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Tropical Hitchhikers

The Hitchhikers Guide to the Gulf Stream

By Katie Rodrigue, Principal Biologist, RI DEM Division of Marine Fisheries


Late summer in Rhode Island is an exciting time – warm weather, beautiful beaches, and a crisp New England autumn just around the corner. It also means a greater diversity of fishes in little Rhody’s coastal waters, partly due to an influx of juvenile tropical fish that arrive in summer and stick around until the water cools.

Angler aboard the charter fishing vessel C-Devil II holding an adult planehead filefish during a recreational saltwater fishing trip in Rhode Island waters.
An adult planehead filefish is displayed aboard the charter fishing vessel C-Devil II during an offshore recreational fishing trip off the Rhode Island coast. Photo: Capt. Kelly Smith

That’s right – species typically found on a snorkeling excursion in the Caribbean, such as groupers and butterflyfish, can be found right here in the Ocean State. But these visitors don’t swim the 1,000+ mile journey to get here – they hitch a ride on the Gulf Stream.

Many fish reproduce by broadcast spawning: releasing eggs and sperm directly into the water column in hopes that they will mix, becoming fertilized, and develop into larvae. These larvae are then at the mercy of ocean currents, drifting along as they develop and sometimes settling far from where they were spawned. The tropical travelers we see in Rhode Island were carried by the Gulf Stream current.

The Gulf Stream is one of the strongest ocean currents on Earth, moving warm water from the Gulf of Mexico and the Caribbean northeast along the coast of the US and Canada. It begins to flow away from the coast near Cape Hatteras, North Carolina. Here the current widens and meanders, and wave-like patterns emerge. These patterns can eventually form loops that pinch off from the Gulf Stream, creating spinning rings of water called eddies. There are two types: warm core rings and cold core rings. Cold core rings form off southward bending meanders, allowing colder nutrient-rich water from north of the Gulf Stream to be moved south towards the Sargasso Sea. Warm core rings form off northward bending meanders between the Gulf Stream and the continental slope, bringing warmer water and any tropical fish larvae living in them towards the coast. Warm core rings move west and are usually reabsorbed back into the Gulf Stream as they are “pinched” between the main flow of the stream and the shallow depths of the continental shelf. Often, these rings come close enough to the shelf to deposit tropical hitchhikers into coastal currents, eventually making their way inland.

The RI DMF conducts several surveys to monitor fish and invertebrate populations throughout Rhode Island state waters. In mid to late summer, tropical species are frequently caught on these surveys. The species encountered can vary widely from year to year, but the most commonly caught on the trawl and seine surveys include blue runner, crevalle jack, Atlantic needlefish, inshore lizardfish, and permit. However, these surveys using nets are not very effective at catching fish that hide in reef structures such as butterflyfish, groupers, short bigeye, and triggerfish. By utilizing other approaches, such as fish traps or SCUBA, reef-dwelling fish can also be observed. Some other species encountered in recent years include grey snapper, spotfin butterflyfish, scamp grouper, flame box crab, buffalo trunkfish, threadfin lookdown, bluespotted cornetfish, and African pompano.

Most of the tropical species that ride the Gulf Stream to RI are juveniles, although adults of some species also make the summer trip and can even be caught by recreational anglers! These fish may thrive when waters are at their warmest in late summer and early fall, especially in protected areas like the coastal salt ponds which act as nurseries for many species. However, tropical organisms are not adapted to our New England winters, and though some may migrate away, most do not survive when it gets too cold. This is why we do not see established populations of these species in RI. However, with a warming climate, we are seeing shifts in the species composition of RI waters away from demersal (fish that live near the sea floor) New England species such as winter flounder and hake, to warm-water pelagic species (fish that live in the water column) more characteristic of the mid-Atlantic, such as butterfish and scup (Collie et al. 2008). Additionally, there has been an increase in the number of tropical fish caught in the RI DMF monthly trawl survey over time, which may suggest that more tropical fish are being carried into our waters now than in the past.

So, when you're enjoying the beautiful marine ecosystems of Rhode Island next summer, keep an eye out for these unusual tropical travelers! You never know what unique species you might find! If you find a mystery fish, take a photo and post it on our Facebook page or email us and staff will help identify what you have observed.

