Journal of Bioresources 3(1): 30-34 (2016) ISSN 2394-4315 Original Research Article Protein Requirement Of Angel Fish Pterophyllum scalare (Schultze, 1823) (Perciformes: Cichlidae) I.K. Pai* 1 , K.N. Mohanta 2 and Maryem Shaikh Altaf 1 1 Department of Zoology, Goa University, Goa-403 206, India 2 ICAR Complex, Ella, Goa-403 402 *Corresponding author: ikpai@unigoa.ac.in Received: January 10, 2016; revised: February 2, 2016; accepted: February 10, 2016 Abstract: Since time immemorial, fishery, which helps in food security and poverty alleviation, has been one of the oldest professions of man and remained to be so, even today. Further, ornamental fisheries has also provides ample scope for improving economy and employment generation. Today, Fish culturing is a major part of aquaculture. Like in other animals, in fishes too, food determines various physiological, developmental or even reproductive aspects. So, several attempts have been made by various workers, to alter food and other environmental conditions to determine optimum growth. However, as there are hardly any attempts to analyze suitable protein requirements for having optimum health and development in fish diet, thus, an attempt has been made to determine the optimum protein requirement for the health growth and development in one of the popular aquarium angel fishes, Pterophyllus scalare by altering protein and lipid contents from 30%-40% protein and 6% -10% lipids in their feed. The parameters such as body weight gain, food conversion ratio (FCR), specific growth rate (SGR), protein efficiency rate (PER) were analyzed. The studies indicate that, the maximum weight gain was at 35% Protein + 6% Lipid (1.99 ± 0.04 g), maximum FCR was 1.71 ± 0.03% at 40% P + 10% L; SGR and PER was maximum at 30% P + 6% L was 2.60 ± 0.06% and 2.33 ± 0.04%), suggesting that food with 30% protein and 6% Lipid is ideal for angel fish for its optimum growth. Key words: Angel fish, Fish food, Protein requirement, Pterophyllum scalare Introduction Among the fishes used in freshwater ornamental fisheries, the majority (> 90%) are bred in captivity, compared to only about 25 of a total of 8000 species in case of marine fishes. The ornamental fish industry relies heavily on the export and import of introduced species (FAO, 2016). In India, like other countries, most popular aquarium fishes used in ornamental fisheries, due to their attractive coloration, sturdiness, stability, ability to withstand considerable environmental variations, relatively easy maintenance etc. are angel fishes, guppy’s, swordtails, platys and molly’s. Production of aquaculture species in semi intensive pond culture system demands the use of artificial feed as a 30 supplementary source of nutrition. Using of such artificial diet for fishes can be traced as early as 1927, by Ida Melon. Akiyama et al. (1991), Tacon (1993) have reported that the most commonly used animal protein sources in the diet are fish meal, whose level could range between 10-50% of the operational costs. Due to increasing cost and short supply of fish meal, cost of fish feed has increased drastically over the years (Higuera and Gardenete, 1989; McCoy, 1990; Bimbo and Crowthber, 1992). So, people have started concentrating on low cost fish feed, by using plant protein sources (Tacon and Jackson, 1985) such as soybean (Dabrowski et al., 1989), which seem to be more promising, as a substitute, as they are I.K. Pai et al., 2016 almost half the price of fish meal. But, the inclination to use substitute plant and animal proteins, as a low cost substitute for fish meal, such alternatives are known to have lower nutritional value, which will result in lower growth rates or a reduced performance of the cultured animals. In addition, such protein sources may cause slight to severe effects on nutritional status of an animal. Despite the above, throughout the world, the search for alternative low cost substitutes is in vogue (Tacon et al., 1983; Stafford and Tacon, 1985; Tacon, and Jackson, 1985; Pongmaneerat and Watanabe, 1991; Rumsey, 1993) By partly replacing dietary proteins by lipids, protein retention in several fish species could be improved. Such protein sparing effects have been experimentally proved in salmon (Garcia et. al., 1981; Johnson et al., 1991), trout (Beamish and Mediandn, 1986), carp (Watanabe, 1987), hybrid striped bass (Nematipour et al., 1992), yellowtail (Shimeno et al., 1979), red sea bream (Takeuschi