EFFECT OF STOCKING DENSITY OF RED HYBRID TILAPIA ...EFFECT OF STOCKING DENSITY OF RED HYBRID TILAPIA...

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