Water flow affects shoaling behavior of zebrafish Danio rerioGrace Blackwell, Alejandra Enriquez, Anna Castillo, Piyumika Suriyampola, Emilia Martins

Indiana University, Bloomington, IN

Results

Questions1. How does group size affect shoal response to changes

in water flow?

AcknowledgementsI would like to thank the STEM Summer Scholars Institute for accepting me into their

program as well as funding me. Furthermore, I would like to thank Delawrence Sykes, Alec Iruri-

Tucker, Roger Morris, Delia Shelton, Ian Chaves, and the Indiana University Biology department

staff for their contributions to the lab and to this study.

Discussion1. (Figure 1) Shoal size of 2 fish is able to effectively respond to changing water flow

rates with a higher percentage of Rheotaxis at higher flow rates. However,

compared to the shoal size of 4 fish, it is less effective in response to both flow

rates. This provides evidence that there is less communication and fish act more

independently within smaller shoal sizes. In comparison, the larger shoal size

increases communication ability which increases water flow detection and

response.

2. The lack of significant change in the shoal size of 2 fish and the significant

decrease in NND in the shoal size of 4 fish indicates that group size affects shoal

cohesion. The shoal size of 2 fish, although insignificant, increased in NND

possibly due to lack of communication ability, and an inability to shoal because of

water turbulence. The shoal size of 4 fish, however, becomes more cohesive at a

higher flow rate compared to a low flow which allows for improved hydrodynamics,

less energy expenditure, and higher feasibility of communication. This reflects that

confusion and distraction within the shoal is not occurring significantly.

Implications

ReferencesA. Chicoli et al. 2014. The effects of flow on schooling Devario aequipinnatus school structure, startle response and

information transmission. Journal of Biology, 84: 1401-1421.

Engeszer, R. E. et al. 2007. Zebrafish in the Wild: A Review of Natural History and New Notes from the Field.

Zebrafish, 4: 21-36. (doi: 10.1089/zeb.2006.9997)

Shelton DS, Price BC, Ocasio KM, Martins EP. 2015. Density and group size influence shoal cohesion, but not

coordination in zebrafish (Danio rerio). Journal Comparative Psychology, 129:72-77. (manuscript) (

doi:10.1037/a0038382)

Rheotaxis

Shoal Cohesion

Figure 1: Shoal sizes of 2 and 4 fish had an increase in Rheotaxis at a faster flow rate. Shoal size of f4 fish had a significant higher percentage of Rheotaxis in both flow rates compared to the shoal size of 2 fish.

• Lateral line function: water flow/ movement/ direction detection• Why zebrafish?

• Social• Model organisms• Various natural habitats• Seasonal fluctuations in natural habitats• Well understood and cited• Easy maintenance

Pros:•Improved aerodynamics/ hydrodynamics•Increased communication

• Predator detection• Predator avoidance• Higher reproductive success

Cons:•Increased predation•Disease•Reduced food supply•Distraction/ confusion

• Sensory systems used for animals to communicate among selves and environment• Social environment has:

Tested groups of two and four fish

Tested fish at flow rates of 4 and 12 cm/s

Random presentation of Flow

Random Flow 2 mins

Scoring:•Paused video when all fish in middle vertically•Recorded NND•Looked at 10 seconds and recorded orientation

Flow Flow

Methods

Figure 2: Shoal size of 2 fish had no significant change of NND. Shoal size of 4 fish increased shoal cohesion at a higher flow rate. Shoal size of 2 fish had a significant higher NND for both flow rates compared to the shoal size of 4 fish.

The data indicates that shoal size affects the efficiency of rheotaxis in

which a higher shoal size is better. The data also indicates group size affects

shoal cohesion, in which a larger shoal size has a higher shoal cohesion.