Progress 10/01/01 to 09/30/07
Outputs
OUTPUTS: Activities: Conducted field research with harbor seals and gray seals. Events: Made presentations of research findings at 14th, 15th and 16th Biennial Conferences on Marine Mammals, at the 2005 meeting of the Scientific meeting of the International Council for the Exploration of the Sea, to the Fish Health Workshop - Atlantic Salmon, the NMFS working group on unusual marine mammal stranding events, and the NMFS workshop on non-lethal alternatives to deter pinnipeds. Services: disseminated information on pinniped interactions with fisheries to several additional individuals and groups. Products: Database of harbor seal and gray seal distribution and numbers over time; available as a database and as a google-map add on.
PARTICIPANTS: James R. Gilbert, Principal Investigator. John Skinner, Graduate Student. National Marine Fisheries Service (Northeast Fisheries Science Center) Maine Department of Marine Resources.
Impacts
Change in knowledge: the status and distribution of harbor seals in New England waters is more widely known and easily accessible by interested individuals.
Publications
- Waring, G.T., J.R. Gilbert, J. Loftin, and N. Cabana. 2006. Short-term movements of radio-tagged harbor seals in New England. Northeast Naturalist, 13(1):1-14.
- Gilbert, J.R., G.T. Waring, K.M. Wynne, and N. Guldager. 2005. Change in abundance of harbor seals in Maine, 1981-2001. Marine Mammal Science, 21(3):519-535.
- Udevitz, M.S., J.R. Gilbert, and G.A. Fedoseev. 2001. Comparison of methods used to estimate numbers of walruses on sea ice. Marine Mammal Science 17(3):601-616.
- Gilbert, J. R., G. T. Waring, S. Wood, S. Billig, and J. Loftin. 2001. Seasonal movements of radio-tagged harbor seals (Phoca vitulina) in New England waters. Abstracts of the 14th Biennial Conference on the Biology of Marine Mammals. Vancouver, British Columbia. Nov. 30-Dec 3, 2001.
- Renner, S., and J. Gilbert. 2003. Factors affecting harbor seal (Phoca vitulina) activity budgets on haul-out ledges shared by grey seals (Halichoerus grypus) on Mount Desert Rock in the Gulf of Maine. Abstract, 15th Biennial Conference on the Biology of Marine Mammals. Greensboro, N.C., 14-19 December, 2003.
- Nelson, M., J. Gilbert, J. Lewis and K. Boyle. 2003. Interactions between harbor seals (Phoca vitulina) and finfish aquaculture in Maine. Abstract, 15th Biennial Conference on the Biology of Marine Mammals. Greensboro, N.C., 14-19 December, 2003.
- Wood, S., V. Rough, J. Gilbert, G. Waring and S. Brault. 2003. The current status of gray seals (Halichoerus grypus) in the United States. Abstract, 15th Biennial Conference on the Biology of Marine Mammals. Greensboro, N.C., 14-19 December, 2003.
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Progress 10/01/05 to 09/30/06
Outputs
Project No: ME08660-01 Project Title: Role of harbor and gray seals in the Gulf of Maine ecosystem. Principal Investigator: James R. Gilbert FTEs on this project: 0.3 Co-Investigator(s): n/a FTES on this project: n/a Project Objectives that were met: 1. Determine the status and distribution of harbor and gray seal populations in New England waters. 2. Determine the role of harbor seals in the escapement in the salmon aquaculture industry. Significant findings: 1. Determine the status and distribution of harbor and gray seal populations in New England waters. a. The harbor seal population in New England has continually increased since 1981, and now numbers approximately 99,000. b. As the harbor seal population has increased, the number and percent pups have increased. This indicates more food is available now than was available 20 years ago. c. As the harbor seal population has increased, the number of ledges used for pupping and for resting has increased. d. The
numbers of gray seals in New England Waters has increased at all times of the year. e. The number of gray seal pups is increasing at three sites in New England. f. Between birth and weaning, harbor seal mother-pup pairs use multiple ledges that are distributed as far as 17 km apart. g. Birth weights of harbor seals in Maine average lower than those in the Gulf of St. Lawrence or elsewhere. 2. Determine the role of harbor seals in the escapement in the salmon aquaculture industry. a. Salmon aquaculture sites greater than 4 km from a harbor seal haul-out ledge had no problems with seal predation over three years. b. Acoustic harassment devices were not effective in reducing predation at aquaculture sites. This could be because they did not deter seals. It also could be because the devices were deployed after the site experienced predation events, and seals were willing to tolerate the harassment when a known reward was available. Project Objectives that were not met and explanation: 3.
