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Climate and Fishing Impacts on the Spatial Population Dynamics of Tuna

Progress reports (PDF): Project Final Report, Project User Manual, FY 2010 progress rpt, FY 2009, FY 2008, FY 2007

The objective of this project is to investigate two intimately linked research questions discussed during the November 2005 meeting of the CLIOTOP Working Group 4:

  1. What is the relative importance of fisheries and the environment in structuring pelagic ecosystem?
  2. What are the mechanisms which explain observed variations across species, trophic pathways, regions, etc.?

A high priority for effective management of large pelagic fishes is the capability to discriminate between the effects of exploitation and climate dynamics on the sustainability of tuna populations. Climate related changes are believed to strongly influence the pelagic habitats of tuna, and thus movement and migration patterns. High frequency ENSO recruitment response appears to play out into low frequency decadal variations of tuna population biomass. Large changes in Pacific tuna catch rates in the 1950s-1960s were associated with natural climatic fluctuations. But not all tuna respond the same way to climate cycles, thus there should be demonstrable differences in survivorship during recruitment and responses to exploitation patterns. Empirical and analytical evidence are needed to explain the relative importance of environmental and fishing variability in structuring pelagic ecosystems. There is need to determine the mechanisms involved in observed variability across species, trophic connections, and oceanic regions. In this proposal, two spatial biophysical models are proposed to be run for several tuna species concurrently with 6-8 long-term (up to 50 years) climate regime datasets. It is anticipated that the model will enable researchers to evaluate potential alternative system states due to physical and anthropogenic forcing and to help determine if the impacts of natural climate variability could be anticipated in such a way as to help establish a management regime that accommodates exploitation pressures and natural variability to build sustainable tuna fisheries.

Spatial dynamic biophysical models have been concurrently developed in the Pacific and Indian Oceans by the principal investigators to simulate the pelagic ecosystem for primary trophic-level connections: tuna species, and their forage base. These spatial ecosystem models (SEAPODYM and APECOSM) use bioenergetic formulations to connect the species and trophic levels to each other and the environment, and include a multi-gear fishery component that allows evaluation of catches, catch rates, and catch size compositions by region. In the proposed research, space-time comparisons of two models with the same 6-8 long-term climatological datasets will be made, and calibrated with historical spatial patterns of fishery catch and effort.

Both SEAPODYM and APECOSM models use the same environmental data sets as forcing variables. They require fields of temperature, currents, wind, dissolved oxygen, primary production, light profiles and/or euphotic depth that can be predicted from coupled physical-biogeochemical models. However, these fields are averaged over three vertical (epi-, meso-, and bathy-pelagic) layers in SEAPODYM while APECOSM uses all vertical layers defined in the coupled physical-biogeochemical models. To explore the sensitivity to the forcing fields, project PIs propose the following strategy: to force two state-of-the-art biogeochemical models PISCES (Aumont and Bopp, 2005) and ESSIC (Leonard et al., 1999; Christian et al., 2003) that are able to produce the desired input forcings for SEAPODYM and APECOSM. These two biogeochemical model outputs will be forced by the two configurations of the global dynamical model ORCA (Madec et al., 1998) performed over the past 50 years.

Year 1 funding for this 3-year project estimated to be available mid-2006.

• Aumont O., and L. Bopp (2006) Globalizing ocean in-situ iron fertilization experiments. Global Biogeochemical Cycles, in press.

• Leonard, C.L., C.R. McClain, R. Murtugudde, E. E. Hofmann, and L.W. Harding, Jr., 1999. An iron-based ecosystem model of the central equatorial Pacific. J. Geophys. Res. 104: 1325-1341

Project Investigators:

Dr. Patrick Lehodey
Marine Ecosystems Modeling and Monitoring by Satellites (MEMMS)
Direction Oceanographie Spatiale
8-10 rue Hermès
31526 Ramonville St Agne cedex
Phone (33) 561-39-47-80
FAX (33) 561-39-37-82

Dr. Olivier Maury
Centre de Recherches Halieutiques Méditerranéennes et Tropicales
Institut de Recherche pour le Développement (IRD)
av. Jean Monnet
B.P. 171
34203 Sète cedex
Phone (33) 499-57-32-28
FAX (33) 561-39-37-82
email: Olivier.Maury@ird.fr


Dr. Olivier Aumont
Plouzané, FRANCE
email: Olivier.Aumont@ird.fr

Dr. Alain Fonteneau
Centre de Recherches Halieutiques Méditerranéennes et Tropicales, IRD
Sète cedex, FRANCE
email: Alain.Fonteneau@ird.fr

Dr. Christophe Eugène Menkes
Université Pierre et Marie Curie
email: Christophe.Menkes@lodyc.jussieu.fr

Dr. Raghu Murtugudde
ESSIC, University of Maryland
College Park, Maryland, USA
email: ragu@vinsanto.essic.umd.edu

Dr. Inna Senina
Pelagic Fisheries Research Program (PFRP)
University of Hawaii
Honolulu, Hawaii, USA
email: senina@hawaii.edu

Dr. George Watters
Protected Resources Division
NOAA Fisheries, SW Fisheries Science Center
Pacific Grove, CA, USA
email: George.Watters@noaa.gov


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This page updated October 4, 2010