Researchers track fish habitation and migrations through ear bones

Researchers studying juvenile fish movement around Red Sea coral reefs tracked habitation patterns by analyzing fish ear bones, according to a press release from the Woods Hole Oceanographic Institution.

Fish ear bones, or otoliths, continually store chemical information about living conditions, said Simon Thorrold, a biologist with the institution, in the release.

Researchers’ analysis of snapper otolith layers revealed that, contrary to popular belief, some juvenile fish moved directly in to coral reefs rather than starting in coastal wetlands. The study also showed that snappers make long migrations from coastal wetlands, across deep open water, to offshore reefs.

A team from WHOI and King Abdullah University of Science and Technology, in Saudi Arabia, conducted the study.

Researchers first collected information on five Red Sea habitat food webs. The habitats included coastal wetlands, coastal reefs and deep water reefs. Then they referenced each layer of otolith to the food webs, allowing researchers to track where a certain fish was living at any age.

The method is a quantitative approach to a study typically done with qualitative observation. “Traditional methods of assessing nursery habitats – visual surveys of abundance and size of fish in different locations – provide important but indirect evidence of connectivity among essential habitats,” said Kelton McMahon, WHOI biologist and lead study author. “We developed a quantitative method that identifies essential nursery habitat, and allows reconstruction of migration within the seascape.”

The next step for researchers is to analyze another reef to see if they find similar trends.

Image: Ehrenberg’s snapper (Credit: Simon Thorrold, Woods Hole Oceanographic Institution)