Breeding and Seed Production of Silver Pompano

Introduction

The Silver Pompano, Trachinotus blochii, is a tropical species and usually distributed around the Indo-Pacific region. It belongs to the Family Carangidae and lives in the coral reef areas of less than 7 m depth. The juveniles inhabit sandy shorelines and shallow sandy or muddy bays near river mouths while adults move out in schools to clear seaward coral and rock reefs. Juveniles are in small schools, while adults are usually solitary. Adults feed primarily on sand molluscs and other hard-shelled invertebrates.

It is a well-recognized promising species for mariculture due to its taste, adaptability to culture environment, acceptability to formulated diet, good meat quality and international market demand. The shape, colouration and meat quality of this fish is comparable with silver pomfret. The silver pompano is caught sporadically in commercial fishing as its availability from nature is scare. The farming can be successfully carried out in ponds, tanks and floating sea cages. The species is pelagic, very active and is able to acclimatize and grow well even at a lower salinity of about 10 ppt and hence is suitable for farming in the vast low saline waters of our country besides its potential for sea cage farming. In India, Central Marine Fisheries Research Institute has done extensive work on farming of silver pompano.

Brood stock development

Broodstock management plays an imperative role in the success of seed production. Broodstock is recruited from cultured stock at the floating net cages/ brood stock tanks. The fish that are selected for broodstock should be weighing about 1 kg, having no abnormalities and the body should be proportionally balanced.

Broodstock is conditioned through regulation of photo-thermal period and also by providing high nutritional feed including trash fish, pellets, vitamins and multi vitamins mixed at about 3-5% of the total body weight to accelerate the gonadal development. Water quality management is vital to succeed in production. The water exchange is about 400% in 24 hours, and water quality parameters such as pH 7.4-7.8, DO 4-6 ppm, water temperature 29-31°C and salinity at 30-32 ppt are maintained.

Spawning technique

The suggested breeding tank should have the capacity 10 m³, and 10 fishes are allowed in that tank with a sex ratio of 1:1 male to female. Normally, the male brooder is smaller than the females. The spawning pattern of silver pompano does not follow monthly lunar cycles. The hormonal treatment stimulates spawning, and no natural breeding takes place. However, the gonadal maturation of silver pompano is evaluated by cannulation biopsy of intra-ovarian eggs. Once the intra-ovarian eggs attain above 500µm, fishes are induced to spawn by using hormones such the gonadotropin-releasing hormone (GnRH) or human chorionic gonadotropin (HCG). The administered of HCG on dorsal muscle is used at the single dosage of 350IU/kg of body weight for the male and female. Spawning occurs between 2 or 3 days after hormone injection. Typically, it takes place between late night and early morning hours and egg release about 50000 to 150000 eggs with size ranged about 800 to 850 μm in size. The fertilized eggs are transparent and unfertilized eggs are opaque; however, the fertilized eggs are floating and are collected by scooping with 500μm mesh size net. The collected eggs are stocked in the incubation tank of 3 – 5 tonnes with a stocking density of 5 – 20 eggs/litre of water. The hatching rate takes places from 18 to 24hrs ranges between 65 – 75 percent.

Larval and fingerlings rearing

The fertilized collected eggs are stocked in the tank of 3 – 5 tonnes with a stocking density of 5 – 20 eggs/litre of water. The hatching rate takes places from 18 to 24hrs ranges between 65 – 75 percent. Initially, the Nannochloropsis sp or Isochrysis sp. are added to the larval rearing tank to maintain the green water system. The tank bottom is siphoned after 10 – 12 days to remove the organic debris, feed waste and dead organisms including fish to maintain the water quality parameters. It is practiced based on the water quality parameter and amount of waste deposited on tank bottom, normally once or twice in a week. The larvae are fed with rotifer Brachionus plicatilis, on 3^rd day to 10^th day, it is maintained in tank 5 – 15 individual/ml and given thrice in a day. The Artemia nauplii is given as feed about 8^th day to 20^th day while weaning feed (350μm) offered in 17^th day. Around 25^th day, the harvest is carried out; size grading should be done. However, anticipated survival is 20 – 25 percent.

The nursery rearing is initiated at 25–30 DPH, at this stage it is fed with an artificial floating diet of 800μm size. The stocking density is 20 individuals/litre, and the water exchange is maintained about 200 percent. A frequent siphoning is required to maintain the water quality parameters in optimum level. In addition to this, water quality parameters the temperature, pH, oxygen level and ammonia should be closely monitored entire larval rearing period. The floating pellet is provided, it varies with the size of fish mouth. Grading should be done to reduce the mortality. An average growth of silver pompano reaches 1mm/day. At 55 DPH fingerlings reach the size of 2.5 – 3.8 cm, which is ready grow in the floating cages. The fingerlings stocking density is 0.5 individual/ litre of water. The survival rate of 21 percent is anticipated. In addition to this, for packing, the water temperature should be maintained at 25°C - 27°C and the ratio of water and oxygen is 1:3 at 200 fingerlings/bag.

