Browsing by Author "Epa, U. P. K."

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Acute toxicity of formaldehyde on the ornamental fish, Cyprinus carpio (koi carp) fingerlings
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Rathnayaka, E. M. S. P.; Epa, U. P. K.
The ornamental fish trade is a multibillion-dollar sector that involves more than 125 countries, including Sri Lanka. Formalin, 37% formaldehyde, is widely used in the ornamental fish industry as a prophylactic measure or therapeutic purposes. It is usually used to treat ectoparasites that reside on the body surface or gills of fish, and it is also used as a fungicide for fish eggs. Chemotherapeutic agent usage has been criticized because the indiscriminate usage of chemicals like formalin may cause severe risks to both fish and human health and the environment. The toxicity of chemicals to fish must be decided prior to using any chemical to fish as a therapeutic agent for their diseases. A 96 h acute toxicity test was conducted to determine the median lethal concentration (LC50) of formalin on Cyprinus carpio (Cyprinidae) fingerlings. Experimental fish were exposed to a static bath in 4 L glass aquaria with formalin concentrations of 50, 55, 60, 65 and 70 mg L-1. Seven fingerlings were added to each tank for the acute toxicity test, and glass aquaria were continuously aerated during the test. The control experiment was conducted using de-chlorinated tap water. All five treatments and the control experiment were triplicated. During formalin exposure, fish behavior was observed. The Number of fish deaths was recorded in each concentration separately and probit analysis was conducted to determine the 96-h LC50 value of formalin. Fish behavior changes were investigated during the acute toxicity test. Fish were aggregated near the aeration, erratic swimming with fast movement, fast opercula beating, and fast opening and closing of the mouth, excess mucus production, opercula beating frequency reduction, slow swimming and jumping-like behavior were observed until the beginning of the first death. Mucus accumulation on the body surfaces and gill filament was recorded on dead fish. The gills of the dead fish were damaged and toxicity symptoms were observed. The 70 mg L-1 concentration was the lethal concentration for C. carpio fingerlings in less than 24 h. The LC50 value of formalin on C. carpio fingerlings at 95% confidence level was 55 mg L-1 for 96 h. It was concluded that acute exposure to formaldehyde causes lethal toxic effects on C. carpio fingerlings. Formalin must be used with due care and management in aquaculture practices.
Effects of a commercial probiotic incorporated feed on growth performance and nutrient digestibility of fancy guppy, Poecilia reticulata (Poecilidae)
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Dissanayake, D. S.; Epa, U. P. K.; Kumara, K. R. P. S.
The ornamental fish industry is one of the most thriving industries worldwide. The incorporation of probiotics into the feeds to enhance the production performance of cultured aquatic organisms is a novel implementation of science and technology. The present study was conducted to investigate the effects of a commercial probiotic incorporated feed on the growth performance and nutrient digestibility of Poecilia reticulata. Three experimental diets (T1- 1.0 x 10-1 cfu/mL, T2- 1.0 x 102 cfu/mL, and T3- 1.0 x 105 cfu/mL of probiotic concentration with four strains of Bacillus subtilis and a control diet (without the probiotic) were fed to fish in three replication glass tanks (30 cm x 15 cm x 30 cm) for 75 days. In each tank, ten P. reticulata with weight and length of 0.09 ± 0.00 g and 0.9 ± 0.00 cm respectively, were stocked after one week of acclimatization. Fish were fed twice a day at 2% of their body weight. Dissolved oxygen (DO) and pH were measured weekly and the standard length and weight of fish were measured biweekly. Fecal matter was collected twice a week from each experimental tank. The nutrient digestibility of P. reticulata was determined using chromic oxide as an inert marker. The proximate composition of the diets was analyzed using standard methods. DO and pH were not significantly different between the treatment and the control tanks (p>0.05, One-way ANOVA) and were within the optimum ranges for guppy (DO> 6 mg/L, pH 6.8- 7.8). Incorporating the probiotic into the commercial feed positively affected the specific growth rate (SGR), average daily growth (ADG), % body weight increase (% BWI), and % total length gain (% TLG) of P. reticulata. T3 had the best growth performance with the highest final weight (3.25± 0.78 g), length (2.6 ± 0.06 cm), %SGR (1.69 ± 0.31), ADG (0.03 ± 0.01 g/day) and % BWI (71.28 ± 6.25). The lowest final weight (2.084 ± 0.22 g), length (1.8 ± 0.15 cm), % SGR (1.15 ± 0.14), ADG (0.02 ± 0.00 g/day), % BWI (56.51 ± 4.30) were recorded in the fish fed the control diet. All the growth parameters were significantly higher in the T1, T2 and T3 than in the control (p>0.05, One-way ANOVA). There was no significant difference in the nutrient digestibility of P. reticulata between each treatment and the control (p>0.05; One-way ANOVA). Further, the proximate analysis showed no significant difference in the crude protein and ash content among the different experimental feeds (p>0.05; One-way ANOVA). The commercial probiotic used in the study did not affect the nutrient digestibility of P. reticulata, water quality in rearing tanks or proximate composition of experimental feeds. The incorporation of a commercial probiotic into the diet of P. reticulata significantly increased its growth performance.
