Empirical Predictive Models of Coastal Cuttlefish Recruitment in the English Channel
CONTEXT
The MERSEA laboratory at the University of Caen Normandy is a European pioneer in the application of exploited population dynamics models to Cephalopod stocks (cuttlefish and squid) and in the study of the ecology of these resources. The results of six defended theses have provided the first descriptions of the influence of environmental factors on abundance (Robin & Denis, 1999) and on spatial distribution (Wang et al., 2003), the first assessments concerning the fishing pressure experienced by cuttlefish in the English Channel (Royer et al., 2006), and the stock-recruitment relationships for this stock (Gras et al., 2014; Alemany et al. 2017).
Cuttlefish is a key component of our ecosystems and represents an important commercial resource, particularly for Norman fisheries (5th in value, Ifremer 2024). This species is characterized by a short lifespan (2 years), very rapid growth, semelparity (death after one reproductive season), and a high sensitivity to environmental variations. Cuttlefish undertake seasonal migrations in the English Channel that are generally known (Boucaud-Camou & Boismery, 1991), the amplitude and chronology of which appear sensitive to variations in temperature, photoperiod, salinity, and turbidity (Dunn, 1999).
The work of Anna Marcout (thesis defended in December 2024) showed that the temperature structure in the English Channel played a key role in triggering the spring migration toward the coast. This work combined the use of VMS data (Vessel Monitoring System) allowing precise localization of commercial fishing operations with fishing results. The migration toward the coast occurs at the moment of the inversion of the temperature gradient between the offshore and the coast (an inversion which involves the equalization of temperatures). This phenomenon does not occur at the same time in all coastal cuttlefish reproduction zones, and other factors likely intervene in the distribution of the stock that overwinters in the center of the Western English Channel toward the different coastal areas.
The study proposed here will consist of analysing the link between winter abundance and the arrival of cuttlefish in one of the four French coastal areas revealed by VMS data (from the Bay of Saint-Brieuc to the Hauts-de-France region), and determining which other environmental factors contribute to favoring or reducing spring recruitment. The study of the influence of environmental variables on coastal distribution is not isolated from other work aiming to test the hypothesis of spawner homing to their area of origin, but at this stage, the possible influence of this phenomenon will only be addressed by testing the influence of local abundances one or two years earlier.
The results of this work may guide the local management of the English Channel cuttlefish stock and should inform stakeholders about the essential zones for resource renewal. They will complement the stock assessments and diagnostics carried out for the entire English Channel by highlighting which stages are most sensitive to high fishing pressure (from coastal birth, overwintering offshore, and return to the coast).
INTERNSHIP OBJECTIVES
- Update the French commercial fishing data transmitted to the laboratory by the SIH (Système d’Information Halieutique) under an agreement with the DGAMPA (Direction Générale des Affaires Maritimes de la Pêche et de l’Aquaculture) (ensure the joining of operation location and catches using existing scripts).
- Update the total catch data from all fleets operating in the English Channel (notably winter British catches).
- Query European platforms (Copernicus, EMODnet) to extract and update habitat data (as performed by Marcout et al. 2024).
- Search for an empirical model describing spring biomass indices in French coastal areas as a function of previous catches and environmental variables.
- Contribute to the communication of this work to the ICES-WGCEPH expert group.
REQUIRED PROFILE
- Second year of Master’s degree, or end of an engineering cycle in marine sciences, marine ecology, fisheries science, biological oceanography, or modeling.
- Particular interest in understanding the functioning of marine ecosystems.
- A strong liking for quantitative ecology (with the use of R, RMarkdown, and GitHub)
APPLICATION INFORMATION
Applications (cover letter and CV/resume) must be sent by email to Jean-Paul Robin (jean-paul.robin@unicaen.fr) by midnight on December 15, 2025.