Reproductive traits of the round sardinella in the Canary Islands (Spain, NW Africa)

The present study aims to investigate the reproductive biology of the small pelagic Sardinella aurita Valenciennes, 1847 in the Canary Islands, to enable its reliable assessment and advise on appropriate management measures for a fishing resource showing a declining trend in landings. Reproductive biology and sexual patterns of round sardinella were examined from monthly random samples of commercial catches landed by the artisanal purse-seine fleet. The landings' length frequencies, ranging between 9–32 cm (based on the total lengths, TL), were recorded from 2013–2019. The overall mean value of TL was 20.9 cm, with annual mean values between 20–22 cm, except in 2016 (TL = 19 cm). The overall sex ratio M:F was 1:0.92, with males significantly predominant. Sex ratios fluctuated as a function of size and month: females were more abundant in the larger length classes, as well as before and after spawning, whereas males were more abundant in the smaller length classes and during spawning. Based on gonad maturity stages and gonadosomatic index, round sardinella spawns during almost all the year, with a peak in January–February and a resting period during October–November. The length at first maturity was estimated at TL of 18.2 cm, notably smaller than the value obtained for the NW African coastal waters where the demographic structure in round sardinellas' landings is totally different.Versión del edito

Comportamiento reproductivo de los principales peces pequeños pelágicos capturados en las Islas Canarias (España, NW África)

Entre 2013 y 2019 se realizaron muestreos biológicos mensuales de las principales especies capturadas por la flota artesanal de cerco en las Islas Canarias, que incluyen la caballa (Scomber colias), el chicharro (Trachurus picturatus), la sardina de ley (Sardina pilchardus) y la alacha (Sardinella aurita). Excepto para la alacha (que se reproduce durante todo el año), el análisis de la evolución mensual del Índice Gonadosomático medio permitió identificar el periodo de puesta de la caballa y el chicharro (de diciembre a abril), así como de la sardina de ley (de noviembre a marzo). Estos periodos de puesta parecen estar prolongándose, probablemente debido a la disminución de contraste estacional de la temperatura y de la disponibilidad de alimento reflejados en la evolución de los parámetros oceanográficos asociados (SST y sus anomalías y concentración de clorofila a), situación que podría intensificarse en el actual escenario de Calentamiento Global. Asimismo, la variación talla media mensual reflejó posibles periodos de reclutamiento del chicharro y la sardina. Finalmente, se estimaron las Tallas de Primera Madurez, obteniéndose la primera estimación para la alacha en aguas canarias (en torno a los 18 cm), valores inferiores a las estimaciones actuales de referencia en el caso de la caballa y del chicharro (19 cm) y un valor similar al encontrado anteriormente (de 15 cm) para la sardina. Esta información actualizada es de gran valor para la evaluación del estado de estos recursos y el diseño de posibles medidas de gestión de esta pesquería.Estudio parcialmente financiado por el Fondo Europeo Marítimo y de Pesca (FEMP) a través del Programa Nacional de Datos Básicos del sector pesquero español para la recopilación, gestión y  uso de los datos del sector pesquero y el apoyo al asesoramiento científico, en relación con la Política Pesquera Común

Influence of environmental variability on population traits of small pelagic fish in the Canary Islands (NW Africa, Spain)

Small pelagic fish (SPF) present relatively short life cycles, with fast growth, high mobility and plankton-base feeding. Therefore, they are highly sensitive to fluctuations in environmental conditions, including those related to Climate Change, and fishing. On the one hand, reproductive traits have been recently described for all these species in the Canary archipelago, which show a clear decreasing pattern of their sizes at first maturity during the last years (Jurado-Ruzafa et al., 2021). On the other hand, a regional increase in the sea water temperature has been observed in NW African waters during last decades (Vélez-Belchí et al., 2015). Foreseeing potential variations in the life history traits of SPF is critical for effective management measures in the current Global Warming scenario.FEM

What scientific observations tell us about catches in the artisanal purse-seine fishery off the Canary Islands

In the Canary Islands, the small-scale fleet performs daily fishing trips, being the small pelagic species usually caught with purse-seines. In 2017, a monthly programme of scientific observations was launched to characterize the catches of the artisanal purse-seine fleet, whose discards were considered irrelevant. Here we present a summary of the species composition recorded during 61 fishing trips and the size structure of the main targeted species (i.e. Scomber colias, Trachurus spp., Sardinella spp. and Sardina pilchardus), including both the retained and discarded catches. In the period under study (2017-2021) discards reached noticeable values of around 25% of the total fish caught, attaining 40% if we look at the catches of S. colias. The main reasons observed for discarding fish are market demand and the mean size of the school caught, which generally lead to the net slipping (i.e. the process to open the purse-seine to release excess or unwanted catch into the sea), a regular practice that remains unrecorded and estimates are difficult to report.Estudio parcialmente financiado por el Fondo Europeo Marítimo y de Pesca (FEMP) a través del Programa Nacional de Datos Básicos del sector pesquero español para la recopilación, gestión y  uso de los datos del sector pesquero y el apoyo al asesoramiento científico, en relación con la Política Pesquera Común