For decades along the U.S. Mid-Atlantic coast, recreational anglers have braved the cold temperatures of late October and November to chase striped bass, one of the region’s most iconic fish species. The fall season was particularly strong this season in New Jersey and just off the coast of New York. “The quantity of fish and [their size] It was really, really high,” said captain Lou Van Bergen. Miss Barnegat Wright90-foot party boat out of Barnegat Light, New Jersey. “We were able to go out every week through Thanksgiving and catch better-sized fish.”
From the looks of boat decks this fall, it would have been easy to assume that striped bass, once overfished in dangerously low numbers on the East Coast, had completed a remarkable comeback. Except in the nearby Chesapeake Bay and Hudson River, where the fish return to spawn each spring, hatching and maturation of fry is “messy,” said John Waldman, an aquatic conservation biologist at the City University of New York. Waldman, an avid fisherman, called low-level striped bass recruitment or spawning success in historically fertile estuaries “a real mystery.”
From the North Sea to the South Sea, warning signs are beginning to be observed in marine ecosystems around the world.
One way to better understand these apparent changes in the recruitment and distribution of striped bass in the Mid-Atlantic Bight, a coastal region stretching from North Carolina’s Outer Banks to Massachusetts, is to look at the behavior of one of their primary food sources. is to look at similar changes in . , Atlantic herring, a forage fish belonging to the herring family. In recent years, herring have been found in abundance off the coasts of New Jersey and New York. Van Bergen described a trip in early November when the herring were thick on the ocean’s surface for about 25 miles. But like striped bass, shad populations have been low in the Chesapeake and other estuaries where the fish were once reliably plentiful.
“I don’t know if this is a larger circulation pattern, management practices, or just because water temperatures have risen,” said Janelle Morano, a doctoral student at Cornell University who has been studying how they are managed. The distribution of herring has changed along the eastern seaboard of the United States over time. “But it’s happening and it’s real.”
Taken together, the behavioral changes in these two interconnected species are similar to aspects of phenomenological mismatch, a phenomenon observed across the globe from land to sea.
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Phenology is the seasonal timing of life cycle events such as spawning and migration. Think of how bees emerge from their hives as spring flowers bloom, or how monarch butterflies migrate south to Mexico in the fall as milkweed begins to die in the United States. However, physiological mismatches occur when these complex, interspecies relationships become unsynchronized due to changes in the environment. Terrestrial examples of phenological discrepancies are well documented. For example, a detailed analysis shows that monarch migration has occurred over the past 29 years. It has been delayed Rising temperatures can cause delays of up to six days, inconsistencies in food availability during the journey, and prevent them from reaching wintering sites.
However, phenological mismatches have been much less studied in the ocean. All of the scientists interviewed for this story noted that while there has been excellent research on single-species phenology in marine environments, there is little understanding of multi-species phenology discrepancies. They said the topic urgently needed more attention because of the potential knock-on effects that discrepancies could cause up and down the food chain. They also warned that all species, both marine and terrestrial, are naturally prone to great change and declines or increases cannot be attributed to any one stressor. Overfishing and resource management are just two external factors that can influence phenological inconsistencies in the world’s oceans. As the author of paper published in natural climate change “Accurately predicting phenological mismatches under climate change is a major test of ecological theory and methods, given the complexities involved,” said a study focusing on this lack of knowledge.
Nonetheless, warning signs are beginning to be observed in marine ecosystems around the world, from herring and zooplankton in the North Sea to baleen whales and herring in the Northwest Atlantic, along with sardines, bottlenose dolphins and striped bass in the South Sea.
In the mid-Atlantic, lobster declines have forced older striped bass to compete for food with younger, more agile fish.
Striped bass are certainly not as dependent on shad as monarch butterflies are on milkweed. But the fish appear to be responding to changes in the behavior and abundance of shad, and experts say both species are likely responding to changes that have occurred in the mid-Atlantic Gulf and the Gulf of Maine over the past 25 years. This is especially true. , for heating water. Collectively, these ecosystem-wide changes could reshape where and how striped bass and shad spawn, migrate, feed, and ultimately interact. Little is still known about how these impacts ricochet throughout the food chain, from impacts on planktonic organisms to human communities that rely on fisheries and marine environments in general for economic and cultural survival.
One of the few certain facts about the marine ecosystem is that water temperatures are rising, and rapidly in the Northwest Atlantic. For example, between 2004 and 2019, the Gulf of Maine warmed more than seven times the global average. In other words, it has warmed “faster than 99% of the world’s oceans,” as the Gulf of Maine Research Institute puts it. In the southern Gulf of Maine and the mid-Atlantic Gulf, heating has virtually eliminated American lobsters, one of the striped bass’ main foods. This reduction in prey diversity can have a negative impact on striped bass, especially older ones, who lack the stamina needed to chase fast-moving prey such as herring or mackerel. The extinction of lobsters left them competing for other resources with younger, more agile fish.
