Friday, 21 April 2017

Space bullethead parrotfish use is influenced more by competition than by fear of predators

Date: April 17, 2017
Source: University of California - Santa Barbara

It's a fish-eat-fish world out in the ocean, and prey species usually fear the predators that would make them into a tasty snack.

Looks like someone forgot to tell the parrotfish, though.

According to new research by UC Santa Barbara marine scientists, Chlorurus spilurus, known as the bullethead or daisy parrotfish, barely reacts to the presence of predators. The findings appear in the journal Oecologia.

Working in the waters off Moorea and the Palmyra Atoll, the researchers observed almost constant competitive interactions between predators and bullethead parrotfish -- the Pacific Ocean's most abundant parrotfish species -- and other herbivorous fishes. "They were constantly chasing each other, and this affected their feeding rates," said lead author Katie Davis, a research scientist in UCSB's Caselle Lab. "However, predators such as sharks, snappers and groupers frequently swam past the parrotfish without eliciting any reaction. Our research indicates that competition among grazers is the real force in structuring both the space use patterns and the feeding patterns of these parrotfish."

Working on Palmyra 1,000 miles south of Hawaii, the researchers first tested the influence of predation risk on prey foraging behaviors in an unexploited predator community that includes a variety of sharks and other fishes. Then, to contrast how predation risk and competition affect space use, they conducted a comparative study on Moorea, where both predatory species and herbivorous species like the bullethead parrotfish are fished.


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