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Preliminary stock assessment for the cuttlefish Sepia pharaonis taken off the coast of the People's Democratic Republic of Yemen









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    Revised stock assessment for the cuttlefish Sepia pharaonis taken off the coast of the People's Democratic Republic of Yemen 1981
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    This paper describes a revised stock assessment for the cuttlefish Sepia pharaonis inhabiting waters off the People's Democratic Republic of Yemen. It differs from earlier assessments in that the male and female cuttlefish are considered separately.
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    Second report of mesh selection studies conducted in the People's Democratic Republic of Yemen on the cuttlefish Sepia pharaonis 1982
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    This paper describes a repeat of an earlier study by the authors, concerning the mesh selection properties of trawl cod-ends of various mesh sizes on the cuttlefish Sepia pharaonic. A brief resume of the findings is as follows: the estimated 50% selection lengths with 95% confidence limits for single braided polyethylene cod-ends of 12.4 cm, 13.6 cm and 16.8 cm mesh sizes were 17.87+0.28 cm, 20.74+- 0.53 cm and 26.95+-1.07 cm; the 50% selection lengths and selection ranges were very similar to t hose obtained in the earlier study in respect to the 12.4 cm cod-end, but higher in respect to the 13.6 cm cod-end; the 16.8 cm cod-end had not been previously used; the previously held assumption that the 50% selection lengths and cod-end mesh sizes were proportionally related was seen as inappropriate, and hence also the estimation of selection factors; the more appropriate relationship was seen to be one of non-proportional linearity, and the regression equation considered most compatible wit h the observations as 50% selection length (cm)=2.03 mesh size(cm) -7.41; for a chosen value of the 50% selection length, this equation gives substantially different values for the choice of appropriate cod-end mesh size, than the selection factors estimated from the earlier study.
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    Third report of mesh selection studies conducted in the People's Democratic Republic of Yemen on the cuttlefish Sepia pharaonis 1983
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    The results of a third cod-end mesh selection trial involving the alternate haul method are described. All cod-ends were made from single braided polyetheylene, and the mesh sizes used were 7.0 cm, 10.3 cm, 12.4 cm, 14.1 cm, 15.2 cm, and 16.9 cm; the smallest size being taken as the standard against which the others were compared. The relationship between the 50% selection lengths and mesh sizes, was found not to be different from those of the earlier two trials; combining the results from all t rials gave: 50% selection length (cm) = 2.15 x mesh size (cm) - 9.34; whose correlation coefficient is highly significant (at P<0.05).

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