Improving the size selectivity of crayfish fyke-net codend, applying the hexagonal mesh and sorting grid
Mehmet Cilbiz
A * and Celalettin Aydın B C
A
B
C
Abstract
Owing to the use of fyke-nets with poor size selectivity in crayfish fishery, 40.7% of the landed undersized catch is discarded as bycatch.
This study investigated the effects of using hexagonal mesh (Hex34) instead of diamond nets (Com34) in the traditional crayfish fyke-net and the application of a sorting-grid (SG20, SG25, SG30) and stiff-rigged net (SRN34, SRN42, SRN50) on size selectivity.
A covered codend technique was used for determining the size selectivity of codends.
The average length at 50% retention probability (L50, in total length) for the trial groups of Com34, Hex34, SG20, SG25, SG30, SRN34, SRN42 and SRN50 was estimated as 9.1, 9.5, 10.1, 11.0, 12.3, 10.0, 10.3 and 11.1 cm respectively. Additionally, the discard rates were computed in the same order as 37.0, 27.3, 14.9, 5.8, 1.9, 19.1, 9.4 and 7.7%.
In conclusion, commercial crayfish (Com34) fyke-nets have a significantly high discard rate. In the modifications tested, the discard rate has been reduced to as low as 1.9%. When taking into account both L50 and fishing efficiency indicators, SRN42 was determined as the most successful trial group.
The application of the study results will make a significant contribution to the sustainability of natural crayfish stocks of Türkiye.
Keywords: bycatch, crayfish, Eğirdir Lake, inland fisheries, SELNET, size selectivity, small-scale fisheries, sustainability.
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