The media and various stakeholders routinely raise questions about potential impacts that may result from the increasing number of seals in New England waters.   The North Atlantic Seal Research Consortium (NASRC) believes that healthy populations of all marine resources including fishes, seals, whales, and other species are important components of healthy marine ecosystems.

We are committed to providing answers to questions about seal populations by using comprehensive research data and analysis. Below are some of the most frequently asked questions and answers from the Consortium.

Are there too many seals?

  • Genetic studies show there is an open population structure between the US and Canada with  seals regularly moving between these habitats.  As a result, the removal of seals in the US will result in replacement of individuals emigrating from Canada.  The entire Western North Atlantic gray seal population is estimated at 350,000 individuals.
  • The growing gray seal population likely reflects recovery from reductions by past bounty programs and possible changes in the marine ecosystem. The rate of growth is similar to that of other seal populations.  Pre-exploitation population numbers are not known.
  • Harbor seals increased in the 1980s and 1990s but may have stabilized or even decreased in recent years.
  • The abundance and increase of seals in recent decades suggests that the marine ecosystem is healthy enough to sustain those populations, even with increasing human uses of marine resources over the same timeframe.

Do seals compete with fishermen for target fish or depredate on target catch?

  • Fishermen and scientists are working together via NASRC and elsewhere to collect data on seal/fisheries interaction to understand as well as reduce these interactions.
  • Ecological interactions between seals and fisheries are likely far more complex than simple predator-prey relationships (e.g. seals eating cod).
  • It is clear that some seals do depredate on catch, but the amount of depredation and its impact on fishermen has not been quantified.  Changes to fishing gear or practices may be able to reduce this depredation, though this has been a challenge in other areas and fisheries with seal depredation issues.
  • Seals have diverse diets including but not limited to red/white hake, silver hake, sandlance, cod, flounders and herring.  Given their diverse diet, it is unlikely that seals are controlling the population of any particular species of fish.  However, additional research is needed to review a wide temporal and spatial scale.
  • The National Marine Fisheries Service (NMFS) estimates that 1,800-2,300 seals were seriously injured or killed  each year between 2009- 2011 for mid-Atlantic gillnet and New England sink gillnet fisheries (Orphanides CD. 2011, 2013). Unlike commercial fisheries, recreational fishery interactions are not regulated and documentation is scarce. These interactions not only impact seal populations, but are costly to the fishing industry as a result of damage to gear and lost catch.  Members of the NARSC are currently working with local weir fishermen to reduce seal interactions with the long term goal of developing fishery modifications that will reduce bycatch in other fisheries.  Working together, partners can help to preserve both seals and fisheries for future generations.

Are seals taking over beaches and causing beach closures due to their feces?

  • The majority of seal haul-outs are on offshore rock ledges (harbor seals), sand bars (both species), or remote islands, so their impacts on beach tourism are likely minimal.
  • A recent Woods Hole Oceanographic Institution (WHOI)  study based on data collected by the Massachusetts Department of Public Health indicated that seals are not driving beach closures.  Over time, water quality closures of beaches near seals did not increase and may, in fact, have decreased, while water quality closures of beaches far from seals remained steady or increased. Additional research is needed to confirm that beach closures are caused by effluent from human sources.

Is the Marine Mammal Protection Act (MMPA) still needed?

  • The Marine Mammal Protection Act is a highly effective and successful federal law. It has enabled us to recover a number of marine mammal populations (e.g., seals, whales, dolphins, etc.) that were reduced to low levels in U.S. waters due directly to human activities.
  • The MMPA also was enacted because of the understanding that data lacking on the effects of removal of these organisms from an ecosystem has detrimental effects to the entire system.

Are seals are attracting white sharks that, in turn, can cause beach closures and threaten tourism and human safety?

  • Although white sharks eat seals, we do not know what influence, if any, seal populations have on the abundance, distribution, or behavior of white sharks.
  • Seals are not the sole prey of white sharks. Therefore any relationship is more complex and may include environmental, individual shark/seal behavior, and efforts to record these events.
  •  Sharks have been known to consume/attack seals on Cape Cod for decades.
  • Shark attacks have occurred in Florida, California and Hawaii yet those states have thriving coastal tourism.
  • Massachusetts is an epicenter for marine wildlife – Healthy and abundant shark and seal populations can sustain ecotourism in the region.

Can seals spread diseases to humans?

  • Data from stranding networks show that disease transmission is unlikely. If it were to occur, it would be limited to people directly handling seals, such as federally permitted stranding response network personnel.
  • Like all wildlife, the public should not approach seals or allow pets to interact with seals. 

Last updated: December 20, 2013