, especially the artisanal sector play a valuable role in the country and care should be taken to see that these are not adversely affected.
    Description: Published
    Keywords: Demersal fisheries ; Continental shelves ; Demersal fisheries ; Continental shelves ; Yield predictions ; Exploitation
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 5
    Publication Date: 2021-05-19
    Description: 342 specimens of sparid Calamus brachysomus ”Palma”, collected during a demersal trawl survey by the R. V. Tohallí in April and May1983, were examined. The different techniques used to prepare scales and otoliths for ageing are described and analysed. The otoliths were determined to be the most reliable for ageing studies; 87% of otoliths were readable. The rings observed were assumed to be annual. The mean lengths at age were used to determine the parameters of the Von Bertalanffy growth formula, giving: Lt=50.13(1-e-0.1473(t+2.0704)). The growth curve obtained must be considered provisional due to possible biases in the interpretation of the otoliths, and also due to those arising from the selectivity of the fishing gear.
    Description: Published
    Keywords: Demersal fisheries ; Growth ; Otoliths ; Age ; Demersal fisheries ; Age ; Growth ; Growth curves ; Otoliths ; Otolith reading
    Repository Name: AquaDocs
    Type: Journal Contribution
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