Modelling the effects of climate change on the distribution of shared fishery species in the subtropical Western Indian Ocean

Climate change that is linked to the build up of greenhouse gases and aerosols in the atmosphere is now a widely accepted phenomenon that has lead to increases in surface temperatures over the last 50 years (IPCC, 2007).
The most obvious changes associated with increased sea surface temperatures around the WIO will be shifts in the distribution and abundance of individual fishery species or species assemblages according to their thermal tolerance and ability to adapt (Clark, 2006; Harley et al., 2006).
Because most communities and populations have undergone dramatic changes through expansions, contractions and crises during past episodes of climatic change, predicting the evolutionary and genetic responses to climate change under these various scenarios and climatic predictions is also critical.

Since past and present environments have shaped current levels of genetic diversity, molecular genetic markers are useful natural indicators of the historical and contemporary cumulative exposure and adaptive reponses of populations to environmental change (Kocher and Carleton, 1997). Genetic markers also provide valuable information about the geographic structure and demographic history of populations (Moritz et al, 1987; Avise, 2000). Therefore, elucidating genetic structure and connectivity in marine taxa is an important component in understanding the
effects of processes and factors that determine adaptation and present ecological connections. This
is critical in understanding the effect of climate change on species or communities and how they may respond to this. Combining molecular genetic data with quantitative environmental and landscape data will allow powerful inferences to ecological condition and population responses to environmental changes.
The goal of this study was to explore the extent to which the range of seven selected shared fisheries species endemic to the subtropical WIO might shift in response to changes in the surrounding environment with climate change. We are also studying the genetic connectivity among different populations of three species and the existing ‘genetic variation’ of these species, as this
provides the raw material for adaptation.

The following key questions were addressed:
· To determine which species are most susceptible to global climate change.
· To determine whether tropical and subtropical species will extend their distribution
northwards
· To determine whether their overall range will contract or expand.
· To estimate the genetic diversity of three commercially important species and their historical demograhic patterns and genetic structure throughout their distribution range.
Analyses of historical geographic patterns relative to current distributions would be central
in understanding the responses of marine species to climate changes in their habitats.
· To determine patterns and scales of genetic connectivity among areas and specifically within
the SWIO subtropical region, by examining the levels of gene flow in three commercially
important target species. The significance of these results in the context of maintaining
adaptive diversity in regional populations that may be threatened with range expansions or reductions as a consequence of climate change will be useful for conservation and management.

A publications was planned on:
1. The publication of at least one paper on each of the three species selected for genetic analysis (i.e. C. puniceus, E. andersoni and P. praeorbitalis).