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Growth And Mortality Of The Malaysian Cockle (Anadara Granosa L.) Under Commercial Culture: Analysis Through Length-Frequency Data - BOBP/WP/47









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    Project
    Report on the regional training course on fish stock assessment 1991
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    Chambo is a species complex consisting of three tilapine cichlids (Oreochromis lidole, O. quamipinnis, O. karongae) endemic to Lake Malawi. Taxonomic identification is problematic at the young stages of the fishes. Chambo constitute the basis of an important commercial and artisanal fishery. Length frequency data were collected three times per month from a commercial midwater trawl. The von Bertalanffy growth parameters obtained by the Bhattacharya method and Gulland and Holt plot are cons idered not valid according to the authors knowledge of the species biology and fishery. Then a set of growth and natural mortality parameters was forced to proceed into the analysis. Catch curve method was applied to achieve an estimate of the total mortality. Virtual population analysis (Jones' length cohort analysis)- shows that only the large size fish are exposed to the fishing mortality. It was also stressed that there is need for more representative samples to get more meaningful res ults. Experimental bottom trawl-survey was carried out between 1981-1986 in the Ugandan side of Lake Victoria. Daily commercial catches from various fish landings were available. The individual length and weight data set used in the analysis was from Jana-Nsadzi area of the lake. Data have been collected in June, September, November and December 1981. Batthacharya method and Gulland and Holt plot were used to estimate the growth parameters. The catch curve analysis supplied the total morta lity value. Jones' length cohort analysis was applied to obtain the exploitation pattern. Finally long term prediction was carried out using the Thompson and Bell model. The total yield and the calculated Maximum Sustainable Yield (MSY) for the Ugandan side of the lake seem to suggest the overexploitation of Synodontis victoriae. This scenario is considered unrealistic.
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    Book (stand-alone)
    Investigations on the Mackerel and Scad Resources of the Malacca Straits - BOBP/REP/39 1987
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    This report summarizes the findings and results of investigations concerning the mackerel resources of the Malacca Straits undertaken during 1984-1986. These were organized by a working group established for this purpose in 1983, consisting of fishery biologists from Indonesia, Malaysia and Thailand. The objectives were to examine available data on the mackerel resources of the Malacca Straits (Indonesia, Malaysia and Thailand) to identify lacunae in the data, suggest improvement to data collect ion systems and analyse the present status of the resources. The first meeting of the group was held in Penang, in December 1983. The outcome of that base line meeting was summarised in an earlier publication (BOBP/WP/30). Following the recommendations of the first meeting, sampling programmes were improved in all three countries and sampling study tours and training programmes were conducted. Progress was monitored and discussed at the second and third meetings of the working group held in Colombo (Oct. 1985) and Phuket (Aug. 1986). This report incorporates the deliberations of these two meetings. This report, the sampling programmes and the working group meetings were sponsored by the “Marine Fishery Resources Management” component of the Bay of Bengal Programme (BOBP). The project commenced in January 1983 and terminated December 1986. It was funded by the UNDP (United Nations Development Programme). Its immediate/objective was to improve the practice of fishery resource s assessment among participating countries and to stimulate and assist in joint management activities between countries sharing fish stocks.
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    Document
    Preliminary estimates of some stock assessment parameters for the mesopelagic species Benthosoma pterotum inhabiting the Western and Northern Arabian Sea 1982
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    This report provides preliminary estimates of the stock assessment parameters for Benthosoma pterotum from data collected onboard the acoustic survey vessel Dr. Nansen. The von Bertalanaffy growth estimates are K=2.0, L=5.2 cm (total length) and t =-0.09, the latter being related to assumed birthday dates of 30 April and 31 December. The constants in the power curve relationship (w = aLᵇ) of total weight (g) to total length (cm) are shown as a = 0.02, and b = 2.79. Four alternative estimates for the natural mortality coefficient M provide values of 3.6, 5, 4.8 and 4.3 for the 1975 and 1976 years. The mean numbers recruiting into the stock each half year is estimated to be 123x10¹². Recruitment is indicated as being confined to the summer to autumn and winter to spring periods, which suggests an explanation for the observed differences between biomass estimates from previous acoustic surveys; the stock numbers peak in spring and autumn from the effect of 'net' recruitment and decline to wards summer and winter from the effect of natural mortality. With the assistance of Yield per Recruit Tables, annual yields for a range of levels of exploitation and lengths at first capture are described. For example, using trawls providing a length at first capture of about 2 cm, the annual yield is maximized at about 17.5x10⁶ tones, at a fishing mortality F of almost double M. It is suggested that the most appropriate levels of future exploitation are likely to be considerably lower than in the example with the identification of the best levels requiring additional knowledge, such as concerning commercial operating costs, availability of markets etc.

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