Occurrence of Infestation with the Isopod, Alitropus Typus M. Edwards (Crustacea: Flabellifera: Aegidae) on Commercially Important Freshwater Fishes of Kerala, India

Rapidly rising temperatures and increasing organic load in the inland and coastal waters has led to a significant increase in parasite population. The isopod Alitropus typus infestation on fish in these waters have become more frequent, causing mortalities in both wild and cultured fishes. The present study was aimed to investigate the infestation on different fish hosts, mean intensity, prevalence, environmental influences on the parasite abundance and the histopathological changes it causes in the host. A total of 219 isopod specimens were collected from 149 infested fishes in two districts of Kerala, India. Among the different fish hosts, Channa striata was found to be the most susceptible, followed by Catla catla, Cyprinus carpio, and Wallago attu, with 81%, 10%, 7%, and 2% occurrence, respectively. The prevalence and mean intensity of infestation were found to be 69.8%, 44.4%, 68.2%, 62.5% and 1.33, 4.25, 1.26, 1.80 in C. striata, W. attu, C. catla, and C. carpio, respectively. The parasite abundance was directly influenced by temperature and rainfall patterns. The histopathology of affected gill tissues showed epithelial lifting, rupture of secondary gill filaments, vacuole formation and hemocytic infiltration. The findings indicated that the isopod parasite, A. typus had a negative impact on fish health and appearance, causing economic losses to the small scale farmers/fishermen. This is the first reported record of the infestation of isopod parasite, A. typus on the Indian major carp C. catla and C. carpio from India.

Changes of Land Use and Land Cover with the Diversity of Fishes, Aquatic Plants, and Bird’s Species at Wetland Ecosystem

Bangladesh is rich in wetland biodiversity with aquatic plants, fishes, and birds. Mohanganj Upazila is known as the capital of lower Bangladesh. The present study focuses on the changes of land use and land cover (LULC) with a diversity of species that are being least concerned (LC), vulnerable (VU), and endangered (EN). Over the last two decades, the wetland species of Mohanganj were gradually declined. Our results showed that 19 fish, 4 aquatic plants, and 7 bird species were LC in 2015. Among the fish and aquatic plant species, 6 fish species (Wallago attu, Ompok pabda, Channa punctate, Chitala chitala, Salmostoma phulo, and Corica soborna) and 2 aquatic plant species (Nymphaea nouchali and Nymphaea lotus) were VU during the dry and rainy season of 2017 and 2019, respectively. In the dry season of 2019, 4 fish species (W. attu, O. pabda, C. punctate, and Ch. chitala), 2 aquatic plant species (N. nouchali and N. lotus), and 7 bird species (Anas platyrhynchos, Ardeola grayii, Gyps bengalensis, Alcedo atthis, Phalacrocorax fuscicollis, Porphyrio porphyria, and Larus ridibundus) were EN. Among the species, W. attu, N. nouchaii, G. bengalensis, P. porphyria, and L. ridibundus were extremely endangered categories. Changes in LULC, the establishment of settlements for the increasing population, indiscriminate use of pesticides, environmental pollutions, and climate change are the potential reasons for declining trends of wetland biodiversity. Stern actions on land use policy, expansion of organic agriculture, bioremediation of industrial effluents, and adoption of sustainable environmental policies should be taken by the Government of Bangladesh for immediate conservation of wetland biodiversity.

Changes in the level of oxidative stress markers in Indian catfish (Wallago attu) infected with Isoparorchis hypselobagri

Background Helminth infection and infestation in fishes are detrimental and have a major effect on fish health and fish production. Among various factors, parasitic infections are known to modulate antioxidant defences in fish. Similar to other aerobic animals, fish are also susceptible to the effect of reactive oxygen species and thus have well established intrinsic and efficient antioxidant defences. ‘Oxidative stress markers are an important indicator of the physiological state of the parasite and its host’. Indian catfish, Wallago attu is a freshwater fish that serves as the definitive host of the adult piscine trematode Isoparorchis hypselobagri. Our two years prevalence data signifies the intensity of the problem revealing a minimum of 5.5% and a maximum of 54% I. hypselobagri infection in Indian catfish W. attu (unpublished data). The present study aimed to achieve baseline data attributed to changes in some oxidative markers due to parasitic infection. Results During the present study, the level of enzyme activities of Catalase (CAT), Glutathione reductase (GR), Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Superoxide dismutase (SOD) and lipid peroxidation was investigated to explore the pathogenic impact on the fish host. The level of these oxidative stress markers was monitored in the swim bladder, liver, intestine and muscle of the host. We also recorded the enzyme activities in the parasite I. hypselobagri. Analysis of data revealed an elevation in GST, SOD, GR, GPx and CAT activity in the infected host tissue as compared to the non-infected fish. Further, we observed presence of GST, SOD, GR and GPx enzymes in the parasite I. hypselobagri while CAT did not show any enzyme activity. Conclusions Increased level of enzyme activity in liver, muscle and intestine of infected host has been recorded which indicates increased oxidative stress in the host due to parasitic invasion. The presence of antioxidant enzymes in the parasites suggests an active antioxidant defence system to avoid immune responses to long term survival and establishment in their host.

