* The following data is the intellectual property of the Riverhead Foundation for Marine Research and Preservation *
An increase in gray seal (Halichoerus grypus) sightings and strandings in New York waters.
Robert A, DiGiovanni Jr., Kimberly F. Durham, Julika N. Wocial, and Allison M. Chaillet.
Riverhead Foundation for Marine Research and Preservation
Over the past three decades the Northeast United States marine mammal rescue organizations have documented an increase in pinniped strandings. This initial increase was attributed to the increase in harp seal (Pagophilus groenlandicus) strandings. Since 1996 in New York State harp seals (P. groenlandicus) had an annual mean encounter rate of 49% (min. 30%, max. 68%) of annual pinniped strandings. In 2007 and 2008, however, the New York State Marine Mammal and Sea Turtle Rescue Program (NYSMMSTRP) observed a shift in species distribution, where harp seal strandings were surpassed by gray seals (Halichoerus grypus) for the first time. This shift was coupled with first time recoveries of gray seal pups (approximately 3-4 weeks in age) occurring early in the season during January and February. Similar changes were noted in observations from the pinniped aerial surveys conducted by the Riverhead Foundation for Marine Research and Preservation. Data obtained from these counts revealed that harbor seals (Phoca vitulina) were the most commonly encountered pinniped species. In recent years there has been an increase in the number of gray seals (H. grypus) observed. This increase has risen from sporadic sightings of one or two gray seals (H. grypus) in or near harbor seal (P. vitulina) haul out sites per survey to 41 animals in 2007, 190 in 2008 and 315 in 2009. To complement these stranding data and better understand gray seal movements in local waters, 14 rehabilitated gray seals, 11 males and 3 females, were affixed with satellite tags prior to release. Tracking data from these animals showed that not only do they go to known seal haul out sites in Massachusetts and the Gulf of Maine, but they also frequent haul out sites in eastern Long Island.
The Riverhead Foundation for Marine Research and Preservation presented a poster on "Post release monitoring of juvenile harp seals (Phoca groenlandica) released in New York waters" at the 15th Biennial Conference on the Biology of Marine Mammals in Greensboro, NC.
Content of the poster:
Post release monitoring of juvenile harp seals
(Phoca groenlandica) released in New York waters
Robert DiGiovanni Jr., Kimberly Durham, Julika Wocial and Katrina Zawacki
The Riverhead Foundation for Marine Research and Preservation
467 East Main Street, Riverhead New York 11901
The increase in strandings of pinnipeds in New York waters has been attributed to arctic species, mainly the harp seal (Phoca groenlandica). Since 1996, The Riverhead Foundation for Marine Research and Preservation has recovered 944 marine mammals, and of these recoveries 84% (n = 791) were pinnipeds consisting of five species: 436 harp (Phoca groenlandica), 191 harbor (Phoca vitulina), 93 gray (Halichoerus grypus), 59 hooded (Cystophora cristata), 1 ringed (Phoca hispida) and 14 unidentified. The survivorship of stranded pinnipeds has increased from 50 % in 1996 to 74 % in 2003. To evaluate rehabilitation success and test the hypothesis that rehabilitated juvenile harp seals (P. groenlandica) return to their native waters and become viable members of the population, satellite, flipper and hat tags were used to monitor post release movements. Unfortunately, few flipper tags were recovered or observed on healthy animals. Due to tag size and placement, flipper tags are not visible when the animal is in the water. Since 2001, four flipper tags were returned from harp seals taken in Canadian waters. In 2001 a flipper tag was recovered from an animal taken in a hunt in Cumberland Sound, Canada. This animal traveled a straight-line distance of 2620 miles in 78 days. To obtain a more in-depth understanding of post release movements, four satellite (SPOT-2) position only tags were deployed on rehabilitated juvenile harp seals released in New York waters. Results suggest that rehabilitated juvenile harp seals spend little time in near shore waters once released and move north to native waters to become viable members of the population. In addition tag return data suggest that there is not a need to transport these stranded animals northward for release as it gets late in the season.
