Damsel Fish Project

Studying Damselfish’s Territorial Behavior with Urchins Group Members: Emily Keefer, Sean Crisco, Sara Gutekunst, and Maggie MacLean The Dusky Damselfish, a common and easily identifiable reef fish, is known to exhibit territorial behavior around its specific coral head. These damselfish will actively chase away foreign organisms, ranging from urchins to other fish, even those much larger than the damselfish itself. A project was carried out the previous year at the same location to determine the behavior of the Dusky Damselfish towards foreign objects, both living and nonliving. This study confirmed that the fish is highly territorial, and concluded that the Dusky Damselfish would interact with foreign inanimate objects. Based on this information, we generated a research project to further investigate the Dusky Damselfish’s behavior when a variety of manmade urchins were introduced to their coral heads. Specifically, we addressed the following question: Do size, reflectivity, and colorfulness of an urchin affect the severity of a Dusky Damselfish’s reaction to that urchin? We hypothesized that a shiny metallic urchin would receive the most attention from the Dusky Damselfish, because of its ability to reflect sunlight. Next we suspect the gumballs made of toothpicks, and then the colorful one to get the second and third most hits because of their level of realistic characteristics. We were also testing to see if size mattered to the damselfish by making a large and small urchin. We suspect that the larger one will get more hits because it would be a larger threat if it were alive. This project was performed at Wee Wee Caye, an island of 2 acres located at 16°.45.877 N and 88°. 8.565 W. It is formed from coral heads that eroded by the waves and a mangrove root that floated to shore and colonized the island (Paul). The mangroves surround the outer edge of the island protecting the inner area from wind and tropical storms. The coral reef surrounding the island stays a constant temperature of about 26°C (measured March 2, 2009) even when the island temperature drops to 22.5°C (March 2, 2009). This temperature stability is mainly due to the fact that the island only has 2 seasons, wet and dry. The dry season is from November to June and that is the season our research was conducted in. The reef is in clear, warm, shallow water and is made of Calcium Carbonate. The Wee Wee Caye coral reef has a diverse population and contains animals in simplicity from sponges to reptiles, but there are not any mammals. A good portion of the reef is coral, so that is the habitat for many of the animals, including the damselfish and sea urchins. In areas where there is little coral, there is manatee grass and turtle grass, where classes such as cartilaginous, mollusks, and echinoderms live. The reef is a closed system because of its balance in creating, using, and recycling nutrients. In order to determine how the dusky damselfish react to different types of urchins and which urchin prompts the most action, we first needed specimens with distinct differentiable characteristics. We decided to make four urchins and use one real urchin. The real urchin, a rock-boring urchin (Echinometra mathaei), would be

used as a control to compare to the trials of the urchin look-a-likes. We brainstormed ideas for fake urchins and decided on the following: •

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A small realistic urchin: to be compared to larger urchins, in order to answer the question of whether or not damselfish react more to certain sized objects. Made from sweet gum seeds with ¾ inch long skewers glued in the holes. Brown in color. Attached two bolts with glue so that it would sink. A large, realistic urchin: to be compared to the smaller urchin and other urchins of its size. Made from two inch long skewers glued in holes of sweet gum seeds. Attached three bolts to make the urchin sink. A shiny urchin: to test our hypothesis that dusky damselfish would be more attracted to shiny objects. Made from a one inch diameter Styrofoam ball wrapped in aluminum foil. Stuck with 2.5 inch skewers wrapped in aluminum foil and two inch nails. A colorful urchin: to test if dusky damselfish are attracted to more colorful objects. Made of one inch diameter Styrofoam ball stuck with colorful toothpicks and wrapped in pink, orange, blue, green, purple, and yellow pipe cleaners. Attached about eight bolts to make it sink.

After testing we modified our models in order to test whether the damselfish would have a preference between different color urchins. After observing the dusky damselfish interact with the urchins, we hypothesized that the urchins’ size and unusual shape may have been an issue with their lack of interaction. We made several colorful urchins which were smaller. We make a multi-colored urchin of two inch pipe cleaners bound together and attached three nails as weights. We also make a blue urchin and a pink urchin to observe how the damselfish react to color on both sides of the light spectrum. To conduct our project we had to take our equipment out to the coral heads located at 16.7636° N and 88.143° W. Coral Head 1 was 45 cm tall and the depth of the water was 100 cm. Coral Head 2, which was slightly northwest of Coral Head 2, was 50 cm tall and the water was 110 cm deep. Coral Head 1 was broken into three segments and we tested urchins on all three and Coral Head 2 had two segments that we tested on. We did four trials with each urchin and frequently shifted position and coral heads to help counteract fatigue and habituation. For the trials we appointed an observer, a recorder and two timers, one of which would place the urchin on the coral head. To begin a trial the urchin was placed on a section of the coral head and overall time was started. Once the fish noticed the urchin, we recorded the total interaction time between the fish and the urchin. Trials ended in two ways: three minutes elapsed without any interaction between the damselfish and the urchin, or the damselfish interacted with the urchin and then left. As a control we first ran trials with a live urchin. After determining that the damselfish would interact with the live urchin we moved on to our man made ones. We tested in this order: shiny metallic, small sweet gum, large sweet gum, colorful, pink and then blue. Our first urchin was alive and the damselfish attacked it forcefully. However, if another fish appeared, it turned and chased after the new fish. The urchins made of tinfoil, blue and pink pipe cleaners, and colorful toothpicks received no attacks and minimal observation. The larger gumball urchin was ignored by the damselfish and the smaller gumball urchin received the most hits from our “non-live” trials. The

damselfish lost interest on several occasions with the small gumball, but the interest was increased once the waves moved the urchin. This urchin was attacked three out of four of the trials and had multiple hits.

