Aquaculture Engineering – Tilapia Research

Tilapia Breeding:

The biology of many individual tilapia species is now well known and the interest

in using these species for fish farming has led to considerable developments in

recent decades.

The principal practical reasons for farming tilapia are:

  • simple reproduction/breeding processes;
  • rapid growth rate;
  • good tolerance to high stocking densities and intensive rearing

conditions;

  • resistance to physical handling.

 

the male is bigger than the female and has higher

production performances for farming (growth speed and food conversion ratio).

 

Mono Sex Tilapia Techniques:

  1. Hormonal sex reversal of fry using Methyltestosterone (steroid) during early stage of birth. Sex-reversal requires obtaining recently hatched fry and rearing them in tanks or hapas where they are subjected to hormone laced feed for about three weeks.
  2. Inter species breeding result in non-fertile offspring.
  3. Genetic code manipulation, this is very difficult and expensive, also requires a of medical knowledge.

 

Sex Reversal Technique:

To do this, you need a tank-based or hapa-based hatchery that will allow fry to be collected at the yolk sac or first feeding stages (no later than one week after they have been released from the female).

Transferred healthy fry of uniform size to the tank or hapa where you will feed them with hormone-laced diet for 21-28 days

The sex reversal feed is prepared as follows:

 

Mix 30 – 70 mg of hormone (methyl or ethynyl testosterone) in 700 ml of 95% neutral ethanol

Add 700 ml of hormone solution to each kg of finely ground feed then mix thoroughly and dry. At this stage you may add any needed supplements

This feed should be kept under refrigeration if it is not going to be used immediately

Feed the fry at a rate of 10 – 30% of body weight per day, at least four times a day for 21 – 28 days.

The fry must eat this feed to sex-reverse

Tilapia males are preferred for culture because they grow faster than females. Females use considerable energy in reproduction and do not eat when they are incubating eggs.

 

Males only culture permits the use of longer culture periods, higher stocking rates and fingerlings of any age. High stocking densities reduce individual growth rates, but yields per unit area are greater. If the growing season can be extended, it should be possible to produce fish of up to 500 grams. Expected survival for all-male culture is 90 percent or greater.A disadvantage of male mono-sex culture is that female juveniles are discarded.

 

Growth rates:

In fish fanning, the growth rate is expressed in individual weight gain per day

(e.g. 1.2 g./day). It can also be expressed as a % of the body weight gain of the

fish per day (e.g. 1.5% for a fish of 25 g.). Better growth performance is achieved when 100 % male populations are used as the stock and also when improved genetic strains are reared. Some fish farmers can obtain growth of 4 g. per day, for fish >350 g. individual size under such circumstances. Standard growth rate after the initial is around 1g per day.

 

Tilapia Feeding Rate:

The commonly bred tilapia species have small stomach and narrow oesophagus. This means the fish cannot be fed a lot of food at once, rather multiple times per day. It is shown both the food conversion ratio and the growth rate are improved if the tilapia food is split into 4 parts every day. More investigation can be done. Time taken for the tilapia fish to absorb and digest the food.

 

The feeding must happen during day light (day time). Tilapia fish does not eat much during the night.

 

Feeding Schedule:

Size of fish

Feeding Frequency

Fry

8 to 4 times a day

fingerlings

6 – 4 times a day

juvenile

4 times a day

Adult

4 times a day

 

 

 

Tilapia Diet:
Tilapia fry are more demanding in their diet than the adults, notably in respect of dietary protein requirements. (around 50% + protein level). Its very important not to feed just plant-based food but some of the protein must come from animal. Animal contains types of amino acid which the plants do not have. Amino acid is very important for growth and protein synthesis.

Appropriate animal protein sources include abattoir by-products (e.g. blood, bone

and meat meals) and fishmeal’s and oils can be integrated as well. Vegetable based

complements such as soya meal, maize meal, cottonseed cake etc. can also

be used. Where possible, the incorporation of a vitamin complex is recommended

in order to account for specific dietary requirements.

 

Feeding rates also depend on different parameters such as:

  • Age and size of the fish.
  • Feed composition and its energetic value.
  • Temperature and oxygen levels of the water.
  • Water turbidity.
  • Rearing system used (intensive, semi-intensive, et)

Tilapia Fish Feeding Rate

Optimal feeding rate:

This is the feeding rate, expressed as percentage of body weight, which allows the

lowest (therefore, the best) food conversion ratio. The fish receives the amount of

food necessary for the maintenance of normal vital functions (swimming,

respiration etc.) as well as encouraging growth.

