Investigation of health status of juvenile exotic carps from various farming conditions of Bangladesh

Health status of juvenile silver carp, Hypophthalmichthys molitrix and silver barb, Barbodes gonionotus were investigated in three fish farms following different farming conditions through clinical and histopathological examinations for a period of nine months. Here the fishes and water quality parameters were sampled on monthly basis. Among the water quality parameters, water temperature has a distinct effect on fish health observed during the winter season. Different clinical signs like scale loss, dermal lesion, fin erosion were observed, while histopathologically necrosis, pyknosis, inflammation, haemorrhage, hypertrophy, vacuoles, missing of gill lamellae and clubbing were evidenced in the investigated fishes. The study showed that pathological symptoms were mainly increased during the winter season and H. molitrix exhibited severe pathological symptoms in compare to B. gonionotus during the investigation. It was also found that fishes of BAU farm was comparatively in the best condition, while, the fishes of other farms were severely affected during the experimental observations. In addition, disease like Epizootic Ulcerative Syndrome (EUS), protozoan disease and suspected bacterial colonies were clearly evidenced in the fishes of Government and NGO fish farms.

Experimental pathogenesis of Aeromonas hydrophila bacteria in shing Heteropneustes fossilis(Bloch)

Pathogenicity of Aeromonas hydrophila bacteria was tested on the stinging catfish Heteropneustes fossilis. Before artificial infection the morphological, biochemical and physiological characters of Aeromonas hydrophila were studied. The infections were done by two different methods, viz., intramuscular (IM) and intraperitoneal (IP) injection. In infection experiment, each group of 10 fish were injected either intramuscularly or intra peritoneally with one dose higher than the LD50 dose (9.6 x 107 CFU/fish). All the fish tested died within 1 to 9 days. Both in cases of intramuscular and intraperitoneal injection, external pathology were found. Haemorrhagic lesions were evident at the site of injection. The posterior end of the body surface was found to develop greyish-white lesion that was extended up to caudal fin. Hyperemic anal region and the fin bases were also observed. Total bacterial loads in liver, kidney and intestine were determined. Aeromonas hydrophila could be isolated from liver, kidney and intestine of the experimentally infected fish. In case of intramuscular injection the highest and the lowest bacterial load was found to be 2.4 x 107 CFU/g of liver and 2.1 x 102 CFU/g of kidney and in case of intraperitoneal injection they were found to be 3.6 x 106 CFU/g of kidney and 1.2 x 104 CFU/g of kidney respectively. It was concluded that A. hydrophila could cause serious disease condition to Heteropneustes fossilis and its pathogenesis in the fish was also very efficient.

Culture feasibility of silver barb (Barbodes gonionotus Bleeker) and GIFT with shrimp (Penaeus monodon Feb.) in brackishwater pond

An experiment was conducted to understand the culture feasibility of sliver barb (Barbodes gonionotus) and GIFT (Genetically Improved Farmed Tilapia) with shrimp (Penaeus monodon). There were three different treatment (T) combinations: (T1) shrimp (10,000/ha) and silver barb (10,000/ha), (T2) shrimp (10,000/ha) and GIFT (10,000/ha), and (T3) shrimp (10,000/ha). Shrimp, after 120 days of culture, attained an average weight of 23.77g in T1, followed by T3 (23.70g). The highest average weight was recorded in T2 (24.93g). The specific growth rate (SGR) of shrimp was 6.9%, 6.94% and 6.9% for T1 T2 and T3, respectively. The SGR for the B. gonionotus and GIFT was 2.56% and 4.26%, respectively. The final weight of silver barb was 69.75g and that of GIFT was 161.83g. Survival of shrimp was higher (65.50%) in T2, followed by T3 (59.97%) and T1 (57.03%). Survival rate of silver barb (58.10%) was lower compared to that of GIFT (78.43%). Sporadic and scanty mortality of silver barb with a symptom of blind-red-protruded eye, swollen belly and body lesion was observed. Production of shrimp was higher of 284.05 kg/ha in monoculture, followed 162.47 kg/ha in concurrent culture with silver barb and 136.77 kg/ha culture with GIFT. In spite of similar stocking density of B. gonionotus and GIFT in T1 and T2, respectively, the production of GIFT was higher (1272.95 kg/ha) than that of silver barb ( 402.72kg/ha). Survival, final weight and production rates of shrimp among the treatments were found insignificant while total production of shrimp/fish was found to vary significantly (P

