Delineating some of the reproductive aspects of Macrognathus pancalus from the river Sessa, Assam, India
Rimle Borah and SP Biswas
Macrognathus pancalus is the common Mastacembelidae species having good nutritional as well as ornamental value. Reproductive biology of the species was studied from June 2016 to June 2017 from Sessa river, Assam. The sex ratio of different month showed wide variation from 1:0.21 (April) to 1:4 (Oct) and overall M: F sex ratio was recorded 1:0.76, indicating a highly skewed distribution of sexes from the expected 1:1 ratio favoured by females in most of the months, (P<0.0079, χ2=14.00). The gonado-somatic index (GSI) sequence revealed prolonged spawning with its peak in August both in female (9.84±0.35) and male (3.29± 0.18).The ova diameter progressively increased from 0.4±0.10 (March) to 1.6±0.048 mm (September) having peak in August. The absolute fecundity of the fish ranged from 275 (fish: 9.5cm; 7.20gm) to 4518 (fish: 17.0cm; 12.80gm) and was high during May-August which falls within the breeding period. Fecundity increases with increase in weight of the fishes which indicate a linear relationship between absolute fecundity and fish weight (r2=0.824, P < 0.01).
KEYWORDS: M. pancalus, Mastacembelidae, spawning, gonad, fecundity.