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
INTRODUCTION
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:
- What
is the relative importance of fisheries and the environment in structuring
pelagic ecosystem?
- 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.
References:
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
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Dr. Olivier
Aumont
IRD-IPSL/LOCEAN
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
LODYC
Paris, FRANCE
email: Christophe.Menkes@lodyc.jussieu.fr
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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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