WhaleNet Report
Harbor Seal

Harbor Seal

Satellite Tagging Observation Report

Name- "Gooch"
Seal Tag - Tag #27569 (215)


So ok, here is the rundown on "Gooch". "Gooch" was a male harbor seal pup, five months old, released from Biddiford Maine on 10/9/97. He was picked up as an abandoned pup from Gooch's Beach (Kennebunk) Maine on 5/11/97,and treated and raised at the New England Aquarium in Boston.

We tracked him from 10/9 until we stopped receiving signals on 11/14/97, a total of 36 days. During this time, we tracked him over 725 miles from southern and central Maine to Cape Cod Bay, where the last signals were received (in Wellfleet Bay). He covered quite a bit of distance (roughly 20 miles per day), never stopping in one location for long. He was as far as 50 miles offshore, and spent several days up the Kennebeck River in Maine. He also made a southerly run, from near Harpswell Maine (Orrs Island) to Wellfleet Bay, a distance of over 175 miles in five days (over 35 miles per day). Although it is commonly believed that seals move down the coast from Maine to Cape Cod in the fall and winter months, this is the first time that this movement has been documented. It also gives us valuable information on the rate at which a young seal can travel.

We received both location data and dive data from the tag. We received locations on 27 days (roughly 75% of the days he was tracked). The largest gap without a location (four days) was during a time he was in a fresh water section of the Kennebeck River in Maine, where the salinity was low enough to confuse the tag and cause it to shut down. Once he left the river, the tag began to signal normally again. In total we received 102 location fixes.

We received dive data on 32 days (or 90% of the days he was tracked). This gave us dive information on over 11,000 dives he made during this time. We estimate that he was doing over 500 dives per day, and that we received information on roughly 60% of the dives he did during this time. We feel this gives us a fairly clear picture of his behavior during this time. The dive data showed that he spent most of his time (over 80%) doing shallow dives of less than 20 meters (65 feet). His dives were also quite short (over 80% of his dives were less than 2 minutes long). He did, however, during his third and fourth weeks at sea, do some deep (but short) dives to over 50 meters (165 feet). These were his deepest dives. None of his dives were over six minutes long.

This information is in sharp contrast to the results we received from tracking another harbor seal released earlier this year ("Balti"). This seal (roughly ten months older) showed much less traveling and more consistent and constantly improving diving behavior. He appeared to be diving longer and more consistently to deeper depths. While this may be partially due to being older, it raises concern that "Gooch" had not established an apparent regular pattern of movement and dive behavior. While the length of time "Gooch" was tracked was enough to verify his survival for the short term, it is not long enough to say for certain that he was able to survive in the long term. Similar studies have shown that tracks of several months are necessary to establish this for certain.

Whenever we loose a signal from an animal we are tracking there are three basic possibilities: that the tag became detached from the seal, that the tag malfunctioned, or the seal did not survive. We received no information form the tag that indicated that it was malfunctioning, and it should have had power for several more months. We also had no indication that the attachment failed, and, in general the tags are not often lost this quickly. While we are concerned that "Gooch" had not established a "normal" movement or dive pattern, we are still in the early stages of studying the way rehabilitated seals reintegrate into the wild. In the wild the survival of young pups is far from assured, and in some populations mortality within the first year of life may be as high as forty to fifty percent. Tracking studies such as this give us an invaluable look into the lives of these animals we still know so little about.

Greg Early
Edgerton Research Laboratory
New England Aquarium
Central Wharf
Boston, Mass 02110
617-973-5246 (phone)
617-723-6207 (FAX)
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