Where Do Young Fish Wander?:
By Malin Pinsky Awards: Miller Writing, Friends, Myers |
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| Have you ever seen an animal in the ocean and wondered where it’s been? The answer might surprise you. Most marine creatures, whether anemonefish or hermit crabs, are relative home-bodies once they’re grown up, and they stick around their local bay or reef. However, the story is dramatically different if we look at what happens when they’re young. When a marine animal hatches from an egg, the emerging larva is small and can’t swim particularly well. These larvae then head out into the open ocean during what’s called the pelagic larval stage. During this time, ocean currents carry larvae around and disperse them, somewhat a kin to the wind dispersing the seeds of a dandelion. However, most larvae stay in the open ocean for much longer than seeds stay in the air. For that reason, marine larvae can travel impressively long distances. |
 A Clark's anemonefish (Amphiprion clarkii) nestles in the tentacles of the anemone it calls home. |
 The larger female maroon anemonefish (Premnas biaculeatus) comes out to defend her anemone from a curious diver while the smaller male stays behind. |
Why should we care? Besides the simple curiosity of knowing how the ocean works, understanding dispersal and where larvae move is critical for effective conservation. For example, if we conserve a group of fish on our coastline and the offspring of those fish stay near their parents, then the next generation will be able to provide local benefits (fish to eat, fish to watch, food for other species, etc.). On the other hand, if larvae disperse long distances, then they’ll instead provide benefits for distant communities. Similarly, ensuring the persistence of a population of fish in one location requires preserving the upsteam source of larvae. It’s for this reason that the design of marine reserves depends strongly on the dispersal abilities of the species being protected. |
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A jumble of fishing boats and houses crowd the shoreline of Caubyan Island, Cebu, Philippines. |
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| The problem is that how far marine larvae travel remains a big mystery, in part because tracking these larvae is exceptionally difficult. A single female fish can produce thousands of larvae, each one of which is microscopic. Adding a tag to any of these larvae, much less finding them again after they’ve found a new home, is not easy. For that reason, many researchers have turned to population genetics where they can use DNA as a “natural tag” to reconstruct past movement patterns. |
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| For my research, I focus on using genetics to study dispersal in species of anemonefish (yes, this is similar to the species made famous by "Finding Nemo"). Anemonefish are easier to study because, besides living in the tropics where the water is warm, their adults don’t move more than a few meters. We know that any movement we detect with genetics comes from larval dispersal. The populations of anemonefish that I work with in the central Philippines are heavily exploited for the marine aquarium trade, and improved understanding of their dispersal can inform future efforts to conserve them. Generous funding from the Friends of Hopkins and a Myers Grant allows me to head back to the Philippines and continue this research. |
 An artisanal fisherman braves the noon sun to hand-line for reef fish near Daanbantayan, Cebu, Philippines. |
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