Trends in Indian Ocean marine fisheries since 1950: synthesis of reconstructed catch and effort data
Andreoli V. and Heidrich K. | June 2023
New publication
Highlights
Indian Ocean marine fisheries catches have been consistently rising since the 1950s, in contrast to declines in all other ocean basins in recent decades.
Indian Ocean small-scale catches grew by 300 per cent from 1950 to 2018, reaching 6.5 million tonnes of fish per year in recent years. This is equivalent to almost 3,000 Olympic-sized swimming pools filled with fish.
Industrial catches, on the other hand, began increasing in the mid–late 1970s but then reached a plateau and have been stagnating since the late 1990s.
Abstract
Context. Contrary to other ocean basins, Indian Ocean catches have increased consistently since 1950, although reported data are known to be incomplete. Fish is a crucial food source in the Indian Ocean; however, ineffective management often empowers over-exploitation. Aims. We synthesised and reviewed Indian Ocean reconstructed catch and effort data by fishing sector and fishing country at the ocean-basin scale. Methods. We aggregated reported and reconstructed unreported catch and effort data for the Indian Ocean and derived catch-per-unit-effort (CPUE) time-series by sector. Key results. Indian Ocean rim country catches dominated in the Indian Ocean. Small-scale catches in the Indian Ocean have grown continuously by over 300% from 1.9 × 106 tonnes (Mg) year−1 in 1950 to 6.5 × 106 tonnes year−1 by 2018. By contrast, total −1 industrial catches from the Indian Ocean have reached a plateau at ~8.5 × 106 tonnes year since the late 1990s, after having steadily risen from very low levels in the early 1960s. Unreported catches declined from 45 to 25% of total catches. Total fishing effort, driven by the industrial sector, has increased 30-fold since 1950 from 0.4 × 109 to 11 × 109 kW-days by 2010, whereas CPUE has declined 78%, with steeper declines in the small-scale (>80% since 1950) than in the industrial sector (65% from its 1981 peak). Conclusions. The different sectoral patterns in the Indian Ocean compared with other ocean basins are likely to be due to the region’s high dependence on small-scale fisheries and the later onset but swift growth of industrial fishing. The declining CPUE suggests strong decreases in stock biomass caused by strongly increasing fishing effort, especially in the industrial sector. Implications. Indian Ocean countries should prioritise lower-impact well-managed domestic small-scale fisheries to maximise long-term, sustainable nutrient supply for local livelihoods
Citation: Zeller D., Ansell M., Andreoli V., Heidrich K. (2023) Trends in Indian Ocean marine fisheries since 1950: synthesis of reconstructed catch and effort data. Marine and Freshwater Research 74, 301-319.doi: 10.1071/MF22148
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Acknowledgements
The authors thank all current and former Sea Around Us and Sea Around Us – Indian Ocean team members, volunteers, students and research partners for their valuable contributions over the past decade.