Puffer proliferation in tropical coastal waters: influence of indiscriminate trawling

Abstract

Intensive mechanized fishing has induced marked alterations in coastal marine ecosystems resulting in proliferation of low-value, nuisance species in marine fish catches. Assessment of 75 shrimp trawl catches taken in the near-shore waters off Goa, west coast of India during active fishing periods from 2006 – 2008 revealed that the demersal pufferfish, Lagocephalus spadiceus constituted ≈ 27 % by weight of the trawl catch during January – March, and its catch was inversely related to prey and predator species. Sub-tidal rock reefs and submerged rocky patches in the study area offer suitable substrates for spawning, and the predominance of adults during these months suggesting spawning migration. Comparison of the present data with published literature indicates a significant reduction in puffer predators (catfishes). Excessive removal of high-value predators favours the proliferation of pufferfish and its establishment as a meso-predator, probably triggering a potential trophic cascade. The paper discusses the role of removal of High Trophic Level (HTL) species in the proliferation of a meso-predator and its impact on ecosystem function.