Growth performance of carp species fed on salt-tolerant roughages and formulated feed in brackish water under polyculture system

A study was carried out to assess the growth performance of four fish breeds suitable for saline environments: catla catla (thaila),hypophthalmichthys molitrix (silver carp),ctenopharyngodon idella (grass carp) and cyprinus carpio (common carp) in a semi-intensive integrated pond system. the experiment was conducted in earthen ponds with brackish groundwater (electrical conductivity 4.7 ds m-1,ph 8.6 and residual sodium carbonate 21.3 meq l-1) for a period of 11 months. feed with crude protein 20% was prepared by using different ingredients,i.e. rice polish,maize gluten,sunflower meal and fish meal. the feeding treatments were formulated feed at 3% body weight alternated with salt-tolerant roughages (t1) or only roughages (t2) including leptochloa fusca (kallar grass),brachiaria mutica (para grass) and kochia indica (kochia). fertilization of all ponds was done with goat droppings at 6000 kg ha-1. results indicated that all four fish species were well adapted to formulated feed and roughages in saline environment. however,significant differences (p≤0.05) were observed in growth parameters under two feeding regimes. c. catla produced maximum weight (986 g) and net production (1721 kg ha-1 year-1),followed by h. molitrix (955 g and 1638 kg ha-1 year-1),c. idella (806 g and 1459 kg ha-1 year-1) and c. carpio (745 g and 1219 kg ha-1 year-1) in t1. survival rate was maximum in c. idella (93%) and minimum in c. carpio (84%). it may be concluded that the salt-tolerant roughages alternate with formulated feed of 20% protein can be used for optimal fish production by reducing feed cost in saline environments. copyright 2015 zoological society of pakistan.