Abstract
Mola, Amblypharyngodon mola is one of the important small indigenous fishes, rich with
micronutrients, having high demand in Bangladesh, Nepal and India. It is important to understand
the reproductive and developmental biology and behavior of mola in order to increase its production
from different systems. Characterization of mola - morphological variations and habitats have been
carried out in four different regions such as Northwest (NW), Northern, Northeast (NE) and Southern
region of Bangladesh. Reproductive biology; sex determination and ratio, gonadosomatic index (GSI),
ova diameter, fecundity and condition factor has been carried out for mola using fish from natural
sources of open and closed system from NW region and using fish produced through induced
breeding. The study also includes the embryonic and larval development of mola using fish produced
through induced breeding. Rearing of broodfish and breeding has been carried out in a private
hatchery in Rangpur and Mini Hatchery, Faculty of Fisheries, Bangladesh Agricultural University,
Mymensingh. The study started on September 2013 and completed on October 2015. All the
populations were found to be with low morphometric variability (CV<25%). The morphometric and
truss distances were significantly correlated (p<0.01) with total length (TL). On the basis of
geographical differences, all morphometric lengths were be significantly (p<0.01) different except
body depth. For morphometric and truss measurements, the first, second and third discriminant
function accounted 64.9%, 23.5% and 11.6% of total variances among the group variability,
respectively. Individual sample of 75.9% were correctly classified into their original populations
according to canonical discriminant function analysis. Mola in Southern and NW regions were the
most well defined populations and NE population was the less defined. According to DFA and HCA
analysis, mola in Southern region was phenotypically distinct population and the higher degree of
similarities of morphometric characteristics were found among NE, Northern and NW regions. All
meristic counts were found to be significantly different except lateral line and pelvic fin rays. Ponds
adjacent to the beels, seasonally flooded low lying areas, haors and canals were found to be the most
suitable habitat for mola. Stocking and conserving of mola, removing of predatory fish, feeding with
finely minced feed, fertilization, no or selective netting during peak spawning season and partial
harvesting of mola were found as special management practices in mola farming. Dhulia beel in NW
region was found as an area of mass mola production. March to December was found to be breeding
season of mola with more than one peak during April-September. GSI showed significant positive
relationship with TL, standard length (SL), body weight (BW) and gonad weight (GW) in all systems
except with BW for male in openwater. Mola is a partial breeder. The absolute fecundity of mola was
found to be 1,329 to 14,784 with a mean of 6,117 ± 3,690 (11=64) and the relative fecundity was 10,17,402
to 31,93,672 eggs kg-1 body weight with an average 19,85,501. The sex ratio of male and female was
found to be 1:1.91 (x2=166.67, p<0.001, df = 1, n = 1,710). Induced breeding of mola was carried out
successfully through combine with environmental stimuli and hypophysation with pituitary gland
(PG). PG at 25 mg kg-1 body weight of female was found to be effective and resulted a fertilization rate
of 84.25%, hatching rate 63% and 678 ± 305 hatchlings per female. Survival of spent mola after
spawning was found to be 67.78 ± 16.41% for female and 54.44 ± 10.14% for male. Mola attained to 5.15
± 0.42 cm in TL and 1.54 ± 0.33 g in BW within 34 days after hatching. The embryonic development of
mola was very rapid and larvae hatched out within 12 h at 26.75 ± 0.35°C. The larvae started first feeding
between 48 and 60 h at 26.77 ± 0.41°C. Morphological variability on geographical differences would be
helpful to establish the improved broodstock of mola. The special management practices for mola will
enhance the mola farming at farmer's level. The detail information on reproductive
developmental biology would be useful to improve the production technology and to assist further
research on molecular biotechnology for the species. The induced breeding techniques would assist
the synchronized seed production in hatchery to enhance the mola culture commercially.