OCEAN COOLING COULD IMPACT NORTHEASTERN FISHERIES

 

In recent years, the Gulf of Maine has been one of the world’s most rapidly warming ocean regions.  But, for a while at least, that may change.

A publication recently released by the National Marine Fisheries Service, titled “2025 State of the Ecosystem, New England,” noted that

“2024 global sea surface and air temperatures exceeded 2023 as the warmest year on record, but colder than average temperatures were observed in the Northeast U.S.  Oceanographic and ecological conditions in the Northwest Atlantic were markedly different in 2024 compared to recent years.

“…Late 2023 and early 2024 observations indicate movement of cooler and fresher water into the Northwest Atlantic, although there are seasonal and local exceptions to this pattern.  Anomalously cold and low salinity conditions were recorded throughout the Northeast Shelf and were widespread across the Slope Sea for much of the year.  These cooler and fresher conditions are linked to the southward movement of the eastern portion of the Gulf Stream and possibly an increased influx of Labrador Slope and Scotian Shelf water into the system.”

The cooler, fresher water wasn’t limited to the Gulf of Maine.  In February 2024, sea surface temperatures along the outer continental shelf were between 2.5 and 5 degrees Centigrade lower than the average February temperature for the years 2000 through 2020, even though waters closer inshore somewhat exceeded the long-term average temperature.  The NMFS publication stated that

“Colder, fresher water detected deep in the Jordan Basin [region of the Gulf of Maine] for the first half of 2024 suggests and influx of Labrador Slope and Scotian Shelf water, which resulted in colder and fresher conditions throughout the Northwest Atlantic and contributed to the increased size and colder temperatures of the Mid-Atlantic Cold Pool.”

A recent, related NMFS news release said that

“Researchers expect the Gulf of Maine to be 0.9 to 1.8 degrees Fahrenheit (0.5 to 1 degree Celsius) cooler this summer [of 2025] compared to the average summer temperature…

“A companion longer-term outlook, also developed by NOAA scientists, suggests that more frequent inflows of cooler deep water may continue to temper warming in the basin for the next several years.”

The 2005 State of the Ecosystem report reveals that

“the center of distribution for a suite of 48 commercially or ecologically important fish species along the entire Northeast Shelf continues to show movement toward the northeast and generally into deeper water.  Habitat model-based species richness suggest shifts of both cooler and warmer water species to the northeast.”

However, since it also notes that

“Long-term oceanographic projections forecast a temporary pause in warming over the next decade due to internal variability in circulation and a southward shift of the Gulf Stream,”

it is reasonable to ask whether the current cooling trend will interrupt the northeastward shift in fish stocks, and how fish stocks will react to the cooling water.

The recent NMFS release provides some insight, stating that

“Bottom-water temperatures influence the productivity of groundfish, like cod, haddock, pollock, and several species of flounder, which prefer cooler water.  Lobster, the most valuable fishery in the northeast, are also temperature-sensitive.  Warming waters along the New England coast in recent decades have contributed to the collapse of the southern New England lobster population while the Gulf of Maine population has boomed.  Researchers expect that cooler waters will impact this economically and culturally important species.”

Given that the cooler water extends into the Mid-Atlantic, it’s hard not to wonder whether anyone might be regretting the Atlantic States Marine Fisheries Commission’s American Lobster Management Board’s decision not to adopt a moratorium on harvest of the southern New England lobster stock, as recommended by the American Lobster Technical Committee in 2010.  At the time, the Technical Committee only recommended a 5-year-long moratorium, but observed that

“Environmental changes, most notably temperature, likely have forced lobster to seek more suitable habitat in deeper water.  Larvae produced by displaced lobster may be lost to traditional inshore nursery grounds.  The fishery has adapted to the changes in the resource by shifting effort further offshore.  However, fishing continues in most inshore portions of [southern New England], and continued harvest represents lost spawning stock.

“A moratorium provides the maximum likelihood to rebuild the stock to a level that can support a sustainable fishery.  Rebuilding the currently depleted [southern New England] stock may take longer than five years.  Cady and Agnew (2004) reviewed stock recoveries of depleted marine resources and reported that invertebrate fisheries most likely to recover were those with reductions in predator pressure, in the center of their geographic range and under favorable regimes.  They that the predicted length of recoveries should be treated with caution and conclude that a few stocks have recovered within a decade, but that most require longer.”