et al., 1991). Cho and Bureau (2001) reported that improving digestibility of diet formulation and optimizing feeding regimens can improve feed utilization efficiency in farmed fishes. It is well known that fish meal has essential amino acid, fatty acids, highly digestible low carbohydrates etc., Cowey and Sargent (1977) reported that lipid is known to be one of the important nutrients next to protein, which plays a major role in optimum utilization of dietary protein for growth. Lipids are almost completely digestible by fish and seem to be favored over carbohydrates as an energy source. Fishes are also known for utilizing protein preferentially over lipid or carbohydrate as an energy source. Therefore, it is important from nutritional, environmental and economic point of view to optimize the ration of protein and lipids levels. In view of the above backdrop, this experiment was conducted to determine the optimum protein and lipid percentage in fish feed, with angel fish as an experimental organism. Materials and methods One of the most popular aquarium fish, Angel fish (Pterophyllum scalare) was utilized in the present experiment. Uniformly sized, healthy fish fingerlings were procured from Protein requirement of angel fish the freshwater ornamental fish hatchery of the Indian Council of Agricultural Research (ICAR) complex, Old Goa, India. The fishes were given pre-acclimatization treatment by treating with 0.05% potassium permanganate solution for two minutes, to make them free from external parasites and pathogens, if any present. Before initiating the feeding trials, they were kept in 1.0 x 1.0 x 1.0 m3 cement tanks provided with aerator for the survival of the experimental animals. These tanks were filled with 70 l of freshwater, for acclimatization to the laboratory condition. During this period, they were fed 5% of their body weight divided in to two feeds daily with locally available commercial diet (Jalaram’s Fish Feed, Premium). During the experimental period, the fishes were fed separately with nine formulations of food having 30% Protein (P) + 6% Lipid (L); 30% P + 8% L; 30% P +10% L; 35% P + 6% L; 35% P + 8% L; 35% P + 10% L; 40% P + 6% L; 40% P + 8% L and 40% P + 10% L. Three replicated with 10 fishes each in 1m x1m x 1m size with 50 l were maintained with water quality as mentioned in Table 1. All the batches were fed twice daily, with the experimental diet. Further, Food conversion Ratio (FCR), Specific Growth Rate (SGR) and Protein Efficiency Rate (PER) was calculated by following Gerking (1971), Brown (1957) and Donald et al. (1976) methods respectively. Food Conversion Ratio (FCR)  G x 100 R G = Weight gain (g) R = amount of food consumed by fish (g) x 100 % g/day Specific Growth Rate (SGR)  LnW2 - LnW1 T LnW1= Ln of initial weight of fishes LnW2= Ln of final weight of fishes T= days of experiment (70 days) Protein Efficiency Rate (PER)  GF g/day G = amount of consumed protein by fish F = Weight gain (g) The data obtained thereby was subjected to statistical analysis like ANOVA and the comparison among the groups was done by Duncan multiple range test at P<0.05. 31 I.K. Pai et al., 2016 Protein requirement of angel fish Results Table 1 provides the data on the quality of water used for the experiment. The water quality was tested following the procedure as prescribed in APHA (1985). The result indicate that the temperature was between 26.0-30.0 0C, pH was 6.5-7.2; DO was 6.72-7.23 mg/l; hardness recorded was ranging from 93.0-106.2 mg/l; alkalinity raged between 94.0-108.3 mg/l; Nitrate was present at a range between 12.0-20.0 mg/l; while nitrite was varied from 0.04-0.09 mg/l, indicating the quality of water is very well within the permissible level. Table 1. Quality of the water used for the experiment Parameter Temperature pH Dissolved Oxygen Hardness (CaCO3) Alkalinity Nitrate Nitrite Range 26.0 - 30.0 0C 6.5-7.2 6.72-7.23 mg/l 93.0-106.2 mg/l 94.0-108.3 mg/l 12.0-20.0 mg/l 0.04-0.09 mg/l 10% L) and 2.66 ± 0.04 % (35% P + 6% L). PER was in the range of 1.47 ± 0.02 (40% P + 10% L) and 2.33 ± 0.04 (30% P + 6% L). The results reveal that, at 30% P + 6% L feed formulation, PER ratio was the maximum, indicating reaching of optimum protein efficiency by the fish. Further, the feed with 35% P+ 6% L recorded for highest total weight gain and SGR, demonstrating the optimum weight gain and specific growth rate in angel fishes. Best feed conversion ratio of 1.71 ± 0.03 was