RI DEM Division of Marine Fisheries surveys: Explore research and data from the Rhode Island DEM Division of Marine Fisheries surveys and publications page.

RI DEM Facebook page: Follow the Rhode Island DEM Facebook page for fishing updates, conservation news, and outdoor recreation information.

Collie, J.S., A.D. Wood, and H.P. Jeffries. 2008. Long-term shifts in the species composition of a coastal fish community. Can. J. Fish. Aquat. Sci. 65:1352-1365.

Small horse-eye jack resting in the palm of a person’s hand during a fisheries survey conducted in Ninigret Pond, Rhode Island.
A horse-eye jack collected during a September seine survey in Ninigret Pond highlights ongoing fisheries monitoring efforts tracking marine species in Rhode Island coastal habitats.

Satellite imagery of sea surface temperature. The red "ribbon" is the Gulf Stream current, carrying warm water from the Gulf of Mexico north.

Ocean temperature map of the Gulf Stream showing warm core and cold core rings in the Atlantic Ocean with labeled arrows identifying circulating water masses.
A Gulf Stream ocean temperature map illustrates warm core and cold core rings, which influence marine ecosystems, fish migration patterns, and ocean conditions along the Atlantic coast. Photo: NASA

Some of the more commonly caught tropical species:

Atlantic Needlefish

Person holding an Atlantic needlefish with a long slender body and pointed beak-like jaws beside coastal waters in Rhode Island.
An Atlantic needlefish displays its distinctive elongated body and sharp beak-like snout during a fisheries survey in Rhode Island coastal waters.

Crevalle Jack

Small crevalle jack resting in the palm of a person’s hand, showing the fish’s deep silver-yellow body and forked tail during a fisheries survey.
A juvenile crevalle jack is examined during coastal fisheries monitoring, highlighting the diverse marine species occasionally found in Rhode Island waters.

Inshore Lizardfish

Small lizardfish resting in the palm of a person’s hand, showing its mottled brown body, pointed head, and elongated shape near coastal waters.
A lizardfish displays its camouflaged markings and streamlined body during marine species monitoring in Rhode Island coastal waters.

Senator Sheldon Whitehouse shared this photo of a mutton snapper caught at Fort Adams in September 2025.

Red-colored snapper resting on a rocky surface, showing its deep body, red fins, and large scales commonly associated with reef fish species in Atlantic waters.
A vibrant red snapper displays its distinctive reddish coloration and reef-dwelling features during a recreational saltwater fishing catch in Rhode Island waters.

A short bigeye makes its home on an oyster reef in Quonochontaug Pond.

A short bigeye fish peeking out from inside a shell on an oyster reef in Quonochontaug Pond, showing its bright red eye and hidden underwater habitat.
A short bigeye shelters within an oyster reef habitat in Quonochontaug Pond, highlighting the rich marine biodiversity supported by Rhode Island coastal ecosystems.
Small bright orange short bigeye fish resting in a person’s hand, showing its large eye, spiny dorsal fin, and vivid coloration.
A short bigeye displays its striking orange-red coloration and oversized eye during marine species monitoring in Rhode Island coastal waters.

Grey Snapper

Small gray snapper resting on a flat surface, showing dark horizontal stripes, a spiny dorsal fin, and bronze coloration during marine species monitoring.
A gray snapper displays its striped markings and coastal reef fish characteristics during fisheries monitoring in Rhode Island waters.

Dwarf Goatfish

Small dwarf goatfish lying on a flat surface, showing its slender silver body, striped tail, and reflective scales during marine species monitoring.
A dwarf goatfish displays its iridescent scales and distinctive striped tail during fisheries sampling in Rhode Island coastal waters.

Lookdown

Small lookdown fish resting beside a ruler for measurement, showing its flat silver body, long fin rays, and yellow markings during marine species monitoring.
A juvenile lookdown fish is measured during fisheries sampling, highlighting the unique body shape and tropical appearance of this uncommon coastal species found in Rhode Island waters.

Flame Box Crab

Flame box crab with striped yellow-and-brown shell markings and raised claws displayed on a white background during marine species identification.
A flame box crab displays its bold striped shell pattern and distinctive body shape during marine species monitoring in Rhode Island coastal waters.


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