Such a moratorium, if sustained until the stock showed strong signs of recovery, would have maximized the number of breeding-age adults that might have been able to take advantage of the current cooling trend, and might have been able to take advantage of the cooler waters to increase lobster recruitment.  However, that opportunity was lost a long time ago.  The southern New England lobster stock is now at the lowest level of abundance ever recorded, and continues to decline.

However, the cooling may come soon enough to bail out the lobster fishery in the Gulf of Maine, where fishermen who failed to learn any lessons from the collapse of the southern New England stock, adamantly opposed modest restrictions intended to prevent a similar decline off northern New England, and caused the American Lobster Management Board to back off from imposing such restrictions in the Gulf of Maine and off eastern Cape Cod.  It is very possible that the cooling water will reverse a trend of declining lobster recruitment in the region, and that lobstermen will feel vindicated in successfully opposing science-based management—at least until the cooling trend reverses, and increasing water temperatures drive Gulf of Maine lobster recruitment down once again.

But the most interesting question may be how the cooler and less saline waters flowing along the outer continental shelf will impact the black sea bass population.

There is no question that the northern black sea bass stock—that is, the fish found north of Cape Hatteras, North Carolina—is healthy, with the biomass at 219 percent of the biomass target at the end of 2023.  However, the 2024 management track stock assessment also predicts that the spawning stock biomass is going to decline significantly over the next few years.

That prediction led to substantial controversy last fall, when the Mid-Atlantic Fishery Management Council’s Scientific and Statistical Committee, after reviewing the 2024 management track assessment, decided that the allowable biological catch, and ultimately recreational and commercial black sea bass landings, should be reduced by 20 percent.  Members of the Summer Flounder, Scup, and Black Sea Bass Monitoring Committee, which is composed of biologists from the various states, ASMFC, and NMFS, strongly disagreed with the Scientific and Statistical Committee’s advice, questioning why, after a long period of above-average recruitment, the SSC believed that recruitment would fall to more historically typical levels.

The ASMFC’s Summer Flounder, Scup, and Black Sea Bass Management Board, which is not required to follow the Scientific and Statistical Committee’s advice, agreed with the dissenters on the Monitoring Committee and refused to reduce black sea bass catch limits.  The Mid-Atlantic Council, which was bound to follow the SSC’s guidance, did cut landings by 20 percent, creating a rift between federal and state management measures, that NMFS—which also claims not to be bound by the SSC’s decisions—resolved by ignoring the Council advice and extending the ASMFC decision into federal waters.

It was a strange debate and an even stranger resolution, but now we have to ask whether the Scientific and Statistical Committee was really right all along.

That’s because black sea bass recruitment—the number of young fish that enter the population each year—is not primarily driven by the size or the spawning stock or by the number of juvenile fish that are produced.  Instead, recruitment is driven by the oceanographic conditions that the first-winter fish experience when they spend that first winter at or near the edge of the continental shelf.  Warmer, more saline water typically results in strong black sea bass recruitment.  The very strong 2011 year class, which was most prevalent north of Hudson Canyon, can probably be attributed to such favorable conditions, as the 2025 State of the Ecosystem report revealed that

“2012 had among the warmest surface and bottom temperatures in New England.  A large proportion of the Georges Bank and Mid-Atlantic regions had bottom temperatures above the 15^oC thermal tolerance for most groundfish, with some days in the Mid-Atlantic exceeding the 24^oC potential mortality limit.”

Now, with cooler, less saline water expected to prevail for “several years,” there is good reason to believe that the 2024 stock assessment’s predictions of lower black sea bass recruitment may have been right on target, if not, perhaps, a little optimistic, and also to believe that the current regulations, which failed to follow the Scientific and Statistical Committee’s advice and allowed higher harvest than the SSC recommended, may have left the black sea bass stock more vulnerable to the predicted change in ocean conditions.

We can only wait and watch how the situation plays out, to learn how long the cooler, fresher water maintains its presence off New England and the Mid-Atlantic, and also to learn how that presence will affect the current and future abundance of various speces.

But as is always the case when changing ocean conditions add to the uncertainty in managing fish stocks, managers should definitely practice precaution when setting management measures.