Top marine predators may suffer massive habitat loss by 2100

A recent study led by the Woods Hole Oceanographic Institution (WHOI) focusing on 12 species of migratory marine predators – ranging from sharks and tuna to billfish like marlin and swordfish – has revealed that a majority could face significant habitat loss and displacement from their current territories in the Northwest Atlantic Ocean (NWA) and the Gulf of Mexico (GOM) by the year 2100. 

Given that these ocean regions are among the quickest to warm, projections suggest a temperature rise of 1-6°C (+1-10°F) by the end of this century, pointing to evident climate-induced marine ecosystem alterations.

Studying marine predators

The experts found that several of these vital and renowned marine predator species – both ecologically and economically – are at risk of losing more than 70 percent of their suitable habitats by 2100, and the effects of these climate shifts can already be discerned.

According to lead author Camrin Braun, a marine ecologist at WHOI, regions off the Southeast U.S. and Mid-Atlantic coasts are anticipated to be the primary zones of habitat loss for marine predators. 

Pervasive habitat loss

The study covered three types of sharks (blue, porbeagle, and shortfin mako), five kinds of tuna (albacore, bigeye, bluefin, skipjack, and yellowfin), and four species of billfish (sailfish, blue marlin, white marlin, and swordfish). 

Despite not accounting for potential adaptive capabilities or thermal resilience of these species, the findings project a pervasive habitat loss for almost all the species under investigation.

“Climate change is expected to fundamentally change the status quo for where these species are and how they live. While we don’t really understand all the details of what that fundamental change might look like, this study is a good step in the direction of trying to nail down what those changes might be, so that we can do something about it,” Braun explained.

How the research was conducted 

To clarify the impact of climate change on these marine predators, the scientists leveraged satellite data, oceanographic models, and firsthand biological records spanning 30 years. These were used to craft dynamic species distribution models, helping gauge the past and future impact of climate change on the species in NWA and GOM.

Senior author Rebecca Lewison, a professor of Marine Biology at the Coastal and Marine Institute at San Diego State University, emphasized the significance of satellite data like NASA’s in comprehending the impact of climate change on crucial marine species. 

“Our research demonstrates that climate-driven changes are happening now, not from projections of climate change, but based on observed empirical data from the last two decades. So while our findings do point to larger species shifts in the near term, it also clarifies the substantial changes in species distributions that have already occurred,” she said.

Implications for marine predators

According to co-author Tobey Curtis, a researcher at the Atlantic Highly Migratory Species Management Division of NOAA Fisheries, it is crucial to incorporate these findings in marine conservation and management strategies. 

As Curtis argued, this study “not only sheds more light on the far-reaching effects of climate change on ocean environments but highlights that marine conservation and management efforts need to plan for these ongoing changes. If migratory fish are on the move, fishing vessels and coastal communities will also need to adapt. Studies like this will help marine resource agencies be even more dynamic in their decision-making.”

Dynamic management strategies needed

Moreover, habitat loss of these critical species will have major ramifications for fisheries, along with socio-economic consequences on fishing communities. And since traditional fishery management is rigid and often outdated, there is an urgent need for dynamic management to adapt to these changes. 

As Braun argued, historic ways to manage fisheries are static, even though fish tend to move around a lot. 

“We basically draw a box in the ocean and say whether you can or can’t fish there,” he explained. To address these issues, dynamic ocean management frameworks that could reliably embody expected changes are urgently needed to address these issues,” said Braun.

“Otherwise, you are left with your static box in the ocean that doesn’t move, even though the fish may have moved, and the ocean may have changed,” he concluded. 

More about marine predators

Migratory marine predators play a critical role in the ecology of marine environments. These creatures, including sharks, tuna, swordfish, and whales, undertake impressive journeys across vast oceanic territories.

Migration patterns

Sharks

Sharks, especially the great white shark, follow migratory paths determined by feeding opportunities and reproductive needs. They travel thousands of miles, navigating with impressive accuracy. Environmental cues like water temperature and the Earth’s magnetic field guide their movements.

Tuna

Tuna species, like the Atlantic bluefin, migrate seasonally for spawning and feeding. They cover immense distances across both the Atlantic and Pacific Oceans. The Gulf of Mexico often serves as a breeding ground for these predators.

Whales

Whale migrations, particularly those of the humpback whale, are well-documented. Whales travel from feeding grounds in polar regions to warmer breeding grounds, sometimes covering over 10,000 miles annually.

Physiological adaptations

Energy efficiency

Migratory ocean predators have streamlined bodies that reduce drag, allowing them to swim long distances efficiently. Tuna, for instance, possess a specialized blood vessel structure that conserves heat, optimizing muscle function during their extensive journeys.

Sensory adaptations

Sharks utilize a unique sensory organ called the ampullae of Lorenzini, which detects electrical signals emitted by prey. This adaptation enables them to hunt effectively in unfamiliar territories.

Reproductive strategies

The timing of migration often corresponds with reproductive cycles. Whales, for instance, time their migration to give birth in warm waters where their calves have a better chance of survival.

Ecological impact

Predation and food webs

Migratory ocean predators help maintain the balance of marine ecosystems by regulating prey populations. Their hunting activities often create opportunities for other species, fostering biodiversity.

Economic implications

Fisheries around the world target migratory predators like tuna, leading to significant economic contributions. However, overfishing poses a serious threat, with potential ecological repercussions.

Conservation challenges

The migratory paths of these predators often cross international boundaries, complicating conservation efforts. Many species, such as the great white shark, face endangerment due to habitat degradation, climate change, and overfishing.

Migratory marine predators are a remarkable testament to evolutionary adaptation and ecological interconnectivity. Their journeys across vast marine landscapes are not just biological phenomena but integral to the health and balance of ocean ecosystems.

Understanding these predators’ behavior, biology, and impact is essential for conservation efforts and the sustainable management of our oceans. The pursuit of scientific research, coupled with international cooperation, is paramount in preserving these extraordinary creatures and the delicate ecosystems they inhabit.

The study is published in the journal Science Advances.

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By Andrei Ionescu, Earth.com Staff Writer

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