The fate of eggs and larvae of three pelagic species, mackerel (<i>Scomber scombrus</i>), horse mackerel (<i>Trachurus trachurus</i>) and sardine (<i>Sardina pilchardus</i>) in relation to prevailing currents in the Bay of Biscay: Could they affect larval survival?

Abstract

SUMMARY:The spatial distribution of eggs and larvae of three pelagic species, mackerel, horse mackerel and sardine, in the Bay of Biscay was studied in 1998, 2001 and 2004. The spatial distribution was clearly different between the years studied and corresponds quite precisely to different water circulation regimes. Mackerel and horse mackerel larvae are more affected by the prevailing currents than sardine, as their spawning grounds are located offshore, far from the shelf break where the current velocities are higher. Survival rates for mackerel and horse mackerel were higher in 2001, when the offshore larval transport was stronger. However, for sardine, the mortality rate hardly varied between years. The abundance of 25-day-old larvae, considered as an index of the survival rate, appears to be a good recruitment indicator, at least for 1998, 2001 and 2004. Our results did not support the hypothesis of Bakun (1996), which states that dispersion of early life stages towards open ocean waters should cause high larval mortality. At least under the conditions observed for the years studied, the retention of larvae offshore appears to have a positive effect on larval growth and/or survival.Keywords: ichthyoplankton, Bay of Biscay, survival rates, larval transport, recruitment. RESUMEN: El dEstino dE huEvos y larvas dE trEs EspEciEs pElágicas caballa, (Scomber ScombruS), jurEl (TrachuruS TrachuruS) y sardina (Sardina pilcharduS) En rElación a las corriEntEs prEvalEntEs En El árEa dEl golfo dE vizcaya. ¿podrían afEctar a la supErvivEncia larvaria? -La distribución espacial de los huevos y larvas de tres especies pelágicas, caballa, jurel y sardina en el Golfo de Vizcaya fue estudiada en 1998, 2001 y 2004. Esta distribución espacial fue claramente diferente entre los años estudiados y se ajustan, bastante bien a los diferentes regímenes de circulación. Las larvas de caballa y jurel resultaron más directamente afectadas por estas corrientes prevalentes que las larvas de sardina. Esto se explica porque las sardinas desovan en la plataforma, relativamente alejadas del cantil, donde las velocidades de las corrientes son más altas. Las tasas de supervivencia larvaria de caballa y jurel fueron superiores en 2001, cuando el transporte de larvas offshore era más importante. Para las larvas de sardina, sin embargo, la tasa de mortalidad apenas varió entre años. La abundancia de larvas mayores de 25 días, considerada aquí como un índice de la tasa de supervivencia larvaria, resultó ser un buen indicador del reclutamiento por lo menos para los años estudiados. Nuestros resultados contradicen la teoría de Bakun (1996), que afirma que la dispersión de las etapas de vida temprana hacia las aguas del océano abierto causa una alta mortalidad larvaria. Por lo menos bajo la condición que se observó durante estos años (temperatura y abundancia de alimento), la retención de larvas en mar abierto parece tener un efecto positivo en el crecimiento larvario y/o supervivencia.

Development, application and evaluation of a 1-D full life cycle anchovy and sardine model for the North Aegean Sea (Eastern Mediterranean)

“…In the case of European sardine, literature information was very limited. The few existing values for egg and early larval mortality, estimated for the Iberian sardine in the Atlantic ([56], [57]) were very similar to the values adopted for the Mediterranean anchovy. We therefore used the same values of natural mortality for the early life stages of the two species (Table 1).…”

Study of the climatic changes in the North Aegean Sea and their effects on the ecosystem dynamics

“…In the case of European sardine, literature information was very limited. The few existing values for egg and early larval mortality, estimated for the Iberian sardine in the Atlantic (Alvarez and Chifflet, 2012) were very similar to the values adopted for the Mediterranean anchovy. We therefore used the same values of natural mortality for the early life stages of the two species (Table 2).…”

Assessing the risk of alternative management strategies in a Mediterranean fishery: protecting the younger vs reducing fishing effort

“…Since there are no available data for the early life stages for sardine in the study area, mean values were unavoidably adopted [3]. The division of the early life groups was: m 1 : 0–35 days and m 2 : 35–182 days (Table 1).…”