Feeding Tilapia in Intensive

8/14/2019 Feeding Tilapia in Intensive

1/4

Benefits of Culturing

Tilapia in Recirculating

Systems

There are m any species of tilapia,

but only a few are w idely cultured

around the world. In the United

States the most common ly cultu red

species of tilapia are th e N ile

(nilotica), Blue (aurea), Mozambique

(mossambicus), Hornoru m

(hornorum), and hybrids such as the

Taiwan ese and Florida red. Choos-

ing a species to culture d ependslargely on customer p reference,

legal status, grow th rate and cold

tolerance.

Tilapia are w ell suited for cultu ring

in ponds, cages, tanks, or raceways.

Using ponds is the most popular

method in the southern Un ited

States due to longer growing

seasons. In the south ern most p arts

of Texas and in Florida w ater

temperatures can remain warmenough for year-round growth. In

the cooler, temp erate regions of the

North an d Midw est, tank culture is

favored. Tank culture has the ad ded

benefit of reducing time and labor

required for harvesting and feeding.

Indoor tank culture is the preferred

method w hen sufficient warm water

is not available du e to climatic

conditions.

There are two typ es of systems used

for tank culture; flow-thr ough

systems, and recirculating systems.

Flow-through systems are only

practical if geothermal w ater or

waste heat are available. Indoor

recirculating systems offer the

advan tages of redu ced land require-

ments, less water u se, and environ-

men tal control for year-round

grow th. Recirculating systems can

recycle as mu ch as 99 percent of the

culture water d aily, although 90

percent recirculation is the p referred

target. To make these systems cost

effective the fish are generally reared

intensively. Intensive r ecirculating

tank culture can prod uce high yields

on sm all plots of land with little

wa ter use. How ever, recirculating

systems tend to be energy intensive

and require high capital invest-

men ts. Therefore, to make them

Feeding Tilapia in Intensive

Recirculating Systems

by Marty Riche1 (United States Departm ent of Agriculture, Agr icultu ral Research Service,

Fort Pierce, FL) and Donald Garling2 (Michigan State University, East Lansing, MI)

pro fitable it is impor tant to increase

efficiency through feeding manage-

ment.

Feed Requirements of

Tilapia in Recirculating

Systems

Most wild tilapia are omnivorous,

mean ing they w ill eat a variety of

things, includ ing both p lants and

anima ls. This is in contrast to man y

other fish that are more sp ecialized.

However, like other animals, tilapiahave specific requirements for

nutrients such as amino acids from

pro tein, fats, minerals and vitam ins.

Fish rear ed in intensive recirculating

systems have different nu tritional

requirements than those in the wild.

Wild tilapia graze on blu e-green

algae and bacteria. This type of

feeding requires a lot of energy du e

to find ing and digesting this type of

food. To meet the energy requ iredfor feeding and growth, they mu st

consum e more food relative to farm

raised fish. In intensive tank culture

natu ral food is limited. Therefore, all

nutrients must be supp lied in a

complete pelleted d iet. An ad van-

tage to feeding a p elleted d iet is the

higher qu ality and consistency of the

diet.

North Central Regional

Aquaculture Center

In cooperation with USDA

North Central Regional

Aquaculture Center

Fact Sheet Series #114

USDA grant # 00-38500-8984

August 2003


2/42

Requiremen ts for each nu trient are

depen dent on a num ber of factors.

Some of these factors ar e biological

such as the size, age, condition, and

repr odu ctive state of the fish.

Environm ental factors such as

temperature, d issolved oxygen,

water qu ality, and p hotoperiod also

affect requ irements. Feeding m an-agement includ ing the amoun t, and

frequency of feeding, are also

factors. Finally, the d iet itself,

including the amou nt and quality of

protein, energy, and the m ethod of

processing w ill affect the requ ire-

ments.

How to Feed Tilapia in

Recirculating Systems

The optimum feeding methoddepen ds on the p hysiology of the

species, and economics of the

prod uction unit. Historically

culturists have em phasized m axi-

mizing intake in the hop es of

maximizing growth. Evidence

suggests this may n ot be the most

effective for fish produ ction. Maxi-

mizing intake can lead to un eaten

feed, lower feed efficiency, and

result in more expensive produ ction.

Uneaten feed also reduces water

quality, fish health, and perfor-

man ce. This is especially tru e in

recirculating system s that u se low

water exchange.

Types and size of feeds

New ly hatched fry are given acomplete diet of powd ered feed. The

feed shou ld be high in p rotein

(about 50 percent) and energy to

meet the deman ds of the fast grow-

ing fry. Feed size is gradu ally

increased in relation to growth . A

good rule to follow is, small fish,

small feed; large fish, large feed.

