OCEAN TEMPS IMPACTING MIGRATION PATTERNS

In 40 years of fishing, Capt. John Williams developed a deep understanding of when he can expect fish to show at his fishing grounds off New York and New Jersey. When things change, he notices.

“Thresher sharks and mako sharks are usually a June thing,” says Williams, who runs Blue Chip Sportfishing out of Southside Marina in Point Pleasant Beach, New Jersey. “Now they’re showing up in May.”

Any experienced saltwater angler knows that fish migrations can vary year to year. And just as unique catches of wayward single fish might not mean much, more than a single captain’s observations are needed to prove a trend. Now, though, the National Oceanic and Atmospheric Administration has put scientific proof behind observations that some saltwater species in the Atlantic are migrating from south to north earlier in the year and making their return trips south later.

A recently released study from NOAA looked at catch data over a nearly 20-year period for Atlantic highly migratory species (HMS), a group of 12 fish that includes tuna, billfish and sharks.

“The study reveals that the spatial shifts appear to be related to increasing water temperatures from Maine through Virginia,” says Lauren Gaches, a spokesperson for NOAA. “Recent studies have found that highly migratory species, among others, are generally shifting northward along the coast and arriving earlier in the year as ocean temperatures warm. It appears that temperature change and prey availability are both factors in these shifts.”

Catches of small and large bluefin tuna, for example, are shifting northward at a rate of 2.5 to 6.2 miles per year. The study found that for each 1 degree C (1.8 degrees F) increase in water temperature, blue and thresher sharks are shifting northward at rates of 19 to 25 miles.

Bluefin tuna catches off Massachusetts in 2019 were estimated to have occurred 80 days earlier than in 2002. Blue shark catches were estimated to

“Shifts in the timing and location of highly migratory species have implications for anglers, including seasonal fishing tournaments.”

—Dr. Dan Crear

have occurred 66 days earlier off Connecticut. Blue marlin catches were found to be 27 days earlier off New York.

NOAA used a complex approach to analyze data collected through its Large Pelagic Survey, mapping the locations and timing of recreational catches of HMS from 2002 through 2019. The survey used three different ways to collect what it calls “intercepts,” or the catch of one of the 12 HMS fish. All told, the study looked at 96,606 intercepts on 53,698 trips.

Analyzing data from NOAA’S Optimum Interpolation Sea Surface Temperature, the Climate Change Institute at the University of Maine’s Climate Reanalyzer determined that the average sea-surface temperature reached an all-time high in the spring of 2023. The North Atlantic has shown the most pronounced warming, with temperatures about 2 degrees F higher than normal.

A number of factors can lead to acute changes in ocean temperatures. They include wellknown atmospheric conditions such as El Niño and La Niña. But global sea-surface temperature averages are tied to warming air temperatures. And just as climate models are predicting continued increases in global air temps, modeling has shown that average ocean temperatures will continue to rise too.

Recreational anglers will likely see firsthand the impacts of the changing migratory patterns.

“Shifts in the timing and location of highly migratory species have important implications for recreational anglers, including seasonal fishing tournaments and coastal communities that rely on these fisheries,” lead author Dr. Dan Crear said in a statement from NOAA. “Fishermen may have to travel farther or fish earlier in the year to find target species. The species found at a favorite fishing spot may be changing over time, with species typically found farther south becoming more common in northern waters.”

Changing migration patterns could also lead to management and regulations changes, such as shifting seasons and bag limits. For example, while cobia were not a specific focus of the study, NOAA predicts that the fish could spend up to 30 more days per year in the Chesapeake Bay by 2050. It’s hard to imagine that such significant changes wouldn’t prompt management changes.

While anglers will have to adapt to changes, that is something they are used to doing.

“There could be a lag because the location or pattern that worked for them five or 10 years ago might not work for them today,” Gaches says. “But anglers are very good at finding fish.”

Take Williams, of Blue Chip Sportfishing. Sure, those sharks are consistently showing up in May now instead of June. But when they do arrive, no matter when, he’s ready for them.