Oxyeleotris marmoratus, predator or by-product in integrated aquaculture ponds

Participating farms in the Muang district of Nong Khai Province, were selected for the investigation of management practices and yields of marble goby, Oxyeleotris marmoratus, in integrated culture with Nile tilapia (Oreochromis niloticus). The research took place from February to May, 2007. The observed production of O. marmoratus in integrated aquaculture ponds indicated a wide range of management practices. The yields of Oxyeleotris marmoratus were between 22.1 to 316 kg ha(-1) (average 81+/-78 kg ha(-1)). The farmers tended to prefer Oxyeleotris marmoratus not only as a by-product, but also as the main product from their ponds. Most farmers realized that Oxyeleotris marmoratus predate Nile tilapia fingerlings from the natural spawning of mature Nile tilapia in the ponds. With respect to consumed prey, the frequency of occurrence of prawns was 73.3%, whilst that of small fish was 43.3%. In terms of prey biomass, prawns were also the most abundant food item, giving the relative abundance of 56.0%. A preliminary trial on predation pressure was conducted to confirm the role of Nile tilapia fingerling as live feed for Oxyeleotris marmoratus in integrated aquaculture ponds and it was found that the daily predation pressure was between 1.90 to 2.46 fish day(-1).