Rainbow Trout Broodstock Management and Seed Production in Turkey: Present Practices, Constraints and the Future

Lack of specialized broodstock or hatchery operators is one of the major characteristics of Turkish trout farming sector. Thus, most of the farms produce their own eggs and fry, and those have not got such facilities buy fingerlings rather than eyed-eggs, but demand for fingerlings vary considerably due to heavy losses as results of water quality fluctuations, disease outbreaks and management issues. There is no genetic breeding or selection programmes and described trout strains. Brood fish are mainly selected on morphological features and no records are kept. Age composition of the broodstocks range from 2 to 7 years, while the sex ratio is often around 1:1. Husbandry and feeding conditions of brood fish are very similar or sometimes worsen than on-growing fish. There is no off-season egg production through genetic or photoperiod manipulations, but natural egg production season ranges from November to April, peaking during January-February. Simply, eggs are stripped, fertilized with milt from at least two males and stocked into incubators of farm-made wooden-wire trays set in concrete or brick troughs, fiberglass troughs with aluminium baskets or vertical-flow stack incubators. Dead eggs are picked during the fist two days or after eyeing. Fluctuating water temperatures and suspended solids are main water quality related problems in hatcheries. Practices such as estimation of egg numbers, disinfections and shocking, and monosex or tripliod stock production are not common applications. Since the water temperature low or fluctuate widely incubation period lasts approximately 45 days and losses may reach 50 percent. Fry are fed commercial starter feeds with containing 45-50% crude protein. Feeding is performed by hand with 3-4 times daily only during the natural day length. Fry can be maintained indoor until size of 0.5-2.0 g and then moved out to small concrete raceways or fingerling ponds with some kind of shading. Growth rates vary widely between the farms and fry may reach mean size of 4-5 g 100 days after hatching. Disorders such as gas bubble, parasites (Ichthyobodo or Costia, Ichthyophthirius, Saprolegnia) and diseases (Flavobacterium branchiophila, Flexibacter columnaris, Yersinia ruckeri) may cause serious losses.

Turkish rainbow trout sector has reached stage of maturation, but it has not utilized most of the biotechnological developments widely practices in northern countries. Thus, developments in seed production as specialization in seed production, selective breeding programmes, all year around egg supply, sterile stock production and recirculating systems can be exploited for further development. Keywords : broodstock, trout culture, seed production, Turkey