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Effects of school size of neon tetras on their response to the presence of a zebra fish
Kelsey and Jenna
Purpose of the experiment
Look at schooling behaviour in neon tetras in the presence of a predator, measured in terms of
distance from a predator
Overview
• Background Information• Hypothesis • Materials• Methods• Results • Discussion• Conclusions
Background Information
• Schooling: anti-predator strategy– Predator confusion– More fish reduces
individual’s chance of attack
– More energy invested in feeding and mating
Background information
Neon Tetras (Cheirodon innessi)– Small, bright, vulnerable to
predation
Zebra fish (Danio rerio)- Aggressive- Territorial
Background Information
• Neon tetras display schooling behaviour• Zheng et. al.– Presence of unfamiliar object– Increase in school size, decrease in timidity• Darting• Time between feeding
• Sloman et. al.– Presence of aggressive fish– Increase in schooling
Hypothesis
The neon tetras would remain further away from the zebra fish when the neon tetras were present in a small school compared to a large
group
Materials
• Dip net• Aquarium• 500mL Jar• Neon tetras• Zebra fish
Materials
• The Aquarium:
1 2 3 4
Materials
• The Aquarium:
Water temperature maintained at 20⁰C
Methods
• Neon tetras placed in aquarium– School sizes: 2 and 8– Acclimation period of 3
minutes• Jar containing a zebra fish
added in section 4
Methods
• Scan sampling – Neon tetras in each section recorded every 30
seconds– Total of 15 minutes– 10 replicates for each school size– Control• Empty jar• 5 replicates for each school size
Results
• Small school:
1 2 3 40
10
20
30
40
50
60
controlexperimental
Section of Aquarium
Perc
ent N
eon
Tetr
as (%
)
Results• Small school: – Chi-square analysis• Experimental: X2(3)= 52.4, p< 0.05• Control: X2(3)= 38.3, p< 0.05• Significant preference for section 3
– Mann-Whitney U• p >0.9999• Insignificant difference between control and experimental
Results
• Large school:
1 2 3 40
10
20
30
40
50
60
controlexperimental
Section of Aquarium
Perc
ent N
eon
Tetr
as (%
)
Results• Large school: – Chi-square analysis• Experimental: X2(3)= 45.3, p< 0.05• Control: X2(3)= 12.0, p< 0.05• Significant preference for section 3
– Mann-Whitney U• p =0.8857• Insignificant difference between control and experimental
Discussion
• Due to insignificant difference between control and experimental, hypothesis could not be accepted or rejected
• Jar was seen as a novel object– Saxby et. al. • Higher prevalence of darting in presence of unfamiliar
object when in small schools
Discussion
• Predator did not cause neon tetras to stay away
• Possible reasons:– Wanted to school with the zebra fish– Zebra fish was not threatening enough• Zebra fish normally school• Separation by the jar
– Curiosity of the neon tetras
Discussion
• Future avenues of research:– Looking at darting behaviour– Use a more aggressive species• Ex: Angelfish
– Using a model predator– Trials without the jar – Collecting more data
Conclusions• No significant difference in the response to
the empty jar versus the predator• Neon tetras were attracted to the jar, despite
the size of the school• Future improvements to the data collection
could provide more useful results