EAPSI: The role of freshwater-marine migratory behaviors on dispersal in Pacific Oceanic Islands fishes

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Many fishes are limited to marine or freshwater environments, but about 250 of 30,000 ray-finned fishes are diadromous, or migrate between fresh and saltwater, usually for reproduction purposes, e.g., Salmon and eel. This behavior is important because many small streams on oceanic islands are subject to variation. Storms, droughts, volcanic activity and pollution can often make small insular streams become uninhabitable for periods of time and can lead to local extinction of a completely freshwater species. Over time, the inability to colonize neighboring streams can lead to a species' extinction. While diadromy limits opportunities for dispersal ability to a specific life stage, many diadromous species have geographic distributions which span multiple oceans. To address these issues, this research aims to understand how variations in migration pattern affect the flow of genes across fish populations. To determine migratory behvior, otolith microchemistry techniques will be used, in collaboration with Dr. Jen-Chieh Shiao, a prominent expert in this technique at the National Taiwan University. Levels of genetic information moving between populations can then be compared to varying migration strategies. Species will be collected from multiple streams around Taiwan (in addition to Guam and Palau). Otolith microchemistry, a technique that identifies chemical compounds in a fish's environment over the course of their life, will be used to classify fishes as diadromous, marine, or freshwater. To understand the importance of these different life-history patterns on dispersal, genetic markers will be used to infer gene flow and population structure of insular oceanic fishes. Variation in DNA sequences will be compared to understand patterns of movement between streams and islands. This project will help bridge the lingering gap between the ecological importance of variation in life history and evolutionary significance of gene flow. This NSF EAPSI award is funded in collaboration with National Science Council of Taiwan.