Determine the role of harbor seals in losses of wild adult Atlantic salmon at the mouths of the Downeast Rivers. I was not successful in obtaining funding to address this objective.
Impacts
Research provided information that was publishable and/or was used in establishing policy or influencing procedures, resulting in the long term in more informed management of seals and their food fishes. We did work with Sea Grant, Maine Department of Marine Resources, National Marine Fisheries Service, and the Maine Aquaculture Industry. Research on this project was integrated with research projects at SUNY-Potsdam, UMass-Boston, Duke University, and the National Marine Fisheries Service. The atlas of harbor seal haul-out sites is an outreach effort.
Publications
- Gilbert, J. R. 2005. Alternative approaches to estimating harbor seal numbers: the role of spatial scale. Poster & Abstract presented to the Annual Scientific Meeting of the International Council for the Exploration of the Sea, Aberdeen, Scotland, September, 2005.
- Nelson, M.L., J.R. Gilbert, and K. J. Boyle. 2006. The influence of sighting and deterrence methods on seal predation at Atlantic salmon (Salmo salar) farms in Maine, 2001-2003. Canadian Journal of Fisheries and Aquatic Sciences, 63(10): 1710-1721.
- Gilbert, J.R., G.T. Waring, K.M. Wynne, and N. Guldager. 2005. Change in abundance of harbor seals in Maine, 1981 - 2001. Marine Mammal Science, 21(3):519-535.
- Dow, W. E., J. Gilbert, and A. J. Reed. 2005. Comparison of harbor seal, Phoca vitulina, distribution and haul-out site use during pupping and molting seasons in Maine. Poster & Abstract accepted for the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA., 12-17 December, 2005.
- Skinner, J., J. Gilbert, and J. Schreer. 2005. Behavior and life history characteristics of neonate harbor seals in Maine. Poster & Abstract accepted for the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA., 12-17 December, 2005.
- Wood, S., J. Gilbert, and S. Brault. 2005. Historical changes in grey seal populations in New England. Poster Abstract accepted for the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA., 12-17 December, 2005.
- Renner, S., and J. Gilbert. 2005. Behavioral interactions between grey and harbor seals on a haul-out site in Maine. Poster & Abstract accepted for the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA., 12-17 December, 2005.
- Kiernan, J. R., J. Schreer, and J. Gilbert. 2005. Comparison of diving capabilities of neonate and weaned harbor seal pups in Maine. Poster & Abstract accepted for the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA., 12-17 December, 2005.
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Progress 10/01/04 to 09/30/05
Outputs
A second field season was conducted during May and June of 2005 in Penobscot and Blue Hill Bays. Eighty-nine neonate and weaned harbor seals were captured, weighed and tagged. Time-depth recorders were attached to 19. Several were recaptured and reweighed. Movement among ledges by mother-pup pairs is common. The median birth date was 23 May. Seal pups in the Gulf of Maine have slower daily mass gains than harbor seal pups in Atlantic Canada. Seal pups spent 58 percent of their time in water. Mean weaning occurred 24 days after birth. A significant fraction of harbor seal pups do not survive until weaning. The development of apnea and brachycardia was monitored in seal pups at different ages before and after weaning. Tissue samples from the harbor seal pups and from gray seal pups were submitted to labs for genetic analyses. Blood samples from the harbor seal pups were collected to establish a baseline for comparison to stranded and rehabilitated pups. We completed an
atlas of historical locations of seal haulout sites from 1981 to 2001.
