The Atlantic Chub Mackerel (Scomber colias) in the Canary Islands (Spain): Fishery and Biological data Update

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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

Canary 2019-updating highlights

Small pelagic fishery in the Canary Islands is carried out by an interannual quite variable artisanal fleet of purse-seiners. Total landings produced by the Canary purse-seiners have experienced a decrease from 2017–2019. However, it is not the case for the Atlantic chub mackerel, which not only is the main of the four species targeted by this fleet (>50%), but whose landings have increased since 2014, with European sardine and sardinellas almost absent in 2019. Concerning the length frequencies present in landings, the most relevant observation is that a noticeable increase in the modal lengths has been registered since the beginning of the monitoring programme in 2013, from around 22 cm to individuals ≥27 cm in 2019. Regarding ongoing studies, a new work has been launched based on the otolith shape analysis of a sizable sample comprising 792 otoliths corresponding to a time period from August 2016 to December 2017. A DIvisive ANAlysis (DIANA) Clustering method using the 4th wavelet obtained from otolith contours resulted in the detection of five different morphotypes or otolith phenotypes. Differences were found mainly in the collicum-antirostrum and the dorsal margin areas of the otolith contours. Two of the morphotypes represents 85% of the samples analysed, whose individuals were slightly larger than the other morphotypes, considering mean lengths (≥25 cm vs ≤24.5 cm). These very preliminary results open many future questions to be explored: 1. Do these results suggest intraspecific variation in the growth rate among phenotypes? 2. Do phenotypes proportions change in relation to seasonal variations? 3. May exist different ecological strategies related to each phenotypes? and 4. Are these otolith phenotypes present in other geographical areas

Adaptive plasticity of otolith shape in Scomber colias from the Canary Islands

Small pelagic fish in the Canary Islands (CE Atlantic, from 29°27'N to 27°37'N and from 18°12'W to 13°17’W) are mainly targeted by artisanal purse-seiners, whose activity is monitored by the Canary Oceanographic Centre (IEO-CSIC) in the Data Collection Framework since 2013. The Atlantic chub mackerel (Scomber colias) is the main of the four species targeted by this fleet (45% of the total landings), with landings quite stable around a mean value of 850 tons/year. From August 2016 to December 2017, 792 otoliths of S. colias corresponding to monthly analyses of the mentioned fleet’s landings have been launched used to identify the potential presence of different morphotypes inhabiting Canary waters, based on otolith shape analysis. A DIvisive ANAlysis (DIANA) Clustering method using the 4th wavelet obtained from otolith contours resulted in the detection of five different morphotypes or otolith phenotypes. Differences where found mainly in the collicum-antirostrum and the dorsal margin areas of the otoliths’ contours. Two of the morphotypes represented 85% of the samples analyzed, whose individuals were slightly larger than the other morphotypes, considering mean lengths (≥25cm vs. ≤24.5cm). These very preliminary results open many future questions to be explored: 1) Do these results suggest intra-specific variation in the growth rate among phenotypes?; 2) Do phenotypes proportions change in relation to seasonal variations?; 3) May exist different ecological strategies related to each phenotypes?; and 4) Are these otolith phenotypes present in other geographical areas?FEM

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