Context
Ocean transport influences the distribution and survival of the eggs and larvae of pelagic species such as mackerel and anchovy in the Bay of Biscay, playing a key role in their recruitment. However, there is still limited knowledge of the effect of transport during the early life stages (i.e. eggs and larvae) and its implications. It is therefore crucial to advance this line of research around the main spawning grounds and at spatial scales covering the entire Bay of Biscay.
Hydrodynamic models and observational data are currently available, including from the BIOMAN and MEGS surveys, making it possible to establish initial egg distributions and analyse transport using Lagrangian models. Although these models provide results with an acceptable degree of uncertainty, validation with drifting buoys helps improve the accuracy of estimates and supports better interpretation of the results.
The use of Lagrangian metrics and satellite technology enables the identification of key ocean structures that influence larval retention and dispersal. It is also important to explore the use of echosounders to detect post-larvae and assess their distribution in the water column. Innovations such as drifting buoys equipped with echosounders offer the opportunity to track post-larval drift while measuring their abundance over extended periods and across large areas.
The combination of these methods and technologies will improve understanding of ocean circulation in early life stages, providing a basis for future research on growth, survival, and the influence of environmental factors such as predation.
Objectives
The main objective is to characterise the effect of ocean circulation on transport and distribution of anchovy and mackerel eggs and larvae after spawning in key areas. To achieve this, the project will address the following specific objectives:
• Characterise transport and distribution patterns of eggs and larvae, as well as the ocean processes affecting them, through historical analysis.
• Validate transport estimates using observational datasets.
• Analyse the feasibility of acoustic echosounders for post-larvae identification.
• Evaluate whether transport plays a critical role in biomass dynamics in the Bay of Biscay.
Expected impact
The results will mainly contribute to EU fisheries conservation policy.
Given that:
i) natural fluctuations in fish stock size are only partly dependent on spawning stock biomass, and
ii) a large proportion of variability in population abundance occurs during pre-recruitment pelagic stages,
focusing on this life stage provides a valuable tool to assess environmental effects on fish populations and fisheries.