Impacts
Data from this research will assist in interpretation of the significant first-year mortality observed in the harbor seal population. The genetics evaluations will assist in population delineation. The movements and abundance information will assist in determining the roles of the seals in the Gulf of Maine Ecosystem.
Publications
- Waring, G.T., J.R. Gilbert, J. Loftin, and N. Cabana. 2006, in press. Short-term movements of radio-tagged harbor seals in New England. Northeast Naturalist.
- Gilbert, J.R., G.T. Waring, K.M. Wynne, and N. Guldager. 2005, Change in abundance of harbor seals in Maine, 1981-2001. Marine Mammal Science, 21(3):519-535.
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Progress 10/01/03 to 09/30/04
Outputs
One MS thesis was completed on this project: Harbor seal (Phoca vitulina concolor) predation has been cited as a major cause of mortality, injury, and escapement at Atlantic salmon (Salmo salar) marine aquaculture sites in the State of Maine. Escapements of farm-raised Atlantic salmon are of particular concern due to the potential for breeding and competition with the endangered wild Atlantic salmon. I documented the nature and frequency of seal predation at finfish aquaculture facilities in Maine and whether the severity of seal predation was related to the proximity of farms from one another and nearby harbor seal haul-outs. Managers at operational finfish aquaculture facilities in Maine were surveyed annually from 2001-2003 and asked specifically about farm management techniques, husbandry practices, predator deterrence methods employed, and predation. Aerial surveys documenting harbor seal haul-outs along the Maine coast were conducted concurrently. Empirical
estimates from generalized linear models, using a negative binomial distribution for the random component, suggest the importance of maximizing the distance between farms and neighboring harbor seal haul-outs and minimizing the number of surrounding harbor seal haul-outs when attempting to deter seal predation at marine salmon farms in Maine. This study further highlighted the ineffectiveness of Acoustic Harassment Devices (AHDs) and the need for further investigation into the effectiveness of different pen types and predator nets at deterring seal predation. A field season was conducted during May and June of 2004 in Penobscot and Blue Hill Bays. Sixty four neonate and weaned harbor seals were captured, weighed and tagged. Time-depth recorders were attached to nine. Several were recaptured and reweighed. Preliminary data suggest movement among ledges during the nursing period is likely.
Impacts
Data from this research will allow future aquaculture site selections to be made so as to minimize the impact of predation. Information from this research will help with our understanding of how harbor seals use their haulouts during the pupping season and how harbor seal pups develop diving capability.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
Harbor seal captures near aquaculture pen sites in February were not successful because of weather and ice conditions. Genetic samples were obtained from 11 harbor seal pups in June. A third year of winter aerial surveys of harbor seals was completed as was a third year of interviews with the aquaculture site managers. These data are being analyzed to determine the effect of distance to the nearest haulout and the effect of predator control measures on seal predation at the pens.
Impacts
Data from this research will allow future aquaculture site selections to be made so as to minimize the impact of predation.
Publications
- No publications reported this period
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Progress 10/01/01 to 09/30/02
Outputs
Gray seal surveys were conducted in Maine during the January pupping period. Between January and May, we conducted bi-weekly aerial counts of harbor seals within 20 km of Atlantic salmon aquaculture sites to correlate with seal attacks at salmon pens. All site managers for the Atlantic salmon aquaculture sites in Maine participated in a second year of interviews regarding seal impact and damage at the pens.
Impacts
This research will allow for reasonable regulations of the Atlantic salmon aquaculture industry and help in the understanding of the dynamics of harbor and gray seals.
Publications
- No publications reported this period
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