Rebuilding Atlantic Mackerel Quickly Is Key for East Coast Fisheries, Ecosystems

Note: This is the second in a three-part series on the plight of Atlantic mackerel, a vital forage fish. Read part one.

Yesterday I wrote about how scientists had recently determined that Atlantic mackerel along the U.S. East Coast were both overfished (at a low population level that requires rebuilding) and subject to overfishing (too much fishing for the population to sustain). This should not have surprised those who follow the Atlantic mackerel fishery. Science had suggested for decades that the species was declining. This year’s analysis—a benchmark stock assessment, the most rigorous and complete scientific analysis for federal fisheries—was just the latest and most irrefutable evidence of this decline.

Atlantic mackerel, like anchovies, sardines, menhaden, herring, and shad, are forage fish—relatively small in size but vital prey for whales, dolphins, sharks, larger finfish, and birds. Forage fish tend to grow quickly, reach reproductive age early (for Atlantic mackerel, that happens in two to three years), and produce many young. They are also sensitive to ocean conditions and much more likely to go through boom and bust cycles than larger fish that grow and mature more slowly.

Scientists increasingly agree that catch levels for forage fish like Atlantic mackerel should be set to maintain high abundance through those natural cycles and ensure that the species’ predators have plenty to eat. But the assessment found that the Mid-Atlantic Fishery Management Council had instead set inappropriately high catch limits for Atlantic mackerel for over a decade, causing overfishing and driving the species to historic lows.

Mackerel have baby booms, too

Mackerel numbers can grow quickly under favorable ocean conditions, as they did in 1970, 1982, 1999, and 2004. But population increases were short-lived, because catch increased  time, effectively preventing enduring gains. The mackerel population continued its downward spiral to where it is today: overfished, with overfishing occurring. 

Now, the council has another chance to get it right. The 2018 benchmark assessment found that more mackerel than usual born in 2015 survived their first year—typically the most dangerous time for fish and many other animals—making it the best year for baby mackerel survival in over a decade. Still, there is reason for caution. Because the last year of data in the assessment is 2016, it is far from certain that the 2015 class is generating the hoped-for population increase. The next assessment is expected in the early 2020s.

There is a lot to gain with a good decision. Appropriate catch limits would mean a high percentage of these juveniles could continue to reproduce for years, providing another boost to the population. In fact—in a rarity for a fish that’s both overfished and experiencing overfishing—if assumptions about the mackerel born in 2015 are accurate, managers probably wouldn’t even have to cut the catch limit to allow Atlantic mackerel rebuild.

Wasting an opportunity to let nature help

What even a recovering population could not sustain, however, is what the council is considering instead: a near-doubling of the catch limit for next year. A far more prudent decision would be to hold catch limits steady until the data confirm that the baby boom of 2015 is indeed driving a big jump in population. At that point, a substantial increase in the quota could be justified, but right now it’s premature and risky.

The council should learn from its mistakes. Increasing catch at the start of previous boom years led to premature catch of the new crop of adults, fewer fish of reproductive age in the water, a return to overfishing, and today’s historic lows. That’s no way to manage a species that is critical to the survival of so much other marine life and is important to the fishing industry.

I’m disappointed that council staff would recommend a significant increase in catch to managers given this history and the uncertainty inherent in the benchmark stock assessment—and that the council would consider a gamble that even its own policy deems unacceptable. The council should follow the Magnuson-Stevens Act’s direction to rebuild mackerel as quickly as possible and should apply the best available science. That means it should not raise the catch limit at all, and certainly not by the large amounts proposed in the five- and seven-year rebuilding time frames.

Tomorrow: Collateral damage of the industrial mackerel fishery: River herring and shad.

Joseph Gordon is senior manager of The Pew Charitable Trusts’ U.S. oceans program in the Northeast.