Atlantic Bluefin tuna (ABFT) constitutes the archetypal example of overfishing and need for effective management policies. The recent regulatory measures of the rebuilding plan have introduced extensive changes in the spatio-temporal patterns of the ABFT fisheries, thus significantly affecting the fisheries-dependent indices traditionally employed for its stock assessment in the Mediterranean sea. This project’s aim is to answer the current needs of alternative methods for the population assessment of ABFT in the Mediterranean Sea, through the development and application of modeling approaches coupled to fisheries-independent data (electronic tagging and aerial surveys) for the derivation of indicators usable to assess the status of ABFT populations.
The project BLUEMED aims at providing novel fisheries-independent indicators of abundance (and their confidence interval) for ABFT in the North-western Mediterranean sea (NWM) based on behavioral models coupled to aerial survey and electronic tagging data.
The specific objectives of the project are:
- Developing a field-based model of ABFT vertical behavior in the NWM. This model will allow connecting the individual behavior recorded by electronic tags to the observations at the population level obtained from aerial survey.
- Collecting new field data based on electronic tagging technologies on depth-temperature time series for juvenile ABFT individuals.
- Studying the role of the possible correlations between vertical behavior and environmental variables (such as sea surface fronts) in the ABFT detectability.
- Providing advice for future experimental protocols in aerial surveys.
- Deriving a fisheries-independent abundance indicator based upon the integration of field data within the model and estimating its uncertainty.
This project implies the following challenges both at the modeling, data analysis and data collection level:
- The project aims at providing a robust index of abundance from scientific information solely, which is necessary but challenging for highly migratory marine fish.
- The project is based on an integrated approach, which relies models to field data. In this respect, model development is constrained by the data, implying a collaborative work between field ecologists, fisheries scientists and modelers.
- Studying the interplay of different factors (e.g. environmental conditions, aerial survey protocol) in the calculation of the abundance indicator constitutes an essential part of the project. These aspects have rarely been considered in the literature of ABFT stock assessment.
- The project aims at providing an estimation of the uncertainty on abundance indicators. Quantifying these uncertainties is significantly contributing to the impact of the indicator.
The project is financed by the French National Research Agency ANR (call @RAction -2014 http://www.agence-nationale-recherche.fr/?Project=ANR-14-ACHN-0002)