M. Meenakshi, S.M. Pillai, C. Gopal and M.D. Bindhuja1
Central Institute of Brackishwater Aquaculture, 75, Santhome High Road, Chennai, India
Visit for more related articles at Journal of Industrial Pollution Control
The banana shrimp Fenneropenaeus merguiensis is an important alternative commercial cultured species. Presently, the industry is on a look out for an alternative species for shrimp culture. An experiment was conducted to determine the growth and survival of juveniles F. merguiensis using live feed (clam meat, and polychaete worms) and a commercial pellet feed. In 45 days of feeding, the weight gain, per day growth, specific growth rate and survival registered by the shrimp were analyzed and compared. Among the feeds given, clam meat showed highest percentage gain in weight (369.8 %) followed by polychaete (240.4 %) and commercial pellet feed (173.9 %). The survival rate amongst the three treatments did not show any significant variation; however the highest rate was recorded in shrimps fed with polychaetes, clam meat and pellet feed. The ammonia and nitrite concentration in water showed distinct fluctuations in the treatments especially shrimps fed with polychaete worms. Live feeds have imparted faster growth and survival in the present study indicating that early stages of banana shrimp have preference over pellet feed and strategies can be developed to have feeding regimes having a combination of live and pellet feeds.
F. merguiensis, Growth, Survival, Clam meat, Polychaete worm, Commercial feed
The banana shrimp, Fenneropenaeus merguiensis ranks third among the farmed shrimp species. Its production in 2005 was 83,392 tonnes (FAO, 2009). The culture of this species worldwide is of low volume but it forms a good candidate species for shrimp farming and domestication through selective breeding programmes (Hoang, 2001). In India along the west coast, it forms a major species and it has immense potential for culture. Availability of quality seed of this species is a limiting factor for its culture and hence it is important to develop captive broodstock and seed production technologies for this species.
Feed plays a vital role in the production of quality shrimp seed. It should contain all the essential nutrients for the cultured organism and be readily available at low cost, highly digestible with the nutrients available for assimilation (Sudaryono et al. 1995). Crustaceans in captivity depend mainly on chopped fresh feed like fresh clam, frozen squid meat and especially chopped oligochaete worm Pontodrilus bermudensis, which has a superior nutritional value than compound diets (Cahu et al. 1995; Laufer et al. 1998; Radhakrishnan et al. 2000). Fresh / frozen feed decays rapidly and easily deteriorates water quality (Sheen and Wu, 1999). But, pellet diet offers many advantages compared to fresh feed, which includes stability, shelf life, reliable supply, minimal preparation time and known nutrient content. However, live feeds like clam meat, polychaetes (Perenereis nuntia vallata), squids, other molluscs, Artemia biomass and rotifers are preferred over commercial feeds, even though they are costly, have high amount of polyunsaturated fatty acids (PUFAs) and maximum efficacy in terms of growth and survival. (Shimma, 1977; Millamena et al. 1985; 1986; Harrison, 1997; Wouters et al. 2001). Live feeds are rich in high unsaturated fatty acids (HUFA) and provide good proteins in the form of essential amino acids, which influence the growth of shrimps in the early phases of life cycle wherein they require higher quantities of HUFA or EAA since their basal metabolic rate (BMR) is higher when compared to sub-adults and adults.
In both live and pellet diets, protein is the most abundant ingredient for shrimp playing a critical role for growth and development (Smith et al. 1992; Sudaryono et al. 1995). Good growth performance and survival of shrimps in captivity /domestication has become phenomenal in recent days because of the necessity to use domesticated and genetically selected stocks for aquaculture due to the crisis caused by the recurring diseases. Hence, growth rate of penaeid shrimps depends on the quality of the diet.
The present study was undertaken to determine the effects of live feed and pellet feeds on the growth and survival of early juveniles of F. merguiensis.
