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Volume 41 Issue 6 • June 16-22, 2011
now in our 41th season

Don't Shoot Me!

by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station

I had planned to write about orchids this week, nice peaceful, law abiding orchids and other unusually named flora and fauna, but the news of the shooting of five adult gray seals on Cape Cod over the past few weeks prompted me to reeducate everyone on why we see so many seals and why they are protected.  Shooting a seal is a senseless crime that does nothing to reduce human-animal conflicts.  It is a federal offense that can also result in a $100,000 fine and a year in prison.  Officials with the National Oceanic and Atmospheric Administration are investigating the incident.  Biologists with the International Fund for Animal Welfare, who run a marine mammal stranding network on the Cape, tracked down the carcasses after receiving reports from various concerned beachgoers.  The shootings occurred on beaches from Dennis to Chatham.  This is the worse incident of intentional violence on gray seals in recent memory.

Seals

You might recall an article in this paper last year (August 19 edition) exploring the increase in gray seals over the past 30 years and the potential for more frequent sightings of great white sharks.  Some basic facts from that article:  “The waters surrounding Nantucket, Tuckernuck, and Muskeget support the southernmost colony of Atlantic Gray Seal.  The Latin name for gray seals is Halichoerus grypus (Fabricius, 1791), or "hooked-nosed sea pig"” —which sounds like the winner of a school yard name-calling contest.  Gray seals are large seals belonging to the family Phocidae or "true seals.  The “true seals” or “earless seals” are one of the three main groups of mammals within the seal suborder, Pinnipedia.  Pinnipeds (the word comes from the Latin pinna for “wing or fin”, and ped-, “foot”) or “fin-footed” mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae (the walrus), Otariidae (eared seals, including sea lions and fur seals), and Phocidae (earless seals).  Phocids also include hooded, harbor, and harp seals in addition to gray seals.  Many people confuse sea lions and seals, if a seal-like creature is clapping its flippers and balancing a ball (or has its own TV show), it’s in the sea lion family.

From Wikipedia (http://en.wikipedia.org/wiki/Pinniped):  “Phocids lack external ears, have more streamlined snouts, and are generally more aquatically adapted than otariids.  They swim with efficient, undulating whole-body movements using their more-developed rear flippers.  The swimming efficiency and an array of other physiological adaptations make them better built for deep and long diving and long distance migration.  These mammals are, however, very clumsy on land, moving by wriggling their front flippers and abdominal muscles.  The two back flippers form a tail-like structure which does not aid walking on land.  True seals generally communicate by slapping the water and grunting rather than vocalizing.”

Gray seals are more frequently seen because their populations are rebounding due to the protection provided by the Marine Mammal Protection Act of 1972.  Gray seal populations plummeted from the colonial era to the 1950s due to hunting and extermination programs by people who believed that the seals were out-competing them for cod.  By 1950, the numbers of gray seals south of the Canadian Maritimes were less than 50 individuals and they were effectively considered extirpated (locally extinct).  A bounty on seals of five dollars per nose caused a decline of all seals in Massachusetts waters.  Then, in 1962, the state outlawed the killing of seals, and since 1972 they have been under federal protection under the Marine Mammal Protection Act, which makes it a federal crime to kill, harass, or disturb a marine mammal by approaching within 150 feet or doing any action that changes its behavior.  Research supported by the UMass Boston Nantucket Field Station conducted by the late Valerie Rough, Clint Andrews and others found that five pups were born at Muskeget (a prime breeding colony location) in 1988.  The number of pups increased to 12 in 1992, 30 in 1993, and 59 in 1994.  By 2005, Stephanie Wood documented that the count had soared to 1892 pups (with approximately 4000 or more adults).  Jim Gilbert, Steve Katona, and Gordon T. Waring have documented populations on Monomoy Island, Muskeget and Penobscot Bay, Maine as they have slowly developed in size over the past 50 years.

Two reasons are given for why people are annoyed with the growing gray seal population: that they might be eating “our” fish and that they may be attracting great white sharks.  Yes, gray seals have been documented opportunistically taking hooked fish off the lines of fisherman as they are being reeled in.  Some pretty amazing footage can be seen on Youtube, and I have personally talked to a couple of fishermen on the receiving end of the “now you see it, now you don’t” fish stealing sleight-of-hand action by the offending seals.  There have been verbal reports of some fishermen feeding seals fish off their boats in the Great Point area, which just encourages the seals to come closer to those hoping to fish the Rip nearby. Marine biologist, Lanny Hall, who is the Assistant Marine Mammal Stranding Coordinator for the Northeast Region for NOAA (National Oceanographic & Atmospheric Administration), visited Great Point in August of 2010 with other NOAA official and they determined that one gray seal, instead of several, was robbing fish from people’s fishing lines on Great Point (original article by Peter Brace in the August 26 edition of the “Nantucket Independent”).

