EFFECT OF STOCKING DENSITY OF RED HYBRID TILAPIA (OREOCHROMIS SP.) ON GROWTH AND SURVIVAL OF JUVENILE TILAPIA AND SHRIMP (LITOPENAEUS VANNAMEI) IN POLYCULTURE.

Alejandro Macdonald-Vera1,2

Neil J. Duncan2

Wilfrido M. Contreras-Sánchez1

Kevin Fitzsimmons3

1Universidad Juárez Autónoma de Tabasco, Tabasco, Mexico. 2CIAD A.C. Unidad Mazatlan, Mexico.3University of Arizona, Arizona, Tucson, USA

• Shrimp Farming Industry in Mexico.– Industry is prospering.– Disease and pricing problems.– Inefficient farms stop

operating.– Over 5000 ha of shrimp ponds

unused.• Shrimp-Tilapia polyculture.

– Increased production.– Maintain or improve shrimp

survival.– Remove disease carriers from

system.

Alejandro Macdonald-Vera who completed the study.

Shrimp ponds in Mexico.

Methods• White shrimp – PL 16 - 0.004g

– Litopenaeus vannamei– Certified free from white spot

• Red hybrid tilapia - 4.6±0.9g– Genetic component of

Oreochromis mossambicus– All males (hormonal treatment)– Acclimatised to 35ppt sea water,

5ppt per day.• Pond preparation.

– Salinity range - 28 to 35 ppt– Temperature range - 16.2 to

25.6°CMosquito mesh divisions to make experimental enclosures

Pond preparation, ploughed and limed.

Methods experimental design

• 9 enclosures (7x30=210m2) in 3 blocks, A, B, C.• All enclosures stocked with 30 shrimp/m2

• Tilapia stocked at 3 densities, 0, 0.25, 0.5 fish/m2

to give the experimental groups T0, T0.25 and T0.5

Waterinlet.

outlet

10

20.5

30.25

40.25

50

60.5

70.5

80

90.25

Block ABlock BBlock C

Experimental pond set up.

Methods• Stocking

– Shrimp and tilapia were acclimatised and randomly stocked into each enclosure.

• Sampling.– Every 2 weeks.– 20 tilapia caught and weighed.– 30 shrimp weighed.

• Harvest.– Experiment lasted for 8 weeks.– All shrimp and tilapia were

harvested, counted and a random sample weighed.Sampling.

Stocking.

Results - Statistics• Weight data was not normal.

– Some shrimp weight distributions were highly skewed towards larger individuals.

– Some tilapia weight distributions had characteristics of a bimodal distribution, 23 to 42% maturing females were found during the harvest.

• 2 way Scheirer-Ray-Hare extension of the Kruskal-Wallis and the DUNNS test were used to compare weight distributions

• Survival distributions were normally distributed and were compared with ANOVA.

ExpectedNormal

VAR7

Upper Boundaries (x <= boundary)

No ofobs

0

1

2

3

4

5

6

7

15 20 25 30 35 40 45 50

ExpectedNormal

NEWVAR13Shapiro-Wilk W=.97111, p<.0110

Upper Boundaries (x <= boundary)

No

of o

bs

0

5

10

15

20

25

30

35

14 16 18 20 22 24 26 28 30

ExpectedNormal

NEWVAR16Shapiro-Wilk W=.97691, p<.0002

Upper Boundaries (x <= boundary)

No

of o

bs

0

10

20

30

40

50

60

70

80

90

100

110

120

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Tilapia distributions

Shrimp distribution

Results – Tilapia Growth.

05

101520253035404550

5 Dec 22 Dec 5 Jan 19 Jan 2 Feb

Wei

ght(

g)

No significant differences were observed for tilapia weights among treatments T0.25 and T0.5 or blocks A, B and C.

Results – Shrimp Growth.

No significant differences were observed among treatments T0, T0.25 and T0.5

0

0.5

1

1.5

2

2.5

3

5 Dec 22 Dec 5 Jan 19 Jan 2 Feb

Wei

ght(

g)

Results – Shrimp Growth.

Significant differences (P<0.05) were observed among blocks A, B and C.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

22 Dec 5 Jan 19 Jan 2 Feb

Wei

ght(

g)Block A

Block B

Block C

a a a

a a

b

aab b

a

b b

Results – Survival.

There were no significant differences among tilapia survivals.There were no significant differences among shrimp survivals fortreatments, T0, T0.25 and T0.5. There were significant differences (p<0.05) among shrimp survivals for blocks A, B and C.

0102030405060708090

100

BlockA

BlockB

BlockC

T0 T0.25 T0.5 BlockA

BlockB

BlockC

T0 T0.25 T0.5

Shrimp Tilapia

Surv

ival

%

a a

b aa

a a

a

a a a

Conclusions• Stocking densities of 0, 0.25 and 0.5 fish/m2 did

not significantly affect growth or survival of juvenile shrimp and tilapia.

• Block or position in the pond did significantly affect (p<0.05) growth and survival of juvenile shrimp.

• These are encouraging results that suggest shrimp tilapia poly-culture has good potential for diversifying the Mexican shrimp culture industry and rehabilitating disused shrimp ponds.

Gracias CRSP

• Gabriela Velasco• Leonardo Ibarra• Rafael Guzman• Ricardo Alvarez

• Michael Achury• Noemi Garcia • Estela Rodriguez.

Juan Manuel Gonzalez and his family