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Historical reconstruction of Indian marine fisheries catches, 1950-2000, as basis for testing the ’marine trophic index’ Bhathal, Brajgeet

Abstract

Presently, fisheries are in deep crisis worldwide due to overfishing. Increasing intensity of fishing throughout the world has had impacts on the target species and their supporting marine ecosystems. Globally, the total catches are declining by some about ½ million t per year since 1988. As well mean trophic level of landings are declining at rate of 0.1 per decade. This threatens the world's food security specifically, its animal protein supply, especially, in developing countries. In order to evaluate the status of marine fisheries in India, the catches were reconstructed over the period of 1950 to 2000. This reconstruction show marine fish catches increased gradually from 0.6 in 1950 to 3.3 million t in 2000. To determine if the Indian marine fisheries trends are ecologically sustainable or not, the mean trophic level of landings were analysed over the five decades. It is found that the fishing down marine food web phenomenon is happening all over India, i.e., in each state and union territory, similar to rest of the world. This trend, however, was generally not visible when the catches of small pelagics fishes were included, i.e., their variability masked the fishing down phenomenon when this was based on the mean trophic level of all shelf species. On the other hand, application of the cut off trophic level of 3.25 (i.e., excluding small pelagics and most invertebrates) made the fishing down effect visible for all states and union territories. This analysis thus confirms the potential usefulness of the MTI (Marine Trophic Index), recently adopted by the Convention on Biological Diversity as one of the 8 indicators of biodiversity. It also confirms that the use of MTI, jointly with a TL cutoff point (i.e., [sup 3.25]MTI) better reveals underlying trend than overall mean TL. The time series of Fishing in Balance (FiB) index show an overall increase for all Indian states and union territories, suggesting a geographic expansion of the fisheries. However, in recent years, a stagnation or decline of FiB index is visible in almost all areas. This indicates a serious problem, presumably the end of the expansion phase in Indian fisheries. Overall, this historical review clearly indicates that India has suffered from sequential depletions of coastal stocks.

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