Size-dependent survival of European hake juveniles in the Mediterranean Sea

Abstract

Most studies on European hake focus on the recruitment process and nursery areas, whereas the information is comparatively limited on the ecology of the juvenile stage (ca. second year of life)—the one most exploited by the Mediterranean trawl fisheries. Using information of the MEDITS programme, we provide a spatial and temporal assessment of the influence of body size and growth on hake survival from recruits (age 0) to juveniles (age 1), along with the impact of surface temperature and chlorophyll variability. At a biogeographic scale, size-dependent survival is supported, with areas with higher mean length of recruits and juveniles yielding higher survival. A similar pattern was observed at interannual level in some western Mediterranean areas, also mediated by a density-dependent effect on growth. However, the most recurrent inter-annual pattern was a negative effect of size on survival, which could be attributed to potential ontogenetic changes in catchability and underrepresentation of intra-annual recruitment pulses that are seasonally inaccessible to the MEDITS survey. Results also evidence that survival in the Alboran and Adriatic seas is dependent on the primary production variability, and that Corsica and Sardinia could be potential feeding grounds receiving juveniles from neighbouring areas. The present study reveals the importance of size- and growth-dependent survival in the juvenile stage of European hake in the Mediterranean Sea.

Cross-scale environmental impacts across persistent and dynamic aggregations within a complex population: implications for fisheries management

“…The environment influences critical ecological processes such as recruitment (Houde 2016), spawning (Di Stefano et al 2023) or mortality (Kerametsidis et al 2023), as well as several life history parameters of fish, such as growth or reproductive scheduling (Perry et al 2005;Clark et al 2020). In fact, in some cases, no clear stock-recruitment patterns can be evidenced, which leaves the environment as the main driver of recruitment with minimal influence of the spawning stock (Szuwalski et al 2015;Hidalgo et al 2019b). Therefore, considering the spatial heterogeneity that exploited stocks are subject to, the hypothesis that spatially structured environmental processes (i.e., environmental processes varying across multiple spatial scales) explain critical ecological and demographic processes seems plausible and needs to be explored.…”

“…Despite the recent implementation of highly promising management plans, such as the Multiannual Plan for Demersal Fish Stocks in the Western Mediterranean Sea (Sánchez Lizaso et al 2000), there are still issues inhibiting the proper management of commercial stocks (Cardinale et al 2021). While recent studies have recommended larger species-specific units for the better assessment of some Mediterranean stocks (e.g., Fiorentino et al 2015;Spedicato et al 2021;STECF 2021), there is also cumulative evidence of the importance of local and regional dynamics (Hidalgo et al 2019b;Paradinas et al 2022), challenging these recommendations and encouraging the implementation of spatially structured stock assessment frameworks (Cadrin 2020;Punt 2023). Obtaining high-resolution information on population spatial structure and connectivity is a prerequisite for spatial stock assessments (Goethel et al 2023) and is logistically feasible for data-rich species and systems.…”