Grow-out culture

CMFRI Experiences of farming in various systems

T. blochii can be reared in cages, ponds and pens. In India, the CMFRI has undertaken farming trials in freshwater ponds, brackish water ponds, and cages installed in the sea. Among all methods, farming of silver pompano in low saline brackish water ponds yielded good harvest. The experiences gained through farming in various systems are given below:

• Earthen pond farming in freshwater (zero salinity) was first attempted in a freshwater fish farm located in Akkiveedu Village, West Godavari district of Andhra Pradesh, India. A sum of 3000 fingerlings was stocked in  0.4 ha pond of 2.5 - 3.0 cm length and 1.5 - 2.0 g were stocked in weight. The fishes were fed with floating pellet feed (32 percent protein and 6 percent fat). Fishes were reared for 240 days and they attained an average weight of 250 - 300g with the survival rate of 45 percent.
• Earthen pond farming in brackish water (low salinity) was first attempted in a brackish water fish pond located in Anthervedhi Village, West Godavari district of India. A sum of 3000 fingerlings was stocked in  0.4 ha pond of 2.5 - 3.0 cm length and 1.5 - 2.0 g in weight. The fishes were fed with floating pellet feed (32 percent protein and 6 percent fat). Fishes were reared for 240 days and they attained an average weight of 450 - 500g with the survival rate of 94 percent. This has created tremendous interest among the brackish water shrimp farmers to grow Silver pompano as an alternative species for shrimps in their abandoned farms, which were hit by frequent outbreaks of diseases.
• Open sea cage farming was attempted in the Gulf of Mannar side of Vedalai Village, Ramanathapuram District, Tamil Nadu, India. A sum of 4000 fingerlings was stocked in the happa (10 m × 10 m) of 2.5 - 3.0 cm length and 1.5 - 2.0 g in weight. When it reached about 25g, the fishes were shifted into the 4 m × 4 m × 3 m size happa.The fishes were fed with chopped lower market value species. Fishes were reared for 240 days and they attained an average weight of 250 - 275 g with a survival rate of 72 percent.

Culture of Silver Pompano in coastal aquaculture ponds

Pond Preparation

The pond has to be dried properly until the cracks appear on the surface. The top layer of the soil containing waste accumulated through previous crop of fish or shrimp has to be removed. Ploughing has to be done to tilt the soil below 30 cm. Feeding areas, corners and side ditches in the pond have to be properly tilled and dried to avoid formation of black soil. The average water pH of 7.5-8.5 would be ideal for pompano farming. The level of lime application during pond preparation depends on the pH of the soil. Hence, the dosage has to be calculated accordingly. Water filling has to be initiated by covering the inlet pipe by using 2 layers of fine nets (100 μ ) to avoid introducing other fishes and predators. A week before stocking, the pond must be fertilized with either organic or inorganic fertilizers to stimulate the plankton bloom.

Salinity

Silver pompano can tolerate vide range of salinities from 5- 40 ppt. However, ideal salinity for farming would be between 15 – 25 ppt. Pond has to be filled with a minimum water level of 100 cm prior to stocking of fish seeds. During the entire culture period minimum of 1.5 meter water depth has to be maintained.

Nursery Rearing and Seed Stocking

Hatchery produced pompano fingerlings of 1 inch size can be stocked in happas/ pens of 2 meter length, 2.0 meter width and 1.5 meter depth. In each happa about 200 fingerlings can be stocked. While stocking care should be taken to avoid agitation of the pond bottom and too many persons getting into the pond may increase the suspended solid load in the water, which may cause gill chocking of the fish fingerlings leading to mortality. Initially the fishes have to be reared in happas for 60 days or until they attain 10 – 15 grams size and thereafter it can be released into the pond. The mesh size of the happa could be initially at 4 mm size and it can be changed with 8mm mesh size happas after 30 days. The stocking density in happa could be maintained as 200 nos/ happa. After attaining 30 grams size ideally 5,000 Nos. can be stocked in a one acre pond.

Nutritional Requirement and Feeding

Silver pompano is a fast moving marine fish and it requires highly nutritive feed to meet the energy requirements. During nursery rearing pompano can be weaned to any type of feeds viz. extruded floating pellet, sinking pellet feed and chopped trash fishes. Ideally pompano can be weaned to extruded floating pellet feed to avoid feed wastage and spoilage of pond bottom. CMFRI has conducted pompano farming demonstration by using the extruded floating pellet feed manufactured by M/s. Rudhra Techno Feeds, Bhimavaram, Andhra Pradesh. During the happa rearing phase, feeding has to be done 4 times a day and in pond culture phase it could be 3 times a day.

