No abstract

During the 1957-58 winter,

This paper reports a new result for the isotopic differences between the left and right sagittal otoliths of Pacific halibut Hippoglossus stenolepis, a flatfish with both eyes on the right side. Using microsampling techniques we were able to collect subsamples from the nucleus and the 5 th and 8 th annulus from 63 pairs of halibut otoliths. Isotopic analyses of δ 13 C and δ 18 O showed that there was a significant difference between the left and right side otoliths from the nucleus in both Washington Coast and Puget Sound samples; but no significant difference from the 5 th and 8 th annuli of the same otoliths. These results were difficult to be explained as the differences in environmental parameters between ocean and estuary, but the mass accumulation from growth bias that was caused by gravitational force. The management implications on the results are clear: when using the nucleus of flatfish samples on stock structure investigations, one should consider the possible isotopic differences between the left and right side otoliths. However, when using the same samples for adult population, one may choose otoliths from either sides.

A previous study found that use of the traditional halibut hook (čibu.d) of the Makah Tribe in present day recreational Pacific halibut (Hippoglossus stenolepis) fisheries significantly reduced bycatch compared to paired 8/0 circle hooks. The study also found that the čibu.d had a significantly reduced catch of halibut, but that the reduction may have been due to manufacturing flaws in the čibu.d used in the study. In this two-phased study, we first compared the fishing performance of redesigned čibu.d made from four different materials: brass, stainless steel, plastic, and wood. In the second phase, we compared the fishing performance of the brass čibu.d with two common recreational fishing set-ups: a single large 16/0 circle hook and paired 8/0 circle hooks. The fishing performance of the redesigned čibu.d was not statistically different for čibu.d made of brass, stainless steel, or plastic. However, the čibu.d made from wood had significantly lower catch of halibut than the other čibu.d. We selected the brass čibu.d for the second phase of the study for continuity with the previous study of čibu.d and found that it had significantly less bycatch and a lower bycatch ratio than both the paired 8/0 and single 16/0 circle hooks. No significant differences were found in catch rates of halibut for paired 8/0 circle hooks, 16/0 circle hook, and the brass čibu.d. This study demonstrates that the improved catching performance of čibu.d on halibut and reduced bycatch compared to other popular approaches can be achieved by using brass čibu.d. Managers of recreational halibut fisheries should consider the use of čibu.d in areas where bycatch is a concern.