Spawning and fry production
Murrels attain maturity at an age between one and two years. Mature C. striatus are above 25 cm in length and C. marulius above 36 cm. As in the case of other species showing parental care, the fecundity of murrels is comparatively low. Depending on the size of the fish and the species, the fecundity has been observed to vary between 2200 and 34 000 among the cultivated murrels. The peak breeding season for C. striatus is during the rainy months, but the speciesseems to breed throughout the year. Channamaculatus appears to breed in Taiwan andHong Kong from April to September.
All species of murrels exhibit parental care and spawn in nests built in shallow marginal areas with cut pieces of aquatic vegetation or similar material. Spawning lasts for 15–45 minutes and the eggs laid by the female in the nest are fertilized by the sperms shed by the male.The golden-yellow or amber-coloured fertilized eggs float in the centre of the nest in a thin film. The eggs hatch out in 20–57 hours in temperatures ranging from 16 to 33°C, depending on the species. The hatchlings measure about 3.5 mm and within about four days, when they measure about 6.8 mm, they are able to swim about freely.
Both males and females take part in caring for the newly hatched young for about 15–20 days, that is until the larvae are about 3.5 mm in length. The newly hatched larvae feed on protozoa and algae. The larval development is completed in about nine weeks, when they move to the bottom and show adult behaviour. The fry feed on animal foods such as crustaceans, insects, young fish and tadpoles.
Induced spawning of most species of Channa has been carried out by hypophysation, although it is not practised to any appreciable extent on production farms, except in Taiwan. Selected brood fish are reared in separate brood ponds, and fed on live food such as fish and tadpoles for about two to three months before spawning. Female C. maculatus spawners of about 1 kg body weight are injected with one or more common carp pituitary together with 20 rabbit units of Synahorin, in two equal doses at intervals of 12 hours. Male fish do not require injection and spawn naturally. The spawners are then kept in 3–4 m3 cages made of nylon netting placed in ordinary fish ponds, for spawning. Each cage contained a male and female pair. Sometimes five or six pairs may be released in small shallow ponds (7–10 m3) without using cages. Spawning generally takes place in about a day. For induced breeding of C. marulius, C. striatus and C. punctatus, hypophysation with carp and catfish pituitaries at doses ranging from 40–80 mg gland/kg female in two injections have been found to be adequate under experimental conditions
Copyright © 2018-2020 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.