ẢNH HƯỞNG CỦA MẬT ĐỘ VÀ TẦN SUẤT CHO ĂN ĐẾN HIỆU QUẢ ƯƠNG GIỐNG VÀ STRESS Ở CÁ LEO – Wallago attu (Bloch & Schneider, 1801)

Nhằm xác định ảnh hưởng của mật độ và tần suất cho ăn đến sinh trưởng và tỉ lệ sống cá Leo Wallago attu giai đoạn ương giống, thí nghiệm được tiến hành với 5 mức mật độ (1, 2, 4, 8 và 16 con/L) và các tần suất cho ăn (1, 2, 3, 4 và 5 lần/ngày). Kết quả nghiên cứu cho thấy mật độ ương và tần suất cho ăn đã ảnh hưởng có ý nghĩa thống kê đến tỉ lệ sống của cá thí nghiệm. Tỉ lệ sống của cá giảm ở mật độ ương nuôi cao (p<0,05). Tỉ lệ ăn thịt đồng loại giảm ở các nghiệm thức mật độ nuôi thấp. Tần suất cho cá ăn có tương quan thuận với tỉ lệ sống, tỉ lệ sống của cá tăng trên 50% khi tăng số lần cho ăn lên 3 – 5 ngày/lần. Tỉ lệ ăn thịt đồng loại của cá có mối tương quan nghịch với tần suất cho ăn. Nồng độ cortisol trong máu cá được xem như chỉ thị đối với mức độ stress của cá. Kết quả của nghiên cứu này cho thấy rằng nồng độ cortisol của cá Leo ở mật độ nuôi cao và tần suất cho ăn 1 và 2 lần/ngày cao hơn so với những nghiệm thức còn lại. Do vậy, mức độ stress của cá Leo có thể được xem như một trong những yếu tố chính dẫn đến hiện tượng ăn thịt lẫn nhau và làm giảm tỉ lệ sống đối với loài cá này ở giai đoạn giống. Những kết quả của nghiên cứu này có thể cung cấp thông tin hữu ích nhằm nâng cao hiệu quả của việc ương nuôi cá Leo giống thông qua quản lý mật độ nuôi và tần suất cho ăn. ABSTRACT In order to elucidate the effects of stocking density and feeding frequency on the growth and survival of Wallago attu, post-hatch larvae were stocked at different densities (1, 2, 4, 8 and 16 individuals per liter) and fed with (1, 2, 3, 4 and 5-times per day). The results indicate that stocking density and feeding frequency had significant influences on the survival rate of the larvae (p<0.05). In particular, the survival rate of larvae decreased at trials with high stocking density (p<0.05) due to the cannibalism. The percentage of cannibalism decreased in treatments with low stocking densities. Regarding effects of feeding frequency, the proportionality between the survival rate of larvae and high feeding frequency was observed in this study (p<0.05). The survival rate of larvae reached 50% when fish were fed 3 -5 times per day. The cannibalism had negative relationship with frequency of daily feeding. The cortisol concentration in fish blood is considered as an indicator of stress levels of fish. The results of this study indicated that cortisol concentration of W. attu reared at high stocking density and fed 1-2 times/day was higher than that in other treatments. Therefore, stress levels of W. attu could be one of the main factors causing cannibalism and reduction of survival rate at larval stages. This study provided useful information to enhance the effectiveness of larval rearing of W. attu via controlling stocking density and feeding frequency.