Health and disease status of Thai pangas, Pangasius hypophthalmus cultured in rural ponds of Mymensingh, Bangladesh

Thai pangas, Pangasius hypophthalmus is one of the important aquaculture species in Bangladesh. Over the last few years spectacular development has been taking place in Thai pangas farming in Mymensingh district. Due to availability of easy breeding and culture techniques as well as quick return, more and more people are converting their rice fields into pangas farms overnight. The present study was carried out to examine health and disease status of Thai pangas mainly through clinical, histopathological and bacteriological techniques. In addition, for collecting primary data on disease and health status of Thai pangas and the resultant socioeconomic impacts on rural households, questionnaire interview and participatory rural appraisal tools were used with selected farming households in three upazilas of Mymensingh district. The most prevalent diseases as reported by the farmers were red spot, followed by anal protrusion, tail and fin rot, pop eye, dropsy and gill rot. Other conditions like cotton wool type lesion, ulceration and white spot were reported but with lower incidence. Four isolates of Aeromonas hydrophila were recovered from kidney and lesion of diseased fish. Hemorrhage over the body especially near mouth and caudal region was noticed in the fishes associated with aeromonad infection. Internally, kidney, liver and spleen became swollen and enlarged. The isolates varied with their pathogenicity. All the four isolates were sensitive to Nitrofurantoin, Cotrimoxazole and Tetracycline but were resistant to Amoxycilline. An attempt was made to treat diseased fish with extracts from neem leaf, garlic and turmeric. Recovery of infection was monitored through mortality and histopathology. General histopathological changes of different organs were also studied. Extract from neem (Azadirachta indica) leaf gave better result. Telangiectasis, lamellar hypertrophy and hyperplasia hemorrhage, lamellar fusion, necrosis of lamellar epithelial cells, presence of parasites and their cysts were the major pathology of gills. Hemorrhagic lesion, pyknotic nuclei and melanomacrophage centers (MMC) were found in the liver of fish. Major pathologies in kidney of fish included presence of MMC, necrotic and ruptured kidney tubules, severe haemopoietic necrosis, and hemorrhage. The economic loss due to disease in Thai pangas farming was estimated from the difference between expected production and actual production. On an average, Thai pangas farmers of Mymensingh incur a loss of Tk. 23,104/ha/cycle due to fish disease (3.6% of expected total production). The loss, however, varied with location and size of farms, type of farmers and management practices. The study also highlighted fish health management related problems and recommended further work for the development of user-friendly farmer-oriented fish health management packages.

Helminth fauna of Oreochromis leucostictus (Pisces: Cichlidae) from a tropical lake, Lake Naivasha, Kenya

The helminth fauna of Oreochromis leucosticus (Trewavas) from Lake Naivasha is described. The study was carried out on 1,050 gillnetted fish caught over a period of 24 months at different sites within the lake. Oreochromis leucosticus which is a commercially important fish was observed to be a host of four helminth parasites. These were an acanthocephalan polyacanthorhynchus kenyensis (Schmidt and Canaris), a nematode contracaecum sp.. a trematode clinostomum sp. and a dilepidid cestode Amirthalingamia sp. Seasonal variation in prevalence, intensity of infection, organs infected and the variation in infection with the size, sex and body condition of the host are described. There was no seasonal variation in prevalence but intensity of infection was observed to increase with the age of the fish. Although male fish were observed to be more heavily infected, the parasites did not seem to have any significant effect on the body condition of the fish.