Ak. Woll et al., Catch rates and hook and bait selectivity in longline fishery for Greenland halibut (Reinhardtius hippoglossoides, Walbaum) at East Greenland, FISH RES, 51(2-3), 2001, pp. 237-246
A joint Norwegian-Greenland longline survey was conducted at East Greenland
in August 1997, using different hook and bait types. Most Norwegian longli
ners use hooks of the type EZ 12/0. This hook was compared to three version
s of a new circle 14/0 hook. A total catch of 2899 Greenland halibut from 4
5,760 hooks baited with squid were used in the hook selectivity analyses. I
n average, CPUE was 281 kg/1000 hook for the EZ hook. CPUE for the circular
hook was 36% higher making an overall significant difference in CPUE betwe
en the EZ hook and the circle hooks, On 6630 hooks squid and grenadier were
used alternately. The CPUE of Greenland halibut was 25% higher for grenadi
er bait. The grenadier bait resulted in a reduction in bycatch compared to
the squid bait (1.1 and 20.7% by numbers, respectively). Catches by EZ 12/0
hook and one of the circle 14/0 hooks were compared in order to examine si
ze selectivity. Using the SELECT approach, expected proportions were fitted
to the observed proportions for five different models of selectivity. All
models resulted in almost identical fits. The absence of non-selective data
requires the choice of selectivity curve to be based on knowledge about th
e capture process. Since the selectivity curves cannot be determined unambi
guously in this study, none of the estimated curves are preferred for the o
ther. (C) 2001 Elsevier Science B.V. All rights reserved.