Feeding niche of two co-existing juvenile catfishes from Caranzalem Bay, Goa
National Institute of Oceanography
National Institute Of Oceanography Dona Paula, Goa, India Pincode: 403004 Mobile: 9867232532 E-mail: firstname.lastname@example.org
Catfishes are meso-predators known to influence both higher as well as lower trophic strata in marine coastal food chains. Their ecological role as predators remain mostly under-studied as many catfishes have low commercial value and are non-target species. The present investigation was carried out for the Caranzalem bay catfish population using specimens from the regular beach-seine and gillnet fishery catch and their gut contents were analysed.
As mega-benthic predator, they mostly have broad feeding niche and can consume new prey. Results reveal two catfishes occupying this bay viz; Plotosus sp. and Arius sp. Percent frequency of occurrence (% FO) and weight (%W) was used to establish trophic position by applying Levins dietary breadth (Bi) and Piankas dietary overlap (O) index to evaluate interspecific relationships in fish assemblage. Both catfish species using this bay are mostly juveniles or sub-adults (07-25 cm) while adult Plotosus sp. occupy reef areas and Arius sp. use deeper shelf areas. Both the species predominantly prefer crustacean as major prey and also consume small fishes, molluscs and polychaetes. Being opportunistic feeders, their diet is based on prey availability and moreover due to their voracious nature, considerable feeding overlap was noted. However, some niche segregation was noted due to discrete feeding modes and behaviour. Plotosus sp. juvenile schools are known to plough the sediments in advancing wave formation while Arius sp. individuals search and attack prey when detected.
Shallow bay areas are intense sites of trophic interaction and known sites for juveniles and small sized species that use this habitat as refuge thus it also attracts large sized top predators. In this bay, apex predator Hydrophis schistosus (hooked nose sea-snake) specifically feeds only on Arius sp. thus catfishes occupy an important function as a link between macro-benthic to large mega- benthic trophic transfer. Whether these two species have a top-down control on the lower trophic strata can only be ascertained by estimating exact predatory populations and the estimates of prey quantities available.