Rainbow
Trout Broodstock Management and Seed Production in Turkey: Present
Practices, Constraints and the Future
İ.
Okumuş-2002
Turkish
Journal of Fisheries and Aquatic Sciences, 2: 41-56
Abstract:
Trout has been cultured in Turkey since early 1970s, but major developments
took place during the 1990s. Currently, with an annual production over
40,000 tons, Turkey became one of the top trout producing countries.
Although, production mainly comes from as portion size fish from freshwater
farms, seafarming in the Black Sea provides around 2000 tons of large-trout.
The paper describes the current rainbow trout seed production practices in
Turkey and discusses areas of improvements.
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 practiced 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.
(Karadeniz Technical University, Faculty of Marine
Sciences, Dept. Fisheries, 61530 Çamburnu, Trabzon, Turkey, Tel.: + 90. 462.752 28 05; Fax: + 90. 462.752 21 58, E-mail: i.okumus@ktu.edu.tr)