seen when the fingerlings were fed with 40% P+10% L feed, signifying the optimum conversion of feed to nutrition. The experiments indicate that feed with 35% P+ 6% L best for angel fish fingerlings during their early growth stage. Discussion Cultured fish require protein, lipids, vitamins and minerals in their diet for growth, reproduction and other normal physiological functions. But most of the works on protein analysis has concentrated upon juvenile fish or upon rapidly Table 2. Effect of protein and lipid levels on growth and nutrient utilization in angel fish Pterophyllus scalare Nutrient level 30% P+6% L 30% P+8% L 30% P+ 10%L 35% P+ 6% L 35%P+ 8% L 35% P+10%L 40% P+ 6%L 40% P+ 8% L 40% P+10%L Initial wt. (g) (Mean ± SD) 1.65 ± 0.03a 1.64 ± 0.02a 1.61 ± 0.01a 1.63 ± 0.01a 1.64 ± 0.03a 1.60 ± 0.00a 1.67 ± 0.03a 1.66 ± 0.02a 1.65 ± 0.03a Final wt. (g) (Mean ± SD 3.60 ± 0.04a 3.21 ± 0.06 a 3.09 ± 0.06bc 3.61 ± 0.07a 3.18 ± 0.04bc 2.96 ± 0.11c 3.61 ± 0.11a 3.17 ± 0.09bc 3.01 ± 0.11bc Nutritional indices Weight Gain (g) (Mean ± SD) 1.95 ± 0.04a 1.57 ± 0.06b 1.48 ± 0.07bc 1.99 ± 0.04a 1.54 ± 0.08bc 1.36 ± 0.10c 1.94 ± 0.07a 1.50 ± 0.10bc 1.36 ± 0.03bc Table 2 exhibits that the body weight of the experimental fishes varied from 1.61 ± 0.01 to 1.67 ± 0.03 g, which is the normal weight range for the angle fish fingerlings. The final body weight, after feeding experimental diet for 70 days, was ranging from 2.96 ± 0.11 (35% P+10%L) to 3.61 ± 0.07g (40% P + 6% L) showing considerable improvement of the body weight. The weight gain varied from 1.36 ± 0.03 (40% P + 10% L) to 1.99 ± 0.04 g (35% P + 6% L). FCR showed a range between 1.44 ± 0.02 (30% P + 6% L) and 1.71 ± 0.03% (40% P + 10% L). SGR range was between 2.00 ± 0.05 (40% P + 32 Feed Conversion Specific Growth Rate Ratio (%) (Mean ± SD) (Mean ± SD) 1.44 ± 0.02 2.60 ± 0.06a 1.53 ± 0.03 de 2.24 ± 0.06b 1.64 ± 0.03ab 2.17 ± 0.08bc 1.47 ± 0.03ef 2.66 ± 0.04a 1.56 ± 0.02cd 2.21 ± 0.06b 1.68 ± 0.03ab 2.04 ± 0.11bc 1.50 ± 0.03def 2.57 ± 0.05a 1.63 ± 0.02bc 2.14 ± 0.09bc 1.71 ± 0.03a 2.00 ± 0.05c Protein Efficiency Rate (Mean ± SD) 2.33 ± 0.04a 2.13 ± 0.04b 2.01 ± 0.03c 1.94 ± 0.03c 1.78 ± 0.04d 1.68 ± 0.02e 1.69 ± 0.02de 1.53 ± 0.03f 1.47 ± 0.02f growing young market fish as these have high protein dietary requirements (Wilson and Halver, 1986). Protein is the main constituent of the fish body thus sufficient dietary supply is needed for optimum growth. Protein is the most expensive macronutrient in fish diet (Pillay, 1990). So, the amount of protein in the diet should be just enough for fish growth, where the excess protein in fish diets may be wasteful and cause diets to be unnecessarily expensive (Ahmad, 2000). Reducing feed costs could be a key factor for successful development of aquaculture. The dietary protein are always I.K. Pai et al., 2016 considered as of paramount importance in fish feeding (Bahnasawy, 2009) and the requirement of the same for fish fry is high and ranges from 35% to 56% (Jauncy and Ross, 1982). Furthermore, Wilson and Halver (1986), Wilson (1989), Pillay (1990) and El-Sayed and Teshima (1991) found that, dietary protein requirements decreased with increasing fish size and age. Keeping in view of the above studies, the present work was undertaken on one of the popular aquarium Angel fish Pterophyllum scalare. Though the Fish do not have a true protein requirement but require a balanced combination of the 20 major essential and nonessential amino acids that make up proteins. Fish utilize dietary proteins by digesting them into free amino acids, which are absorbed into the blood and distributed to tissues throughout the body where they are then reconstituted into new specific proteins of the fish tissues. Dabrowski (1979) reported different patterns of changes in PER in relation to dietary protein level and found that, the relationship between dietary protein and PER differs from species to species. In the present studies also PER was analyzed and the results obtained, is in agreement with Dobrowski (1979) observations. In the present studies, the feed with 35% P+ 6% L was proved to be the best, for angel fish fingerlings, during their early growth stage. Which is in agreement with studies of Ahmad (2000), who also reported that, diets containing 35% protein is recommended for fingerlings Nile tilapia Oreochromis niloticus L (~0.5 g) and adult (grow out) fish (20-40 g). 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