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- An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic OceanPublication . Coelho, Rui; Fernandez-Carvalho, Joana; Lino, Pedro; Santos, Miguel N.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, logistic 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.
- Standardized CPUE and size distribution of the shortfin mako shark in the portuguese pelagic longline fishery in the AtlanticPublication . Coelho, Rui; Rosa, Daniela; Lino, PedroThis document provides fishery indicators for the shortfin mako shark captured by the Portuguese pelagic longline fishery in the Atlantic (standardized CPUEs and size distribution). The analysis was based on data collected from fishery observers, port sampling and skippers logbooks (self sampling), between 1995 and 2015. The mean sizes were compared between years, seasons (quarters), stocks (north and south) and sampling areas. The CPUEs were analyzed for the North Atlantic and compared between years, and were standardized with Tweedie and Delta GLM approaches. In general, there was a large variability in the nominal CPUE trends in the North Atlantic, and the final standardized series was flatter than the nominal. For the size distribution there were no major trends in the time series, with the sizes tending to be larger in the South Atlantic. The data presented in this document can be considered for use in the upcoming 2017 shortfin mako stock assessment, specifically the standardized CPUE for the North Atlantic and the size distribution for both hemispheres.
- Fishery indicators for the shortfin mako (Isurus oxyrinchus) caught by the portuguese pelagic longline fishery in the Atlantic: nominal CPUEs, catch-at-size and at-haulback mortalityPublication . Coelho, Rui; Rosa, Daniela; Lino, PedroThis paper provides an overview of fishery indicators for the shortfin mako shark captured by the Portuguese pelagic longline fishery in the Atlantic, in terms of catch-at-size, nominal CPUEs and at-haulback mortality. The analysis is based on data from fishery observers, port sampling and skippers logbooks (self sampling), from 1997-2015. In general, there was a large variability in the nominal CPUE trends for the north Atlantic, with a slight increase during the period. For the catch-at-size there were no major trends in the time series, but the sizes tended to be larger in the South Atlantic and with a larger variability. The at-haulback mortality was similar between sexes, with a trend for decreasing mortality rates with increasing specimen size. The data presented in this working document should be considered preliminary and is presented in preparation for the 2017 shortfin mako stock assessment in the Atlantic Ocean.