No abstract

We examined the effects of different hook style and bait type combinations on the catches of targeted, bycatch, and discarded fishes in equatorial atlantic waters. in total, 221 longline sets (>305,000 hooks) were deployed from portuguese pelagic longline vessels (sElEct-pal project) during the february-october fishing season. Three different hook styles and two bait types were tested: the traditional J-hook was compared to two circle hooks (one non-offset and one with 10° offset), and squid bait was compared to mackerel. catch per unit effort (cpuEs) were calculated and compared between the different hook style and bait type combinations, which indicated that the effects of hook style and bait on the cpuEs were species-specific. for example, swordfish cpuEs were higher with J-hooks baited with squid, while for targeted tunas and blue shark only the bait effect was significant, but with opposite effect (i.e., higher catches of tuna with squid bait and higher catches of blue shark with mackerel bait). for the discarded species, at-haulback mortality was also species-specific. proportions of alive vs dead specimens at time of fishing gear retrieval did not vary significantly by hook style or bait type combinations. The total retained catch was analyzed in value per unit effort (VpuE), and indicated losses in fishery revenue when mackerel was used instead of squid, but not when circle hooks were used instead of J-hooks.

-Hooking (or "at-haulback") fishing mortality was analysed in elasmobranchs captured by Portuguese longliners targeting swordfish in the Atlantic Ocean. Information was collected by on-board fishery observers who monitored 834 longline fishing sets between August 2008 and December 2011, and recorded information on 36 067 elasmobranch specimens from 21 different taxa. The hooking mortality proportions were species-specific, with some species having relatively high percentages of live specimens at time of haulback (e.g., blue shark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others had higher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeye thresher). For the most captured species (Prionace glauca, Pseudocarcharias kamoharai, Isurus oxyrinchus and Alopias superciliosus), logistic generalized linear models (GLMs) were carried out to compare the mortality rates between sexes, specimen sizes and the regions of operation of the fleet. The sex-specific proportions of hooking mortality were significantly different for blue and crocodile sharks, with the males of both species having higher proportions of hooking mortality than the females. Specimen size was significant for predicting the hooking mortality for blue and shortfin mako sharks: in both cases, the larger specimens had lower odds of dying due to the fishing process. There were differences in the hooking mortality depending on the region of operation of the fleet, but those differences were also species-specific. For blue and crocodile sharks, the hooking mortality was higher in the Equatorial and southern Atlantic areas (when compared to the NE Atlantic region), while the opposite was observed for the shortfin mako, with lower mortality rates in the NE tropical area compared with the other regions. The results presented in this paper can be integrated into future ecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the new information can be used to evaluate the impact of recent recommendations prohibiting the retention of some vulnerable elasmobranch species.

From February 2005 to September 2007, a total of 490 crocodile sharks Pseudocarcharias kamoharai, caught as by-catch in the swordfish and tuna longline fishery that operates in the tropical western Atlantic Ocean, was studied in regard to their reproductive biology. Maximum observed total lengths (L(T)) were 1220 and 1090 mm for females and males respectively, with a high proportion of the catch being composed of mature specimens. Sexual maturity was attained at 760-810 mm L(T) for males (L(T50) = 800 mm) and 870-980 mm L(T) for females (L(T50) = 916 mm). The size at birth was estimated at 415 mm L(T). Temporal variation in gonad morphology and mass suggests that in this region P. kamoharai, an aplacental viviparous species with oophagy, does not show a well-defined reproductive seasonality, with mating and parturition occurring possibly over an extended period of the year. Mean +/-S.D. fecundity was estimated to be 3.9 (+/- 0.6) pups per reproductive cycle.