The annual mean trophic level (TrL) of marine fish landings along the Indian coast consisting of 53 exploited species/groups was estimated for the period 1950-2002. The landings as well as TrL increased along the northwest (NW) and southwest (SW) coasts. However, increase in the landings was associated with decrease in mean TrL along the east coast, particularly along the southeast (SE) coast at the rate of 0.04 per decade. The increasing trend of the FIB index ceased in the last 5-10 years along three coasts. A backward-bending signature in the landings versus TrL plot for the SE coast in the last 6 years indicates fisheries-induced changes in the ecosystem owing to low productivity of the coastal waters and high density of fishing craft. The landings of most of the large predators increased along the Indian coast, but higher removals appear to have helped proliferation of their prey, the mid-level carnivores. Fishing the food web has been influenced by environmental fluctuations, advanced fishing technologies, and market-driven, deliberate fishing on low-trophic level (TL) invertebrates such as the penaeid prawns.
A biomass dynamics modelling study to derive biological reference points and management requirements of 223 commercially important fish stocks in different maritime states of India was conducted. Two decades (1997–2016) of fishery-related data on the harvest of resources by different types of fishing fleets formed the input. The multigear nature of the fishery situation was solved by introducing a gear standardization parameter into the biomass dynamics model. The relative positions of the fish stocks were depicted through Kobe plots generated for the ten maritime states/union territory, and the fish stocks were categorized, based on the status, into sustainable, overfished, recovering, and overfishing. The results indicate that 34.1% of the assessed fish stocks in the country are sustainable, 36.3% are overfished, 26.5% are recovering, and 3.1% are in the overfishing status. Regionally, the percentage of sustainable fish stocks were high along the southwest coast (51.6%), overfished stocks were high along the northwest coast (54.2%), and recovering fish stocks were high along the northeast coast (47.8%). The national mean B/BMSY was estimated as 0.86, which is a strong reason for strengthening fisheries management. Fishing fleets harvesting overfished stocks were examined for each maritime state, and recommendations regarding reduction in annual fishing hours are made.
The marine fisheries sector in India supports livelihood of four million people and earn a significant amount of foreign exchange through export of marine fish and its products. Historic data showed that the total marine fish production in India maintains an overall upward trend with fluctuations. Periodic assessment of major fishery resource groups is necessary to manage the fishery for sustainability. Among different species groups, 50 commercially important resource groups accounting for about 97% of the national annual landings were individually studied by Markov Chain modeling of annual growth rates in landings. In addition, the time series data on landings of these marine fishery resource groups were analyzed randomness using 'runs test'. Limiting probabilities for all the nine defined states of each Markov Chain process were determined and status of the resources was derived based on limiting probabilities. Runs test on the time series sequences showed 19 of them having random behavior. It was found through Markov Chain modeling that 16 of the marine fishery resources have probability more than 0.8 to confine their annual growth rate between-0.25% and +0.25% providing high confidence regarding stable yield from harvest indicating stability of their stocks.
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