Abstract

Heteropneustes fossilis were collected at monthly intervals from different fish farms in Haryana to monitor the incidence of any disease in cultured fish. At each fish farm 25 fish samples were collected through nets; each sample contained 40–50 fish and the percentage of diseased fish was determined. Red patches were the most prevalent symptoms of the disease reported, followed by fluid accumulation in the abdomen, creepy curved backbone, spinal deformities, hanging symptoms in water, ragging and splitting of fins. Other conditions, such as ulcers along with cotton like fungal hyphae growth, haemorrhages on body, and injury were also reported but with a lower frequency. Symptoms revealed that disease is the leading cause of mass mortality in various fish farms. Disease control and treatment methods have also been studied. This study emphasized health management issues associated with H. fossilis farming. Thus, the findings of present investigation can be appropriately employed as valuable information on diseases and health management.

1. Introduction

The world population is increasing day by day, so the need to provide food for it is very necessary. This has put pressure on aquaculture. Fish farming is becoming an important industry for the demand of food. India contributes about 6.3% to the global fish production and is the second largest fish producer worldwide. The main objectives of aquaculture are to provide high quality nutritional fish, sustainable development, increasing feed conversion ratio and overall production ^{1, 2}.

Diseases affect the overall productivity of the aquatic ecosystem, directly affecting feeding management practices and aquatic health. The general public refrains from eating sick and dead animals as food because there is a general possibility that they may become ill due to contaminated aquatic food. Skin ulcers on fish are generally avoided by people as food. Some diseases of fish may contain toxins that can affect humans. Therefore, diseases must be controlled to provide healthy nutritional food ³. Farmed fish are more susceptible to disease than wild ones because of artificial conditions imposed by intensive rearing ^{4, 5}. Huge economic losses occur during fish culture due to pathogenic bacterial, fungal, viral, protozoan and parasitic diseases like dropsy, ulcerative disease, bacterial gill disease, motile aeromonas septicaemia, hemorrhagic septicaemia, edwardsiellosis/edwardsiella septicaemia, bacterial kidney disease, fin and tail rot, columnaris, vibriosis, epizootic ulcerative syndrome (EUS), saprolegniasis, enteric red mouth disease, dermocystidiosis, brachiomycosis, enteric septicemia, blue slime diseaseandwhite spot disease ^{5, 6, 7, 8, 9, 10, 11}. Bacteria are the major group from pathogens causing high mortality in aquaculture. Most of the diseases causing pathogens are opportunistic pathogens that can invade fish tissue and make them susceptible to diseases ^{5, 11}. Contaminated and poor quality of water can directly and indirectly affect normal fish behaviour, physiological changes, reproductive behaviour and overall, the fish survival and productivity ¹². Therefore, it is necessary to identify the diseases for fish to have timely treatment, to avoid economic loses for farmers.

Commercial catfish plays an important role in uplifting the socio-economic status of the farmers. The H. fossilis (stinging catfish) commonly called ‘Singhi’, belongs to family Heteropneustidae (air sac catfishes) found in India, Bangladesh, Myanmar, Pakistan and Thailand. H. fossilis was reported throughout India ¹³. This fish lives in freshwater as well as slightly brackish water which have a pH range of 6.0 - 8.0. It is a demersal fish and its main habitats include ponds, ditches, swamps, marshes and muddy rivers ^{14, 15, 16, 17}. This fish easily adapts to the local environment and can be cultured relatively on low oxygen. It is preferred by the local people due to its high nutritional value, delicious taste, high protein and low fat content ^{18, 19, 20, 21}. Very few studies were reported on diseases of H. fossilis. Therefore, we have conducted a survey of diseased fish in different districts of Haryana (India).

2. Method

Specific biofloc, RAS and fish farms from different areas of the districts of Haryana, India were selected for collection of disease outbreaks during H. fossilis rearing. The Biofloc, RAS and fish farms located at different districts were

i) Panipat (Biofloc) having stocking density 3000-3500/10000 litre Biofloc tank: Site 1

ii) Ambala (RAS) having stocking density 10000/10000 litre water capacity: Site 2

iii) Jind (Biofloc) having stocking density 65000/10000 litre Biofloc tank: Site 3

iv) Kaithal (Biofloc) having stocking density 25000/10000 litre Biofloctanks: Site 4

v) Rohtak (Biofloc) having stocking density 25000/10000 litre water capacity: Site 5

vi) Bhiwani (RAS) having stocking density 4000/10000 litre water capacity: Site 6

A Survey of these fish farms was conducted from March 2021 to August 2021 at monthly intervals to monitor the disease incidence in farmed fish. In each fish farm 25 samples of the H. fossilis were taken through the net, each sample contained 40-50 fish and the percentage of diseased fish was determined. Diseased fish samples from different fish farms were transported to the department of Zoology and Aquaculture, Chaudhary Charan Singh Haryana Agricultural University, Hisar (India). The clinical symptoms of the diseased fish were recorded and compared to those enlisted by Sahoo and Mukherjee ²², Sudheesh et al. ²³, Goni et al. ²⁰, Lilley et al., ²⁴, Muthu ²⁵, Silbernagel et al., ²⁶, Andrades, et al., ²⁷, Srivastava ²⁸, Shahjahan`et al., ¹², Wakida-Kusunoki and del Ángel ²⁹, Wildgoose ³⁰, Duc et al., ¹⁷, Schwebel et al., ³¹, Rani and Singh ³², Durborow et al., ³³. To better understand fish health care practices in fish farms, we also examined the mortality rate and treatment and disease control practices selected by the farmers. The diseases were then classified accordingly.