Real Urchin Trial

Time (sec)

1 2

Action 13 Attacked 3 times, lost interest; suspect that we scared it away 1 attack: stared at for 8 seconds, then attacked; picked up, 21 dropped, swam away 4 Looked at, then went after another fish 44 2 hits, swam away

3 4

Shiny Urchin Trial

Time (sec)

1 2 3 4

Action 0 No activity; damselfish did not interact 12 Realized it was present, looked at it and left; no attack 0 No interaction after 3 minutes No interaction after 3 minutes, despite urchin replacement closer 0 to fish

First 3 trials, urchin was placed on top of coral head. Urchin placed closerto damselfish for the last trial. Moved to another coral head after the first trial.

Small Urchin Trial 1 2 3 4

Time (sec)

Action 6 hits, swam away. Relatively fast action after placing on coral head 7 Observed, lost interest, swam away after 3 minutes 15 Attacked once, swam back to bottom 54 Observed, attacked twice, observed again 83

First three trials, urchin placed in same spot on top of coral hear; last tiral, placed on side of coral head Relocated to different coral head after trial 3

Big Urchin Trial

Time (sec)

Action

1 29 Hit twice, lost interest 2 0 No interaction after 3 minutes 3 0 No interaction after 3 minutes; we suspect the fish is fatigued 4 15 Observed and swam away We believe another damselfish arrived after trial 1 Moved to another coral head for the last trial

Colorful Urchin Trial 1 2 3 4

Time (sec)

Action 0 6 0 0

Fish did not notice urchin, was on opposite side Swam up, swam backwards, swam away Did not pay any attention Nothing

After carefully observing the damselfish react with each of the urchins and then analyzing the times they spent observing, attacking, and/or ignoring the urchins, we were able to make several conclusions. We noticed that the damselfish were able to analyze potential threats to their environment with some kind or reasoning. The first conclusion we made was that the damselfish tend to pay less attention to urchins which look less realistic. The urchins make of tin foil, pipe cleaners, and colorful toothpicks all received less attention than the real urchin and the small urchin, which closely resembled the real urchin. We saw that the movement of the water caused the urchins to sway with the motion of the ocean. These swaying movements made the urchin appear more realistic and attracted the damselfish. Despite our original hypothesis that the damselfish would be more attracted to the shiny urchin, the damselfish did not respond more to the shiny

urchin. We also conclude that the damselfish tend to prioritize. We noticed that the damselfish will drop whatever is holding their attention and chase after other impeding fish on their territory. Other projects could be carried out to study damselfish behavior further such as whether the fish can prioritize between two or more different kinds of urchins. It would also be plausible to test whether movement of the sea urchin affects the number of attacks it receives.

Blue Urchin Time Trial (sec) 1 2 3 4

4 0 0 0

Action Swam up, looked at, swam away distracted by other fish swam past a few times, no attack looked at once, didn’t pay attention to it

Pink Urchin Trial 1 2 3 4

Time (sec)

Action 0 glanced at twice, no attack after 3 minutes swam up, looked at, appeared to clean rather than attack, swam 18 away 0 fish did not interact 0 fish did not come close to urchin

Sampling in residents, there are many sources of error that could not have been controlled by us, but a few of the errors we made we could have corrected. We suspect that the size of the urchins was too large that they were not realistic for the environment we put them in. To correct this we should have made them all the same size as the small live urchin we used. Also, distractions by other fish and us caused our results to be skewed because it took the damselfish’s attention away from the urchin. The time that we spent working with the fish was around the same time as a storm and the waves were rough. This seemed to have caused the fish to be less active and less defensive about their territory. The fish appeared to have been fatigued either by the storm or the number of trials we attempted in a short period. The damselfish started to ignore the urchins after the first few trials and this habituation caused a large error in our results because we could only get a few accurate trials. Our last source of error was from our limited resources on the island. If we would have been in a lab with unlimited materials, the sea urchins could have been more realistic. Further research can be done to study damselfish behavior further such as whether the fish can prioritize between two or more different kinds of urchins. It would also be plausible to test whether movement of the sea urchin affects the number of attacks it receives.

Bibliography DeLoach, Ned. Reef Fish Behavior Florida, Caribbean, Bahamas. Chicago: New World Publications, 1999. Ogden, J.C., Lobel, P.S. 1977. "Role of herbivorous fishes and urchin in coral reef communities." Environmental Biology of Fishes. Volume 1, Number 1, 49-63. Sammarco, P., Williams, A. 1982. "Damselfish territoriality: Influence on Diadema distribution and implications for community structure." Marine Ecology -- Progress Series. Vol. 8 53-59. Personal Conversations with: Brinson, Leslie 2009 Foreman, Udell 2009 Shave, Paul 2009