For decades, recreational anglers along the U.S. mid-Atlantic coast have braved the cold temperatures of late October and November to pursue striped bass, one of the region’s most iconic fish species. Fall runs have been especially strong this season off the coasts of New Jersey and New York. “The amount of fish and [their size] It was really, really high,” captain Lou Van Bergen said. miss barnegat righta 90-foot party boat out of Barnegat Light, New Jersey. “You can go out and catch better-sized fish every week all through Thanksgiving.”
From the looks on boat decks this fall, it would have been easy to guess that striped bass, once overfished and dangerously low on the East Coast, have made a remarkable comeback. Outside of the nearby Chesapeake Bay and the Hudson River, where they return to spawn each spring, juvenile hatching and maturation is “abysmal,” said John Waldman, an aquatic conservation biologist at the City University of New York. Waldman, himself an avid fisherman, said the low recruitment and spawning success of striped bass in the historically fertile estuary is a “real mystery.”
Signs of danger are beginning to be observed in marine ecosystems around the world, from the North Sea to the Southern Ocean.
One way to better understand this apparent shift in the recruitment and distribution of striped bass in the Mid-Atlantic Bay (a coastal region extending from the Outer Banks of North Carolina to Massachusetts) is to examine the behavior of one of its primary food sources. It’s about paying attention to similar changes. , Atlantic menhaden, a forage fish of the herring family. Menhaden have also been seen in large numbers off the coasts of New Jersey and New York in recent years. Van Bergen explained that on a trip in early November, menhaden covered about 40 kilometers of water. But like striped bass, menhaden populations in the Chesapeake and other estuaries that were once reliably fish-rich have declined.
“We don’t know if this is a larger cyclical pattern, a result of how we manage the water, or whether it’s a result of rising water temperatures,” said Dr. Petersen, a doctoral student at Cornell University who studies rising water temperatures. says Janelle Morano. The distribution of menhaden has changed over time along the east coast of the United States. “But something is happening, and it’s real.”
Taken together, the interrelated changes in the behavior of these two species resemble aspects of phenological discord, a phenomenon observed across the globe from land to sea.
Yale University Environment 360
Phenology is the seasonal timing of life cycle events such as spawning and migration. Think of honey bees emerging from their hives as spring flowers bloom, or monarch butterflies migrating south to Mexico in the fall as milkweed begins to die in the United States. However, phenological mismatch occurs when these complex interspecific relationships become out of sync due to environmental changes. Terrestrial cases of phenological mismatch are well documented. For example, a detailed analysis shows that over the past 29 years, the movement of monarchs has I’m late Rising temperatures are causing inconsistencies in food availability during migration and inability to reach wintering grounds.
However, phenological discordance is less studied in the ocean. All scientists interviewed for this article agreed that while the phenology of single species in marine environments is well studied, phenological discordance between multiple species is poorly understood. I pointed out. They said the issue urgently needs further focus because of the potential knock-on effects that mismatches cause up and down the food chain. They also cautioned that all species, both marine and terrestrial, tend to undergo natural population fluctuations, and declines or increases cannot be pinpointed to specific stressors. Overfishing and resource management are just two external factors that may be influencing phenological mismatches in the world’s oceans. as the author of paper Published in nature climate change Highlighting this lack of knowledge, the researchers wrote, “Given the complexity, accurately predicting phenological mismatches in response to climate change will be a major test of ecological theory and methods.” ”.
Yet signs of danger are beginning to be observed in global marine ecosystems, from herring and zooplankton in the North Sea, to sardines and bottlenose dolphins in the South Sea, to striped bass as well as baleen whales and menhaden in the Northwest Atlantic.
The decline of lobsters in the mid-Atlantic is forcing older striped bass to compete for food with younger, more agile fish.
To be sure, striped bass aren’t as dependent on menhaden as monarch butterflies are on milkweed. But the fish appear to be responding reliably to changes in menhaden behavior and abundance, and experts say both species are particularly vulnerable to changes in menhaden bays and the Gulf of Maine over the past quarter century. It is likely that they are reacting to changes. , warm the water. Taken together, these ecosystem-wide changes could reshape where and how striped bass and menhaden spawn, move, feed, and ultimately interact. Little is known about how these effects ripple through the food chain, from impacts on planktonic organisms to human societies that rely on fisheries and the marine environment in general for economic and cultural survival. .
One of the few certainties in marine ecosystems is that water temperatures are trending upward, and are warming rapidly in the northwest Atlantic. For example, between 2004 and 2019, the Gulf of Maine warmed more than seven times the global average, or “at a rate faster than 99% of the world’s oceans,” according to the Gulf of Maine Research Institute. In the southern Gulf of Maine and mid-Atlantic bays, heating has virtually wiped out American lobster, one of striped bass’ main food sources. This decline in prey species may be negatively impacting striped bass, especially older individuals, who may lack the physical strength needed to pursue fast-moving prey such as menhaden and mackerel. there is. The disappearance of lobsters has forced them to compete with younger, more agile fish for other resources.