I especially was bothered by the baloney coming out of the mouth of a fisherman talking on a local TV channel last week who stated they eat half their body weight in fish every day.  A typical female adult gray seal will weigh around 400 pounds; a male can weigh 800 pounds or more.  Even with non- stop eating they could not gulp down that much fish, and in fact, the average daily food requirement is estimated to be 5 kg (11 lb).  In addition, seals do not feed every day and females fast during the breeding season.  According to the Massachusetts Division of Marine Species and this website http://www.stripers247.com/Massachusetts-Striper-Profile.php, stripers and seals do depend on some of the same food species for the diets like sand lance and menhaden.  That site also does a good job of synthesizing the ups and downs of the striper population along the entire Atlantic coast over the past hundred years.  Years of extremely low populations of stripers were followed by rebounds and the primary drivers of these occurrences in the Chesapeake Bay area were the presence or absence of a variety of pollutants in spawning grounds, fishing pressure, and feeding and nutritional problems of larvae.  The data for these fluctuations goes back over a hundred years to cover times in which the gray seals were in greater abundance.  It is important to remember that stripers are migratory and influenced by environmental factors, fishing pressure, and management up and down the coast.  I highly recommend looking at all the striper info on that site.  I learned a lot and will share more striper facts and figures in a future column here.

Marine mammal scientists such as Dr. Kristin Ampela, who has presented her research at past Nantucket Biodiversity Initiative conferences on island, have established gray seal diets by examining and sorting scat (excrement) samples collected on Muskeget and at other shoals and breeding colonies in North America.  This is a common practice as is the examination of stomachs from recently deceased seals caught in fishing gear.  Obviously, this type of research is not the number one chosen by graduate students.  Fish otiliths, which are fish ear “bones” or hard parts that grow in size and form rings to indicate the number of months and years the fish have been alive are the clues that Ampela used to determine dietary sources.  Each fish otilith is relatively unique to that type of fish.  She also measured any hard parts found such as vertebrate or teeth.  These types of surveys are more definitive than looking at the chemical composition of the blubber, although they can miss the occasional partially eaten prey.  She sampled across all seasons in order to pick up variations in seal diet.  The prey typically consumed by gray seals includes windowpane flounder, silver hake, sand lance, skates, and to a lesser extent, gadid species such as cod, haddock, and pollock.  Sandlance (Ammodytes spp.) and red/white hake (Urophycis spp.) together accounted for 65% of prey individuals recovered. Skate (family Rajidae) was recovered most frequently, in 38% of samples.  Cod (Gadus morhua) was recovered infrequently and comprised fewer than 2% of total individuals.  Significantly more skate was recovered in fall than in other seasons.  Her entire paper can be found at http://www.ices.dk/products/CMdocs/2006/L/L1406.pdf. Other scientists have analyzed how these hard parts travel through the guts of captive seals (“Robust digestion and passage rate estimates for hard parts of grey seal (Halichoerus grypus) prey” by Kate Grellier, Philip S Hammond; Canadian Journal of Fisheries and Aquatic Sciences, 2006, 63:1982-1998, 10.1139/f06-092), yes, they feed the seals and then watch them poop and see what survives the trip and how long it takes!  Good times.  These prey species are confirmed in research done on the Nova Scotia populations, in which researchers also found capelin, flatfish, Atlantic herring, Atlantic mackerel, and squid on the menu.  These researchers have determine that most of the time, gray seals swallow their meals whole and that the size of the fish consumed is normally 30 cm or less.  None of the food habit studies to date have shown that there are lobsters in stomachs or scat.  Occasionally seals will raid bait from lobster pots and mangle gear as they search for their bottom dwelling ground-fish targets.

Please do not feed seals from boats or the shoreline, and be aware that they may go after landed fish.  Seals are opportunistic eaters, somewhat like we are at art openings, and they are not too proud to chase after someone’s bluefish.  This is not behavior you want to encourage, and the Trustees of the Reservations who are in charge of monitoring and protecting seals and people at Great Point are asking that visitors to Great Point be especially careful to avoid any interactions with the seals.

Massachusetts shark expert Dr. Greg Skomal tagged eight Great White sharks last summer in order to track their movements and see how closely associated they are with the seal haul out sites (official data and updates at http://www.mass.gov/dfwele/dmf/spotlight/white_shark_2010.htm).  He spoke on island last October and will hopefully be back this year to give us an update on the behavior and frequency of great white sharks in the area. You can watch a talk he gave last year at this link http://forum-network.org/lecture/tracking-great-white-shark which is sponsored by WGBH and New England Aquarium.  He agrees that the increasing concentration of gray seals will attract more great whites.  He advises people to get out of the water and away from seals if you want to reduce your chances of a shark and/or seal bite to zero.  As to the real danger from shark attacks, only three fatal shark attacks have been documented in the past 300 years in Massachusetts. The lightning storm we had about a week ago is a much more dangerous occurrence; in fact you are more likely to be hit by lightning twice than to be attacked by a shark (http://www.flmnh.ufl.edu/fish/sharks/attacks/relarisklightning.htm).  But that doesn’t mean I would recommend putting on a big seal costume and splashing around at Great Point and if you HAVE been hit twice by lightning, perhaps this is the start of the land-loving part of your life.  This site does an excellent job of synthesizing some of the research that has gone into investigating shark attacks around the world over the past one hundred or more years: http://www.elasmo-research.org/education/white_shark/patterns.htm.  You can access a form online to report a shark at http://www.masharks.com/Pages/sightings.html (state report form) and to call in a stranded seal call the New England Aquarium’s 24 hour marine mammal hotline at 617-973-5247 (more info at http://www.nantucketstrandingteam.org/).

Last but not least, anyone with information about the seal shootings is urged to call NOAA law enforcement at 508-990-8752. It is our responsibility to share the beaches with the seals and I think with a little foresight and planning, we can all get along.

 

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