Abstract:
Ompok ceylonensis is an endemic food fish distributed in the dry zone of Sri Lanka
and has been a good protein source for rural fishing communities. Selective fishing
pressure, habitat losses and many anthropogenic reasons are blamed for their
declining populations in natural habitats. Stock enhancement of O. ceylonensis
through induced breeding may not only pave the way for species conservation but
also secure a sustainable protein source for the rural poor in Sri Lanka. However,
different hormones and concentrations have been tried in freshwater fish breeding
with varied success rates. Hence, it is confusing for small-scale fish breeders and
conservationists on what type and concentration should be ideal for the breeding of
butter-catfish. This study, therefore, aimed to evaluate the best hormone and
concentration for captive breeding for O. ceylonensis using two different hormones,
LHRH-a and GnRH. A sexually mature female and two males each were transferred
into seven separate cages in cement tanks, and a water flow throw system was
arranged. GnRH was injected at 0.3, 0.4 and 0.5 ml/kg rates for females and 0.2 ml/kg
for males in three separate tanks. A similar procedure was practised to induce LHRHa
for fish in three other tanks with 20, 25 and 30 μg/kg. One tank was kept without
fish being injected. After a latency period of 8 - 12 hrs, eggs were spawned in 5 tanks,
but not in the concentration of GnRH 0.3 ml/kg and without hormone administrated
tank. Water quality parameters were measured during the period of breeding and
embryonic development period as temperature 29.5oC± 0.49 oC, dissolved oxygen at
6.85 ± 0.32mg/l, and pH at 7.34 ±0.42. The highest relative fecundity, 143.9 eggs
per/g of body weight and the highest hatchability, 84% was, recorded as the best
performing concentration of hormone LHRH-a at the 25ug per kg of body weight of
O. ceylonensis.
