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BIOS
Bermuda
It was a chilly October morning and the sun had yet to rise when we left for the airport. Groggy-eyed we got onto the plane heading for Bermuda, and a remarkably long two hours later we arrived at the airport. Leaving the plane the first thing that I noticed was that it was not longer cold, it was warm, not hot, but just right. Later in the afternoon we proceeded to learn the fine are of mopeding, and as we left for our first snorkel location I became the first one to have a moped accident.
The coral reefs of Bermuda are teeming with a diverse group of fish each with their own unique set of colors and behaviors. As with fish that live in the open seas, many fish of the coral reef tend to school together with others of their kind for a variety of reasons that range from protection from predation to advantages in foraging time (Hall, 1986; Overholtzer,2000). What I was curious about since our first snorkel trip into Whalebone Bay was if different species of fish will school together when foraging. It definitely appeared that several species of parrot fish, surgeon fish, doctor fish, and grunts seemed to be foraging in a pack of sorts those first couple of days in Bermuda, but I wanted to know if that pack was actually a pack or they all happened to be in the same place at the same time.
Methods
In order to test my theory out I decided that best way to go about it would be through observation, given that I had about 5 days to get enough results to give myself some sort of answer. Obviously swimming near fish generally scares them away, or at least affects their behavior in some way but I figured that if I could get a rough count of what was there before they all scurried away it wouldn't be too bad. For the most part I was right, in fact they usually kept within a school and just swam in the opposite direction that I was coming. To keep track of the fish in the school I had a plastic pad that I could write upon under water with a pencil. Some of the species looked very similar to one another I would mark which ones I wasn't sure about when I was in the field and used a field guide to review the species once I got back to base. I tested 3-7 samples for 3 different sites: 6 at Whalebone Bay, 3 at North Rock, and 7 at Tobacco Bay. Testing took place across 3 days and weather for all 3 days was pretty consistent, that is to say sunny with some wind (making the water choppy and stirring up sediment). I defined a school as 4 or more individuals together, and I only looked at foraging groups, which are groups of fish that appeared to be feeding. For me this was them moving and "pecking" at a substrate, whether that be coral or the bottom.
Once I got my data I decided to test the number of samples that had schools vs. those that did not with a Chi-Square test to see if the schools were there by random chance. In other words were the multi-species schools that I saw there by random chance or were these groups actually significant.
Literature Cited
Overholtzer et al., 2000. Effects of Mixed-species Foraging Groups on the Feeding and Aggression of Juvenile Parrotfishes. Enviromental Biology of Fishes. 58
Hall et al., 1986. Predator evasion in a fish school: test of a model for the fountain effect. Marine Biology. 91