As Atlantic waters warm, striped bass are migrating north along the East Coast of the United States.
Shaun Lowe via iStock
“Variations in prey populations may lead to a decline in predator status by inducing predators to consume less energy-dense but more abundant prey,” say Robert Murphy, a social scientist at the Northeast Fisheries Science Center, and colleagues. wrote From a 2022 study on striped bass feeding behavior. While observing striped bass, Waldman actually noted a contraction in their diet. “Striped bass would come in small schools along the coast throughout the fall to feed on cockles, eels, crabs and lobsters,” he said. “But now the focus is almost completely on large aggregations of bait fish.”
Similar dietary changes are also observed in South Africa’s Southern Ocean, where the annual KwaZulu-Natal sardine flight is one of the most dramatic seasonal events on Earth. As winter approaches in the Southern Hemisphere in May, large schools of sardines emerge from deeper waters and gather along the South African coast to travel north on cold water currents. For thousands of years, numerous species, from bottlenose dolphins to sharks, penguins and gannets, have adapted their life cycles (how long they survive) to events.
Krill didn’t just move north. Instead, it condenses into pockets of cold water wherever it occurs.
But over the past 60 years, the sardines have been arriving increasingly later, as their instinct to follow cold water has been confused by the warm water creeping south. As a result, the arrival of many sardine predators did not coincide with the feast. Scientists studying KwaZulu-Natal sardine farming have hypothesized that this inconsistency has reduced the abundance and distribution of Cape gannets and African penguins. One study found that bottlenose dolphins shifted the focus of their diet from sardines to mackerel. “When events like this are disrupted, there can be a knock-on effect,” said Stephanie Plön, a marine biologist at Stellenbosch University in South Africa and co-author of the study. told the BBC In June.
Phenomenological inconsistencies such as these are not limited to the upper levels of the food chain. There is a high possibility that reverberation will reach the bass.
In the northeastern Atlantic and North Sea, zooplankton and phytoplankton have been declining over the past half century. For herring, plankton is critical to the success of a spawning class in a particular season. In one study North SeaThe researchers found that the success of herring larvae was closely related to the abundance of zooplankton and phytoplankton, which are highly temperature-sensitive. Like other maritime regions of the world, North Korea is experiencing this. significant warming. “Although the causal mechanisms are unclear, the decline in the abundance of key planktonic life forms in the Northeast Atlantic… is a major cause for concern for the future of the food web,” said the authors of another study on North Atlantic zooids and phytoplankton. conclusion.
Larval herring prey on zooplankton, which is becoming increasingly scarce in the northeastern Atlantic.
Solvin Zankl via GEOMAR
One of the most important zooplankton in the marine food chain is krill, a shrimp-like crustacean. All creatures, from whales to penguins, squid and seabirds, depend on krill for their survival. In 2021, a team of French and British scientists discovered that krill rapid decline North Atlantic theater. Krill also didn’t simply move north in response to the steady flow of warm water toward the Arctic. Instead, they are experiencing “habitat pressure.” Essentially they are condensing into pockets of cold water everywhere. “We expect krill populations to simply move north to escape warming environments,” said Martin Edwards, one of the study authors. “But this study… shows that marine populations in the North Atlantic are not simply shifting their distribution northward.”
Dave Secor, a professor of fisheries science at the Chesapeake Biological Laboratory at the University of Maryland’s Environmental Science Center, noted that the behavior of North Atlantic right whales, which feed primarily on krill in the Mid-Atlantic Bight, has behaved otherwise in recent years. It clearly traces what is called the “Kyokujin Army” theory. “There is actually evidence that their concentrations have shifted south,” Secor said. “Oceanography is not linear. “Things are going smoothly.” When it comes to striped bass in the area, Secor said there has definitely been a change in spawning and migration times. “The question is whether it can sufficiently adapt to the more rapid changes we have experienced in recent years.”
Striped bass and herring are vital to local economies from recreational fishing in the United States, just as the stocking of sardines in KwaZulu-Natal is important to South Africa’s commercial fisheries and the availability of herring in the North Sea sustains the cultural and culinary traditions of European countries. . Mid-Atlantic and New England. Ultimately, this means that the knock-on effects of phenological change and interspecific mismatch will reverberate beyond marine ecosystems into more entrenched and less dynamic human ecosystems. As Waldman puts it, we may be the species least able to adapt to the changes underway in the ocean. “Some people will lose the fishing industry they grew up in and make a living from,” he said. “And there may be nothing we can do about it.”