3. Result and Discussion

There is no doubt that water plays an important role in controlling diseases during fish farming and must be maintained for proper growth of fish. Therefore, the water quality parameters (physico-chemical parameters) during the survey of different fish farms were recorded in Table 1 to check for any association with diseases of H. fossilis. pH was recorded by using pH meter.

Timely water changes are the most important factor to control diseases. All farmers conduct timely water changes about two-third capacity depending on water quality parameters. All farmers can follow the recommendations of Wedemeyer et al., ³⁴ and Meyer ³⁵ as seen in Figure 1, which can reduce the chances of diseases in fish. Thus, they were able to control diseases upto some extent, but not completely, using conventional methods and the different types of drugs listed in Table 2.

High mortality rates were recorded in the samples collected from various fish farms. The initial stocking sizes at the Site of 1, 2, 3, 4, 5, and 6 were 0.5, 1, 0.5, 1, 1 and 1 g respectively. During the initial period of culture, disease outbreaks were recorded at days 30, 15, 12, 10, 15 and 30 and the overall mortality rate was represented in Figure 2. Mortality was highest during the fry stage of fish in all these farms and transport injuries were a significant factor in mortality and spread of diseases in these fish. Meyer ³⁵ reported that diseases in fry and fingerlings resulted in loss of about 90% (104 million) of catfish and about 4.54 x l0⁶ kg of fry and fingerling catfish died and many catfish were lost due to diseases.

Floating feed was used in all these farms. At Site 1 farm, they used a feed containing 40% protein with 8% feeding rate; 38-40% protein with 8% feeding rate at Site 2 farm; 38% protein with 7% feeding rate at Site 3 farm; 32% protein with 10% feeding rate at Site 4 farm; 34% protein with 12% feeding rate at Site 5 farm; and 35% protein with 10% feeding rate at Site 6 farm. For optimal growth and efficient feed utilization of H. fossilis, Ahmed ³⁶ recommended feeding as 4 to 4.5% BW/day, having 14.46-16.27 kcal energy g100 g^-1 of the diet/day and 1.60-1.80 g protein while 2–3% ration levels (7.23-10.84 kcal energy and 0.80-1.20 g protein) to meet the maintenance requirement of this fish approximately.

The present study shows the clinical symptoms of diseased H. Fossilis collected from distinct fish farms such as red patches, accumulation of fluid in abdomen, cannibalism, stress, body injury, red spots, hanging symptoms in water during maximum hours of throughout the day, wounds, skin rashes, creepy curved backbone, spinal malformation, ulcers along with cotton like fungal hyphae growth and haemorrhages on body, dorsal and lateral skin lesions, fins appear ragged and split and loss of appetite. The external symptoms of diseased fish were similar to those reported by ^{12, 17, 25, 26, 27, 28, 29, 30, 31, 32, 33}. Diseases were identified mainly on the basis of history and morphological symptoms of fish. Based on these symptoms, diseases that are the main causes of mass mortality and the probable diseases have been listed in Table 3.

Various diseases in catfish such as hemorrhagic septicemia, Motile Aeromonas Septicemia (MAS), ulcer disease or red-sore disease are caused by Aeromonas hydrophila, A. veronii Biovar Sobria, A. sobria Biovar Sobria (Motile aeromonads). Epizootic ulcerative syndrome (EUS) is caused by Edwardsiella ictaluri and Enteric septicaemia is caused by Edwardsiella tarda ²³. Epizootic ulcerative syndrome (EUS) has been given several names like, red spot disease (RSD) in Australia, mycotic granulomatosis (MG) in Japan and epizootic ulcerative syndrome (EUS) in Southeast and South Asia. EUS is caused by fungus Aphanomyces invadans, A. piscicida, A. invaderis and ERA (EUS-related Aphanomyces). Rhabdoviruses are secondary bacteria associated with EUS ^{24, 25}. According to the World Organisation for Animal Health (OIE) EUS occurs after the rainfall and during low temperature for long period or 18-25°C. Various pathogenic bacteria: A. hydrophila, E. tarda, Haemophilus piscium, Flavobacterium columnare, and Pseudomonas sp. were isolated from diseased catfish H. fossilis that caused skin lesion, haemorrhages, swollen kidney and spleen, accumulation of fluid in the body cavity, necrosis of tissue, fin and tail rot. A. hydrophila was responsible for disease MAS also known as Dropsy ^{20, 22}. Faruk ³⁷ also observed fin and tail rot, red spot, dropsy, gill rot, anal protrusion, pop eye, cotton wool like lesion, ulceration and white spot in Pangasius hypopthalmus catfish. Fin damage, also known as fin rot or tail rot, is mainly caused by poor quality water and stress conditions ³. Ferguson et al., ³⁸ have described bacillary necrosis in Vietnamese catfish Pangasius hypophthalmus that later identified to be caused by E. ictaluri by Crumlish et al., ³⁹.

