Study shows impact of climate change on fishing economy

By Doug Fraser

Posted Dec 22, 2019

Warmer ocean waters are believed to be a factor behind declining number of jobs

With the Gulf of Maine warming faster than 99% of the world’s oceans, it makes sense there would be impacts on fish stocks and the fishermen who depend on them for a living.

While several studies have demonstrated that marine inhabitants are on the move trying to find cooler water, the data on how climate change is affecting fishermen has been hard to come by. Other factors — cuts to fish quotas, the closing of more areas to fishing, and gear changes to rebuild fish stocks or protect endangered species such as the right whale — also could affect the fishing industry and disguise the impact of ocean warming.

But a new study by Kimberly Oremus, a researcher at the University of Delaware, used existing data to show that fishing jobs in New England’s coastal counties declined by an average of 16% between 1996 and 2017 due to climate variation.

Oremus focused her research on what is known as North Atlantic Oscillation (NAO), the relative pressure differential between massive oceanic high pressure and low pressure systems in winter.

When the subtropical high pressure off the Azores is stronger than usual, there is a greater pressure differential with a low over Iceland. That means stronger winter storms crossing the Atlantic to Europe, and mild, wet winters in the eastern United States.

When that subtropical high is weak, the pressure differential between the two large systems is low. That leads to fewer, weaker storms crossing the Atlantic, meaning a milder winter in Europe but a colder, snowier winter in the Northeast U.S. as the weaker boundary allows cold air to seep down from Canada.

“Biologists for over a decade have known there is a linkage between the NAO and productivity,” Oremus said.

Land dwellers in New England associate winter with barrenness, the absence of life, but colder ocean waters are actually more productive than warm ones.

Decaying vegetable and animal matter rains down from the sea surface to the ocean bottom. Deep currents bring those vital nutrients to the surface to sustain phytoplankton, the base of the marine food web. When surface waters are cold, the boundary between denser bottom water and lighter, warmer surface waters is weakened and it is easier for nutrient-rich deep water to rise into surface layers where the phytoplankton use the power of the sun to grow. It’s why Arctic and Antarctic waters explode with life when those regions shift from round-the-clock winter darkness to midnight sun each spring.

The wind and storms of winter also help to mix the lower and upper layers of the ocean.

An abundance of plankton means more food, particularly for keystone species such as herring that feed on these plankton blooms and are in turn consumed by species further up the food chain. Critically, plankton also provides food for fish larvae.

“For a lot of stocks, it’s more productive in a colder year than a warmer one,” Oremus said. “It’s always generally linked to the first year of fish life.”

The study, “Climate variability reduces employment in New England Fisheries,” was published in the Dec. 9 edition of the journal Proceedings of the National Academy of Sciences. In it, Oremus looked at fishing data and regulations on 22 Atlantic fish stocks representing 75% of the catch and revenues. She also researched wages, employment, bankruptcy and other economic data within those fisheries.

What was important about the NAO was that it was random and tended to change every winter. Oremus felt that any response — higher or lower landings, higher revenues, more employment — that followed shifts in the NAO would indicate the impact of temperature and climate on fishermen.

“It seems like this signal doesn’t appear to be correlated with those other things,” such as regulatory measures, fish prices, etc., she said.

Oremus found that employment in the New England fishery, which has about 34,000 commercial fishermen and harvesters, was linked to the North Atlantic Oscillation. Between 1996 and 2017, the NAO tended toward a strong subtropical high pressure system, which leads to a warmer, less productive ocean and less fish and a drop in employment in the fisheries.

“Labor is clearly coming from how much they catch, and that comes from how much fish there are in the fishery,” Oremus said.

Atlantic cod populations boomed in the 1960s and ’70s, when the NAO was in a negative phase and the ocean was colder and more productive. By the 1990s, the NAO had reversed and populations decreased.

Reductions in employment lagged a few years behind the particularly warm years, as it took time for the fish to grow enough to be caught or surveyed by scientists and the population decrease to become known.

Oremus did not notice a similar trend in Mid-Atlantic fisheries, where there were more fish stocks that prospered in warmer water and where fishermen simply switched to a warm water species.

Oremus said her study also showed the need to incorporate environmental variability into fish stock estimates and include the potential impact of changing environmental conditions on fishermen in management plans.

Change is not always as smooth as predicted in computer modeling of fish stock responses to management changes in harvest levels and closures, she said. What is happening in the environment can be hugely significant, particularly if there is a big change from one year to the next.

“It can be fluctuating so much that you can unintentionally overfish or underfish,” catching less than could be allowed, she said.