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Tailoring codend mesh size to improve the size selectivity of undifferentiated trawl species
Author(s) -
Hunt D. E.,
Maynard D. L.,
Gaston T. F.
Publication year - 2014
Publication title -
fisheries management and ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 55
eISSN - 1365-2400
pISSN - 0969-997X
DOI - 10.1111/fme.12099
Subject(s) - fishery , biology , flathead , fish <actinopterygii>
Tiger flathead, Neoplatycephalus richardsoni (Castelnau), and sand flathead, Platycephalus bassensis Cuvier, are undifferentiated and managed with a common legal minimum length ( LML ). The Commonwealth Trawl Sector ( CTS ) and the Tasmanian Danish‐seine fishery ( TDSF ) use a minimum codend mesh sizes of 90 and 70 mm, respectively. The codend mesh size should be tailored to the LML , which is based on the length of first maturity of females ( M 50 ). This study found the length–girth relationship of N. richardsoni and P. bassensis was not significantly different. Using the covered codend method, these two species had 50% retention lengths ( L 50 ) of 294 ± 2 and 307 ± 3 mm, in 70‐mm and 90‐mm codends, respectively. L 50 estimates for mesh sizes from this study and others produced a curvilinear relationship: y = 120 ln( x ) − 214, with an r 2 of 0.8504. The size at maturity ( M 50 ) for female N. richardsoni was 337 mm, which is larger than the estimate for female P. bassensis (247 mm). There is a mismatch between the estimates of L 50, the estimates of M 50 and the LML s in each fishery, leading to suboptimal exploitation of female Platycephalus . The model produced in this paper recommends a codend mesh size of 98 mm for both fisheries to exploit Platycephalus species sustainably.