Long-Term Observations of a Harbor Seal Haul-Out Site in a Protected Cove in Casco Bay, Gulf of Maine

Harris, David; Lelli, Barbara; Gupta, Sat

doi:10.1656/1092-6194(2003)010[0141:looahs]2.0.co;2

Cited by 5 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Brown & Mate, 1983; Thompson et al , 1997; Huber et al , 2001) or moulting (e.g. Thompson et al , 1989; Boveng et al , 2003; Harris et al , 2003) period. The highest number of adult harbour seals observed hauled out in this study occurred during the pupping season (late May to early July) although numbers of seals declined rapidly after this peak.…”

Section: Discussionmentioning

confidence: 99%

“…In the UK (e.g. SCOS, 2008) surveys take place during a three-week survey window (31 July to 23 August) within the annual moult when, in most areas, the greatest numbers of seals are hauled ashore (Thompson & Harwood, 1990; Boveng et al , 2003; Harris et al , 2003). The survey window is further restricted to within two hours of low tide when the greatest numbers of harbour seals are thought to be ashore (Allen et al , 1984; Yochem et al , 1987; Thompson et al , 1989; Watts, 1996; Simpkins et al , 2003).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Variation in harbour seal counts obtained using aerial surveys

2010

View full text Add to dashboard Cite

Aerial surveys of harbour seals (Phoca vitulina) are usually carried out to provide an index of population size. This can be normalized, either by design or by post-hoc analysis to reduce the effects that date, time of day, tide and weather might have on the number of seals counted. In order for long-term trends to be determined from these counts it is assumed that the mean number of seals at a particular site does not vary during the survey period, and that the start and duration of the survey window does not vary with location or between years. This study used a combination of repeat land-based and aerial surveys to test the assumption for constancy of counts during the survey period. The study focused on harbour seal abundance at haul-out sites around the Isle of Skye in north-west Scotland. The coefficient of variation in these counts was estimated to be 15%, based on repeat aerial surveys using thermal imaging. Land-based counts were used to examine the effect of covariates on seal numbers using generalized additive modelling. This site-specific model predicted that the current aerial survey window for harbour seals in the UK, which is a three-week period during the moult, is about a week too early and that count variation could be reduced by surveying 1 1/2 hours earlier in the tidal cycle. Furthermore, the pupping period showed even higher (though more variable) abundance of hauled out seals than during the moult.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variation in harbour seal counts obtained using aerial surveys

2010

View full text Add to dashboard Cite

show abstract

“…The number of seals declined steadily thereafter throughout the remainder of the year. Generally, two seasonal peaks in abundance at haulout sites have been identified across the harbour seals' geographical range, a peak during May/-June associated with pupping and during August/September associated with moulting (Thompson and Harwood 1990, Thompson et al 1997, Jemison and Kelly 2001, Huber et al 2001, Harris et al 2003, Reijnders, et al 2003.…”

Section: Discussionmentioning

confidence: 99%

A modelling framework to optimize timing of haulout counts for estimating harbour seal (<i>Phoca vitulina</i>) abundance

2010

View full text Add to dashboard Cite

The time of year and day, the state of the tide and prevailing environmental conditions significantly influence seal haulout behaviour. Understanding these effects is fundamentally important in deriving accurate estimates of harbour seal abundance from haulout data. We present a modelling approach to assess the influence of these variables on seals' haulout behaviour and, by identifying the combination of covariates during which seal abundance is highest, predict the optimal time and conditions for future surveys. Count data of harbour seals at haulouts in southwest Ireland collected during [2003][2004][2005] were included in mixed additive models together with environmental covariates, including season, time of day and weather conditions. The models show maximum abundance at haulout sites occurred during midday periods during August and in late afternoon/early evening during September. Accurate national and local population estimates are essential for the effective monitoring of the conservation status of the species and for the identification, management and monitoring of Special Areas of Conservation (SAC) in accordance with the EU Habitats Directive. Our model based approach provides a useful tool for optimising the timing of harbour seal surveys in Ireland and the modelling framework is useful for predicting optimal survey periods for other protected, endangered or significant species worldwide.Cronin, M.A., Ingram, S.N., Zuur, A.F. and Rogan, E. 2010

show abstract

“…Harbour seals are year-round inhabitants in the coastal waters off Maine and eastern Canada (Katona et al 1993, Baird 2001, Jacobs and Terhune 2000, Harris et al 2003, Hammill et al 2010, and occur seasonally along the Massachusetts to New Jersey coasts (Fig. 1) between September and May (Schneider and Payne 1983, Barlas 1999, Hoover et al 1999, Slocum et al 1999, Schroeder 2000, deHart 2002.…”

Section: Distributionmentioning

confidence: 99%

“…Rocky areas (i.e. small islands, isolated rocks, tidal ledges) are the predominant haulout substrate in coastal waters from the Maine-Canadian border south to Plymouth, Massachusetts (Richardson 1976, Schneider and Payne 1983, Harris et al 2003, Gilbert et al 2005, Renner 2005). Rocky substrates are also used during the pupping, breeding and moulting seasons when harbour seals are concentrated in Maine coastal waters (Richardson 1976, Katona et al 1993, Guldager 2001, Gilbert et al 2005.…”

Section: Habitatmentioning

confidence: 99%

A review of the status of harbour seals (<i>Phoca vitulina</i>) in the Northeast United States of America

et al. 2010

View full text Add to dashboard Cite

We conducted a review of the literature and unpublished databases to describe the distribution, abundance, ecology and status of harbour seals (Phoca vitulina concolor) in U.S. Atlantic waters. The harbour seal is the most abundant and widespread seal species in this area. Since passage of the U.S. Marine Mammal Protection Act of 1972, the number of harbour seals observed during the pupping season in this region has increased from about 10,500 animals in 1981 to 38,000 animals in 2001 (uncorrected counts), an average annual rate of 6.6%. This increase has been

relatively consistent over the 20 years, and there is no indication that the population size has stabilized. Correspondingly, the seasonal distribution has expanded and interactions between seals and anthropogenic activities have increased.

show abstract

Long-Term Observations of a Harbor Seal Haul-Out Site in a Protected Cove in Casco Bay, Gulf of Maine

Cited by 5 publications

References 12 publications

Variation in harbour seal counts obtained using aerial surveys

Variation in harbour seal counts obtained using aerial surveys

A modelling framework to optimize timing of haulout counts for estimating harbour seal (<i>Phoca vitulina</i>) abundance

A review of the status of harbour seals (<i>Phoca vitulina</i>) in the Northeast United States of America

Contact Info

Product

Resources

About