New insights into the early life ecology of <em>Sardina pilchardus</em> (Walbaum, 1792) in the northern Iberian Atlantic

Abstract

SUmmarY: in the atlantic iberian estuaries, sardines tend to be a minor component of the ichthyoplankton assemblages, with rare occurrence largely restricted to estuarine mouths. However, this was not the case of the lima estuary (nW Portugal), where sardines were the most abundant and frequently occurring marine taxon of the larval fish assemblages. abundance of sardines collected during a two-year survey (2002)(2003)(2004) ranged from 0.5 to 60.8 larvae/100 m 3 , with the majority still showing yolk and unpigmented eyes. moreover, 80% of sardines were 8 days old or less and the total length ranged from 2 to 16 mm. Seasonal variations of sardine occurrence in the lima estuary correlated with temporal variations of salinity and temperature in the water column. The unusually high river-flow observed during the winter of [2002][2003], which preceded the spring-summer abundance peak, seemed to act as a signal for the estuarine recruitment that was encountered. in addition, the estuarine occurrence of sardine larvae was also correlated with the intensity of summer upwelling, which was responsible for coastal depletion of sardine larvae resulting in estuarine low catches during the summer of 2002. The lima estuary also revealed another peculiarity related to the lack of temporal synchrony between coastal spawning activity and occurrence of larvae within the estuary. The abundance peaks of newly-hatched larvae (autumn 2002 and spring-summer 2003) did not coincide with the winter-spring spawning pattern described earlier for the northern iberian coast. modifications of the spawning strategy of the northern iberian sardine stock are discussed based on these new insights into the early life of S. pilchardus.Keywords: Sardina pilchardus, larval stages, spawning strategy, environmental forcing, upwelling, lima river estuary.reSUmen: Nuevos aspectos sobre la ecología de los estados iniciales de desarrollo de Sardina pilcharduS (Walbaum, 1792) en el norte del Atlántico ibérico. -las sardinas tienden a ser un componente menor del ictioplancton de los estuarios atlánticos ibéricos. Su aparición es rara y restringida, en gran parte, a las desembocaduras de los ríos. Sin embargo, éste no fue el caso del estuario del río lima (nW Portugal), donde las sardinas fueron la especie marina más abundante del ictioplanton estuarino. las sardinas fueron recolectadas durante un período de dos años (2002)(2003)(2004), y su abundancia varió entre 0.5-60.8 larvas/100 m 3 . la mayoría de dichas larvas todavía presentaban saco vitelino y ojos no pigmentados. Por otra parte, el 80% de las sardinas tenían 1 semana o menos de vida y su longitud total varió entre 2 y 16 mm. las variaciones estacionales en la aparición de larvas de sardina en el estuario del río lima se correlacionaron con fluctuaciones temporales de salinidad y de temperatura de la columna de agua. los elevados caudales del río observados durante el invierno 2002-2003, que precedieron el pico de abundancia del primavera-verano, parecieron actuar como señal para el reclutamiento al...

Larval fish dispersal along an estuarine–ocean gradient

“…On the other hand, sardine S. pilchardus larvae were more abundant at the sea and were only present in small numbers in the lower sections of the estuary. Such spatial distribution is typical of marine stragglers, although S. pilchardus was classified as marine migrant species, in accordance with the classification proposed by Franco et al (2008) and also corroborating previous studies in the Lima estuary during which high abundances of S. pilchardus larvae were observed in the inner sections of the estuary (Ramos et al 2009). European sardine larvae tend to dominate the D r a f t ichthyoplankton community in the Western Iberian upwelling ecosystem, particularly during colder months of the year (Garrido et al 2009) and are thought to be limited to coastal areas (e.g.…”

“…Spring was chosen as many winter/spring marine spawning species colonize northern Portuguese estuaries during this season (Ramos et al 2006), including important marine resources as sardine (Ramos et al 2009) and flounder (Ramos et al 2010).…”

Immigration and early life stages recruitment of the European flounder (Platichthys flesus) to an estuarine nursery: The influence of environmental factors

“…larvae (Santos et al, 2004Ramos et al, 2009b). On the other hand, the increase in intensity and frequency of upwelling events during the winter spawning season of small pelagic species off the coast of Portugal was found to have a negative impact on recruitment, limiting their survival success (Santos et al, 2001).…”

A multi-model approach to evaluate the role of environmental variability and fishing pressure in sardine fisheries

“…Yearly peaks in sardine recruitment are generally found in winter (1985Stratoudakis et al, 2003) but general models did not identify seasonal relationships in this season to be detrimental to sardine fisheries. Other studies showed that S. pilchardus recruitment is linked to local winter wind conditions that can have both positive and negative effects on larvae survival (Santos et al, 2011;Porteiro et al, 1996;Ramos et al, 2009) and recruitment of pelagic species (Bakun and Parrish, 1991;Lloret et al, 2004), suggesting that larvae survivorship is closely related to vertical mixing and, consequently, to wind stress as a contributing mechanism to fisheries.…”

“…Variability in the distribution, abundance, and size of populations of pelagic fish may also in some cases be better explained by hydrographic properties, such as currents and geographical features of the coast and bottom (Checkley et al, 2009). The underlying mechanisms for population variability of small pelagic fish have also been described and discussed in regard to future climate variability Borges et al, 2003;Cury et al, 2000;Porteiro et al, 1996;Ramos et al, 2009;Silva et al, 2006;Lloret et al, 2004).…”