 

Maximal feeding rate:

This is the feeding rate that allows the highest growth speed. The FCR is usually

not as good as that obtained with the optimal feeding rate since the fish are

induced to consume more food than is necessary, which leads to waste.

Maintenance feeding rate:

The ‘maintenance’ feeding rate is used to keep the fish at the same body weight

where only the food necessary for sustenance is given. This is generally applied to

adult fish and is not recommended for young fish. Tilapia, in case of environmental

problems such as oxygen depletion or an abrupt drop in temperature,

spontaneously adopts the maintenance rate. Generally, the normal feeding of fish that are stressed results in very poor food conversion.

 

 

Daily feeding rate is calculated as a percentage of the biomass of the feeding sample. For example, to calculate the feeding rate / amount:

  1. Take x amount of tilapia from the population
  2. Measure using a scale of the total weight
  3. Find the single weight by dividing the total weight by x amount of fish
  4. Use the look up table to determine percentage of biomass from what stage of development the fish is at.

It is the amount of feed being fed daily to the fish. It is also expressed as percentage of fish biomass.

Fish Size (Rapid Growth)

Feeding of Biomass % Daily

Fry (<10g)

10 – 5

Fingerlings (10 – 40g)

5 – 3

Juvenile

3-2

Market Size

3-2

 

Formula: (x amount of fish weight / x amount) * total amount fish * % biomass (from table above)

Feeding rates are affected by water temperature. Fish of all size eat less and stop taking feed as water decreases or increases beyond their optimum range.

Optimum production temperature is approximately 28/27 degree Celsius with a range between 24 -30 degree Celsius. More information below

Tilapia Fish Feed

Fish Size (grams)

Protein Level % level

< 0.5g

50%

0.5 – 10g

35% – 40%

10g – 35g

30% – 35%

35g – market size

25% to 30%

 

 

ABW (g) total wt. of fish randomly sampled /

No. of fish sampled

DFR

= ABW * stocking density * feeding rate

 

TFR

= DFR * feeding duration

 

FCR

Amount of feeds consumed (kgs.) /

Wet weight gain of fish (kgs.)

 

The closer the FCR to 1.0 kg. the better is the feed. Good feeds have FCR’s of between 1.5 to 2.0 kg.

Tilapia Food Size:

Mash or powder form

This is given to fish weighing < 0.2g. to 5.0g./pc. This is known as the fry mash

Crumbles

This is given to fish weighing 5.1g. to 30.0g./pc. This is also known as the starter crumble.

Pellets a. b.

  1. This is given as soon as the mouth of fish is big enough to swallow the smallest size of pellet.

Juvenile Pellet. This is known as the grower pellet. It is given to fish weighing 30.1 to 90.0g./pc.

  1. Adult Pellet. This is known as the finisher pellet. It is given to fish weighing greater than 90.0g./pc.

 

Tilapia prefer smaller pellets and dislike hard pellets. As a rule of thumb, small fish should be provided with small feed particles while large fish should be provided with large feed particles.

 

 

Water Chemical

There should be a initial chemical analysis of the water supply. 

All potential sources of pollution of the water source of a site must be identified

and assessed for impact

 

Tank system water rate exchange: 1 – 3 times per hour

 

Water Temperature

For the farming of tilapia, a permanent water temperature of 27°C would be

described as an ideal situation. These conditions are rare in real situations.

However, the temperature must not drop below 18°C (except for a very short

period) and must not exceed 34°C (dependent on stocking densities).

Lethal extremes of temperature for tilapia (dependent on species and stocking

densities) are around 12°C and 42°C.

 

Water turbidity (dirtiness of water due to dirt / earth)

Turbidity (cloudiness) has an effect on fish appetite, feeding and, therefore, on

growth. Turbidity due to plankton production (phytoplankton) is, on the contrary, rather beneficial

to tilapia and especially for the microphagous species.

 

NOTE TO MYSELF: RESEARCH:  phytoplankton production

 

Water turbidity due to the presence of mineral materials (sediments and silt) are

always unfavourable for tilapia resulting in poor growth, disease and other

pathological symptoms leading to fish losses.

 

In an extensive system (or semi-intensive), 1 m3/hr. is necessary to produce one

tonne offish per year, remembering that this is only a rough estimation.

 

Intensive Rearing; Growing fish at high stocking densities (20-120 kg/m3 for

tilapia and more than 300 kg/m3 for catfish)

@todo Investigate stocking densities more

 

Masum Ahmed