Out of the blue: New nuisance neonative may invade the Gulf of Maine
Summary
Climate change has led to significant increases in ocean temperatures in the northeastern United States, which may increase tolerable ranges for many marine species. The blue crab, Callinectes sapidus, is one such species that is potentially shifting northward from its historical northern limit of Cape Cod, Massachusetts. As a result, the blue crab threatens to become an invasive “nuisance neonative”. This study combines three years of observational data, anecdotal evidence through surveying colleagues, literature and internet searches, and an analysis of changes in near-surface ocean temperature data to determine if climate change is a driver of range shifts in C. sapidus to the Gulf of Maine. Field surveys conducted in 2012-2014 found only five blue crabs in the Gulf of Maine, corresponding with a mean increase of 1.3˚C in ocean temperature than the average of the previous decade. Surveys of managers revealed several other recent observations of blue crab in the Gulf of Maine. These results are not enough to determine if the blue crab has established in the Gulf of Maine, but the documented recent sightings and steadily increasing ocean water temperatures in the area suggest this outcome is forthcoming. The establishment of the blue crab in the Gulf of Maine would disrupt fisheries and food-webs, which need to be monitored by ecologists and managers alike.
Take home points
Recent repeated observations of the blue crab, Callinectes sapidus, have been reported as far North as the mid coast of Maine.
Although the observational and anecdotal reports may not definitively conclude that the blue crab has established in the Gulf of Maine, as of 2015, continued warming in combination with these observations signal a permanent poleward expansion.
Establishment of the blue crab in the Gulf of Maine would affect fisheries and food-webs.
Management implications
As ocean temperatures continue to warm, the blue crab will shift further north from Cape Cod which we should keep an eye out for. Egg bearing/reproductive females found are especially significant.
The blue crab (Callinectes sapidus) is a predator of the invasive European green crab (Carcinus maenas) as well as commercially important soft-shelled clams (Mya arenaria). Their effect on coastal food-webs needs to be monitored as a potential net-positive or net-negative as they arrive in the Gulf of Maine.
Keywords
Range Expansion; Changing Biotic Interactions (Competitiveness); Callinectes sapidus; Blue Crab; New England; Gulf of Maine; Nuisance Neonative