ACCESS NUMBER: TO-15162

STUDY TITLE: Correction Factor for Ringed Seal Surveys in Northern Alaska 

REPORT TITLE: Correction Factor for Ringed Seal Surveys in Northern Alaska 

CONTRACT NUMBER: 1435-01-98-CA-30909; TASK ORDER (TO): 15162 

SPONSORING OCS REGION: Alaska 

APPLICABLE PLANNING AREA: Beaufort Sea 

FISCAL YEAR OF PROJECT FUNDING: 1998 

COMPLETION DATE OF REPORT: February 2005 

COSTS: FY 1998: $15,540, FY 1999: $82,082, FY 2000: $77,232 

CUMULATIVE PROJECT COST: $174,854 

PROJECT MANAGER: Brendan P. Kelly 

AFFILIATION: University of Alaska 

ADDRESS: School of Arts and Sciences, University of Alaska Southeast, Juneau, AK 99801 

PRINCIPAL INVESTIGATOR*: Brendan P. Kelly 

KEY WORDS: ringed seal, survey, population size, nearshore Beaufort Sea 

BACKGROUND: 

Ringed seals depend on sea ice as a platform for resting, birthing, nursing their young, and molting. 

Young are born in snow caves on the ice where they spend the first couple of months of their lives. 

Densities of ringed seals are highest in the shorefast ice and oil exploration, development, and production 

activities in that habitat potentially will negatively impact seal populations. Monitoring ringed seal 

populations in the vicinity of offshore oil exploration and production activities has depended principally on 

counting seals in aerial surveys. In this project, radio telemetry was used to determine the proportions of 

local seal populations available to be counted during aerial surveys. Those proportions can be used to 

correct estimates from surveys for the unseen fractions of the population. 

OBJECTIVES: 

Our objectives were to determine: 

1. if there is a predictable period when the proportion of seals visible is constant, 

2. the correction factor(s) necessary to adjust counts of seals visible to yield estimates of population size, 

3. the environmental conditions that influence the proportion of seals visible, and 

4. whether the distribution of seals basking in May and June reflects the distribution of seals during winter 

months. 

DESCRIPTION: 

Breathing holes and snow caves excavated by ringed seals were located using dogs trained to alert at the 

odor of ringed seals in April, May, and June 1998, 1999, and 2000. Seals were live-captured in breathing 

holes using pursing nets and fitted with VHF radio transmitters and ultrasonic transmitters. Movements 

were tracked by way of the transmitter signals, and the home range of each seal was recorded. The dates 

of lair abandonment also were determined by monitoring the seals’ locations each time they came out of 

the water. The proportion of the local population available to be counted was estimated from the 

proportion of tagged seals resting on the ice outside of snow caves. 
ACCESS NUMBER: TO-15162

SIGNIFICANT CONCLUSIONS: 

Comparisons of ringed seal densities between regions and between years based on aerial surveys should 

account for the proportion of the population visible during each survey. Surveys in the Alaskan Beaufort 

Sea should be conducted between 12:00 and 18:00 (Alaska Daylight Saving Time). Until more is known 

about factors influencing the proportion of seals visible, aerial surveys should coincide with independent 

estimates, by telemetric or other means, of the proportion of seals visible. Comparisons of ringed seal 

densities should be limited to appropriate geographic scales. Seals may move several kilometers during 

the late spring and early summer, and comparison of densities at finer scales may be spurious. 

STUDY RESULTS: 

Radio tracking proved effective for determining when seals were available to be counted. The transition 

period, defined as the period during which the majority (75%) of the tagged seals began resting outside of 

lairs, was longer in 2000 (24 days) than it was in 1999 (7 days). The midpoint of the transition period, the 

day by which 50% of the tagged seals began resting in the open, was 31 May in both years. Only once 

each year was a lair used subsequent to each seal’s first appearance outside of it. Changes in the 

number of seals counted during ground-based, visual surveys of seals resting on the ice corresponded to 

changes in the number of radio-tagged seals basking. Tagged seals spent approximately 20% of the time 

out of the water before appearing outside of lairs and approximately 30% of the time out of the water after 

they began to abandon lairs. The transition from lair use to resting in the open appeared related to 

measurable characteristics of the snow, and backscatter radar, sensitive to the liquid moisture content of 

snow, offers promise for remotely determining when seals have abandoned their subnivean lairs. Aerial 

surveys underestimated actual ringed seal densities by factors ranging from 2.33 to >13, because the 

proportion of seals visible during the survey periods changed rapidly from day to day. Interannual 

comparisons of seal densities based on aerial surveys have been further compromised by a shift in 

survey dates from mid-June in the 1970s to late May in the 1990s. The proportion of seals visible on the 

ice was more stable between 12:00 and 18:00 (ADT) than between 10:00 and 16:00, the current standard 

for aerial surveys of ringed seals in Alaska. In April, May, and early June, most radio-tagged ringed seals 

remained close to their capture and release sites, with 88% of their home ranges measuring less than 500 

ha in area. One seal, however, had a home range of almost 600 ha and another of almost 3,000 ha. 

