Welcome to our second installation of Fish Friday (on a Thursday)! Last week, we focused on the Atlantic sturgeon, a species listed as endangered or threatened throughout the mid-Atlantic – it’s no surprise these fish are off the menu. But what about Atlantic salmon, the most-consumed species of salmon (the second most-consumed type of seafood) in the U.S.?
In 2013, Americans ate 2.7 pounds of salmon per person, second only to shrimp. As such a prominent American (and international) menu staple, wild Atlantic salmon populations must be flourishing, right? Wrong – commercial Atlantic salmon fisheries in the U.S. have been closed since 1948, and most recreational fisheries were shut down decades ago. Global stocks have been declining since the early 1800’s. So what’s going on? And what have you been eating?
Atlantic salmon is the only salmon species native to the East Coast of the United States. Like Atlantic sturgeon, Atlantic salmon are anadromous fish, meaning they are born in freshwater, spend a majority of their lives in salt water, and return to freshwater to spawn. The life cycle of Atlantic salmon is fairly complex, as the salmon mature through multiple life stages during their first 1-2 years before they migrate to the open ocean.
In late autumn, female salmon bury their eggs along freshwater stream bottoms. Come March or April, the eggs hatch into alevin, which mature into fry after about 3-6 weeks, and then quickly become parr. As parr grow, they become territorial and move to areas with larger substrate and deeper, faster flowing water. Parr go through a physiological process called “smoltification” in which they develop a tolerance for saltwater and imprint on the chemical nature of their stream so they can later return to spawn.
As smolts, Atlantic salmon (now about 2 years old) migrate to the open ocean. They typically spend their first winter south of Greenland, where they mature into adults. During this time, the fish replace their old dietary preferences of small crustaceans and krill with prey fish such as Atlantic herring and rainbow smelt.
After about 2 years, they will return to Maine to spawn in November. Unlike other salmon species, Atlantic salmon are iteroparous, meaning they may spawn more than once.
The Atlantic salmon has been a commercially valuable fish since the fishery opened in Maine in the 1600’s, but due to overfishing, the global population began to decline around the 1800’s. In 1947, fishery landings plummeted to as low as 40 salmon, prompting an effective closure the following year. It wasn’t until 1989, however, that all state and federal commercial salmon fisheries in New England were officially closed by law. Most recreational fisheries in New England also closed decades ago, but a few remain open today under strict regulation.
In 2000, NOAA Fisheries and the U.S. Fish and Wildlife Service declared the Gulf of Maine Distinct Population segment endangered under the Endangered Species Act. In 2009, the agencies extended the ESA protection to include more territory and, with the help of Conservation Law Foundation, identified Atlantic salmon critical habitat.
To monitor the Gulf of Maine DPS, the U.S. Atlantic Salmon Assessment Committee measures the number of adults returning to rivers in Maine to spawn each year. While some populations in the Northern Baltic Sea may be recovering, the Gulf of Maine DPS is still in trouble. In 2006, the Atlantic Salmon Biological Review Team estimated Atlantic salmon extinction risk at 19-75%.
With U.S. fisheries closed, why is the Gulf of Maine population still at risk of extinction?
Climate change effects, such as warming sea surface temperatures, increased water acidity and aluminum toxicity, and altered predator distributions, dramatically limit juvenile survival. Increased harvests in Greenland may also severely decrease the number of adults returning to Maine to spawn. Finally, New England coastal development and dam sites threaten species that must travel up and down river throughout their life cycles. Restoration efforts have been introduced by the State of Maine, NOAA, and the U.S. Fish and Wildlife Service in order to reduce the effects of national risks, and environmental groups such as the Atlantic Salmon Federation are calling for stricter catch limits on European countries in order to protect the Gulf of Maine DPS.
The Fish Farm
Since 1864, Atlantic salmon have been hatchery-raised to supplement the crashed wild populations. U.S. Atlantic salmon aquaculture produces about 12,000 live lbs per year in Maine and 8,000 live lbs per year in Washington. We import about 28,000 live lbs of farmed Atlantic salmon each year mostly from Canada, Chile, Norway, or Scotland.
Over 20 environmental and food safety laws govern U.S. salmon farming in order to prevent issues such as nutrient discharge, animal escape, disease and pathogens, and coastal use conflict. However, as NOAA puts it, “zero environmental risk is not realistic for any type of human activity.” Farming may cause waste build-up, escaped farmed fish may introduce parasites to the wild, and breeding between farmed and wild salmon may decrease genetic adaptations to environmental conditions. Regulations are in place, but the industry is still far from perfect.
Save the Salmon!
NOAA’s National Marine Fisheries Service (NMFS) selected the Gulf of Maine Atlantic salmon DPS as one of eight endangered species to feature in their “Species in the Spotlight: Survive to Thrive” initiative. Hopefully, the agency’s concentrated efforts (and subsequent increased global awareness) will begin to stabilize Atlantic salmon populations in the Gulf of Maine and around the world.
Image credit: Timothy Knepp, FWS