New England Fisheries

Booming New England Seal Population Creates a Management Challenge

A harbor seal pup. Image via NOAA.

Congress passed the Marine Mammal Protection Act (MMPA) in 1972, forty years ago.[1] Intended to slow the precipitous decline of marine mammal populations due to human activities, the act prohibited the killing, harassment, or excessive disturbance of marine mammals in United States waters. The MMPA was just one of numerous environmental and conservation initiatives launched during the Nixon era.

For seals in New England—mainly harbor seals and gray seals—the MMPA’s protections effected a massive boom in population.  Previously, the animals were considered a nuisance to fishermen and tourists.  Coastal states frequently offered bounties for the killing of seals. One study estimates that between 1888 and 1962, over 100,000 seals were killed in the bounty hunt in Maine and Massachusetts alone.  This mass killing was enough to trigger significant regional declines in numbers.  In 1973, a survey of Maine waters counted just 5,800 harbor seals; this was likely almost the entire population at that time.[2]

The MMPA effectively stopped the bounty hunt in its tracks, and seal numbers have risen rapidly as a result.  Each female harbor seal pups once a year and survival rates in New England without predators are high.[3]  In 2001, the estimated population of harbor seals in New England had recovered to 99,340 individuals; the observed number rose by 28.7% just between 1997 and 2001.[4]  Gray seals have seen a similar increase in numbers.  On Muskeget Island, just 19 adult gray seals were observed in 1994; in 2011, a census estimated between 3500 and 3800 seals.[5]  The overall observed population of gray seals in Massachusetts has increased from 5,611 to 15,756 between 1999 and 2011.[6]

This booming, unrestricted seal population has costs.  Seals eat commercially valuable fish like cod and herring, often taking the catch right out of fishermen’s nets.  They can also cause costly damage to fishing gear.  In 2011, the Canadian Department of Fisheries and Oceans determined that gray seals were hindering cod stock recovery, and the minister of fisheries proposed a cull of 140,000 seals.  It’s possible they may be having a similar effect in the Gulf of Maine.[7]

To some degree, nature is responding to this abundant, high value food source. Rising seal numbers have been linked to the apparent increase in great white sharks around Cape Cod, particularly near the large seal colonies on Muskeget and Monomoy.[8]  Sightings of great whites have increased notably in the past decade, and this summer, a swimmer off Cape Cod was attacked by one for the first time since 1936.[9] Killer whales and other high level predators also once controlled seals in this region and may return in the future in greater numbers.

In the mean time, seals are becoming a growing political problem. A local fisherman recently pointed out the seal problem to John Bullard, the new Regional Administrator for NOAA, at an open meeting in Scituate.[10]  Tensions are also rising between the seals and local residents.  Last summer, five gray seals were found shot on Cape Cod beaches.[11]

Coming to agreement about the appropriate management response to this situation is challenging.  On the one hand, the rising numbers can be viewed as a remarkable success of the MMPA and a return to natural conditions.  One conservation response is to argue that the seal population will start to limit itself as numbers approach carrying capacity or as recovering shark numbers or other marine predators catch up with the new abundance of prey.[12]  On the other hand, some stakeholders have called for new, direct methods to limit seal numbers, including culling.  The Seal Abatement Coalition has circulated a petition calling for “an amendment or exception to the Marine Mammal Protection Act which would permit the humane dispersion of [gray] seals.”[13]

The original text of the MMPA allows the secretary of commerce to make some exceptions to the no-take rules, taking into account “the conservation, development, and utilization of fishery resources[,]”[14] provided that “the taking of such marine mammal is in accord with sound principles of resource protection and conservation.”[15] These have included the issuance of permits for marine mammals caught incidentally by commercial fishing operations.[16]  NOAA has also previously allowed the dispersion of sea lions in California that damage fishing gear and has permitted the killing of sea lions that were eating endangered salmon in the Pacific Northwest.[17]

Nonetheless, it is unlikely that culling of New England’s seals will be allowed.  Beachgoers like spotting the animals and seals remain charismatic animals. Seal watching tours, indeed, have become popular in some coastal communities.  Harbor and gray seals are not widely regarded by the public as a nuisance, unlike California sea lions.  In this context, it would take an “act of god” (as one state administrator put it)—or at the very least an act of Congress—to begin culling seals in New England.[18]  As a Chatham fisherman told NPR last month, “There’s not a congressman in his right mind that’s going to be the first one out that says, ‘Let’s go harvest seals.’”[19]  Even with fisheries, the case for seal culling is modest. A recent study suggests that even if marine mammals were completely removed from the environment, potential catch from fisheries may not be dramatically improved.[20]

There may be technologies that act or could act to reduce seal-fishing gear interactions non-lethally.  “Pingers” like those used to deter porpoises from gill nets could be used to scare seals away from fishing gear.  Still, this technology could be expensive to implement and may be ineffective on seals, which are highly intelligent animals and might even become attracted to the noise over time as they learn to associate it with readily available fish.[21]

The solutions to New England’s exploding seal populations are not obvious, but the pressure for responses is growing and will continue to build. Seals are no longer just the stuff of children’s books and aquaria exhibits; they are back in force and growing rapidly. Natural seal mortality rates will undoubtedly increase over time, but as long as people and seals are both chasing after the same scarce fish resources, soon may not be soon enough for some.


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