STUDY PRODUCTS: 

Conway, J.E., B.P. Kelly and E. Hood. 2004. Predicting lair abandonment by ringed seals based on 

physical properties of the snowpack. Abstract. 34th International Arctic Workshop, 10–13 March 2004, 

Institute of Arctic and Alpine Research, University of Colorado, Boulder. 

Harding, O.R., B.P. Kelly, L.T. Quakenbush and B.D. Taras. 2001. Importance of snow for ringed seal 

pups, p. 64. In Abstract Book. Aquatic Sciences Meeting, 12–16 February 2001, American Society of 

Limnology and Oceanography. 

Kelly, B.P. 2001. Climate change and ice breeding pinnipeds, p. 43–55. In G.-R. Walther, C.A. Burga 

and P.J. Edwards [eds.], ‘Fingerprints’ of Climate Change: Adapted Behaviour and Shifting Species’ 

Ranges. Kluwer Academic/Plenum Publishers, New York and London. 

Kelly, B.P., O.R. Harding and M. Kunnasranta. 2004. Timing and re-interpretation of ringed seal surveys, 

p. 32–37. In University of Alaska Coastal Marine Institute Annual Report No. 10. OCS Study MMS 2004-

002, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., and L.T. Quakenbush. 1998. Correction factor for ringed seal surveys in northern Alaska, p. 

62. In University of Alaska Coastal Marine Institute Annual Report No. 5. OCS Study MMS 98-0062, 

University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

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Kelly, B.P., L.T. Quakenbush and B.D. Taras. 2000. Correction factor for ringed seal surveys in northern 

Alaska, p. 51–64. In University of Alaska Coastal Marine Institute Annual Report No. 6. OCS Study MMS 

2000-046, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., L.T. Quakenbush and B.D. Taras. 2000. Correction factor for ringed seal surveys in northern 

Alaska, p. 14–23. In University of Alaska Coastal Marine Institute Annual Report No. 7. OCS Study MMS 

2000-070, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., L.T. Quakenbush and B.D. Taras. 2002. Correction factor for ringed seal surveys in northern 

Alaska, p. 3–15. In University of Alaska Coastal Marine Institute Annual Report No. 8. OCS Study MMS 

2002-001, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., L.T. Quakenbush and B.D. Taras. 2003. Correction factor for ringed seal surveys in northern 

Alaska, p. 3. In University of Alaska Coastal Marine Institute Annual Report No. 9. OCS Study MMS 2003-

003, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., L.T. Quakenbush and B.D. Taras. 2004. Correction factor for ringed seal surveys in northern 

Alaska, p. 3. In University of Alaska Coastal Marine Institute Annual Report No. 10. OCS Study MMS 

2004-002, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Kelly, B.P., L.T. Quakenbush, B.D. Taras and O. Harding. 2001. Snow conditions predict optimal survey 

periods for ringed seals. Abstract. 14th Biennial Conference on the Biology of Marine Mammals. 

Vancouver, BC. 

Presentations on this project have been delivered in several venues. On 23 February 1999, Oriana 

Harding presented a seminar on the study at the University of Alaska Southeast, and on the same date 

Brendan Kelly presented an update to the Coastal Marine Institute. In February 2001, Oriana Harding 

presented a poster at the American Society of Limnology and Oceanography [see above], Lori 

Quakenbush presented an update to the Coastal Marine Institute, and Brendan Kelly presented a paper 

at an international conference in Switzerland [see above]. In April 2001, Brendan Kelly presented on the 

project at the Minerals Management Service Information Transfer Meeting in Anchorage and at the 16th 

U.S.–Russia Marine Mammal Project Meeting in Santa Cruz, California. In May 2001, he also presented 

aspects of the work at the Mountain Film Festival in Telluride, Colorado. A report on the work was 

presented orally at the 14th Biennial Conference on the Biology of Marine Mammals held in Vancouver, 

British Columbia [see above]. 

*P.I.’s affiliation may be different than that listed for Project Manager. 

ACCESS NUMBER: TO-15162
The study was conducted on the shorefast sea ice of the Beaufort Sea between Prudhoe Bay, Reindeer 

Island, and the man-made Northstar Island. 

Applicable planning area: Beaufort Sea area of the Arctic Subregion.