Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- 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.
- Leader material and bait effects on target and bycatch species caught in an Atlantic Ocean pelagic longline fisheryPublication . Casaca Santos, Catarina; Santos, Miguel N.; Rosa, Daniela; Coelho, RuiThe influence of bait type and leader material on target and bycatch species was assessed through fishing experiments in the Portuguese shallow pelagic longline fishery in the Atlantic Ocean. Wire leaders were found to decrease catch rates of commercially valuable species such as bigeye tuna and yellowfin tuna, while increasing catch rates of elasmobranchs, including the blue shark and shortfin mako. The odds ratios of capture swordfish and tunas also decrease when using wire leaders, while elasmobranchs have higher odds ratios of capture and athaulback mortality when using wire leaders. Squid bait led to higher catches of targeted tuna species, however it also resulted in higher catches of marine turtles. For most of the taxa caught at-haulback mortality risk was found to be higher on squid bait, which may be related with increased deep-hooking events. While bait type and leader material did not significantly affect size selectivity for most species, wire leaders were found to retain larger blue sharks and fish bait attracted smaller-sized swordfish. This study showed that banning wire leaders on pelagic longline fisheries is an effective measure for reducing the retention of pelagic shark species, particularly of large size blue sharks.