Creepy curved backbone and spinal malformation often occur in varying degrees of severity. Spinal curvature deviations are identified, particularly when looking at the lateral line. These include ventral curvature (lordosis), dorsal curvature (kyphosis) or an S-shaped curvature of the spine (scoliosis) ²⁶. Vertebral axial deviations (e.g., lordosis, kyphosis, scoliosis) in intensive culture have been linked to notochord alterations in embryogenesis ²⁷, water current velocity ⁴⁰, parasitism ⁴¹, Vitamin C deficiency ⁴², poor gaseous expansion of swim bladder in larvae ⁴³, exposure to sub-lethal concentration (0.73 ppm) of malathion ²⁸ and sumithion ¹². Jawad and Luckenbill ⁴⁴ also observed the skeletal deformities in the Indian Catfish (H. fossilis) caught from natural population in Ganges River of India.

Acetodextra amiuri was a parasite responsible for swim bladder disease in Ameiurus melas (bullhead catfish), A. natalus and A. nebulos ^{45, 46}. Fusarium incarnatum-equiseti caused the swollen swim bladder in cultured striped catfish (Pangasianodon hypophthalmus). External clinical symptoms were impaired swimming, anorexia and swelling of abdomen whereas internal symptoms were swelling, necrosis and accumulation of fluid in the abdomen ¹⁷. Affected fish poorly maintain the proper buoyancy and hang vertically in water ²⁶. This disease affects the growth, feed conversion, energy distribution and fish become lethargic ³¹.

Mostly fungal diseases in catfish were caused by water molds of the Saprolegniaceae family, so it is commonly known as saprolegniosis. This disease was observed as a secondary infection between October and March when water temperatures are below15°C and mortality occurs in early spring when temperature rise. Affected fish have cotton-like growths on their skin and gills, depigmented skin and sunken eyes. In more severe cases, cotton-like growths can spread to muscle tissue ³³. Members of Saprolegniaceae family Saprolegnia parasitica ³² and Achyla Americana ⁴⁷ were identified in H. fossilis.

Good aquaculture practices are important to limit fish diseases. Poor water quality, low oxygen levels, high stocking density and insufficient feed are the stressors that may lead to potential pathogens to cause disease outbreaks. According to the World Organisation for Animal Health (OIE), water quality improvements along with early removal of infected fish are effective in reducing the mortality due to EUS in small closed water bodies. Fish ponds are disinfected from EUS by liming and sundry. Dropsy can be treated by salted water, tetracycline, neomycine, furaltadone, nitrofurazone, nifurpirinol, sulfonamides or quinolones. After treatment, approximately 50% of the water should be replaced or the dose given for 3-5 days or as recommended ^{48, 49}. Vertebral axial deviation can be cured by multivitamin supplemented feed ⁵⁰ among them vitamin-C plays an important role in curing this disease ²⁶. Salted water can cure the swim bladder disease in catfish, but these species are sensitive to salt. Water should be changed regularly to maintain optimum water quality. Over feeding should be avoided. Ahmmed et al., ⁵¹ observed that comparatively the 6ppt salinity is better for proper growth of H. fossilis. Saprolegnia infections can be prevented by formalin (25 ppm), diquat (0.125 ppm),copper sulphate (dose according to the total alkalinity of water), especially in late summer and reducing dissolved oxygen to 4 to 5 ppm, maintaining water quality and reducing stress ³³. Fin or tail rot is mainly caused by different types of bacteria. So the different types of drugs depend on the bacteria. Optimal water quality is important to control any kind of diseases. By various researchers, residual effects of these drugs were observed in fish. Therefore, it was suggested that the farmer should use traditional medicinal plants and earthworms to cure the disease.

4. Conclusion

Farming of H. fossilis becomes very important for the upliftment of socio-economic status of the framers. However, during their farming diseases are among the most common problems and were responsible for huge economic losses for the farmers. There are health management problems in H. fossilis farming. Thus the findings of the present investigation can be appropriately employed as valuable information on diseases and health management in Haryana. There is a need for development of farmer oriented disease control and health management practices.

Acknowledgments

The authors are highly obliged to the Department of Zoology and Aquaculture, CCS Haryana Agricultural University, Hisar (India) for providing all the required materials.

References