Floating feeding zones made of 3 inch size PVC floats of 2 meter length and 2 meter width has to be installed in the ponds. Feed has to be dispensed inside the feeding zone to avoid dispersal of floating feeds due to wind. At least 4 – 6 nos. of feeding zones have to be created in a one acre pond. The feed size should be lesser than the mouth size of the fish and hence, suitable sized feed has to be selected for feeding the fishes. The details of feed and feeding schedule of pompano are as follows:-

A mix of two sizes of feed pellet can be used if there is any size variation of the fishes found during the regular sampling. If sinking pellet feed is used, at least 4 – 8 feed trays (80 cm x 80 cm) per pond could be placed. Regular sampling of fishes once in 15 days has to be carried out to determine growth rate and to calculate the FCR. In the first farming demonstration, FCR was 1: 1.8 with the above formulations.

Water Quality Management

Plankton bloom is essential for early stages of pompano (until 100 grams) culture. If the color of the pond water is clear a mixture of organic (10-30 kg./ha.) and inorganic fertilizers (1-3 kg./ha.) can be applied to obtain algal bloom. Sufficient water level must be maintained in the ponds to reduce risks of the growth of benthic algae. The water depth in the shallowest part of the pond should be at least 100 cm. Water quality can be maintained by exchanging 10% of the water once in a week; 20% per week after 3 months and 30% per week after 6 months. If water colour is too dark, the quantum of water exchange can be proportionately increased. To maintain water pH within an optimum range of 7.5 - 8.5, agri-lime has to be applied regularly. Dissolved oxygen (D.O) level should be maintained above 5 ppm at all times. Paddle wheel aerators can be placed in the pond to create minor water current and to maintain the DO level. Aeration is a must during late evening to early morning period when the fishes attains 200 grams size and above.

Health Management

Silver pompano is a much hardier species and does not get much disease problems. When it is reared in high salinities parasitic infection of copepods may occur. Periodical application of commercially available pond management chemicals like Iodine solution would help to keep the fi shes healthier. Feed supplements like LIV- 52 syrup can be given by mixing with the feed to improve the immunity levels.

Harvesting

Harvesting of silver pompano could be carried out by using drag net as in the case of fresh water fishes. To maintain the freshness and quality of harvested fish, washing in clean water and chill killing can be done. Harvested fishes can be stocked in plastic crates by adding layers of ice in equal quantities at the bottom and top of the fish. It is suggested that harvesting of fish can be carried out during the off season period of April to June to get a better price. In the domestic market, silver pompano has demand starting from 250 grams size onwards.

References

• Gopakumar, G., A. K. Abdul Nazar, R. Jayakumar, G. Tamilmani, M. Sakthivel, C. Kalidas, P.Ramesh Kumar, Hanumantha Rao, R. Premjothi, V.Balamurugan, B.Ramkumar, M.Jayasingh and G. Syda Rao. 2012. Broodstock development through regulation of photoperiod and controlled breeding of silver pompano, Trachinotus blochii (Lacepede, 1801) in India. Indian Journal of Fisheries. 59 (1): 53-57.
• Gopakumar, G., Abdul Nazar, A .K., Jayakumar, R., Tamilmani, G., Sakthivel, M., Ramesh Kumar, P. and Kalidas, C. (Eds.). 2012. “Hand book on breeding and seed production of Cobia and Pompano”. Published by: Central Marine Fisheries Research Institute, Mandapam, India. 48 pp.
• Jayakumar, R., Nazar, A K A., Tamilmani, G., Sakthivel, M., Kalidas, C., Ramesh Kumar, P., Rao, G Hanumanta and Gopakumar, G (2014) Evaluation of growth and production performance of hatchery produced silver pompano Trachinotus blochii (Lacépède, 1801) fingerlings under brackishwater pond farming in India. Indian Journal of Fisheries, 61 (3). pp. 58-62.
• Kalidas, C., Sakthivel, M., Tamilmani, G., Ramesh Kumar, P., Abdul Nazar, A. K., Jayakumar, R., Balamurugan, V., Ramkumar, B., Jothi, Prem, R. and Gopakumar, G. (2012). Survival and growth of juvenile silver pompano Trachinotus blochii (Lacepède, 1801) at different salinities in tropical conditions. Indian Journal of Fisheries, 59 (3): 95-98.
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• Nazar, A. K.A., Jayakumar, R., Tamilmani, G., Sakthivel, M., Kalidas, C., Ramesh Kumar, P., Anbarasu, M., Sirajudeen, S., Balamurugan, V., Jayasingh, M. and Gopakumar, G. (2012) Larviculture and seed production of the silver pompano, Trachinotus blochii (Lacepede, 1801) for the first time in India. Indian Journal of Fisheries, 59 (3): 83-87.
• Pakingking, R., Mori, K.I. Bautista, N.B. Ayson, E.G.J. and Reyes, O. 2011.Susceptibility of hatchery-reared snubnose pompano Trachinotus blochii to natural betanodavirus infection and their immune responses to the inactivated causative virus. Aquaculture 311, 80–86
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