EFFECT OF STOCKING DENSITY ON GROWTH

Abstract:

The study was conducted to evaluate the effect of different stocking densities on growth performances and production potential of monosex tilapia (Oreochromis niloticus) under cage culture conditions for a period of 120 days from 20 August to 16 December 2016 in Dekar haor of Sunamganj district. Three stocking densities under the experiment were maintained viz. 35, 40 and 45 fish m-3 and designated as treatment 1 (T1), treatment 2 (T2) and treatment 3 (T3), respectively and each having three replicates. Stocked fry of tilapia were fed commercial floating diet at a decreasing rate of 10-5% of body weight at thrice daily until the previous day of harvest. Average initial weight of the fingerlings was 11.0 g. Water quality parameters like water temperature, transparency, dissolved oxygen, pH, total alkalinity and ammonia nitrogen were found within favourable aquaculture range. Survival rate of tilapia varied from 91.40 to 96.10% and the highest survival rate was found in T2 (96.10%) followed by T3 (95.40%) and T1 (91.40%). Gross yield of tilapia obtained from all treatments ranged from 5.60 to 6.50 kg m-3 with the highest yield (6.50 kg m-3) in T2 and the lowest yield (5.60 kg m-3) in T1. Daily weight gain of tilapia was recorded as 1.36, 1.31 and 1.10 g in T1, T2 and T3, respectively. The highest (Tk. 383.94 m3) net profit obtained in T2 followed by T3 (Tk. 337.10 m-3) and T1 (Tk. 285.91 m-3). Cost benefit ratio (BCR) was also the highest in T2 (1.97) and the lowest in T1 (1.74). Result of the study indicates that tilapia stocking density of 40 no. m-3 is better among three treatments in respect of survival rate, growth, fish yield and economic return. Therefore, the farmers could be suggested to rear tilapia at lower stocking density (40 no. m-3) in cages to get higher growth, survival and production in a short period of time.

Cite this article

Umashing Marma, M S Islam, M Biswas, P Das and P R Das. 2017. EFFECT OF STOCKING DENSITY ON GROWTH AND PRODUCTION OF MONOSEX TILAPIA (OREOCHROMIS NILOTICUS) IN FLOATING CAGES AT DEKAR HAOR IN SUNAMGANJ, Journal of the Sylhet Agricultural University 4(1): 121-128.

Farmers get monosex tilapia to boost production

Feeding of monosex tilapia fish in Nyakach. Fish farmers have been supplied with 134,000 monosex tilapia fingerlings Nyeri County to boost their fish production and ensure the region's fish industry thrives. PHOTO | JACOB OWITI | NATION MEDIA GROUP 

In Summary

A plan to boost fish production in a Sh61 million processing plant has kicked off with the distribution of 134,000 monosex tilapia fingerlings to farmers in Nyeri County.

The project, to cost the county Sh2 million, is aimed at enabling the plant to operate for 24 hours a day and helping farmers restock their fishponds.

After six months, the farmers are expected to take their produce to the county-owned Wamagana fish processing plant where they will be bought at Sh300 per kilogramme.

After processing the fish, the county government sells a kilo at Sh400 to the locals through a refrigerated truck.

According to agriculture executive Robert Thuo, fish farmers from the county had been experiencing low production levels especially where tilapia species are stocked due to the high rate of breeding resulting to inbreeding and therefore stunted growth.

“To overcome this challenge and boost fish production, we have procured a total of 134,000 monosex tilapia fingerlings. We expect that the monosex fingerlings will attain the required market size faster if properly fed,” said Mr Thuo.

New Guide to Farming Tilapia: Breeding and Hatchery

Breeding of tilapia is conducted in ponds, tanks or hapas. The stocking ratio for females to males is 1-4:1 with 2 or 3:1 being the most common.

The brood fish stocking rate is variable, ranging from 0.3-0.7 kg/m2 in small tanks to 0.2-0.3 kg/m2 in ponds. The popular hapa-in-pond spawning system in Southeast Asia uses 100 g brood fish stocked at 0.7 kg/m2. Spawning ponds are generally 2000 m2 or smaller. In Southeast Asia, a common hapa size is 120 m2.

Brood fish are given high quality feed at 0.5-2 per cent of body weight daily. Swim-up fry gather at the edge of a tank or pond and can be collected with fine-mesh nets. Fry collection can begin 10 to 15 days after stocking.

Multiple harvests (six times per day at five day intervals) are conducted up to a maximum of eight to 10 weeks before pond drainage and a complete harvest is necessary.

