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Preliminary assessment of hook sink rates using two branchline types (PDF, 1,200 K)

Summary

Time depth recorders (TDRs) were used to compare the rate at which baited hooks sank on two types of branchlines aboard the pelagic longliner, F.V. Ikatere. A normal monofilament branchline was compared with an experimental branchline which had a short terminal wire section with a lure. The mean depth of the hooks 30 seconds after deployment (i.e. at the end of the protection zone
afforded by the tori line) was 8.31 ± 0.56 m (range 5-10 m) for the normal branchlines and 10.56 ± 64 m (range 8-13 m) for the experimental ones. The tori line coverage was estimated as 100-144 m behind the vessel (or c. 30-40 s) at the normal setting speed of 3.6 m/s, which appears to be above average for the vesselís size. Further research should investigate whether the gain in sink rate achieved with the experimental branchline can be replicated on other vessels.