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