Climate change : Challenging the sustainability of marine fisheries and ecosystems

Abstract

Changes in the important oceanic climate features such as sea surface temperature, sea level, pH, and rainfall are becoming evident as a result of climate change. In this review, the influence of the primary factor, the water temperature on the biological systems is presented. Seawater temperature influences biological systems at four levels: organismal, population, community and ecosystem. At organismal level, temperature has direct influence on two vital life traits of fish, namely, food utilisation and spawning. Growth rate of fish increases with increasing temperature within the optimal temperature window. It is likely that the food utilization parameters may be operating at an elevated level in fishes at higher temperatures, demanding higher food supply to attain faster growth rate. Fishes may change their phenology of reproductive activity to adapt to elevated temperatures for spawning and larval survival. At population level, temperature and other factors related to climate change may strongly influence distribution and abundance, evidences for which are accumulating in Indian seas. As the tolerance and adaptation capacities are different between species, the species that adapt and gain from warming are increasingly becoming dominant. On the other hand, those species, which are already at the threshold limits are vulnerable and lose to adaptable ones. At community level, this is reflected as changes in species composition over the years. All these changes have the potential to alter the structure and function of ecosystems. Habitat destruction, pollution, energy production, mining, fisheries, aquaculture, and invasive species are all affecting marine ecosystems and may exacerbate the effects of climate change. Effectively reducing climate change and other human-related threats requires integrated management actions with the goal of increasing adaptive capacity of ecosystems. As a first step, robust indicators need to be developed to understand the changes at ecosystem level. With regard to fisheries, the changes pose problems on the effectiveness of fisheries management measures. Reducing fishing pressure would be a major step to increase the capacity of fish stocks to adapt to environmental changes. It is important that a concerted effort is made to address the issues related to sustainability of tropical marine fisheries and ecosystems by considering climate change as a component of a suite of anthropogenic interventions.