Enrichment of Panagrellus redivivus (microworm), culture media with waste materials to increase the yield
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ama, W. D. I.; Epa, U. P. K.
The production of low-cost, nutrient-rich live feed is essential for sustained aquaculture. As a result, the aquaculture industry uses "microworms," which are tiny nematode worms. The selection of culture medium has a significant impact on nematode yield. By adding waste products to the culture medium, such as fish meal, sugar molasses, and potato peels, this study aims to maximize production and reduce the production cost of Panagrellus redivivus microworms. Further, moisture levels in the culture media that maximize microworm yield and Panagrellus redivivus microworm survival in water were studied. As the control medium, bread, milk powder, and water culture mixture, which Sri Lankan aquaculture farmers commonly use in culturing microworms, was utilized. In the experimental units, increasing amounts of waste materials, potato peels, fish meal, and sugar molasses were incorporated into the control culture medium by replacing its constituents, with 33.33% to 50% potato peels, 5% to 15% fish meal, and 2% sugar molasses. The impact of varying moisture content on microworm yield was investigated by adjusting water volume in successive batches of culture media. Each medium was divided into three replicates, and 2×105 numbers of P. redivivus were inoculated into each. After five days, microworm yield was determined by counting in a Sedgwick Rafter cell under a light microscope. Microworm survival in water was assessed by inoculating eight sets of three plastic containers with live microworms to take, their initial and subsequent daily counts over seven days using a Sedgwick Rafter cell under a light microscope. According to the results, waste potato peels enhanced the microworm yield compared to the control culture medium, possibly due to the presence of readily utilized carbohydrate sources for microworms (p < 0.05). However, fish meals and sugar molasses do not have beneficial effects because the protein and carbohydrate sources in these ingredients may not be easily utilized by microworms, even though ingredients are rich in protein and carbohydrates. Furthermore, to maximize the microworm yield, 45 ml of water needed to be added for every 50 g of culture media. It was observed that, after 5 days in water, harvested microworms exhibited over 50% survival rate, affirming their suitability as a live food. These results highlighted the possibility of using waste materials and microbes to increase P. redivivus production.
Incorporation of pumpkin, Cucurbita maxima (Cucurbitaceae) peel as a feed additive for the growth and color enhancement of Guppy, Poecilia reticulata (Poeciliidae)
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Cassim, N.; Epa, U. P. K.
Ornamental aquaculture relies greatly on the colors of fish and nutrient-rich feed is a major contributing factor. Carotenoid sources are the main ingredients that enhance fish color. Here, as a cost-effective alternative for commercial carotenoid sources we aimed to test the effect of Cucurbita maxima peel as a color enhancer for Poecilia reticulata. Three diets, incorporating 5% (T1), 10% (T2), 15% (T3) and 0% (control) C. maxima peel with respect to total feed weight were fed to fish in three replicate tanks arranged in a completely randomized design. Ten male P. reticulata fries with average weight and length of 0.019 ±0.00g and 0.7 ±0.0 cm, respectively, were stocked in each tank. Fish were fed experimental diets of 2% of body weight twice a day for 75 days. Fecal matter was collected semiweekly. DO and pH of water were measured weekly using a multimeter. Fish weight and length were measured fortnightly using an electronic balance and a measuring board. Water quality parameters weren’t significantly different among treatments and control and remained within the optimum ranges (DO>6mg/L, pH 6.8-7.8) for P. reticulata. Incorporating C. maxima peel into the feed positively influenced the growth of P. reticulata. Among the treatments, the highest values for final weight (FW); 0.16 ±0.002g, body weight increase (BWI); 0.14 ±0.00g, percent body weight increase (%BWI); 88.12 ±0.15%, specific growth rate (SGR); 1.89 ±0.0, apparent digestibility coefficient (ADC); 59.97 and the lowest feed conversion ratio (FCR) of 1.42 ±0.02 were recorded in T3. In contrast, the minimum growth was recorded from T1 with the lowest FW (0.130 ±0.00g), BWI (0.11 ±0.00g), %BWI (85.38 ±0.11%), SGR (1.879 ±0.0), ADC (14.00), with the highest FCR; (1.80 ±0.02). Adding C. maxima peel increased the length parameters and survival rate (SR%) but showed no significant statistical difference with the control (P>0.05). T3 had the maximum SR% (76.67 ±5.77%), while the control had the minimum (70 ±0.00%). The maximum body length was recorded from T3 (3.0 ±0.2cm) while T1 (2.6±0.2cm) and control (2.7±0.3) had the minimum. According to the results, the maximum brightness and carotenoid contents were recorded in T3 (Gray value=50.99 ±4.02, carotenoids=4.05 ±0.27 μg/g wet weight) while lower brightness (and carotenoid levels were in T1 and the control. In conclusion, C. maxima can be used to enhance the coloration of P. reticulata, but it needs to be in higher concentrations. The incorporation of C. maxima exhibits a positive influence on fish growth. Changing the process of C. maxima powder or extracting carotenoids from peels is recommended for better results.