As Atlantic ocean temperatures warm, striped bass are making their way north along the U.S. East Coast.
Sean Lowe (via iStock)
“Fluctuations in prey abundance can lead to predators consuming less energy-dense but more abundant prey, leading to a decline in predator status,” said social scientists at the Northeast Fisheries Science Center. Robert Murphy et al. I wrote In a 2022 study on the feeding behavior of striped bass. Waldman did note dietary restrictions in his observations of striped bass. “Striped bass used to come to the coast in small schools throughout the fall, feeding on cockles, eels, crabs and lobsters,” he says. “But now the focus is almost entirely on large schools of baitfish.”
Similar dietary changes have been observed in the Southern Ocean off the coast of South Africa, and the annual KwaZulu-Natal sardine migration is one of the most spectacular examples of phenology on Earth. As winter approaches in the southern hemisphere in May, large schools of sardines emerge from the depths of the ocean, gather along the coast of South Africa, and ride the cold currents northward. For thousands of years, countless species, from bottlenose dolphins to sharks to penguins to boobies, have timed their life cycles, or survival, to this event.
Krill didn’t just migrate north. Instead, it condenses in pockets of cold water, no matter where it occurs.
But over the past 60 years, the arrival of sardines has gradually slowed. The sardines’ instinct to follow the cold water was disrupted by the warmer water creeping south. As a result, the arrival of many of the sardine’s natural enemies is out of sync with the festival. Scientists who studied the sardine migrations of KwaZulu and Natal hypothesized that this mismatch had reduced the abundance and distribution of Cape gannets and African penguins. According to one study, bottlenose dolphins have shifted their diet from sardines to mackerel. “When events like this are disrupted, there can be ripple effects,” says Stephanie Plon, a marine biologist at South Africa’s Stellenbosch University and co-author of the study. told the BBC In June.
These phenological discrepancies are not limited to the upper echelons of the food chain either. The reverberations may have reached the roots.
Zooplankton and phytoplankton have been declining in the Northeast Atlantic and North Sea over the past half century. For herring, plankton is essential to the success of a given seasonal spawning class. In a study conducted in North SeaThe researchers found that the success of herring larvae is closely related to the abundance of zooplankton and phytoplankton, which are highly sensitive to temperature. As in other maritime regions of the world, in the North Sea significant global warming. “Although the causal mechanisms remain unclear, the decline in the abundance of key planktonic organisms in the Northeast Atlantic is a cause for great concern for the future of the food web,” says another study on North Atlantic flora and plankton. the authors state. concluded.
Herring larvae feed on zooplankton, which is becoming increasingly rare in the Northeast Atlantic.
Solvin Zankul (via GEOMAR)
One of the most important types of zooplankton to marine food webs is krill, shrimp-like crustaceans that everything from whales to penguins to squid to seabirds rely on for survival. In 2021, a team of French and British scientists discovered the presence of krill. plummeting Throughout the North Atlantic. Krill didn’t simply migrate north in response to warmer waters steadily rising toward the North Pole. Instead, they are experiencing “habitat pressure.” Essentially, wherever they originate, they condense in pockets of cold water. “We expect krill populations to simply migrate north to avoid warmer conditions,” said Martin Edwards, one of the study’s authors. “However, this study shows that…in the North Atlantic, marine populations are not simply shifting their distribution northward.”
Dave Secor, a professor of fisheries science at the Chesapeake Biological Laboratory at the University of Maryland Environmental Science Center, said the behavior of North Atlantic right whales, which feed primarily on krill in the Mid-Atlantic Bay, has changed in recent years. This is clearly consistent with what is called the “march to the poles” theory. “There is evidence that those concentrations have actually moved south,” Secor said. “Oceanography is not linear. Things are happening in bursts.” Regarding striped bass in the region, Secor said there has been a clear change in the timing of spawning and migration. “The question is whether it is sufficiently adaptable to the more rapid changes we have experienced in recent years.”
Just as the sardine migration between KwaZulu-Natal is crucial to South Africa’s commercial fishing industry, and the availability of herring in the North Sea underpins the cultural culinary traditions of European countries, striped perch is available in the United States. and menhaden are critical to the local economy, which is driven by recreational fishing. Located in the mid-Atlantic region of New England. This ultimately means that the ripple effects of phenological changes and interspecific mismatches will extend beyond marine ecosystems to more established and less dynamic human ecosystems. As Waldman said, we may be the species least able to adapt to the changes underway in the ocean. “Some people are going to lose the fishing industry that they grew up in and made a living out of,” he says. “And there may be nothing we can do about it.”
