Effect of Epinephelus coioides , Chanos chanos , and GIFT tilapia in polyculture with Penaeus monodon on the growth of the luminous bacteria Vibrio harveyi Eleonor A. Tendencia * , Armando C. Fermin, Milagros R. dela Pen ˜a, Casiano H. Choresca Jr. Aquaculture Department, Southeast Asian Fisheries Development Center, Tigbauan 5021, Iloilo, Philippines Received 31 December 2003; received in revised form 12 June 2005; accepted 18 June 2005 Abstract Studies have shown that the presence of Tilapia hornorum hybrid has antibacterial effect against luminous bacteria. The present study aims to determine the effect of different fish species such as grouper, milkfish and tilapia in polyculture with shrimp on the growth of luminous bacteria. Results showed that stocking of tilapia Oreochromis niloticus hybrid and grouper Epinephelus coioides at a biomass of 500 g/m 3 efficiently inhibited the growth of luminous bacteria in shrimp (biomass = 80 g/ m 3 ) rearing water and positively affected shrimp survival. Results also showed that the presence of milkfish Chanos chanos at a biomass of 500 g/m 3 did not inhibit the growth of luminous bacteria in shrimp (biomass = 80 g/m 3 ) rearing water. D 2005 Elsevier B.V. All rights reserved. Keywords: Vibrio harveyi ; GIFT tilapia; Grouper; Shrimp; Milkfish 1. Introduction One of the major problems of the shrimp industry in the Philippines is disease due to luminous bacteria (Lavilla-Pitogo et al., 1998) and different technologies have been tried to prevent or control them. Tendencia et al. (2003) reported that the presence of Tilapia hornorum at a biomass not lower than 300 g/m 3 efficiently inhibits growth of luminous bacteria in shrimp (biomass = 80 g/m 3 ) rearing water. Several reports on the antibacterial activity of different fish species have been published (Austin and McIntosh, 1988; Magarin ˜os et al., 1995). Extracts from the epidermis and epidermal mucus of Pollachius virens , Labrus berglta , Platichthys flesus , Solea solea and Scophthalmus rhombus have antibacterial, antifungal, and cytotoxic activities (Hellio et al., 2002). Ebran et al. (1999) mentioned that fish secrete proteins that have antibacterial pro- perty. Therefore, the effect of different fish species in 0044-8486/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2005.06.028 * Corresponding author. E-mail address: sidgigit@iloilo.net (E.A. Tendencia). Aquaculture 253 (2006) 48 – 56 www.elsevier.com/locate/aqua-online