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  • 1
    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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  • 2
    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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  • 3
    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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