Gillnetting for small indigenous cyprinids in a Sri Lankan reservoir where culture-based fisheries are practiced

Abstract

In Sri Lankan reservoirs, small, indigenous fish species (SIS) are abundant and can be differentially exploited using small mesh (15-38 mm stretched mesh sizes) gillnets without any detrimental effects on the cichlid fisheries. However, in the recent past a paradigm shift in the reservoir fisheries of Sri Lanka is observed from total dependence on exotic cichlids to exploitation of exotic carps, stocked in reservoirs for the development of culture-based fisheries (CBF). As fingerlings of Chinese and Indian major carps and common carp are regularly stocked in reservoirs for the development of CBF, it is essential to investigate the potential impact of the use of small mesh gillnets to catch SIS on stocked fish fingerlings on CBF. In the present study, small mesh gillnets were used to exploit SIS during September 2011 to March 2013 when carp fingerlings were stocked in Chandrika wewa, Sri Lanka. The results revealed that no carp fingerlings (except 2 specimens of Indian carp species) were caught in any of the fishing trials with small mesh gillnets. As juvenile fish and stocked fish fingerlings occur in shallow littoral areas of reservoir, and as small mesh gillnets are laid at the depths ≥ 1.5 m, there is a habitat segregation of these two categories of fish. It is therefore possible to introduce a subsidiary fishery with small mesh gillnets to exploit SIS, which can co-exist with CBF in reservoirs of Sri Lanka.

Sustainable aquatic resource management and inland fisheries in tropical Asia: Interdisciplinary and transdisciplinary approaches

“…Despite increasing evidence of high fishery potential of SIS in Asian reservoirs (Pet et al 1996 ; Amarasinghe et al 2016 , see below), this nutritionally rich resources remain widely underexploited or unexploited. Examples from Sri Lanka, Thailand and Laos show the potential for productive subsidiary fisheries on small fish (Mattson et al 2001 ; Athukorala and Amarasinghe 2020 ; Amarasinghe and De Silva 2015 ). A SIS fishery is also reported from small waterbodies in Bangladesh (Islam et al 2023 ).…”

“…In Sri Lanka, previous studies have shown that SIS could be differentially exploited using gillnets of stretched mesh sizes, 15–38 mm without adverse effects on the fishery of larger commercially important fish species such as Oreochromis mossambicus and O. niloticus (e.g. Pet et al 1996 ; Amarasinghe and De Silva 2015 ), and on the stocked carp fingerlings for culture-based fisheries (CBF) development (Athukorala and Amarasinghe 2020 ). Such a strategy for SIS exploitation without adverse impact on existing commercially important fish species is possible since they occupy different micro-habitats: juvenile tilapias and stocked carp fingerlings that are susceptible to small-mesh gillnets occupy littoral areas, whereas SIS occupy limnetic areas (Amarasinghe et al 2016 ).…”