Broad salinity tolerance in the invasive lionfish Pterois spp. may facilitate estuarine colonization

The ongoing invasion of non-native Indo-Pacific lionfish (Pterois spp.) represents a significant ecological threat throughout the Western Atlantic and Caribbean. As a generalist species, lionfish have been able to rapidly colonize a wide variety of ecosystems, including coral reefs, seagrass beds, mangroves, the sea floor at depths as great as 300 m, and even brackish estuaries. While lionfish have been encountered in a number of estuarine systems, the spatial distribution of lionfish in estuaries is likely limited by the species' ability to tolerate low salinities. Here, we experimentally identify minimum salinity tolerance in lionfish by measuring survival salinity minimum-the lowest salinity at which all individuals survive for 48 h. Additionally, we examine whether long-term exposure to low (but sub-lethal) salinities has negative effects on lionfish. Field observations in the Loxahatchee River estuary (Jupiter, FL) showed that lionfish can survive brief exposure to salinities as low as 1 aEuro degrees. At one estuarine location, fish survived exposure to salinity fluctuations of similar to 28 aEuro degrees every 6 h for several days. In laboratory trials, survival salinity minimum for lionfish was 5 aEuro degrees; however, some individuals survived at 4 aEuro degrees for up to 94 h before dying. Lionfish that were held at 7 aEuro degrees for 28 days showed no differences in mortality, behavior or growth, when compared to control fish held at 35 aEuro degrees (typical ocean salinity). This broad salinity tolerance may allow lionfish to colonize estuaries throughout their invaded range, and may facilitate dispersal across the Amazon-Orinoco plume. Because of the ecological and economic importance of estuaries, this facet of the lionfish invasion warrants further study.