Colombian Tilapia production takes full advantage of natural freshwater lakes and reservoirs with constant annual water temperatures in the mid twenties. Such environments provide ideal conditions for Tilapia aquaculture. Colombia is also one of the wettest regions of the world with some parts of the country receiving over 7 metres of rainfall per year. As shown in table 1, Colombia is not only a significant producer of tilapia, but with plentiful land mass and water has further potential for expansion of their aquaculture industry into the future.

 

Table 1. Tilapia production in Latin American nations

Country	2006 MT	2007 MT	2008 MT	Area Sq Km	2008 Prod. Per Sq Km (kg)
Brazil	71,253	95,091	96,000	8,514,877	11
Colombia	23,146	27,324	27,300	1,138,914	24
Costa Rica	13,456	19,763	21,180	51,100	414
Ecuador	19,368	20,000	21,000	283,561	74
Honduras	28,400	28,356	20,494	112,090	183

Source: FAO

 

Culture conditions

The grow-out phase of Colombian tilapia production often occurs in lakes and reservoirs. A significant advantage of tilapia cage culture is that there is a disruption in the reproductive lifecycle as any eggs (fertilised or unfertilised) drop through the floor of the cage. This helps to maintain more uniform sized fish within cages throughout the duration of the grow-out. Bacterial infections from Streptococcus are a significant cause of reduced productivity and can cause total average mortality between 30-40%. Annual yields with typical stocking densities of 200-400 fish/m³ can be in the range of 80-120 kg/m³.

Juvenile rearing of tilapia is much more dependent on feed quality and quantity as well as fish farming husbandry. Being an omnivorous fish, tilapia have longer intestines than salmonid species (about six times their body length). The morphology of their stomach and gut is also different. If the stomach is full, additional consumed feed will bypass the stomach and be partially undigested. The low pH of 2 in the stomach breaks down the tough cell walls of algae enabling an additional source of nutrition, especially in juveniles. Blue-green filamentous and planktonic algae which grow rapidly in Colombian water bodies can also be an excellent supplementary source of protein in young tilapia. The time interval between feeding juvenile tilapia is very important. The ideal time interval between feeding for optimal feed digestion is about 4 hours during daylight hours. Compound extruded aquaculture feeds should be nutritionally balanced with a good amino acid profile and protein levels around 45% for young fish. The correct quantity of feed relative to water volume or stocking density and the optimum physical size of feeds should also be used.

 

Table 2. Daily feeding allowances of Tilapia at 28^oC

Size	Feeding Allowance (% fish weight)	Times fed daily
2 days old to 1g	30-10	8
1-5 g	10-6	6
5-20 g	6-4	4
20-100 g	4-3	3-4
>100 g	3	3

Source: Nutrient Requirements of Fish, NRC, 1993

 

Immune challenges

Juvenile tilapia have a range of stressors which confront them in aquaculture systems and test vulnerable biological defence mechanisms centred on their developing immune systems. Some of these stressors are physio-chemical parameters affected by water quality. Other stressors act directly on or via the gastrointestinal tract. In addition to the consumption of formulated feeds, tilapia consume a range of natural feed items including plankton, aquatic macrophytes, benthic and planktonic aquatic invertebrates, larval fish, detritus, and decomposing organic matter. These natural feed items provide extra nutrition, but can also be vectors of transmission of unwanted parasites, bacterial or fungal infection which can be of detriment to aquaculture operations.

 

Maximising Production

This transitional period in the aquaculture lifecycle beyond being alevins but before fish have developed full immunological competency is one where there is the potential for the highest rates of mortality and greatest losses in profitability. There are two major ways in which detrimental damage to tilapia operational productivity and aquaculture earnings can be done. Firstly, high mortality in juveniles can necessitate either over-compensatory stocking or re-stocking of juvenile fish or secondly, feed conversion and disease challenges in larger market sized fish can compromise final harvest weights and yields. Both of these are preferably to be avoided, but disease incidents have and remain to be the greatest constraints to profitable aquaculture production.

 

Trial parameters

One of Colombia’s largest commercial aquaculture feed companies supplied a 45% balanced protein tilapia diet for the trial. The experimental group used Orego-Stim Aquatract powder at 500g/MT and the control group used standard feed with no additives. The trial period covered the first three weeks of life on commercial diets between July and August 2010 at a commercial tilapia farm at Neiva, Colombia. The first two trials used red tilapia fry and another trial used black tilapia fry. All juvenile fish were between 2 and 7 grams average weight and there was between 400 and 700 kg of biomass for each trial. Water chemistry parameters were: Dissolved oxygen 5ppm, water temperature 24C, pH 7, dissolved ammonia 1ppm, Alkalinity 136ppm and total water hardness 140ppm. During the course of the trial the daily number of fish mortalities was recorded, feed cost, Orego-Stim cost and fry cost enabled calculation of return on investment.

 

Table 3. Biometric parameters of the trial

Trial 1 - 3rd August 2010
	Orego-Stim	Control
Number of Fry	200,000	100,000
Average weight (g)	2	7
Average Biomass (kg)	400	700
Trial 2 - 17th August 2010
	Orego-Stim	Control
Number of Fry	150,000	150,000
Average weight (g)	1.5	1.5
Average Biomass (kg)	225	225
Trial 3 - 17th August 2010
	Orego-Stim	Control
Number of Fry	150,000	150,000
Average weight (g)	2	2
Average Biomass (kg)	300	300

 

Results

Cumulative mortality - Trial 1

 

 

 

 

 

 

 

 

Cumulative mortality - Trial 2

 

 

 

 

 

 

 

 

Cumulative mortality - Trial 3

 

 

 

 

 

 

 

 

Table 4. Economic calculations

 

 

 

 

 

 

 

 

 

Conclusion

In all three trials there was a huge reduction in mortality by 28%, 20% and 51% respectively in the Orego-Stim groups after the end of the first three weeks. These cost savings provided a high return on investment of 6, 16 and 32 times the cost of Orego-Stim during the initial phase of the production lifecycle. Fry are one of the most vulnerable stages of the production lifecycle, so reducing mortality early can increase production of harvest sized fish a few months later, resulting in even more return on investment for the Tilapia farmer! In these particular trials these future savings are likely to account for a saving of a quarter, a fifth and a half of total expected final harvest weights in each of the respective trials, in the event that early mortalities are not replenished or that there are no more serious losses in the remainder of the production cycles.

Orego-Stim Aquatract Powder will be of interest to end users at farm level, as this specific formula is for use not within a feed but as a powder to be coated onto feed pellets at the time of feeding. Orego-Stim is a unique 100% natural feed additive/flavour. These unique essential oils contain natural phenolic compounds which have beneficial properties for fish and shrimp aquaculture. Trials have proven that Orego-Stim Aquatract can provide many benefits for ultimate productivity and animal health, leading to better profits and a higher return on investment for the aquaculture producer.

Sincere gratitude to Dr Alfonso Diaz, Comervet S.A This e-mail address is being protected from spambots. You need JavaScript enabled to view it for the collaboration and collection of the trial data from Colombian Tilapia farmers described in this article.

 

 

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