SOCIAL INTERACTIONS AND FEEDING BEHAVIOR OF TWO
CICHLIDS, MIDAS Amphilophus citrinellum AND NILE TILAPIA
Oreochromis niloticus REARED AT HIGH DENSITIES
Gustavo Rodriguez, Konrad Dabrowski and Karen Treadway
Economic value and social interactions of
cichlid
• Fish of the family Cichlidae are considered of economic
importance because of utilization either as a food fish (Nile
tilapia) or as ornamental fish (for instance, Midas).
• It has been reported that many cichlid species exhibit marked
territorialism and aggressive feeding behavior when kept in
captivity.
• Changes in social conduct can be attributed to several factors
including food availability, space, and community
assemblages.
• Growth rate for each species may reflect specific changes in
behavior; therefore, we evaluated the performance of two
different cichlid species when reared simultaneously.
Nile tilapia and polyculture
• Diversification of species cultures in production
unit with:
–
–
–
–
Carp
Catfish
Large mouth bass
Crustaceans
• Mostly related to fish food production
• One species complements the other, i.e. unused space, food
source, etc.
• Tilapia is considered an aggressive species;
therefore, is it possible to match such
competitive behavior?
Midas cichlid
• Origin: Nicaragua and
Managua Lakes, Central
America.
• Some peculiarities:
– Young feed on parents
mucus
– Extremely aggressive and
territorial
– Monogamous fish
– Model species in research
on evolutionary
mechanisms
Barluenga et al 2006. Nature. 439:719
“Example of sympatric speciation….”
Methodology
• Initial density: 30
fish/tank
– Initial weight:
• Tilapia: 0.81±0.06 g
• Midas: 0.83±0.09 g
– 4 treatments
• 30 tilapias
• 30 midas
• 20 tilapias and 10
midas
• 15 tilapias and 15
midas
No major differences in
coloration until completion of the
study
Methodology: feeding trial
• Commercial diet 40-12% protein/lipid
• Feeding rate: 5% tank biomass per day,
adjusted weekly
– Two feeding regimes
• Week1-3: automatic feeders, 8 h/day, every 20
minutes
• Week 4-6: manual feeding, twice a day
Rearing facilities
Week 1-3: Automatic feeders
Week 4-6: Manual feeding
Methodology: social interaction
• Scale to establish degree of social
interaction related to feeding behavior, i.e:
attacking, aggression.
•
•
•
•
•
1:No
2:Little
3:Mild
4:Strong
5:Severe
• A minimum of 5 observations were made
through feeding trail
Biomass increase per week/tank
180.0
T 30
160.0
M 30
Total Biomass (g)
140.0
T 15 M 15
120.0
T 20 M 10
100.0
80.0
60.0
40.0
20.0
0.0
0
1
2
3
Week
4
5
6
Mean Individual weight (g) per tank
8.00
T 30
M 30
T 20 M 10
T 15 M 15
7.00
Mean weight (g)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0
1
2
3
WEEK
4
5
6
Individual weight per species/density
Automatic
8
Manual
Automatic
8
Manual
Midas 30
Tilapia 30
7
7
Midas 15
Tilapia 20
Tilapia 15
5
4
3
5
4
1
1
0
0
2
3
Week
4
5
6
b ab
ab b
3
2
1
a
a
2
0
Midas 10
6
Weight (g)
Weight (g)
6
0
1
2
3
Week
4
5
6
Results: proximal composition
Moisture
%
Protein
% DM
Lipids
% DM
Ash
% DM
Midas
Initial
74.1
54.7
26.2
17.8
Tilapia
Initial
81.5
61.8
21.6
13.9
All Tilapia
All Midas
Tilapia 20
Tilapia 15
Midas 15
Midas 10
Moisture
%
79.4±6.1a
74.2±0.5b
75.1±0.6
75.5±0.1
74.4±0.5
74.5±0.5
Protein
% DM
62.9±1.0a
57.4±0.4b
62.6±0.7a
61.9±1.1a
57.8±0.9b
58.1±0.5b
Lipids
% DM
19.5±2.7
24.7±1.9a
22.3±0.8
15.7±3.0b
26.1±2.6a
26.2±3.9a
Ash
% DM
15.6±0.7a
14.0±0.5b
15.3±0.7a
15.9±0.7a
14.4±0.5b
14.7±0.5b
Results: Social interaction
Obs.
M30
T30
T20/M10
T15/M15
T1
T2
T3
T1
T2
T3
T1
T2
T3
T1
T2
T3
D1
2
4
2
4
4
2
4
4
4
3
4
4
D2
5
2
4
2
4
2
4
4
4
4
4
4
D3
4
4
4
1
4
2
4
4
4
3
4
4
D4
2
3
3
1
4
2
4
4
4
4
2
4
D5
3
4
3
4
4
2
2
4
4
4
4
4
3.2
3.4
3.2
2.4
4
2
3.6
4
4
3.6
3.6
4
Overall
Mild
3.3
Overall
Mild
2.8
Overall
Strong
3.9
Overall
3.7
Strong
Social interaction
• Tilapia 30 and Midas 30: low-mild
interspecies aggressiveness
• Tilapia plus Midas tanks: strong
interaction was observed, intra and
interspecies .
– In most cases Midas matches tilapia
feeding aggressiveness in order to
have equal access to available food
General Conclusions
• Tilapia has higher growth rate than Midas
• Midas can match Tilapia’s feeding
behavior (surface feeding) and increase
competition for food and space
Conclusion cont…
• Midas can be reared
with Nile tilapia for
exotic fish markets to
increase profitability
• Tilapia: US$4.99/lb
fillet at local market
• Midas: 1-2” aprox.
US$4.00/fish local
pet store