Experimental Set up
The experiment was conducted with juveniles of F. merguiensis produced at the Shrimp hatchery at the Muttukkadu Experimental Research Station (MES) of Central Institute of Brackishwater Aquaculture (CIBA) for a period of 45 days. The average size of the shrimps was 18 mm – 32 mm / 0.1– 0.8 g @20 nos. in 100 l oval FRP tanks in duplicate for each tank. The tanks were provided with continuous aeration and covered to prevent the shrimps from jumping out of the tank. Prior to the initiation of the trial, the shrimps were acclimatized to the experimental conditions for 2 days and fed with a commercial feed. They were starved for 24 hours before starting the trial. Individual weight of the shrimps at the start of the trial and at fortnightly intervals till the end of the experiment was recorded.
Daily 100% water exchange was followed in the tanks with fresh filtered seawater. Moults, faecal matter and uneaten feed were siphoned out before water exchange. The shrimps were fed @12% of biomass (Polychaete worms, clam meat and commercial pellet feed) 4 times a day (06.00, 12.00, 18.00 and 24.00 h), at 40 : 60 ratio in day and night respectively. Temperature, salinity and pH of the water (table 4) were recorded daily twice at (10.00 and 15.00 hrs). Ammonia and nitrite were analyzed at fortnightly intervals following the standard methods (APHA 1989).
Feed and shrimps (initial and final) were analysed for proximate composition using standard methods. The feed was analyzed for protein (Kjeltech), lipid (Soxhtech), fibre & and ash (AOAC, 1990). Initial and final shrimp samples were analysed for protein by Biuret Method (Gornall et al. 1949), total lipid by chloroform-methanol method (Bligh and Dyer, 1959), carbohydrate by phenol-sulphuric acid method (Dubois et al. 1958), fiber and ash by crucible method (AOAC, 1990).
Growth and survival of the shrimps were calculated as
Data of growth and survival were statistically analysed using one-way analysis of variance and treatment differences were tested by Duncan’s Multiple Range Test (Snedecor and Cochran, 1968).
In 45 days rearing F. merguiensis fed with clam meat, polychaete worms and pellet feed have shown weight increment of 1.95, 1.12 and 0.79 g respectively. Among the feeds tested clam meat has shown significant (p < 0.05) gain in weight (`1.95 g) and length (27.45 mm) compared to that fed with polychaete worms or pellet feed (Table 3). The fortnightly sampling of the shrimps showed there was a progressive increase in weight and length in all the three treatments, but after 30 days of culture, there was a sudden spurt in growth in shrimps fed with clam meat. There was no significant variation in growth between shrimps fed with polychaete worms and pellet feed but for a slight increase in case of polychaete fed shrimps. Shrimps fed with polychaete worms showed highest survival (72.5%) than clam meat and commercial pellet feed (Table 3). The specific growth rate (SGR) was however significantly (p < 0.05) higher (3.56) in clam meat fed shrimps followed by polychaete worms and pellet feed fed shrimps.
The proximate composition of the three feeds and the shrimps after feeding with respective feeds (tables 1 & 2) shows that the shrimps fed with clam meat had 46.73 % protein content and those fed with polychaete worms had significantly (p < 0.05) highest lipid content of 17.47%. The carbohydrate content was higher in the pellet feed as well as in the shrimps fed with the same feed (18.80% and 18.53%) respectively.
The water quality parameters, ammonia and nitrite are good indicators to test the feed efficacy. In all test groups, ammonia was found in the range of 0.358 - 0.392 ppm which were however not significantly different. Shrimps fed with live feeds showed 0.095 – 0.101 ppm of higher nitrite content compared to pellet feed. During the experimental period, the nitrite levels were significantly higher (p < 0.05) during 15th day in case of shrimps fed with clam meat. However nitrite levels were not significantly different in all the treatments.
