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PubMed | University Putra Malaysia, Freshwater Fisheries Research Division and National Fish Health Research Center
Type: | Journal: Fish & shellfish immunology | Year: 2016

A tilapia farm experiencing endemic streptococcosis was selected to study the effect of vaccination with a feed-based vaccine on naturally ocurring streptococcosis. A total of 9000 red tilapia, Oreochromis niloticusOreochromis mossambicus of 10020g were divided into 9 cages. Fish of Group 1 in cages 1, 2 and 3 were not vaccinated. Group 2 in cages 4, 5 and 6 were vaccinated on days 0 and 14 (single booster) while Group 3 in cages 7, 8 and 9 were vaccinated on days 0, 14 and 42 (double booster). Vaccination was done by oral administration of the feed-based bacterin vaccine at 4% bodyweight. Samples of serum for antibody study and the brain, eyes and kidney for bacterial isolation were collected at 14-day intervals. The study was carried out during the critical months between April and June. Following vaccination and booster, there was significant (p<0.05) increase in the antibody levels in all vaccinated groups from week 1 that reached the peak at week 3 before declining gradually until week 6. However, second booster on week 6 significantly (p<0.05) increased the antibody level that remained high until the end of the 16-week study period (double booster). Streptococcus agalactiae was isolated at the start of the experiment (day 0) at an average of 105.0% of the sampled fish. In week 4, the isolation rate was 135.7% but increased to 187.6% in week 8, to 2510.0% in week 10, to 285.8% in week 12 and 257.3% in week 14. The average isolation rate was 287.2%, 187.1% and 138.2% of the fish sampled from unvaccinated, single booster and double booster groups, respectively. At the end of the study period, the survival rate was 45.22.45% for unvaccinated, 65.34.8% for single booster and 75.12.1% for double booster groups. Vaccinating fish in endemic farm might not eliminate the disease but was able to significantly improve the survival rate.

Song L.M.,University of Malaya | Munian K.,University of Malaya | Munian K.,Malaysian Forest Research Institute | Abd Rashid Z.,Freshwater Fisheries Research Division | Bhassu S.,University of Malaya
The Scientific World Journal | Year: 2013

Conservation is imperative for the Asian snakeheads Channa striata, as the species has been overfished due to its high market demand. Using maternal markers (mitochondrial cytochrome c oxidase subunit 1 gene (COI)), we discovered that evolutionary forces that drove population divergence did not show any match between the genetic and morphological divergence pattern. However, there is evidence of incomplete divergence patterns between the Borneo population and the populations from Peninsular Malaysia. This supports the claim of historical coalescence of C. striata during Pleistocene glaciations. Ecological heterogeneity caused high phenotypic variance and was not correlated with genetic variance among the populations. Spatial conservation assessments are required to manage different stock units. Results on DNA barcoding show no evidence of cryptic species in C. striata in Malaysia. The newly obtained sequences add to the database of freshwater fish DNA barcodes and in future will provide information relevant to identification of species. © 2013 Li Min Song et al.

Tominaga A.,Freshwater Fisheries Research Division | Hanzawa H.,Freshwater Fisheries Research Division | Yanai T.,Freshwater Fisheries Research Division | Arayama K.,Freshwater Fisheries Research Division
Japanese Journal of Limnology | Year: 2013

We evaluated the relationships between decreased commercial catch and the standing crops of fish and crustaceans in Lake Kasumigaura, Ibaraki Prefecture. We analyzed the changes in weight and individual numbers for 38 fish and 2 crustacean species. The organisms were collected in set nets from the littoral zone at two sites (north and south) in the lake between 1986 and 2005. The mean weight of all 40 species captured at each sampling event increased gradually during the study period. Similarly, we observed an increase in the mean weight of individuals collected at both the north and south sites over time. The change in mean catch weight per sampling event varied among species. For example, at the northern site the mean catch weight per collection increased signif cantly for 11 species, including Plecoglossus altivelis altivelis, Hemibarbus barbus, Cyprinus carpio, Carassius spp., and Ictalurus punctatus, but decreased for 6 species; Hypomesus nipponensis, Hyporhamphus intermedius, and 4 Gobiidae species (e.g., Tridentiger brevispinis). Our results strongly suggest that there is a large standing crop of fish and crustaceans that has increased in the lake over the last 20 years, although the size of the standing crop differs among the various species, and the commercial catch has decreased. They also highlight the need to monitor the standing crops of fish and crustaceans as opposed to relying on analysis on fishery statistics. Furthermore, the increase in the standing crops of all 40 species was caused by an increase in the standing crops of mid- and large-sized individuals but not of small individuals.

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