Abstract
The morphological and genetic variation, reproductive parameters, induced spawning,
larvae rearing and pond culture of threatened snakehead, Channa punctata were studied
at the Fisheries Field Laboratory Complex, Faculty of Fisheries, Bangladesh Agricultural
University (BAU), Mymensingh during March 2009 to August 2012. Morphological and
genetic data of C. punctata were collected from three different locations viz., Sylhet,
Chandpur and Mymensingh of Bangladesh. The results revealed that the Mymensingh
population differentiated than Sylhet and Chandpur populations and maintained low
level genetic variation among the populations. The reproductive parameters such as sex
ratio, gonadosomatic index (GSI), ova diameter and fecundity data of C. punctata were
collected from Mymensingh region. The sex ratio of C. punctata was found quietly male
dominant but did not deviate significantly from parity (1:1) and the males were longer
than that of females. The GSI and ova diameter data revealed that C. punctata spawned
during April to August but the peak spawning season was in June. Fecundity was
estimated by gravimetric method; the observed fecundity ranged from 2,368 to 17,586 in
fish of 12.07-21.05 cm total length and 24.95-111.23 g body weight. Highly significant
(P<0.01) linear relationship was found between fecundity and body weight and
fecundity and gonad weight and the equations expressed as: F=169.1BW-0.196.3
(r=0.964) and F=2017GW-435.6 (r=0.964), respectively during the spawning season. The
average relative fecundity was calculated as 163.1±23.1 g-1 body weight and 560.1±181.1
cm-1 total length. Three different inducing agents were tested to evaluate the breeding
performances of C. punctata in terms of ovulation, fertility, hatchability and
survivability. During screening tests, the breeding performance indicated that HCG
(3000 IU kg-1) was little bit better than cPG double dose (15 mg kg-1 1st and then 6 hrs
interval 25 mg kg-1 2nd dose) and Ovupin-super (0.7 ml kg-1 body weight). The 23:19
ratio showed significantly (P<0.05) higher spawning success compared to same hormone
dose treated of 13:19 ratio of C. punctata and without injecting of any hormone, no
ovulation was occurred during the experiment. Rearing of C. punctata larvae was studied
with different stocking densities and dissimilar feeding regimes for a period of four
weeks in the metallic trays. The growth (weight gain, ADG, SGR and health condition)
and survival of C. punctata larvae showed inverse relationship with the stocking density
and 10-15 individuals 11 were showed significantly (P<0.01) better performance
compared to stocking densities of 20-25 individuals 11 when larvae fed on tubefex
worms. Furthermore, the growth and survival of larvae was directly affected by feeding
regimes and larvae were preferred live feed compared to solid feed. The water quality
parameters were in suitable ranges for fish culture. The growth, survival and yield
performances of C. punctatus were evaluated under monoculture and polyculture
system in earthen pond. After six month, the growth and survival of C. punctata showed
significantly (P<0.01) higher in monoculture compared to polyculture system, but total
fish production was obtained significantly (P<0.01) higher from polyculture than
monoculture system. The total production indicated that C. punctata culture with carps
was better and economically profitable than monoculture.