Fecundity and Gonadal Development of Copper Mahseer, Neolissochilus Hexagonolepis (McClelland, 1839) from Tamor river, Nepal
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Institute of Science and Technology
Abstract
The present work was intended to assess the fecundity and gonadal
development of Neolissochilus hexagonolepis from Tamor River, Nepal. The study
was conducted for the duration of two years, from December 2014 to November 2016.
Monthly samples of N. hexagonolepis were procured from the river. Altogether one
hundred ninety eight samples were examined. The length-weight relationship (LWR)
was found to be following the model of Le Cren (1951). The value of the regression
coefficient (b) for all the LWR was close to 3, which indicated that the fish showed an
isometric growth pattern. The general well being of the fish from the river was found
to be satisfactory. The assessment of fecundity unveiled N. hexagonolepis as a low
fecund fish. The number of eggs in the ovaries of N. hexagonolepis increased
proportionately with increasing length, body weight and gonad weight of the fish. The
enumeration of gonado-somatic index (GSI) showed the species as an annual breeder
with peak spawning activity from July to August. The egg size estimation revealed the
species as a multiple spawner. Male individuals dominated the smaller size classes and
female individuals dominated the larger size classes. The testes and ovaries were
observed at six stages of maturation viz. Immature, maturing virgin, ripening, mature,
spawning and spent. The developing oocytes within the ovigerous lamellae of the
ovaries were observed at the chromatin-nucleolus stage, early and late peri-nucleolus
stages, early and late yolk vesicle stages and early and late yolk stages. The species
showed an extended breeding period from May to November. Male and female
individuals attained the first sexual maturity at size 25.5 cm and 32.9 cm, respectively.
Environmental variables played an essential role in governing the reproductive biology
of the fish. Temperature contributed positively to the development of the fish’s gonads
during its breeding season.