Abstract
For the domestication and conservation of H. menoda, the food and feeding habits, reproductive
biology, induced breeding protocol, early life stages and fry nursing technique of the fish were
studied at the Field Laboratory Complex, Faculty of Fisheries, Bangladesh Agricultural University,
Mymensingh from November 2015 to February 2017. The frequency of occurrence, volumetric
(points) methods and index of preponderance were used to assess the composition and importance
of food items within the diet of the fish in its natural habitat. The species reprcxluctive parameters
such as sex ratio, gonadosomatic index (GSI), ova diameter, fecundity and gonad histology data
were obtained from Kangsha River Netrakona, Bangladesh. Double hormone doses of PC and HCG
extracts at 29:ö1 ratio were tested to evaluate their efficacy on ovulation, fertilization, hatching and
survival rates of H. menoda using the induced breeding method. The ovulated eggs were placed in
convex slides and the embryonic and larval developmental stages studied under the microscope.
Nursery rearing of larvae in relation to different supplementary feeds and varied stocking densities
was carried out in trays and hapa placed in earthen pond. Based on index of preponderance, the
detritus, small fish and polychaetes were found to constitute the 1st, 2nd, and 4th ranks
of the food items consumed by H. menoda. Gastrosomatic index was highest in September (6M ±
1.03) and in November (634 ± 0.41), for males and females, respectively, indicating the period of
highest feeding activity of both sexes. Sex ratio (female: male) was found to be female biased
(1.03:0.97). The monthly mean GSI of female H. menoda started to increase from May to June and
reached the peak (12.50±4.97) in July, indicating the peak spawning season of the fish. Mean
fecundity estimates based on mature females was 77273.77±276.82 for fishes with mean length of
31.85±2.39 cm, and lowest (22954.99; 25.(1) cm) was in May and highest (222171.8; 40.20
cm) was in July. Fecundity correlated positively with standard length (Log F 0.0135 + 4.399 log
SL; - 0.774), body weight (F -193.7 BW - 47602; r2=o.805) and ovary weight (F 1066 OW + 6124;
r2 —0.832). In the mature ova, the ova diameter ranged from 0.77mm (standard length = 31.5±2.15
cm) in May to 1.66mm (standard length — 40.2±3.54 cm) in July, and spawning takes place once in a
year but with longer duration spanning from May to July. Oxytes in the Premature (PM) and
mature (M) stages were abundant from April to August samples of ovary, indicating the spawning
season. Successful ovulation occurred in the females injected 24, 25, 26, and 27 mg PG and 35(L
4500, and IU HCG/kg body weight. Optimum doses of hormones were obtained from
spawners injected double dose of 35001U and 26 mg HCG and PG/kg body weight, respectively, in
a 23:12 ratio. Unfertilized eggs were sticky, mean egg diameter increased from 0.8 ± 0.00 mm to 1.10
± 0.01 mm and hatching at 19.3() hr after fertilization at 24.1 oc water temperature. The egg
yolk became completely absorbed within 68 hours at mean length of 6.5 ± 0.05 mm. The larvae
reared in trays in treatment fed on tubifex worms showed significantly (p<O.05) higher mean final
length (33.77±7.56 mm), mean final weight (452.22±634 mg) and Specific Growth Rate 83R), over
commercial feed and egg milk paste fed larvae. The SGR, 10.91±1.30 (%/day) and Average Daily
Gain, ADG, 38.00±2.43 mg/ day in weight in larvae reared in hapa was higher in the tubifex raised
larvae followed by the commercial feed and egg milk raised larvae. Significantly (p<0.05) higher
weight gain (mg), ADG, mg/ day, SGRw ( % / day), survival rate (%) and FCR was obtained in larvae
stocked at 6 fry/m2 density. Water quality variables were within acceptable limits for larval rearing.
Spawning period of H. menoda and technique for its breeding has been identified.