The increase in strandings and frequency of encounters of arctic seal species has propelled rescue programs to evaluate and modify their existing treatment protocols while attempting to identify factors contributing to the increase in strandings. Since the mid 1990’s arctic seals (Phoca groenlandica) have become the most commonly stranded animal encountered in New York waters (DiGiovanni et al. 2000) (Figure 1.0). This bias in strandings towards harp seals has also been coupled with a bias towards males (DiGiovanni et al., 2000). Since 1996 the New York State Marine Mammal and Sea Turtle Rescue Program has tagged and released 208 harp seals. Of the 208 harp seals tagged with flipper tags only eight revealed any post release data through tag returns. Therefore satellite tags were employed to assess post release movements.
The twelve pinnipeds included in this study were obtained through the New York State Marine Mammal and Sea Turtle Rescue Program that is operated by the Riverhead Foundation for Marine Research and Preservation (Figure 2.0). Four of the animals were tagged with Smart Position and Temperature Transmitting (SPOT2) tags (figure 3.0) obtained from Wildlife Computers. The SPOT2 tag was configured with one C-cell battery and measured 3 1/4" long by 1 3/4 “ wide by 1 1/4" high and weighed 190 grams. The SPOT2 transmitters in accordance with service ARGOS are able to determine the position of an animal while on the surface. These tags were set to transmit between 400 and 600 transmissions a day and were not duty cycled to account for gaps in satellite coverage. This was done at the expense of battery life as the target window for this phase of the study was 90 days post release. The SPOT2 tags were attached to the fur of rehabilitated harp seals with Devcon five-minute epoxy. The tag attachment point is located just posterior to the head on the dorsal surface along the midline.
The remaining eight animals were opportunistic tag returns reported by the public to the organization identified on the tag. All of these animals were previously recovered by the rescue program as stranded animals, evaluated and treated in accordance with veterinarian protocols, and deemed fit for release. Upon clearance for release a plastic Allflex sheep tag (5/8" wide by 2" long) (Figure 3.1), was attached to the hind flipper of each animal. Each tag was embossed with a three-digit number on the front and organization information with a contact number on the back. In 2002 the Riverhead Foundation began placing hat tags (Figure 3.2) as presented in Hall 2000 on selected pinnipeds. Each tag was attached to the seals’ fur using Devcon five-minute epoxy, and the attachment point was located on the cranial region (Figure 3.3).
All the animals tagged with SPOT2 tags were juvenile males as there is a bias to male harp seals stranding in New York waters (DiGiovanni et al. 2000) (Table 1.0). Of the four tags, one of the tags stopped transmitting after twelve days, most likely due to failure of the mount as a different epoxy was used for attachment (Figure 3.0). The remaining tag returns and time in rehabilitation are listed in table 1.0. The average distance traveled was 22 miles per day with an average of 54 days between the first and last position received. The data received from tag returns were from animals reported taken in a harvest or that had interacted with a fishery.
Although harp seals strand all around Long Island it is not imperative to release these animals in the same location where they stranded. Animals released within Shinnecock Bay, located on the south shore of Long Island, NY (Lat: 400 04’ 12” Lon: 730 30’ 10”), spend a short time in the Bay before exiting through the inlet to offshore waters and then head in a northeast direction to northern latitudes. This behavior is similar to the animals released into the Atlantic Ocean.
The tag returns for animals released in March and April indicate that these animals traveled on average 20 miles per day and ended up in northern waters. Although we were unable to do a within year comparison, animals released late in the season (May to July) moved in a similar manner to animals released earlier in the season. There does not appear to be a need to subject a harp seal that strands in New York waters to a long transport for release simply because it is getting late in the season. Tag return data coupled with satellite data can add power to our assessment of post release movement of these animals.
Funding for this study was given in part by a grant received from the John H Prescott rescue assistance program grant # FNAO3NMF4390049. We wish to thank Stacie Marchionne and the many staff of the Riverhead Foundation for Marine Research and Preservation for Program for providing the data presented in this report and all of the stranding team volunteers too numerous to name here who have helped in the collection of samples and on rescues. In addition we would like to thank local citizens, police officers, and marine patrol, along with the New York State Department of Environmental Conservation’s “Return a Gift to Wildlife” program.
© 2003 The Riverhead Foundation for Marine Research and Preservation
DiGiovanni Robert Jr., Durham Kimberly, and Spangler-Martin Debra A., 2000. Report to the New York State Department of Environmental Conservation, Marine Mammal and Sea Turtle Stranding Program 1996 to 1999.
Hall Ailsa, Simon Moss and Bernie Mcconnell, 2000. A New Tag for Identifying Seals.
Marine Mammal Science, 16 (1): 254-257