Amphidromy can be a flexible life history strategy in some Hawai'ian gobies

Abstract

Back in 2007, I handled a review paper for the journal Fish and Fisheries (McDowall, 2007) which dealt with amphidromous fishes, a life-history strategy about which I was ignorant at the time. However, one of the advantages of undertaking the editorial role on a journal is that you get to read papers that otherwise would pass you by. Reading this paper introduced me to the endemic fish fauna of the Pacific islands that typically spend some or all of their larval stage at sea before returning to freshwater, whereupon they can migrate upstream to altitudes of over 700 m above sea level. That paper has stuck with me ever since, probably because of the incredible feats achieved by such small body-sized fish. In this issue, Heidi Heim-Ballew and colleagues (Heim-Ballew et al., 2019) investigated variation in life histories adopted by four endemic amphidromous gobies inferred from the stable isotopic signatures found in the otoliths of the fish which provided a powerful indication of when (if) the fish had migrated from fresh to seawater. They found that all four species of goby were amphidromous, but that three of these species were partially amphidromous, meaning that some fish did not enter the seawater phase, but could remain entirely within the freshwater system throughout their life history. The flexible life histories shown by these species probably makes them more resilient to anthropogenic factors that might interfere with diadromous life histories, and further emphasizes the need for a fuller understanding of fish life history to support effective conservation and management interventions.