Shrimps are omnivorous detritus feeders and they prefer natural live feed over the pellet feed. Growth rate in shrimp is influenced by the quality of feed. Generally, growth performance depends on the feed digestibility, its energy content and on its composition (Pina et al. 2006). Obviously, at younger stage, shrimps assimilate nutrients more efficiently than the older individuals. In addition to the type of food, the physiological efficiency, utilization and assimilation of diets also influence the growth of shrimps (Yong et al. 2004).
In the present study, the growth performance of F. merguiensis fed with live and pellet feed has shown that clam meat and polychaete fed shrimps have resulted higher weight gain of 369.8 % and 240.4 % compared to 173.9 % of pellet feed fed shrimps. Similarly, comparing the specific growth rate, clam meat fed shrimps has increased by two times to that of pellet feed fed shrimps. Shrimps fed with polychaete worms have registered 1.93 % of specific growth rate. Live and pellet diet fed shrimps have gained highest protein and lipid content than the other diet fed shrimps. The level of carbohydrate and ash was highest in shrimps fed with pellet feed. Tidwell et al. (1997) have proved that all live feeds support higher growth rate than the prepared diet. Various authors have stated that live feeds are rich sources of high amount of polyunsaturated fatty acids (PUFAs) like Arachidonic acid (C20:4n-6), EPA (C20:5n-3), DHA and (C22:6n-3) are known to be essential for growth promoters (Shimma, 1977; Middleditch and Missler, 1980; Millamena et al. 1985; Lytle et al. 1990). Obviously in the present study of F. merguiensis, these nutrients without processing could have played significant role in attractability, assimilation and for the growth of the shrimps compared to pellet feed. On the other hand, shrimps fed with pellet feed take more time for digestion and hence it delays the utilization of nutrients for physiological purpose whereas shrimps fed with live feed consumes without any delay.
F. merguiensis in the present study has shown variation in the survival rate of shrimps fed with live and pellet diet. The highest survival of 72.5% was observed in polychaete fed shrimps followed by 70% in clam meat and 67.5 % in pellet fed shrimps. Number of authors have reported that artificial diets generally promotes higher growth when compared to live diets, where as the survival rates were almost similar in both the cases (Sedgwick, 1980; Galgani and Aquacop, 1988; Kurmaly et al. 1989; Kamarudin, 1992). However, in the present study the shrimps fed with live diets have shown the highest weight gain and survival compared to those fed with the pellet feed.
Ammonia is the principle end of nitrogenous product excreted by crustaceans (Claybrook, 1983), which has deleterious effect on the growth of the animal (Cold & Armstrong, 1981). Lin et al. (1993) have stated that the rate of ammonia excretion depends on number of factors such as salinity, pH, temperature, molting stage, type of feed consumed and other physiological factors. Stanier et al. (1976) have found that ammonia is known to accumulate in culture systems followed by microbial decomposition of organic material with some fertilization practices, which can significantly affect the culture of shrimps (Boyd, 1982). In this study, ammonia was found to be higher in the tanks, where live feeds were used compared to pellet feed. This may be due to the higher catabolic activities of shrimps fed with live feed. Ammonia excreted is converted to nitrite by bacterial population in water and then to nitrate. Kureshy and Davis (2002) have stated that excess dietary proteins are excreted by aquatic organisms which in turn influence the water quality of the rearing medium. This study has clearly shown that high nitrite concentration was observed in the tanks, where shrimps fed with live feeds. This suggests that the nitrite excretion by shrimp is enhanced so that amino acid balance could be maintained for physiological purpose.
This study has clearly shown that clam meat has resulted in higher growth efficacy over polychaete worms and pellet feed in the early stages of F. merguiensis. The higher survival in polychaete and clam meat fed shrimps may be due to the better management practices followed during the experimental period.
This research was granted by Indian Council of Agricultural Research as part of the Agricultural Produce Cess fund project. The authors would like to thank the Director of CIBA, Chennai for providing research facilities in the Muttukkadu Experimental Station of CIBA.