Research projects



Multi-species estimation procedure for Dynamic Energy Budget models

The objective of this collaboration project is to go to the next level on parameter estimation procedures for standard Dynamic Energy Budget (DEB) models. Estimating the parameters of a mass and energy budget model such as the standard DEB model requires a number of datasets in controlled conditions, throughout the life cycle of the organisms, that is rarely available for marine mollusks and fish species. The full panel of predictions that a standard DEB model can provide is therefore rarely used due to this lack of information at the species level. In this project, we propose to simultaneously estimate the parameters of phylogenetically related species. This method will mainly help in two important aspects:

This collaboration with G. Marques on multi-species parameter estimation was initiated in Nov. 2014 thanks to the support of the Axis 6 of the LabexMER. G. Marques came to Brest for a 2-week period to work on a new set of MATLAB routines. This method was presented during a 1-day workshop (25/11/2014, 12 participants) to researchers and students of the LabexMER. A second 4-day workshop will take place in Brest in September 2015 (7-11 sept. 2015), with the support of the GdRI RECHALGO (Ifremer-MPO Canada) and the LabexMER.

Reconstructing environmental conditions using fish otolith and bivalve shells proxies

During my PhD research, I developed a method to couple the metabolism of an individual fish to the formation of its otoliths. This model, when complemented with a temperature-specific effect on CaCO3 precipitation can solve opacity patterns that are seemingly contradictory by considering the food and temperature environment experienced by individual fish. The coupling of the otolith model to a DEB model furthermore revealed a potential for food history reconstruction, which would considerably improve the quantity and the quality of information that we can obtain from these archives. Extracting and analyzing fish otoliths is labor- and cost- intensive but it is often the only way we have to go backward in time and providing tools to extract more information from these archives is a particularly stimulating area of research.

Using a similar approach, I am currently studying mechanisms underlying the patterns in &delta13C measured in otolith and bivalve shells. These carbon isotope measurements in otoliths and bivalve are used as proxies for Dissolved Inorganic Carbon (DIC) and primary production in marine and freshwater environment. However, the incorporation of carbon from both metabolic and inorganic origin impedes a clear reconstruction of the environment signal from both otoliths and shells. In addition, studies on otoliths and shells show different patterns of &delta13C in the same environment which suggest differences in underlying mechanisms. In contrast, by approaching these questions in a common bioenergetic framework, the results of my research suggest we can overcome these issues by studying how fish and bivalves incorporate inorganic carbon to their calcified structures, which had not been previously addressed.



Understanding the impact of metabolism on stable isotope dynamics

I am currently developing a theoretical framework in the context of the DEB theory to understand how metabolism impact isotope dynamics within an organism (Pecquerie el al. 2010). Stable isotope analysis is a powerful tool to identify food-web structures, reconstruct individual life histories, and track the flow of elemental matter through ecosystems. However, the large variability in incorporation rates and discrimination factors observed in field data is difficult to interpret and limit the conclusions of studies solely based on field data. Experimental studies have shown that a variety of metabolic factors can explain the observed variability but we are lacking a theoretical framework to understand the underlying mechanisms.

Life history variability in Pacific salmon

I am currently studying the life cycle of salmonids and the impact of the environment on their life histories. An integrative approach is particularly challenging for Pacific salmon that use river, estuarine and marine environments. Given that performance at a given life stage is known to impact subsequent life stages and hence the dynamics of the population, we need to understand impacts on all life stages. Therefore, in contrast to previous bioenergetic approaches that usually focus on the impact of the environmental conditions on a single life stage, I am developing a bioenergetic model that predicts development, growth and reproduction of a Pacific salmon, from an egg to a reproducing female in a dynamic environment. This approach is particularly relevant for anadromous fish species with largely unobservable ocean stages.

My current work on life cycles of salmonids is part of a project that aims to evaluate how variations in river flow affect the development and growth of young Chinook in the Merced River. More generally, this project aims at developing quantitative tools that integrate bioenergetics approaches, spatial scales and population dynamics in inflow stream assessments. We show that that our salmon model reproduces the differences in egg size, fry size and fecundity among the 5 North American salmon species.



Contact Info

Laboratoire des Sciences de l'Environnement Marin (LEMAR)
Institut Universitaire Européen de la Mer (IUEM)
Technopole Brest-Iroise
rue Dumont d'Urville
29280 Plouzané
France

Tel : +33 2 90 91 53 52
laure (dot) pecquerie (AT) ird (dot) fr