The Gulf of Mannar (GoM) coral reef area is located off the southeast coast of India. The reefs are distributed around a chain of twenty one islands, which occur at about 8-10 km from the mainland. The islands and the surrounding shallow coastal waters covering an area of 560 Km2 was declared as Gulf of Mannar Marine National Park in 1986. Out of the original reef area of 110 Km2, the extent of live corals is only about 80 Km2 at present. The main factors now affecting the reefs are destructive fishing practices and elevated temperature.
Due to its proximity to the mainland the reef area is strewn with several kinds of debris. Torn nets from destructive fishing operations like shore seine, push nets and gill nets cause physical damage and mortality to corals not only by breaking the coral branches but also destabilizing the community structure. They endanger the associated fish life too. The chiefly affected species are the branching corals Acropora sp. and Montipora sp. An estimated 10-12% of live branching corals are affected by different kinds of torn nets of varied sizes, wherein the massive corals have less impact (<2%). The torn nets occupying the dead coral areas with deposited sediment and other debris restrict coral recruitment and induce algal proliferation. Coral rehabilitation measures to restore degraded reefs are in place in GoM since 2008. Of the 7.2 hectares of rehabilitated area, about 25-30% has sustained physical damage and mortality from torn nets.
Suganthi Devadason Marine Research Institute (SDMRI), is conducting coral reef survey, monitoring and restoration work in Gulf of Mannar from 2000 onwards in association with Tamil Nadu Forest Department. The Institute collected detailed baseline data of entire reef areas in Gulf of Mannar (GOM) during 2003-2005. The status of corals is GOM was 37% in 2005, which increased to 39% in 2015, but the climate change caused bleaching due to the severe 3rd global bleaching event resulted in 16% coral mortality in 2016 and reduced the coral status to 23% in 2016.
Presently climate change poses prime and serious threat to corals in GOM. In order to reduce the stress to corals and to maintain healthy reef environment, SDMRI is involved in the removal of torn fishing nets from the reef areas.
1. Removal of torn fishing nets from the reef areas to reduce the stress to the corals, which are severely affected by climate change - caused 3rd Global Bleaching Event in 2016, and are since slowly recovering.