However, tilapia prefer smaller size

feed than other commonly cultured

species, such as salmon , trout or

catfish.

The size should be increased

through various sizes of crumbles

for fingerlings 5 to 40 grams (Table

1). Fish larger th an 40 gram s shou ld

be fed pellets. The m ost common

pellet sizes for tilapia are 332 inch18inch. Floating p ellets are the p re-

ferred typ e because they allow

Table 1. Suggested standard pellet sizes used forfeeding tilapia from hatching to market size.

Size of fish (grams) Standard Feed Size03 # 00, or # 0

310 # 1

1025 # 2

2540 # 3

40100 332larger than 100 18

Table 2. Example of daily feeding allowances for differentsizes of tilapias at 28C (82F). Source: NationalResearch Council. 1993. Nutrient Requirements of

Fish. National Academy Press, Washington, D.C.

Size of fish (grams) Amount of daily feed (% of fish weight)

01 3010

15 106

520 64

20100 43

larger than 100 31.5

culturists to observe feeding re-

spon ses. Additionally, the process-

ing method used in m aking floating

pellets increases the amou nt of

energy available to tilapia.

Recomm end ed p rotein levels for

tilapia diets range from 32 to 36

percent in fingerling feed, and 28 to

32 percent in feed for fish larger th an

40 gram s. The am oun t of energy

pr ovided from fat is generally

restricted to 4 to 8 percent of the d iet.

The higher fat content is fed to small

fish and is gradually decreased with

increasing size.

Feed selection and storage is imp or-

tant w hen feeding fish in an inten-sive recirculating system . A high

quality feed w ith few fine dust-like

particles should be u sed to redu ce

waste prod uction and m inimize the

load on th e biofiltration and oxygen

systems. Feed should be kept in a

dry, cool place to ensure m aximu m

quality and avoid m old formation.

Feed rates

Feeding rates w ill vary w ith fish size

and w ater temperatu re. The app ro-priate amount is measured as a

percent of the average body weight.

As the fish weight increases, the

percent body weight fed d ecreases

(Table 2). The da ily feed r ation m ust

be adjusted to compensate for

growth.

Fry grow rapidly and will gain close

to 50 percent in bod y w eight every 3

days. The feed rations shou ld be

ad justed accordingly. Daily feed

rations should be ad justed w eekly

between the ran ge of 530 grams,

and once every two w eeks beyond

30 gram s.

Because of their rap id grow th, high

energy requirements, and small

stomachs, fry require frequ ent

feeding. Fry should be fed as man y


3/43

Figure 2. Amount of food eaten at different time intervals between

meals. The stomach capacity is the amount of room in thestomach before eating again. The shaded area is the amount

of food eaten that by-passes the stomach because of lack ofroom.

as 8-10

times a day.

Because

frequent

feedings can

be labor

intensive, an

alternative is to feed fry continu-

ously throughout the day w ithautomatic feeders. Automatic

feeders should be checked fre-

quently and adjusted if necessary to

avoid over feeding wh ich can foul

water qu ality.

Fingerlings also grow fast and

shou ld be fed at least four times a

day. Fish shou ld be fed less when

water temp erature d ecreases.

Feeding FrequencyThe interva l between feedings may

be more important than the total

nu mber of feedings. Feeding strate-

gies for tilapia hav e trad itionally

been to feed a little bit of feed a t

frequent interv als. This strategy

comes from early work on wild

tilapia that eat algae. How ever, the

higher qu ality and consistency of

pelleted d iets eliminate the need for

many frequent feedings.

The optimal interval between

feedings will depen d on the return of

app etite. Fish eat available food

depen ding on stomach fullness, and

at intervals determined by the time it

takes to empty th e stomach. The

speed the stomach empties depend s

on temp erature, fish weight, meal

size, feed composition, and feeding

frequency.

In som e fish species, the first food

entering th e stomach is the first food

to leave. However, food eaten by

tilapia can mov e past the stomachand enter d irectly into the intestine

(Figu re 1). Fish fed at 23 hour

intervals eat more feed than their

stomachs can h old (Figu re 2). The

extra feed eaten p asses over the

stomach and is considered w asted.

The result is an increased cost of

prod uction and low er profits. Fish

fed at 45 hou r intervals eat nearly

the same amou nt of feed needed to

refill their stomachs. This suggests

the optima l interval between

feedings is 45 hou rs,

dep ending on the energy

and composition of the d iet.

