Fish In Vietnam Research Articles

ACOUSTIC PROPERTIES OF INDIAN MACKEREL (RASTRELLIGER KANAGURTA), YELLOWTAIL SCAD (ATULE MATE) AND JAPANESE SCAD (DECAPTERUS MARUADSI) BASED ON FREQUENCY RESPONSE ANALYSIS

Multi-frequency acoustic data collected during ex situ target strength measurements in Catba Island, Vietnam was used to calculate frequency response for Japanese scad, Indian mackerel and Yellowtail scad. Total of 168 echotraces of Yellowtail scad, 291 of Japanese scad and 53 of Indian mackerel were generated for frequency response analysis. Results indicated significantly different in r(f) of three species (Post Hoc Tukey Test, p < 0,001). A discriminant function analysis used frequency response at 38, 120 and 200 kHz and backscattering cross section at 38 kHz as independent variable was able to differentiate between species. Approximatly of 87% echotraces of these species was classified correctly. Frequency responses at 38 kHz, 120 kHz and backscattering cross section at 38 kHz were the most important independent variables. This study revealed that Japanese scad, Yellowtail scad and Indian mackerel could be identified acoustically; a finding may be important for acoustic surveys for small pelagic fish in Vietnam.

Prevalence and risks for fishborne zoonotic trematode infections in domestic animals in a highly endemic area of North Vietnam

Fishborne zoonotic trematodes (FZT) are endemic in humans and cultured fish in Vietnam but little is known about FZT in domestic animals. A study was designed to determine FZT prevalence and species diversity, and risk factors for infection, in dogs, cats and pigs. Faecal samples from 186 dogs, 94 cats and 168 pigs belonging to 132 households in Nghia Hung district, Nam Dinh province, were examined for small trematode eggs; those were trematode eggs with length less than 50 μm. Prevalence of FZT varied significantly between cats (70.2%), dogs (56.9%) and pigs (7.7%). Forty-nine of the egg-positive animals (25 dogs, 20 cats and 4 pigs) were necropsied to obtain adult trematodes for identification. The liver fluke, Clonorchis sinensis, and 11 species of intestinal flukes including Haplorchis, Stellantchasmus, Stictodora and Centrocestus were recovered from the infected animals. The practice of feeding raw fish to the animals was a significant risk factor for infection; this risk was reduced if the animals were periodically treated with anthelmintics. Based on the high prevalence of FZT and certain risky husbandry practices, domestic animals are likely to be major contributors of FZT eggs to the environment. Therefore, education of farmers to avoid feeding raw fish and to perform regular anthelmintic treatment of dogs, cats and pigs is needed in integrated FZT control programs.

Prevalence of Zoonotic Trematodes in Fish from a Vietnamese Fish-Farming Community

The prevalence of fish-borne zoonotic trematode (FZT) metacercariae was investigated in fish farmed by rural households in Nghe An Province, located in northern Vietnam. In total, 716 fish, including tilapia (Oreochromis niloticus) and 6 carp species, i.e., grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mrigal (Cirrhinus mrigala), common carp (Cyprinus carpio), silver carp (Hypophthalmychthys molitrix), and roha (Labeo rohita), collected from 53 fish farms were examined. The overall prevalence of FZT metacercariae was 44.6%, ranging from 12.5% to 61.0% in fish species collected from grow-out ponds, which are the production system for growing fish from fingerling size to market size. The overall prevalence was 43.6% in fingerlings cultured in nurseries, ranging from 7.4% to 62.8% for different fish species. The FZT species recovered were heterophyids and echinostomatids and included Haplorchis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus, Stellantchas musfalcatus, and Echinochasmus japonicus, all of which are intestinal flukes in humans, other mammals, and birds. This is the first report of H. yokogawai and E. japonicus in fish in Vietnam, and the first record for S. falcatus in northern Vietnam. Although a previous cross-sectional survey of the people living in these fish farm households revealed a very low prevalence of FZTs (< 1%), our results demonstrate that intestinal flukes are common in farmed fish in this area, suggesting that reservoir hosts such as dogs, cats, and pigs are more important in sustaining the life cycles of these flukes in fish farms than human hosts. This has implications for the effectiveness of control programs focused mainly on treatment of humans.