Tanks must be drained and recycled every one to two months because escaped fry are very predaceous on fry from subsequent spawns. Alternatively tanks or ponds are harvested completely after a 2-4 week spawning period. Production of optimum-sized (<14 mm) fry ranges from 1.5 to 2.5 fry/m2/day (20 to 60 fry/kg female/day).

In the South East Asian hapa method, fish are examined individually every five days to collect eggs.

This system is much more productive, but it is labour intensive. Brood fish are more productive if they are separated by sex and rested after spawning.

Sex-reversal

Commercial tilapia production generally requires the use of male monosex populations. Male tilapia grow approximately twice as fast as females. Therefore, mixed-sex populations develop a large size disparity among harvested fish, which affects marketability.

Moreover, the presence of female tilapia leads to uncontrolled reproduction, excessive recruitment of fingerlings, competition for food, and stunting of the original stock, which may not reach marketable size. In mixed-sexed populations, the weight of recruits may constitute up to 70 per cent of the total harvest weight. It is therefore necessary to reverse the sex of female fry.

This is possible because tilapia do become sexually differentiated for several days after yolk sac absorption. If female tilapia receive a male sex hormone (17 a methyltestosterone, MT) in their feed, they will develop as phenotypic males.

Fry collected from breeding facilities need to be graded through 3.2 mm mesh material to remove fish that are >14 mm, which are too old for successful sex reversal. Swim-up fry are generally <9 mm.

MT is added to a powdered commercial feed or powdered fish meal, containing >40 per cent protein, by dissolving it in 95-100 per cent ethanol, which is mixed with the feed to create a concentration of 60 mg MT/kg feed after the alcohol has evaporated.

The alcohol carrier is usually added at 200 ml/kg feed and mixed thoroughly until all the feed is moist. The moist feed is air dried out of direct sunlight, or stirred in a mixer until dried, and then stored under dark, dry conditions.

Androgens break down when exposed to sunlight or high temperatures. Fry are stocked at 3000 to 4000/m2 in hapas or tanks with water exchange. Stocking densities as high as 20,000/m2 have been used if good water quality can be maintained.

An initial feeding rate of 20-30 per cent body weight per day is gradually decreased to 10-20 per cent by the end of a three to four week sex-reversal period. Rations are adjusted daily, and feed is administered four or more times per day.

If sex-reversal is conducted in hapas, the feed must be of a consistency that allows it to float.

Otherwise a considerable amount of feed would be lost as it settles through the bottom of the hapa.

Sex-reversed fry reach an average of 0.2 g after three weeks and 0.4 g after four weeks. The average efficacy of sex-reversal ranges from 95 to 100 per cent depending on the intensity of management.

Hatchery

After sex-reversal, fingerlings are generally nursed to an advanced size before they are stocked into grow-out facilities. This procedure increases survival in the grow-out stage and utilises growing space more efficiently.

Sex-reversed fingerlings are stocked at approximately 20-25 fish/m2 in small ponds and cultured for two to three months to an average size of 30-40 g.

The ponds should be filled immediately before stocking to prevent the build-up of predaceous aquatic insects. Final biomass at harvest should not exceed 6000 kg/ha. In ponds, fingerlings are given extruded feed (30 per cent protein) at an initial rate of 8-15 per cent of biomass per day, which is gradually decreased to a final rate of four to nine per cent per day.

A series of small cages (<4 m3) with increasing mesh size can be used to rear advanced fingerlings.

Sex-reversed fingerlings can be stocked at a rate of 3000 fish/m3 and grown for six weeks until they average 10 g.

Fish of this size can be restocked at 2500 fish/m3 to produce 25-30 g fingerlings in four weeks. These fish can be stocked at 1,500 fish/m3 to produce 50-60 g fingerlings in four weeks.

A recirculation system stocked at 1 000 fish/m3 will produce 50 g fingerlings in 12 weeks. Fingerlings should be fed three to four times daily.

Growth and Production Performance of Monosex Tilapia

Growth and Production Performance of Monosex Tilapia (Oreochromis niloticus) Fed with Homemade Feed in Earthen Mini Ponds