Increased feeding frequen -

cies d ecrease aggressive

behav ior in some fishspecies. This results in faster

growth and less size varia-

tion. How ever, there is a

limit to the frequency that

will result in ben efits. There

are man y fish species that

are less efficient w hen fed at

short interva ls. Evidence suggests

tilapia fed too frequ ently utilize

feed less efficiently.

Water quality concernsFish are sensitive to wa ter quality.

Feeding shou ld be redu ced or

stopp ed if water quality falls below

certain levels. Shortly after feeding,

dissolved oxygen levels decline

rap idly. Dissolved oxygen levels

should be maintained above 5.0

pp m for best growth. At d issolved

oxygen levels betw een 3.05.0 pp m

feeding should be reduced, and

feeding should be stopped at

dissolved oxygen levels below 3.0

ppm.

Figure 1. Stomach and intestine oftilapia. White arrows show

path of feed when fish arefed before the stomach

empties. Grey arrows showpath of feed when fish are

fed at proper intervals.


4/44

Amm onia and nitrite are a concern

in intensive recirculating system s

and shou ld be monitored regularly.

Amm onia prod uction is directly

related to feeding and dep ends on

the qu ality of feed, feeding rate, fish

size, and tem peratu re. Followingfeeding activity ammon ia levels

begin to r ise. In m ost species of fish,

amm onia prod uction p eaks 46

hou rs following feedings.

In water, amm onia exists in two

forms, ammonia (NH3, or unionized

ammonia) and ammonium (NH4

+, or

ionized am mon ia). The form th at is

most toxic to fish is N H3. Both form s

are presen t at all times in the water,

but the p ercentage of each d epend son temperature and p H of the

system. Warmer w ater and h igher

pH in the system favors the more

toxic NH3.

Unfortunately the term amm onia is

often used to refer to both the toxic

NH3(given as mg/ L NH

3-N) and th e

two forms(NH

3+

NH

4

+) add ed

together. This often leads to confu-

sion, therefore cultur ists often refer

to (NH3+

NH

4

+) as the total amm onia

nitrogen (given as mg/ L-TAN).

When m easuring or discussing

amm onia concentrations it is imp or-

tant to be clear wh ich term is being

used.

The lethal ammon ia concentration

for most warm water fish is between

0.62.0 mg/ L NH3-N (1 mg/ L = 1

pp m). Tilapia begin to d ie when

unionized am monia concentrations

are higher than 2.0 mg/ L NH3-N.

How ever, un ionized ammon ia

concentrations as low as 1.0 mg/ L

NH3-N w ill decrease growth and

perform ance in tilapia.

Generally smaller fish are m ore

sensitive to the toxic effects of

amm onia. Low dissolved oxygen

also increases the toxicity of amm o-

nia and lowers the concentration th at

affects fish. When am mon ia concen-

trations rem ain elevated, or fish

show signs of stress, feeding shou ld

be redu ced or stopped.

Conclusion

Tilap ia are well suited for aqu acul-

ture. Tilapia grow rap idly and are

fairly resistant to stress and disease.

However, due to climatic cond itions,

the cultur e of tilapia in most of theUnited States requires the use of

intensive recirculating system s and

formu lated d iets. Recirculating

systems can be expensive to build

and operate therefore it is imp ortant

to maximize prod uction efficiency.

To maximize p roduction efficiency

and minim ize costs, tilapia shou ld

be fed:

Nu tritionally complete dietsformulated to m eet their dietary

requirements;

Optimu m crumble or pellet size;

Optimu m feeding rate (% of fish

body w eight);

Optimu m time intervals (4 5

hours dep ending on the energy

and composition of the diet);

based on the size of the fish and

the culture conditions.

Any opinions, findings, conclusions, or recommendations ex-pressed in this publication are those of the author(s), and do notnecessarily reflect the views of the United States Department of

Agriculture.

Additional ReadingMany extension articles on tilapia and their culture can be dow nloaded from th e AquaN IC web site: http:/ /

aquanic.orgCheck out Tilapia and Recycle und er the Beginner drop d own menus for Species and Systems,

respectively.

1 United States Departm ent of Agricultu re, Agricultural Research Service, Harbor Branch Oceanograp hic

Institu tion, Fort Pierce, FL2 Departmen t of Fisheries and Wildlife, Michigan State Un iversity, East Lansing, MI

Series Editor: Joseph E. Morris, Associate Director, North Central Regional

Aquaculture Center.

Originally published by Iowa State University, Ames, Iowa

Documents

Feeding Tilapia in Intensive