Estimation of the parameters of the selectivity of the gill nets used in whiting fishery

SUMMARY ESTIMATION OF THE PARAMETERS OF THE SELECTIVITY OF THE GILL NETS USED IN WHITING FISHERY In this study, the parameters of the selectivity of gill nets used of 20, 22 and 24 mm bar mesh for whiting in the Eastern Black Sea were studied. Additionally effect of color and twine diameter on the sellection factors of gill nets used were also investigated. Two methods were used. One is indirect method which is based on Holt and second one is Sechin model based on the measurements of body girth. The common selection factor for the Holt method was found to be 4.25, whilst the optimum lengths of whiting caught for the 20 and 22 mm of bar mesh were 17.28 and 19.01 cm with the selection factor of 4.32 respectively. These figures were 18.49 and 20. 17 cm for 22 and 24 cm of bar mesh, corresponding the selection factor of 4.20. Using the Sechin method, the optimum lengths of whiting caught due to 20, 22 and 24 mm of bar mesh were estimated to be 17.2, 19.0 and 20.8 cm resulting the selection factors as 8.60, 8.63 and 8.66 respectively. The effect of color of the gill nets used and diameter of the twine on the selectivity of gill net were also investigated. As a result it was found that those nets in different colors did not affect the selectivity since they are supposed to be used in deeper waters where visibility is too low. But the investigation has shown that twine No:0 was more selective that of No: 1 (both in 1 10 denier). Key Words : Whiting, Gill nets, Selectivity, Holt method, Sechin method. VI