Juvenile Snakehead Research Articles

Size and feed dependent cannibalism with juvenile snakehead Channa striatus

Size and feed dependent cannibalism with juvenile snakehead Channa striatus

Size and feed dependent cannibalism with juvenile snakehead Channa striatus

Abstract A linear regression model was developed to predict cannibalism in juvenile snakehead Channa striatus . Based on morphological measurements of mouth width, head width and body length, the model relates maximum prey length (TL; mm) to predator TL (TL prey = 26.168 + 0.278 TL predator ). This model was verified with a set of independent data, indicating an underestimate of maximum prey size for a certain predator size. The revised model should be: TL prey = 25.809 + 0.405 TL predator (mm). Size differences substantially increased the rate of cannibalism, but prey: predator TL ratios decreased with increased predator TL. Cannibalism rate was 100% during a 5 day trial when the TL ratio of smaller fish to larger fish was 0.35; but the cannibalism rate decreased to 43% when the TL ratio of smaller fish to larger ones increased to 0.64. Increased availability of formulated feed also reduced cannibalism. With no feed offered, cannibalism was 83%; but decreased to 43% when daily feeding rate was 15% of the larger fish's body weight. Our results indicate that cannibalism is unavoidable with this species, but can be greatly reduced among juvenile fish by size grading and ad libitum feeding.

Effects of Feed Application Rates on Growth, Survival, and Feed Conversion of Juvenile Snakehead Channa striatus

AbstractGrowth, survival and feed conversion ratio of juvenile snakehead Channa striatus were evaluated when fed a dry, formulated feed (50% crude protein) at 24 ± 1 C. Six daily feed application rates were used (0%, 5%, 10%, 15%, 20%, and 30%), as a percentage of fish body weight, with three replicates per treatment. After 29 d, final weights were all significantly greater (P < 0.01) than initial weights, except for the 0% application. Feed applications higher than 5% did not result in increased growth (P > 0.05). Feed conversion ratio was 0.99 at 5% feed application, and 6.3 at 30% feed application. Fish survival was increased by providing formulated diet, but no further improvement was found when feed applications exceeded 5%. Cannibalism was reduced by providing formulated feed, but it was unavoidable when substantial differences in fish size existed, even when feeding ad libitum. Our results indicate that the optimal feed application rate is close to 5% body weight/d for juvenile snakehead.

Clinical response of snakeheads ( Ophicephalus striatus) to experimental infection with snakehead fish rhabdovirus and snakehead cell line retrovirus

Abstract Juvenile snakehead fish ( Ophicephalus striatus ) susceptible to epizootic ulcerative syndrome (EUS) were exposed to experimental infections with an EUS-associated rhabdovirus by intraperitoneal inoculation or bath challenge, and to a snakehead cell line derived retrovirus by intraperitoneal inoculation. Experimentally infected groups of fish were held under observation at ambient temperature for 4–25 days in either clean, laboratory groundwater or pond water obtained from a field site contemporaneously affected with EUS. No obvious lesions indicative of EUS developed in any of the infected fish in either aquatic environment over the observation period.

A preliminary study on the dietary protein requirement of juvenile snakehead.

The dietary protein requirement of juvenile snakehead Channa micropeltes was in vestigated by feediung eight semipurified diets containing varying levels of dietary protein within a range of 25.5 to 56.5% by weight over a 56-day feeding period at 28°C. On the basis of daily weight gain and daily protein deposition these results indicate that the requirement by juvenile snakehead for dietary protein was about 52% of protein in the diet when fish meal is used as the sole protein source. The relationship between dietary protein level and food conversion ratio, protein efficiency ratio, apparent net protein utilisation, apparent protein digesti-bility, apparent dry matter digestibility, hepatosomatic index, and gross carcass composition were determined and discussed in relation to other fish species.