Inland fisheries provide millions of people with their primary source of nutrition and livelihoods, especially in the world’s largest tropical rivers. While climate change and a global boom in tropical hydropower development have raised concerns due to their potential impact on fish yields, overharvest remains a key challenge to sustainable inland fisheries. Assessing the state of tropical inland fisheries using common tools developed for marine systems are often inadequate because tropical river fisheries are indiscriminate, have diverse and complex food webs and lack regular monitoring data. Here we develop new metrics to assess indiscriminate fisheries based on a theoretical generalized Lotka-Volterra model, and test them against an unprecedented tropical inland fisheries timeseries.
Results/Conclusions
We find that, while yields remain stable, catch species composition changes according to a three staged development model. In early stages, when exploitation is light to moderate, indiscriminate fishing causes catch Shannon-diversity to increase as large, dominant and high revenue species, are developed into. In middle stages, when exploitation is moderate, Shannon-diversity plateaus as these previously dominant taxa are replaced by a high diversity of other species. Finally, while few locations included in our dataset have reached high levels of exploitation, at these late stages, catch Shannon-diversity is expected to decrease as fast-growing species become dominant in catches. We conclude that this inverted U-shaped Shannon-diversity curve is characteristic of indiscriminate and diverse inland fisheries development and can aid in assessing the sustainability of data-limited tropical river fisheries.