Spatio-Temporal Changes in Ecology and Fisheries in a Tropical Large Indian Reservoir: Insights From a Long‐Term Data Series For Sustainable Development

The geographic information systems (GIS) play an important role in all geospatial aspects of assessment, monitoring and management of inland open water resources for strategic development in fisheries sector. In India, reservoir fisheries development is one of the flagship programme and several initiatives have been taken up towards enhancement and sustainable development. The present study investigates spatio-temporal changes in ecology and fisheries in Hirakud reservoir, Odisha build across river Mahanadi which features one of the largest dam in South Asia. The reservoir is mainly utilized for electricity generation, irrigation and offers tremendous scope to support fisheries and livelihood. As per the seasonal variation analysis, water spread area was at the minimum during premonsoon period. Most of the water quality parameters including nitrate, phosphate, BOD and alkalinity were higher in the premonsoon period and overall the parameters were under favourable range for fisheries. The present investigation from the fish landing sites of the reservoir, recorded merely 40 fish species, indicating loss of fish diversity as compared to the historical reports. The IUCN conservation status showed that among the 40 species only one species, Wallago attu is under VU category and 4 species Chitala chitala, Ompok bimaculatus, Ailia colia and Bagarius bagarius are under NT category. The analysis of time series annual fish catch data using ARIMA model forecasted the increasing trend of fish production. The water quality parameters were presented in GIS platform for better understanding of the spatial variations over time. Habitat protection of fish breeding grounds, closed seasons, mesh size regulations, scientific management and community participation are recommended as the measures for conservation of fish diversity and sustainable enhancement of fish production in the reservoir.

Indigenous Freshwater Ichthyofauna in the Dhanu River and Surrounding Wetlands of Bangladesh: Species Diversity, Availability, and Conservation Perspectives

A checklist of the native fishes of the Dhanu River and adjacent waters at Mithamain Upazila under the Kishoreganj district of Bangladesh is prepared with details on their availability, conservation status, habitat preferences, population trends, and threats. Data were collected monthly by field survey, focus group discussions, and personal interviews by using a semi-structured questionnaire and a pictorial check list of fish species. A total of 91 indigenous fish species of 59 genera belonging to 29 families under 11 orders were documented where 17.6%, 27.5%, 31.9%, and 23.1% species were abundantly available, commonly available, moderately available, and rarely available, respectively. Among those, 24 fish species (26.4%) were under the threatened category (3 critically endangered, 11 endangered, and 10 vulnerable) according to the IUCN Bangladesh. Notably, the globally threatened Cirrhinus cirrhosus, Channa orientalis, and Wallago attu were available in the study area. Fish population trends of 24.2% and 59.3% of the entire fish species were found in decreasing trends at the global and national level, respectively. The leading threats to the fish diversity were indiscriminate overfishing followed by fishing by dewatering of wetlands, the katha fishing method, the use of deprecated fishing gears, etc. Minimizing anthropogenic impacts, enacting fishing laws, installing and managing fish sanctuaries, and raising public awareness can be effective for the conservation of existing fisheries resources.

A NEW SPECIES OF PHYLLODISTOMUM (TREMATODA: GORGODERIDAE, LOOSS, 1899) FROM FRESHWATER FISH WALLAGO ATTU IN AKOLA DISTRICT (M.S.) INDIA

The present investigation deals with the systematic observation of a new species of Phyllodistomum khadensis Sp. Nov. from fresh water fish Wallago attu. The worm is close to all species of genus phyllodistomum in general the body is narrow while the posterior portion of the body is broad and triangular in shape. The oral sucker is terminal. The ventral sucker is rounded in structure and larger than oral sucker. The bladder is long and tubular.The anterior testis is smaller than posterior one. Vas deferans is long, tubular and forms vasa efferentia. Female reproductive organ includes single ovary having its duct. The vitelline glands are two in number compact lobes on either side of the ootype. The eggs are oval to round in shape.

​Bioactive Compounds from Selected Fruits Improve Quality and Oxidative Stability of Wallago Attu Fish Nuggets

Background: This study determined the potential of fruit powder as natural preservatives in fish nuggets and indicated that fruit powder can successfully be incorporated in them without altering their acceptability. Additionally, a comparative study was carried out to find which fruit powder has the best antioxidant and antimicrobial activity, contributing towards the stability of the nuggets. Methods: The guava (Psidium guajava L.) powder, bael (Aegle marmelos L.) pulp powder and dragon fruit (Hylocereus undatus L.) peel powders were incorporated at the rate of 1.5% (w/w) respectively in fish nuggets and its effects on various physico-chemical, textural and sensory attributes of products were evaluated against control. Result: Incorporation of fruit powder significantly (P less than 0.05) increased emulsion stability, cooking yield, moisture, fat and protein percentage. Textural attributes were improved in treated nuggets, however overall acceptability scores were significantly (P less than 0.05) higher for control as adjudged by the panelists. Fruit powder was found to slow down the lipid peroxidation of fish nuggets, as measured by thiobarbituric acid (TBA) value. They also maintained the microbial stability of nuggets upto 10 days during refrigerated storage (4±1°C).