Tropicalization of mid-western Atlantic coastal bays by pinfish Lagodon rhomboides: a combined ecological and oceanographic perspective

As climate change continues to shift the distributions of species worldwide, understanding where, why, and how organisms move beyond their historical ranges is of critical importance. Here, we report on the expansion of pinfish Lagodon rhomboides poleward along the mid-western Atlantic in response to rising temperatures. Pinfish are a key interactor in nearshore subtidal habitats like seagrasses in the southwestern Atlantic and Gulf of Mexico, but they have been historically sparse north of the ecotone at Cape Hatteras, North Carolina, USA. Using multi-decadal trawl surveys, we show that while pinfish have been present both below (North Carolina) and above (Virginia and Maryland) this ecotone for many years, they have increasingly intruded into restored eelgrass ( Zostera marina ) meadows in the coastal bays of Virginia over the past decade. In 2022, for instance, pinfish abundances in Virginia equaled those observed historically in North Carolina. To understand the factors promoting these changes in abundance, we used a passive drifter model to show that these increases are not necessarily tied to changes in offshore currents. Instead, linear models revealed that the local abundance of pinfish in Virginia correlates most with inshore summertime water temperatures. Thus, favorable environmental conditions of the recipient bays appear to encourage greater recruitment and therefore greater abundance of pinfish. Given their outsized ecological role in subtropical ecosystems, and that the climate will continue to warm, our findings suggest that pinfish may soon come to dominate the structure and functioning of temperate seagrass meadows in Virginia and beyond.