An assessment of the catching performance of circle hooks and J-hooks in the Demersal longline fishery in the Sultanate of Oman

The objectives of this study were to evaluate performance in efficiency and selectivity of two hook types, namely, circle hooks and J-hooks used in demersal longline gear in Omani waters. To achieve these objectives, in December 2004 a longline experiment was conducted at three fishing locations at Masirah Island in the Sultanate of Oman. A total of 6 120 baited hooks (3 060 (no. 6) J-hooks and 3 060 (no. 6) circle hooks) were deployed over a 17-day period. The results indicated that 90% and 89% of circle- and J-hooks respectively were retrieved. Of the total catch of 581 fish (924 kg), the circle hooks caught 63% by numbers and 51% by weight. It was found that the catch of both hook types were dominated by one family (Lethrinidiae) and one species (Lethrinus microdon), which accounted for 38% by weight and 48% by number of all total catch. The noncommercial species accounted for 12% by weight and 7.4 % by number of the total catch. With particular reference to the total catch, where the commercial catch is significantly higher than the non-commercial catch, the effectiveness of the circle hook is significantly higher than that of the J-hook. In the absence of output control in the fishery (that is, total allowable catch limit), and given the equal soak time for both hook types, the implication of this finding is that the circle hooks are more efficient than Jhooks in harvesting commercial species. In other words, all else being equal, the use of circle hooks could minimize the costs of fishing effort. This finding is promising from both management and fishing operational perspectives as the use of circle hooks could be promoted in the fishery. It was also found that about 90% of the commercial catch by circle hook was hooked in the corner of the mouth. However, the J-hook figure was less than 24%. This result clearly indicates that the use of circle hooks can minimize gut hooking and thereby minimize physical damage to fish caught. An important implication of this finding is that the fish caught by the circle hook would remain fresh due to less physical damage and could therefore be expected to command higher market prices for fishermen. In terms of non-commercial catch, there was no significant difference between hook types. An implication of this finding is that the circle hook does not increase the number of by-catch compared to the J-hook and thereby does not undermine the conservation of non-commercial species. The market value of catch was calculated for all commercial species. The results indicate that the average price per kg for circle hook catch was higher because more highly valued species where caught with the circle hook. Based on these findings, it could be concluded that the performance of circle hooks in relation to catching efficiency and selectivity is comparatively better than that of its counterpart and the management authority could encourage their use fully in Oman