Please select your home edition
Edition
38 South - Marlin 795 - LEADERBOARD - Sept2021

Northern shrimp population collapse linked to warming ocean temperatures, squid predation

by NOAA Fisheries 10 Oct 2021 19:36 UTC
Pink shrimp © NOAA Fisheries

An extreme heatwave in the Gulf of Maine in 2012 resulted in the warmest ocean temperatures in the region in decades. By 2013, the Atlantic northern shrimp population in the gulf had experienced a stock "collapse."

That is what fishery scientists call a rapid decrease in numbers that is not a natural fluctuation in stock size. Scientists studying the collapse have found that during this time, warmer temperatures were linked to increases in longfin squid, a major shrimp predator. They arrived in the Gulf of Maine sooner than usual and in more areas where shrimp occur.

"Our results suggest that longfin squid may have been a major player in the collapse of Gulf of Maine northern shrimp during an extreme heat wave event," said Anne Richards, a biologist at the Northeast Fisheries Science Center's laboratory in Woods Hole, Massachusetts.

Richards co-authored the study with Margaret Hunter from the Maine Department of Marine Resources Division of Biological Monitoring and Assessment. They recently published their conclusions in the online journal PLOS ONE.

Temperature is everything

A northern shrimp's early life is highly influenced by temperature. The Gulf of Maine population is at the southern edge of this species' distribution, and they are mostly found in the cooler western part of the gulf.

Recruitment success—how many shrimp survive their first year to become one-year-olds—is related to both spawning biomass and ocean temperatures. Higher spawning biomass and colder temperatures produce stronger recruitment of new, young shrimp into the population. In 2012 waters in the region were 2 degreesC above the 1982-2011 average, and remained above average in all months of the year.

The Gulf of Maine has been warming rapidly. The northern shrimp population had shown signs of stress before 2012, with low survival of young shrimp to age 1 in 2010 and 2011. Even though 2012 was a very warm year, it did not seem that high temperature was enough by itself to cause the population collapse that occurred.

Other factors driving the collapse

To study other possible factors in the shrimp decline, Richards and Hunter used data collected between 2003 and 2017. Gulf of Maine warming accelerated in that period and was the most intense in more than 30 years. They examined data from the commercial fishery and extensive ecosystem monitoring data gathered on scientific surveys in the Gulf of Maine in the spring, summer, and fall. Those surveys were conducted by:

  • Northeast Fisheries Science Center
  • State of Maine
  • State of New Hampshire
  • Atlantic States Marine Fisheries Commission, which manages the northern shrimp fishery

By reviewing survey data, Richards and Hunter showed that shrimp did not change their distribution in 2012. A look at existing studies showed that while the water temperatures were high enough to have affected shrimp physiological processes at some level, they were probably not high enough to kill them outright. Commercial landings data showed that fishing removed some shrimp, but not enough to account for the population collapse.

Looking at temperature data, it was clear that 2012 was a hot year. It was also clear that the warmer temperatures caused spring to come early in the Gulf and last longer than in an average year. That meant that female shrimp stayed inshore longer, delaying their migration to offshore areas.

Could a predator have taken advantage of this mismatch and tipped the population into collapse?

Catching a predator

If you want to know who is eating whom, you look at stomach contents. Researchers next analyzed stomach content data for all species caught during the four scientific surveys in 2012. No new predators were identified, but 11 species exhibited a population peak in one or more seasons during 2012.

Of these, longfin squid was the only species that clearly increased, and also increased in areas where shrimp were also present in 2012. Their numbers were also relatively high in all four seasonal surveys and in the 2013 spring surveys, both inshore and offshore. The early onset of spring in the Gulf in 2012 also meant that female shrimp were still inshore when the longfin squid arrived, in areas shrimp would have left in cooler years. This increased the opportunity that squid had to feed on shrimp.

Shrimp population has not recovered

"Despite a fishing moratorium beginning in December 2013, the population has not recovered and the fishery is still closed. Our study provides further evidence that changing species interactions will have major impacts as ecosystems reorganize due to climate change," said Richards.

Today, an increase in other northern shrimp predators—spiny dogfish, redfish and silver hake—may also be contributing to a decline in the stock. Ocean temperatures in the Gulf of Maine remain high.

Related Articles

Protection measures for North Atlantic right whale
A message from NOAA Fisheries Assistant Administrator on a meeting among U.S. and Canadian officials Fisheries' Deputy Assistant Administrator for Regulatory Programs, Sam Rauch, and our Regional Administrator for the Greater Atlantic Regional Fisheries Office, Mike Pentony, joined me for this meeting. Posted on 22 Jan
Measures to rebuild shortfin mako
To help increase U.S. Western Atlantic bluefin tuna quota The U.S. and other countries from around the world tackled management challenges for Atlantic tunas and sharks at the 2021 annual meeting of the International Commission for the Conservation of Atlantic Tunas (ICCAT) that concluded on November 23. Posted on 11 Dec 2021
Preserving genetic diversity
Giving wild populations their best chance at long-term survival The paper, by a NOAA Fisheries Northwest Fisheries Science Center researcher, examined decades of theoretical and empirical evidence. It was published in the Proceedings of the National Academies of Science. Posted on 22 Nov 2021
Focus on adaptations to changing ocean conditions
Janet Coit reflects on the urgency of addressing climate change and its impacts on marine ecosystems Not too long ago, the impacts of climate change felt somewhat far off for many Americans. Despite NOAA scientists' reports, in many cases, people viewed these warnings as on the horizon rather than at our doorstep. Posted on 12 Nov 2021
Survivor salmon provide a lifeline for chinook
NOAA Fisheries recovery goals include reintroduction to save the late-migrating fish In drought years and when marine heat waves warm the Pacific Ocean, late-migrating juvenile spring-run Chinook salmon of California's Central Valley are the ultimate survivors. Posted on 5 Nov 2021
Fishing for sport and seafood
All seafood is local when you catch it yourself Our celebration of National Seafood Month would not be complete without highlighting a special source of seafood: the fish we catch ourselves! Posted on 1 Nov 2021
Invasive reef fish may boost Hawaii food security
NOAA-supported project seeks to build a market for the non-native fish taape It's relatively small and found in schools. It's bright yellow like the sun and covered with brilliant sky-blue stripes. It's not originally from Hawaii but can now be found throughout the main Hawaiian Islands. Posted on 1 Nov 2021
7 ways to celebrate national seafood month
When it comes to sustainable seafood, we have a lot to celebrate in the United States Temperatures are cooling, leaves are changing colors, and the smell of pumpkin spice fills the air—all signs of fall in the United States! This time of year is meaningful for many reasons. Posted on 17 Oct 2021
Growing potential for toxic algal blooms
A warming Arctic presents potential new threats to humans & marine wildlife in fast-changing region Changes in the northern Alaskan Arctic ocean environment have reached a point at which a previously rare phenomenon—widespread blooms of toxic algae—could become more commonplace. Posted on 8 Oct 2021
Recreational fishing: A favorite American pastime
Learn how you can participate in recreational fishing in your state or region Recreational fishing is a beloved American pastime, with millions of anglers taking to the water every year. It's a simple activity that is great on your own or with family and friends alongside. Posted on 8 Oct 2021
38 South - Marlin 695 Series 2 - FOOTER - Sept2021Sea Sure 2020 - SHOCK-WBV - FOOTERCoast Guard Foundation FOOTER 3