OBSERVATION ON THE INDUCED SPAWNING PRACTICES IN THE HATCHERIES OF RAJSHAHI DISTRICT OF BANGLADESH
An investigation was conducted during the period from March to December 2009 to investigate the induced spawning practices in 22 hatcheries of 6 Upazilas of Rajshahi District of Bangladesh. It was observed that, 6 native fish species viz. rui ( Labeo rohita ), catla ( Catla catla ), mrigal ( Cirrhina mrigala ), calibaush ( Labeo calbasu ), bata ( Labeo bata ), gonia ( Labeo gonius ) and six exotic fish species such as silver carp ( Hypophthalmichthys moltrix ), bighead carp ( Aristichthys nobilis ), grass carp ( Ctenopharyngodon idella ), common carp ( Cyprinus carpio ), Thai pangus ( Pangasius sutchi ), rajputi ( Puntius gonionotus ) were used in the surveyed hatcheries for induced spawning purpose. The average length limit was 41.70±13.02 to 72.81±25.98 cm, average age limit was 1.96±0.75 to 3.08±0.90 years and average weight limit was 1.83±0.79 to 7.54±3.92 kg of the brood fish. Two types of hormone injections like PG (pituitary gland) and HCG (human chorionic gonadotropin) were used for induced spawning. The rate of 1st doses of injections of PG were from 1 to 4 mg/kg and HCG from 150 to 500 IU/kg and the rate of 2nd doses of injections of PG for native and exotic species were from 4 to 8 mg/kg and 4 to 10 mg/kg respectively. The incubation period and hatching rate in different fish species varied from 10 to 72 hours and 55% to 80%, respectively. DOI: http://dx.doi.org/10.3329/jles.v6i0.9723 JLES 2011 6: 65-68
Use of Hormones in Induced Spawning of Carps
The role of hormones in regulating the ovulation and spawning in fishes is still controversial and inconclusive. Although remarkable progress has been made during the last decade in studying the effect of various hormones on the reproductive physiology of a number of fishes, little information is available on the regulation of hormones in the spawning of the difficult-to-spawn carps, namely the major Indian and Chinese carps. These important cultivated species, although they attain maturity in ponds, fail to reproduce in that environment in the absence of external stimuli which are essential for the release of gonadotropins resulting in ovulation and spawning.Attempts made to breed these carps by injections of mammalian hormone preparations did not meet with much success. Administration of fish pituitary hormones, on the other hand, induced ovulation and successful spawning in these fishes. While extensive use of crude pituitary treatment for production of carp seed is in vogue in pisciculture all over th...
Experiments on second spawning of major Indian carps in the same season by hypophysation
Abstract The major Indian carps, rohu ( Labeo rohita ), catla ( Catla catla ) and mrigal ( Cirrhinus mrigala ), were hitherto known to breed only once a year—during the monsoon season—either in their natural habitat or by hypophysation in captivity. It has been found possible to mature and induce these carps to spawn twice in the same season, within an interval of about 2 months, and thus augment the spawn production. The technique in brief is as follows. (i) The fish are bred by hypophysation early during the monsoon, in June. (ii) After the first spawning, prophylactic measures are adopted. (iii) The fish are fed supplementary feed consisting of groundnut oil cake and rice bran at a ratio of 1 : 1 and 2–5% body weight of the fish. The spent fish, under favourable weather conditions, were found to mature for a second time and were ready for a second spawning, using hypophysation, in about 2 months. This finding is a breakthrough in the field of fish culture at it helps to obtain more spawn from the same specimens in one season. These results demonstrate the possibility of extending this practice to other cultivated species and thereby augmenting the supply of quality fish seed.