Ecology of recruitment in European hake: Interaction between maternal effects, environment and fisheries
- Autores: Cristina García Fernández
- Directores de la Tesis: Rosario Domínguez Petit (dir. tes.), Fran Saborido Rey (dir. tes.)
- Lectura: En la Universidade de Vigo ( España ) en 2021
- Idioma: inglés
- Tribunal Calificador de la Tesis: Dolores Garabana Barro (presid.), Hilario Murua Auricenea (secret.), María Amalia Grau Jofre (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencias Marinas, Tecnología y Gestión por la Universidad de A Coruña; la Universidad de Santiago de Compostela; la Universidad de Vigo; Universidade de Aveiro(Portugal); Universidade de Porto(Portugal); Universidade de Trás-os-Montes e Alto Douro(Portugal) y Universidade do Minho (Portugal)
- Materias:
- Enlaces
- Tesis en acceso abierto en: Investigo
- Resumen
The European hake (Merluccius merluccius) is one of the most important economic fishery resources in Spain and a key species in the demersal marine ecosystems of the temperate regions of the north-eastern Atlantic Ocean. Based on its economic importance, it is essential to understand the recruitment dynamics (i.e., the process by which new individuals are introduced into the population after the high larval mortality phase), in order to achieve a sustainable exploitation of the stock, which presents great variability. This study focuses on the southern stock, and more specifically on the Galician Shelf (northwest of the Iberian Peninsula), identified as one of the main spawning grounds of this stock.
European hake in the Atlantic is under significant fishing pressure. Both stocks (north and south) have been heavily exploited and in 2004-2005 reached a critical state due to overfishing which led to the implementation of specific recovery plans. In the second half of the 2000s, both stocks experienced a recruitment pulse. The reproductive capacity of the northern stock has fully recovered while the southern stock is in a reduced reproductive capacity, although it maintains a healthy state. However, the low recruitment per unit of spawning biomass in the southern stock in recent years suggests that the stock has a low reproductive potential, probably due to intense exploitation.
European hake is characterised by its high plasticity and adaptive capacity, that allow adapting its reproductive potential to the external influences according to changes in energy availability, environmental conditions and fishing pressure. The motivation for this study is to understand how European hake recruitment works in the Galician shelf and which the main drivers of its variability are. As explained above, this species presents great biological and ecological complexity. This feature causes population spawning asynchrony and a protracted spawning season with several spawning peaks throughout the year whose contribution to annual recruitment remains unknown. In order to understand the complex recruitment process holistically, several interrelated drivers have been considered, with attention to the demographic and environmental causes; and establish the role of fishing activity (which modifies population demography and reduces reproductive potential) and environmental variability in recruitment pulses.
Results suggest that the spawning stock of European hake is composed of different spawning sub-stocks, spawning in different seasons with different reproductive potential and, therefore, relative contribution to annual recruitment. Differences in the specific traits of each spawning component, such as oocyte dynamics, maternal effects on offspring or spawning intensity, would be the result of the adaptive capacity of this species. These differences between sub-populations become an advantage to ensure the recruitment and resilience of this stock. If the existence of distinct and isolated temporal components of spawning is confirmed, the inclusion of this temporal variability in fishery assessment models would reduce uncertainty and improve the predictive capacity of these models.
