How coral reef fish group size and habitat influence growth

Graduate Student: Jessica Nielson

diver diver

Jessica is interested in understanding how coral reef fish populations are affected by the size of their family and the amount of available habitat.

Jessica is studying the threespot damselfish, Dascyllus trimaculatus, which are planktivorous fish that make their home on sea anemones. The relationship between threespot damselfish and their anemone is called a mutualism. The fish rely on the anemone for protection from predators and in return, the fish gives the anemones nutrients. Jessica experimented with different numbers of fish on different sized anemone habitats and observed how quickly each fish grew and how vulnerable they were to predation by bigger fish based on their family size and how much space they shared on the anemone. She also used underwater video cameras to look for interesting patterns in their feeding behavior. This type of fish eats plankton, which are tiny animals that drift with currents in the ocean. When she watched the videos, Jessica measured how often and how quickly the fish ate, how much they fought with their family members, how brave they were and how far each fish was willing to swim away from the anemone's shelter for food.

Results from Jessica's experiment show that fish that live in larger families on a small anemone home grow more than small families living on a big home. This is because they spend less time chasing each other and are brave enough to swim far from their anemone for their favorite food. However, there is a tradeoff, because since they are brave enough to swim away from home, they are also more in danger of being eaten by bigger fish.


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