Essential habitat for sardine juveniles in Iberian waters

Abstract

Summary:In a period when the Iberian sardine stock abundance is at its historical minimum, knowledge of the sardine juvenile's distribution is crucial for the development of fishery management strategies. Generalized additive models were used to relate juvenile sardine presence with geographical variables and spawning grounds (egg abundance) and to model juvenile abundance with the concurrent environmental conditions. Three core areas of juvenile distribution were identified: the Northern Portuguese shelf (centred off Aveiro), the coastal region in the vicinity of the Tagus estuary, and the eastern Gulf of Cadiz. Spatial differences in the relationship between juvenile presence and egg abundances suggest that essential juvenile habitat might partially differ from the prevailing spawning grounds. Models also depicted significant relationships between juvenile abundance, temperature and geographical variables in combination with salinity in the west and with zooplankton in the south. Results indicate that the sardine juvenile distribution along the Iberian Peninsula waters are an outcome of a combination of dynamic processes occurring early in life, such as egg and larva retention, reduced mortality and favourable feeding grounds for both larvae and juveniles.Keywords: Portuguese coast; Gulf of Cadiz; acoustic survey; fish habitat; Sardina pilchardus; juveniles; fisheries management. Hábitat esencial para los juveniles de sardina en aguas IbéricasResumen: En un periodo de mínimo histórico para el stock de sardina ibérica, el conocimiento de la distribución de los juveniles de sardina resulta crucial para el desarrollo de estrategias de gestión pesquera. Se usaron modelos aditivos generalizados para relacionar la presencia de los juveniles de sardina con las variables geográficas y las principales zonas de desove (abundancia de huevos) y a su vez para relacionar la abundancia de los juveniles con las condiciones ambientales adyacentes. Se identificaron tres zonas centrales: la plataforma norte portuguesa (centrada enfrente de la localidad de Aveiro), la zona costera próxima al estuario del Tajo y la parte este del golfo de Cádiz. Las diferencias espaciales encontradas en la relación entre la presencia de juveniles y la abundancia de huevos sugieren que el hábitat esencial de los juveniles puede diferir parcialmente de las zonas de desove existentes. Los modelos también señalaron relaciones significativas entre la abundancia de juveniles, la temperatura, y las variables geográficas combinadas con la salinidad en el oeste y con el zooplancton en el sur. Los resultados indican que la distribución de los juveniles de sardina a lo largo de las aguas de la Península Ibérica resulta de la combinación de procesos dinámicos que se dan en edades tempranas, cómo la retención de huevos y larvas, una mortalidad reducida y zonas de nutrición con condiciones favorables tanto para larvas cómo para juveniles.Palabras clave: costa portuguesa; golfo de Cádiz; campaña acústica; hábitat de peces; Sardina pilchardus; juveniles; gestión ...

Interactions between the common dolphin, Delphinus delphis, and the Portuguese purse seine fishery over a period of 15 years (2003–2018)

“…Thus, being an area of high productivity (Fiúza, Macedo & Guerreiro, 1982;Fiúza, 1983), the north-west coast is suitable for small pelagic fish species and is therefore attractive to a large number of cetacean species (Zwolinski et al, 2010;Veiga-Malta et al, 2019). It is the area in Portuguese waters with the greatest abundance of sardine, the preferred prey of the common dolphin, and is the main nursery and recruitment area of this pelagic fish, centred off Aveiro-Figueira da Foz (40 -41 N) (Silva et al, 2009;Rodríguez-Climent et al, 2017). Massé et al (2018) reported an overlap between the sardine and the common dolphin in one of the core areas for sardine off central Portugal (39 -41 N).…”

Depth and temperature preferences of meagre, Argyrosomus regius, as revealed by satellite telemetry

“…While summer shallow warm water habitat use around large estuary mouths such as the Guadalquivir, Tejo and the Gironde in the northeastern Atlantic has been associated with A. regius spawning [18,19,22], these estuaries are also important summer aggregation and spawning sites for small pelagic fishes. These include the European anchovy Engraulis encrasicolus [46] and the sardine Sardina pilchardus [47] both small pelagic fishes that can form an important part of adult A. regius's diet [48]. This suggests that A. regius may be exhibiting an income breeding strategy, advantageously spawning in areas of high prey abundance so that they have the required resources during gamete production and courtship.…”