2. Publication: Modelled
spatial distribution of marine fish and projected modifications in the North
Atlantic Ocean
Modelled spatial distribution of marine fish and
projected modifications in the North Atlantic Ocean
Running head: Niche modelling and fish
biogeography
S. Lenoir, G. Beaugrand, É. Lécuyer
Global Change Biology 17(1) 2010
2.1. Abstract
The objectives of this work were to examine the past, current
and potential influence of global climate change on the spatial distribution of
some commercially exploited fish and to evaluate a recently proposed new
Ecological Niche Model (ENM) called
Non-Parametric Probabilistic
Ecological Niche model (NPPEN). This new
technique is based on a modified version of the test called Multiple Response
Permutation Procedure (MRPP) using the generalized Mahalanobis distance. The
technique was applied in the extratropical regions of the North Atlantic Ocean
on 8 commercially exploited fish species using three environmental parameters
(sea surface temperature, bathymetry and sea surface salinity). The numerical
procedure and the model allowed a better characterisation of the niche
(sensu Hutchinson) and an improved modelling of the spatial
distribution of the species. Furthermore, the technique appeared to be robust
to incomplete or bimodal training sets. Despite some potential limitations
related to the choice of the climatic scenario (A2 and B2), the type of
physical model (ECHAM 4) and the absence of consideration of biotic
interactions, modelled changes in species distribution explained some current
observed shifts in dominance that occurred in the North Atlantic sector, and
particularly in the North Sea. Although projected changes suggest a poleward
movement of species, our results indicate that some species may not be able to
track their climatic envelop and that climate change may have a prominent
influence on fish distribution during this century. The phenomenon is likely to
trigger locally major changes in the dominance of species with likely
implications for socio-economical systems. In this way, ENMs might provide a
new management tool against which changes in the resource might be better
anticipated.
Keywords: ecological niche modelling, climate
change, marine fish distribution, ecological niche, projections,
biogeography
2.2. Introduction
Fish stocks fluctuate in space and time and the better
understanding of these fluctuations have occupied scientists for several
decades (Rosenzweig 1995; Barange & Harris 2003; Brander 2007). While it
has been difficult to identify causes for some stock fluctuations, changes have
often been attributed to stochastic events (Hsieh et al. 2005),
hydro-climatic anomalies (Edwards et al. 2002; Lehodey et al.
2006), climate change (Drinkwater 2006; Brander 2007) or both direct and
indirect anthropogenic impacts (Hutchings 2000; Jennings et al. 2001;
Pauly et al. 2005). Among anthropogenic pressures, overfishing is an
important driver of change in marine fish stocks, acting probably in synergy
with climate forcing (Hsieh et al. 2006; Brander 2007).
The impact of climate warming on marine ecosystems has become
prominent (Root et al. 2003; Intergovernmental Panel on Climate Change
2007b; Rosenzweig et al. 2008). Among these effects, there is a
central and growing concern about possible changes in species geographical
distribution (Parmesan & Yohe 2003; Deutsch et al. 2008;
Thuiller et al. 2008). For example, northward movements in calanoid
copepod zooplankton have been observed in the North Atlantic Ocean at a mean
rate of up to 23.16 km.y-1 for some species assemblages in a
period of 48 years (Beaugrand et al. 2009). These changes in plankton
composition were paralleled by a northward migration of both commercial and
un-commercial fish species (e.g. Quero et al. 1998; Stebbing et
al. 2002; Brander et al. 2003; Beare et al. 2004a;
Perry et al. 2005).
Despite the recognition of the importance of ecosystem
processes to better manage fish stocks (e.g. Ecosystem Based Fisheries
Management; see Cury et al. 2008), current management plans rarely
consider that the carrying capacity of the ecosystem may fluctuate and that the
natural spatial distribution of the target species may vary. The biosphere is
now experiencing a period of rapid and sustained climate change that might even
accelerate in the future (Intergovernmental Panel on Climate Change 2007b). A
fundamental challenge for future sustainable exploitation and conservation is
to dispose of valid estimations of potential changes in future species
distributions (Pearson & Dawson 2003; Schwartz et al. 2006;
Thuiller 2007). To do so, an increasing number of statistical tools (e.g.
bioclimatic envelop models, ecological niche modelling; Guisan & Zimmermann
2000; Thuiller 2003; Austin 2007) have been developed to determine the
potential response of species to global warming in both the terrestrial
(Harrison et al. 2006; Murphy & Breed 2007; Huntley et
al. 2008) and the marine realms (Guinotte et al. 2006; Beaugrand
& Helaouët 2008; Cheung et al. 2008a). Based on the
Hutchinsonian concept and the relation between species niche and distribution
(Hutchinson 1957; Pulliam 2000), these models project the multidimensional
distribution of species into an environmental (or Euclidean) space or into a
geographical space (Soberón & Peterson 2005; Austin et al.
2006; Hirzel et al. 2006).
The aim of this work is to formulate different scenarios of
changes in the spatial distribution of some North Atlantic fish in response to
ocean warming. First, the ecological niche (sensu Hutchinson, 1957) of
eight exploited fish in the North Atlantic is characterised. Second, the
spatial distribution of these species is modelled for the period 1960-1969.
Third, an evaluation of the consequences of changes in temperature on spatial
distribution of species is carried out during the period 1960-2005. Fourth,
scenarios of changes in the spatial distribution of these species are proposed
for the middle and the end of this century using two moderate scenarios (A2 and
B2). Results are commented in the context of global climate change and
associated to the pronounced influence of fishing on exploited resources and
marine ecosystems.
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