Influence of hook size and type on short-term mortality, hooking location and size selectivity in a Spanish recreational fishery

Short-term mortality and size selectivity resulting from different hook types and sizes were studied. Special emphasis was on derbio, Trachynotus ovatus, as it is commonly caught as an undersized species in recreational fisheries of the Balearic Islands (Western Mediterranean). Results showed that mortality was generally low (0-17.9%). The anatomical hook location (AHL) (the anatomical region where the hook penetrated) was the main significant predictor of mortality, as more than 85% of fish caught in deep locations of the body, such as the oesophagus, stomach or gills, died over a 2 h-holding period. Hook size was also a significant predictor of mortality because the mortality rates caused by the smallest hooks (sizes 14 and 12) were higher than those of the largest hooks (sizes 10, 8 and 6). For circle hooks, mortality and deep-hooking incidences were not observed, confirming the conservation properties of this hook type. To estimate size selectivity parameters, applied logistic models normally used in commercial fisheries were fitted to estimate descriptors of slope of selectivity curves and L(50) (length at 50% selection). Results showed that larger hooks were more size-selective than smaller hooks, but also fewer fish were caught. However, the yield (g h(-1)) between hook sizes did not change dramatically (large hooks 1345.0 +/- 179.8 g h(-1); small hooks 1467.8 +/- 66.5 g h(-1)), since large hooks tended to catch much larger fish than the smaller hooks. As a strategy to conserve resources the use of larger hooks in recreational fisheries is therefore recommended since they result in minimal mortality to released fish and reduce incidental catch of undersized fishes.