No abstract

No abstract

No abstract

No abstract

No abstract

-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.

SUMMARY: Fishing trials with monofilament gill nets and longlines using small hooks were carried out in Algarve waters (southern Portugal) over a one-year period. Four hook sizes of "Mustad" brand, round bent, flatted sea hooks (Quality 2316 DT, numbers 15, 13, 12 and 11) and four mesh sizes of 25, 30, 35 and 40 mm (bar length) monofilament gill nets were used. Commercially valuable sea breams dominated the longline catches while small pelagics were relatively more important in the gill nets. Significant differences in the catch size frequency distributions of the two gears were found for all the most important species caught by both gears (Boops boops, Diplodus bellottii, Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, Spondyliosoma cantharus, Scomber japonicus and Scorpaena notata), with longlines catching larger fish and a wider size range than nets. Whereas longline catch size frequency distributions for most species for the different hook sizes were generally highly overlapped, suggesting little or no differences in size selectivity, gill net catch size frequency distributions clearly showed size selection. A variety of models were fitted to the gill net and hook data using the SELECT method, while the parameters of the logistic model were estimated by maximum likelihood for the longline data. The binormal model gave the best fits for most of the species caught with gill nets, while the logistic model adequately described hook selectivity. The results of this study show that the two static gears compete for many of the same species and have different impacts in terms of catch composition and size selectivity. This information will be useful for the improved management of these small-scale fisheries in which many different gears compete for scarce resources.Key words: gill nets, hook, longlines, artisanal, multi-species, selectivity, Portugal, Algarve. RESUMEN: CUANTIFICANDO EL PAPEL DE ARTES ESTÁTICOS EN COMPETENCIA: SELECTIVIDAD COMPARADA DE PALANGRES Y REDES DE ENMALLE EN UNA PESQUERÍA MULTIESPECÍFICA EN EL ALGARVE (SUR DE PORTUGAL). -En aguas del Algarve (Sur dePortugal) durante un año se han llevado a cabo pescas experimentales con redes de enmalle monofilamento y palangres con anzuelos pequeños. Se utilizaron cuatro tamaños (Calidad 2316DT, números 15, 13, 12 y 11) de anzuelos curvados y aplanados, de la marca: "Mustad", y redes de enmalle monofilamento de cuatro tamaños de luz de malla 25, 30, 35 y 40 mm. Por su valor comercial, los espáridos son las especies más importantes de las capturadas por los palangres mientras que los pequeños pelágicos son los de mayor importancia relativa de las capturadas por las redes de enmalle. Se han encontrado diferencias significativas entre los dos tipos de artes en las distribuciones de frecuencias de tallas para todas las especies más importantes capturadas por ambas artes (Boops boops, Diplodus bellottii, Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, Spondyliosoma cantharus, Scomber japonicus y Scorpaena notata). Con los palangres se capturaro...

No abstract