Assessing the sustainability of subsistence fisheries of small indigenous fish species: fishing mortality and exploitation of hill stream loaches in India

Abstract

Small, least conspicuous fish species are targeted through subsistence fisheries in many regions of the world, but little is known about their population dynamics or exploitation levels. In the Western Ghats of India, part of a global biodiversity hotspot and an exceptional region of freshwater fish diversity and endemism, several small species of loaches are caught and sold in the local markets by marginalized communities through an unmanaged fishery, resulting in high levels of exploitation. Of particular concern is the fishery for the spiny loach, Lepidocephalichthys thermalis whose exploitation rates at various sites in the northern part of the Western Ghats region were observed to be greater than their E50 (exploitation rate where the stock is reduced to half its virgin biomass). A comparison of various fishing sites showed that populations in the high anthropogenic impact areas (located close to urban settlements with high human population density, and impacted by various threats, i.e. introduced species, pollution) are exploited at a rate greater than 86% of their Emax (exploitation producing maximum yield). The first quantitative information on population dynamics and exploitation levels of small indigenous fish species in tropical rivers indicates their potential vulnerability to over fishing, and is an important starting point for further investigations into similar fisheries in other regions of Asia and Africa.