Aspect of reproductive biology of Parachanna obscura, Gunther 1861 in a southwestern Nigerian reservoir

Abstract

African snakehead (Parachanna obscura) is a highly valued freshwater fish species in Nigeria, but its availability for economic and nutritional benefits is being threatened as a result of overdependence on wild source. Effort at bringing it to culture is, however, being limited by paucity of information on its biology among other challenges. Therefore, key aspects of the reproductive biology of this species were investigated as a prelude to artificially propagate it. 688 live samples comprise of 394 females (12.6-45.0cm TL) and 294 males (12.8-41.6cm TL) were fortnightly obtained in Eleyele Lake between November 2014 and October 2016 from fishermen majorly using longline, cast nets and gillnets of various mesh sizes. Morphometric parameters of fish were taken, and each sample dissected for sex identification following standard method. The maturation stages were analysed using macroscopic and standard histological techniques. The sex ratio of samples varied significantly (p< 0.05), with 1.34 females for every male. Five stages of oogenesis and three stages of spermatogenesis were obtained from samples analysed. Mean gonadosomatic index were significantly higher in May (2.26±0.86%), June (2.08±0.80%) and January (1.98±0.77%) for female samples and in June (0.18±0.06%) and December (0.21±0.06%) for male, implying peaks of gonadal development for the sexes. Length at first maturity calculated was 26.6 cm for males and 25.8 cm for females. The diameter of ova, however, varies from 0.60 to 1.42 mm. Absolute fecundity ranged between 336 (at 20.5cm total length) and 7,033 (at 36.7 cm total length). The relationship between fecundity and total length, weight, ovary length and ovary weight was linear and positive. This research provides key information necessary for artificial propagation of P. obscura.

Aspect of Reproductive Biology of Chrysichthys nigrodigitatus (Lacepède 1803) in Asejire Reservoir, Nigeria

“…More fish was recorded in the dry season than in the wet season. This was in direct contrast with the findings of Kareem et al 11 (1:1.55) across the seasons, which showed an almost doubled female species over their male counterpart as with Olowo et al 12 and Ikpi and Okey 13 . This study however compared favorably with Akombo et al 18 and Taiwo and Odunaiya 19 where almost equal proportions of male and female numbers of these species were observed even though their abundance was in favour of female specimens.…”

“…The sex of each sample was identified by visual examination and separated based on external morphology. The sex ratio was calculated according to Kareem et al 11 using the formula:…”

“…Similarly, there have been several bodies of work on different fishes like the Sex Ratio, Gonadosomatic in Diet Composition and Fecundity of African Pike, Hepsetus odoe in Eleyele Lake, Nigeria by Kareem et al 10 and similar studies on Parachanna obscura 11 , Synodontis Shall 12 , Labeo coubie 13 , Clarias gariepinus and Clarias macromystax 14 . However, there is less work on the bionomics of C. nigrodigitatus especially in Asejire Reservoir.…”

Seasonal Changes of Length-Weight Relationships and Condition Factor of Three Fish Species from the Tanoe-Ehy Swamp Forest (Côte d’Ivoire)

“…The length of first maturity of C. buettikoferi (♀ = 13 cm SL ; ♂ = 14.8 cm SL) and T. ansorgii (♀ = 6.9 cm LS ; ♂ = 8.1 cm LS) showed that most samples were from adult individuals, which indicates a low impact of fishing on fish size in the TESF. Although information on the length at first sexual maturity (Lm) of P. obscura is lacking in TESF, data from the literature (♀ = 25.8 cm LT ; ♂ = 26.6 cm LT) also indicated a heterogeneous population [37].…”