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


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Al-Qartoubi, IAR 2009 , 'An assessment of the catching performance of circle hooks and J-hooks in the Demersal longline fishery in the Sultanate of Oman', Research Master thesis, University of Tasmania.

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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
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 Omani

Item Type: Thesis - Research Master
Authors/Creators:Al-Qartoubi, IAR
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Copyright 2009 the AuthorAuthor - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
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