Infection with digenetic metacercariae of Yellow Grub, Clinostomum sp. (Trematoda, Clinostomidae) in a wild fish population in Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Jayakody, J.A.H.C.; Epa, U. P. K.
Spike tail paradise fish, Pseudophromenus cupanus (Cuvier, 1831) is a freshwater fish found only in Sri Lanka and South India. P. cupanus was sampled using a hand net from a freshwater lake, Dadagamuwa wewa in Gampaha district. Adult fish with length range of 2-5cm (n=210) were examined for parasites by cutting the ventral side from the anal opening to the lower jaw. Large number of internal parasite was observed with the naked eye in the abdominal cavity of P. cupanus that were sampled from May to October 2018. The metacercariae collected from the abdominal cavity were fixed in 70% alcohol and permanent slides were prepared after staining in heamotoxyline and eosin. According to the morphological features observed through binocular microscope, the parasite was identified as Clinostomum sp. The main morphological characters of the metacercaria were stout body, slightly wider in gonadic region; 4000-6000μm long, 2560-3000μm wide. The elongated oval shaped metacercaria possessed small oral and a ventral sucker. Testes arranged in tandem between middle and posterior third of body. Clinostomum sp. has a heterogeneous life cycle and both vertebrates and invertebrates act as hosts and assist them in completing life cycle. Humans may become accidental hosts if they ingest raw freshwater fish containing metacercaria of Clinostomum sp. which causes pharyngitis or laryngitis. This was the first time, metacercarial stage of Clinostomum was recorded in a wild fish population in the country. Further studies are warranted to assess the impact and the pathogenicity of the parasite on native fish varieties in Sri Lanka
The potential use of aquaculture pond sludge and fish waste to produce Eisenia fetida (Lumbricidae), Vermiwash: an approach towards sustainable aquaculture and fisheries industry of Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Madhusanki, F. H. S.; Epa, U. P. K.
Pond bottom sludge and fish waste are considered as major environmental pollutants in the aquaculture and fish processing industries and managing them are necessary to reduce their negative environmental impacts. In pond aquaculture practices, different amounts of nutrients are generated depending on the culture conditions and biological processes of fish and the environment. In the present study, aquaculture sludge and fish waste were used as bedding materials to produce vermiwash using Eisenia fetida. Under field conditions, vermiwash was prepared using three combinations of substrates, including (i) cow dung & Gliricidia leaves (control as industrial practice), (ii) cow dung & aquaculture sludge and (iii) cow dung & fish waste in a 2: 1 ratio and three replicates from each combination. E. fetida (250 earthworms per 6 kg of bedding materials) were introduced to each vermiwash preparation unit and fresh vermiwash samples were collected weekly after 15 days of introducing E. fetida to experimental units for four consecutive weeks. Chemical parameters including pH, conductivity, chemical oxygen demand (COD), total nitrogen (TN), orthophosphate (Ortho-P) and total potassium of vermiwash samples were measured. A germination test was conducted using Phaseolus vulgaris seeds with experimental vermiwash samples extracted in the fourth week. After three months, the number of earthworms in vermiwash units was counted to assess their survival ability. TN in aquaculture sludge vermiwash (0.22±0.20%) was comparatively higher than the fish waste (0.09±0.04%) and the control (0.16 ± 0.15%). However, TN among the control and treatment vermiwash solutions were not significantly different (P = 0.783). P. vulgaris seeds treated with aquaculture sludge vermiwash had the highest percentage of seed germination (63.3%). The germination of seeds (%) in the distilled water was 61.7% and 47.2 % in the control. The lowest seed germination was observed in the fish waste vermiwash (33.7%). The number of E. fetida in vermiwash preparation units of the control and aquaculture sludge increased by 49.2% and 33.3%, respectively, from the initial introduction. Higher mortality of E. fetida was observed in the fish waste vermiwash preparation, and only 9.2% of E. fetida survived at the end of the experiment. It can be concluded that, aquaculture sludge can successfully be used as a bedding material for vermiwash production as it supports the multiplication of E. fetida which also contains higher TN content and higher seed germination of P. vulgaris. Except for the low K level, aquaculture sludge vermiwash is chemically comparable with the control vermiwash. However, fish waste was not suitable to prepare vermiwash in the proportions tested in this study as E. fetida couldn’t multiply and survive in this bedding material. The seed germination in fish waste vermiwash treated P. vulgaris seeds is also low. Aquaculture sludge can successfully be used as a bedding material for vermiwash production as it supports the multiplication of E. fetida, contains comparatively higher TN content and increases the seed germination (%) of P. vulgaris.