| dc.description.abstract | In the present study, habitat ecology and the aspects of reproductive biology of Arius gagora were assessed through
histology of gonads in Monu River from July 2013 to June 2014. Twenty species of catfish belonging 8 families were
identified. The yearly mean Shannon-Weaver diversity index, Margalef richness index, Pielou’s evenness index and
Simpson dominance index were found to be 1.86, 1.48, 0.95 and 0.83, respectively. The diversity indices showed
significant differences except Pielou’s evenness index in catfish assemblage structure. At the similarity percentage
(SIMPER) 85.65, three groups were attained while summer showed separate clustering from other groups. The Nonmetric
Multidimensional Scaling (n-MDS) showed 60% similarity in all seasons based on Bray-Curtis similarity
matrix. The CCA (Canonical correspondence analysis) ordination indicated that TDS and transparency were the two
most important environmental parameters shaping the catfish assemblage structure in river Monu. Ovarian
development of A. gagora was assessed macroscopically and microscopically. The fecundity found to be ranged from
43333.12±829.83 to 53948.81±1743.28 in April to August. The relationship of fecundity with ovary weight, ovary
length, total length and total weight found to be positively correlated. Length weight is found to be strongly
correlated with r
2
value of 0.986 and 0.982 for male and female respectively. Results of the study revealed female
dominance of the species over male with a ratio of 1:1.82 (female: male) and showed earlier maturation than male
too. Three gonadal maturity stages namely immature (early primary oocyte, late primary oocyte and yolk vesicle
oocyte), maturing (early and late yolk globule) and matured for female and immature (spermatogonia, primary and
secondary spermatocytes), maturing (spermatid) and matured (spermatozoa) were identified for male fishes. Monthly
study of gonado somatic index (GSI) revealed that the breeding season for this fish species may be extended from
July to August with a single peak spawning month in August. Presence of mature oocytes in ovary samples during
June-August indicated mature phase of oocytes ready to spawn. The histological study of ovary over the year
indicated that female gametes of A. gagora are asynchronous in nature. | en_US |