Abstract
Field experiment was conducted to evaluate the growth performance of monosex tilapia using homemade feed with Peninsula Group fish meal and commercially available feed with local fish meal in earthen mini ponds from June-September 2010. Three ponds (T1) were supplied with prepared feed and the other three ponds (T2) with commercially available fish feed. Fish were fed at the rate of 10% of their body weight for the first thirty days then gradually reduced to 6% for the next ten days, 2% for the next ten days and 3% for remaining days. The temperature were ranged from 31.5-33.0°C, DO from 5.5-15 mg L-1 in T1 and 6.5-14 mg L-1 in T2, pH from 7.1-8.0 in T1 and 7.1-7.7 in T2, alkalinity from 105-160 mg L-1 in T1 and 100-145 mg L-1 in T2, nitrate was 0.06 mg L-1 in both treatments and ammonia from 0.02 and 0.04 mg L-1 in T1 and T2, respectively. The results of the present study showed that the best weight gain was observed as 123.48 g in T1 than T2 (111.82 g). The Specific Growth Rate (SGR) was recorded 3.09 and 2.97 and the Food Conversion Ratio (FCR) was 1.51 and 1.40 in T1 and T2, respectively. There was significant (p<0.05) variation among the survival rate (%) of fishes which were 75.55 and 90.37% in T1 and T2, respectively. The fish productions were 19076 and 16312.11 kg ha-1 in T1 and T2. The highest net profit (Taka/ha/70 days) of Tk. 15, 83,213 was obtained with T1. So, the prepared feed showed better performance with monosex tilapia in compared with commercial fish feed with local fish meal.

                                         

NTRODUCTION

Monosex tilapia (Oreochromis niloticus) is a fast growing popular cultivable fish (Chowdhury et al., 1991; Shamsuddin et al., 2012). It can easily survive in derelict water bodies at minimum oxygen level and wide range of temperature and eat all types of feed (Hussain et al., 1989). They may be cultured with low inputs which are locally available. Monosex tilapia is high yielding, excellent breeder and efficient converter to organic and agricultural wastes in to high quality protein, very hardy and resistant to disease, tolerant to over crowding conditions and able to grow in either fresh or brackish water. Tilapia, an omnivore, is assumed to be reared on number of cheaply available foodstuffs containing sizeable amount of carbohydrate. Monosex tilapia growers generally use different supplemental feeds in culture. Only natural food cannot afford high production in commercial monoculture system. Traditionally, fish meal is the preferred dietary protein source for many farmed fish species and is appreciated for its amino acid balance, vitamin content, palatability and un-identified growth factors (Azim et al., 2012; Soltan et al., 2008). Fish meal is considered the most desirable animal protein ingredient in aquaculture diets (Al Mahmud et al., 2012) because of its high protein content, balanced amino acid profiles, high digestibility and palatability and as a source of essential omega-3 polyenoic fatty acids. Among the Southeast Asian countries, Bangladesh in particular abounds with hundreds and thousands of seasonal water bodies in the form of ditches, shallow ponds, road side canals and borrow pits which retain water for 4-6 months, where carp species can not be cultured. No doubt, these water bodies have tremendous potential for aquaculture of fish species with short life cycle and characteristics of faster growth rate and require low input support (Hussain et al., 2000a). Though tilapia is not yet a widely cultured species in South Asian countries, however, its culture practices is increasing rapidly in Bangladesh. There are many homestead derelict mini ponds; proper use of those ponds with any short time culture fish like tilapia can open a new avenue for the poor farmers of Bangladesh.

Thus the aim of the present investigation was to observe the growth performance of monosex tilapia in mini earthen mini ponds using homemade feed and commercial feed.

ATERIALS AND METHODS

The experiment was conducted in 6 experimental ponds each of 0.60 decimal, located in the northern side of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. The study was carried out for 70 days from 26 June to 03 September 2010. The water depth was maintained at a level of 1.0-1.3 m.

To eradicate all undesirable fish, insect and other aquatic organism ponds were drained out completely. Aquatic weeds were removed manually. Lime was applied at a rate of 1 kg/decimal. Lime was soaked for overnight in a metallic container and then applied by spreading homogeneously in the ponds.

Two treatments were considered having 3 replicates in each, treatment 1 conducted with prepared feed (having Peninsula Group supplied fish meal) and treatment 2 conducted with commercially available fish feed named Quality Fish Feed (nursery-2, starter). The fries of monosex tilapia were supplied by Agro-3 Fish Hatchery and Culture farm, Bailor, Mymensingh and transported to the pond site with polythene bags having oxygenation facilities. The proximate compositions of feed ingredients were determined by using standard methods. A prepared feed (55.24% protein) composed of 37.24% fish meal, 15.00% mustard oil cake, 18.38% rice bran, 18.38% maize, 10% wheat flower and 1% vitamin premix was used in T1. Fish were fed at a rate of 10% of their body weight for the first thirty days then was gradually reduced to 6% for the next ten days, 2% for the next ten days (because, during the period water temperature was suddenly increased between 35-38°C) and 3% till the termination of the experiment. The water quality parameters were recorded throughout the experimental period. Water samples were collected between 9:00-10:00 a.m. at fortnightly interval. The physico-chemical parameters like temperature (°C), dissolved oxygen (mg L-1), pH, alkalinity (mg L-1), nitrate (mg L-1) and ammonia (mg L-1) were determined at fortnightly i

Monosex Tilapia Farming | Modern Farming Methods

Monosex Tilapia Farming | Modern Farming Methods

Monosex tilapia farming has taken an important role in the fish farming business throughout the world. Monosex tilapia has great demand and value in the local and international market. As a result monosex tilapia farming rate is growing day by day. There are some other important reasons for gradually increasing the monosex tilapia farming.

Generally, they have high ability of taking natural feed from pond, good interest in supplementary feed, surviving capacity in adverse weather and they have high diseases resistance power. Along with this, the demand of this fish in international market is increasing day by day. Tilapia fish can survive in 12° to 40° centigrade temperature and grow well in 16° to 35° temperature. You can produce monosex tilapia in your pond for twice a year.

The main problem of tilapia fish farming is it’s unconditioned propagate. As a result we can see different aged and sized tilapia fish in the pond and we can’t get desired production. Naturally male tilapia grows rapidly than female. Separating the male tilapia and raising them separately is called monosex tilapia fish farming. This types of fish grow faster and well adopted to supplementary feed. You can raise them in high density and they never make hole in the pond for breeding. Commercial monosex tilapia farming is very profitable business. I am describing the methods of monosex tilapia farming below.

Monosex Tilapia Farming Method

Monosex tilapia are raised through two steps in two ponds. They are raised in nursing and stocking pond. This type of farming system can maximize production.A pond with 1.5 to 4 feet depth is ideal for monosex tilapia nursing. Consider the followings while selecting nursing pond.

• The pond must have to be free form flood.
• Sufficient amount of sunlight is very important.
• The pond must have to be free from all types of harmful aquatic weeds.

Nursing Pond Management

Nursing pond management systems for monosex tilapia farming are shortly described below.

• First of all remove water from the pond and make it dry. If it is not possible to dry the pond, use medicines or chemicals for eradicating cannibalistic and unwanted fishes from the pond.
• After that apply 100 kg lime, 500-700 kg dung, 10-15 kg urea, 5-7.5 kg TSP and 2 kg MOP per acre.
• Prevent entrance of frog, snakes and other harmful predators by making a fence with net surrounding the pond.
• After 5-7 days of applying fertilizers, stock 21-28 days aged monosex tilapia in the pond. Stock 100000-200000 monosex tilapia minnow per acre.
• Apply highly protein enriched (about 35%) feed at the rate of 10-15% of the body weight of total stocked fish. For example if you stock 100 kg fish in the pond then apply 10-15 kg feed daily. Don’t serve all the feeds at once a day. Instead serve the feed 3-4 times a day. Raise the fish in this system for 40-60 days and after that transfer them to stocking pond when each fish weights about 20-30 grams.

Stocking Pond Management

• Remove all types of cannibalistic and unwanted fishes from the pond by drying, pulling net or using medicines or chemicals.
• The depth of stocking pond may vary in accordance with your location. There are no problems if the depth of stocking pond become more than nursing pond.
• After that apply 100 kg lime, 500-700 kg dung, 10-15 kg urea, 5-7.5 kg TSP and 2 kg MOP per acre in the pond.
• After 5-7 days of applying fertilizer, natural fish feeds will automatically grow in the pond. Stock 20-30 grams body weight fish in the stocking pond that you have raised in your nursing pond. You can stock 20000-25000 fish per acre.
• To ensure natural feed in the pond you can apply 400-500 kg dung, 200-300 kg chicken excreta, 3.5 kg urea and 2 kg TSP per acre after every seven days. Stop applying fertilizer if you feed your fish supplementry fish feed.
• Try to change the water of pond daily at the rate of 5% when the fish reach more than 100 grams body weight. Doing this will make good result in total production.
• Monosex tilapia reach 200-250 grams body weight within 100-120 days after stocking. You can start selling from this time. But for high rate you have to wait until they reach 300-500 grams.

Feeding

Feeding the fish good and nutritious food is very important for commercial monosex tilapia production. You can feed the fish those foods that are available in the market for tilapia fish. Feeding chart of different aged tilapia are shown below.

Average Body Weight of Fish	Daily Feeding Rate	Times a Day
20-25	8-10%	3-4
50-100	6-8%	3-4
100-200	5-6%	3
200+	1.5-4%	3

Commercial monosex tilapia farming can play an important role for making the people economically strong and fulfilling the protein and nutritional demand. Popularity of monosex tilapia farming business is increasing rapidly. They are very fast growing, strong and diseases are less. So, if you are thinking about staring fish farming business then you can start monosex tilapia farming. I have discussed with may people and it’s really very profitable business.