Mathews et al.: Effects of vessel disturbance on Phoca vitulino on glacial ice in Tracy Arm, Alaska 
187 
tection Act (Calambokidis et al. 1 ; Allen 2 ; Suryan and 
Harvey, 1999; Henry and Hammill, 2001; Johnson and 
Acevedo-Gutierrez, 2007; Jezierski, 2009; Young, 2009; 
Jansen et al., 2010; Hoover-Miller et al., 2013). From 
May through September, approximately 850 cruise ship 
trips carrying a total of nearly 1 million passengers 
visit southeastern Alaska each year (Nuka Research 
and Planning Group 3 ). Commercial and private ves- 
sels with overnight accommodations bring thousands 
of additional passengers into Alaskan fjords through- 
out the summer months (Nuka Research and Planning 
Group 3 ). 
Frequent exposure of harbor seals to vessel traffic, 
especially during the critical stages of pupping and 
nursing (May-July) and molting ( July-September), can 
alter seal behavior (Allen et al., 1984) (e.g., increased 
vigilance, premature entry into the water). Such altera- 
tions might affect seal fitness and pup survival (John- 
son, 1977; Renouf et al., 1983; Jemison, 1997; Osinga 
et al., 2012). Captive seals deprived of haulout access 
compensated later by hauling out to rest for longer pe- 
riods, indicating a physiological need for resting out of 
water even when they were not molting or breeding 
(Brasseur et al., 1996). Before weaning, pups remain 
almost constantly with their mothers, especially when 
hauling out on moving glacial ice (Hoover, 1983). The 
first few hours after a pup is born are the most im- 
portant for establishing the mother-pup bond (Johnson, 
1977; Lawson and Renouf, 1987), and separation of 
mother and pup during the first 2-3 weeks after birth 
can result in permanent abandonment and starvation 
of a pup (Johnson, 1977; Renouf et al., 1983; Osinga et 
al., 2012). 
Even disturbances that do not cause permanent 
separation may have negative consequences for pup 
survival, as seen with gray seals (Halichoerus grypus ) 
(Robinson, 2014). In addition, harbor seal pups are born 
with a relatively thin insulative-blubber layer (Bigg, 
1969; Newby, 1973; Pitcher, 1986; Hoover-Miller 4 ). 
Given the cold surface-water temperatures in glacial 
fjords, repeated disturbances that cause pups to spend 
>50% of their time in frigid glacial waters could be det- 
rimental; the energy deficit incurred by increased me- 
tabolism could reduce blubber deposition in pups and 
overall fitness (Jansen et al. 2010) or possibly increase 
energetic costs for lactating females to compensate for 
increased pup energy requirements. 
1 Calambokidis, J., L. E. Healy, and G. H. Steiger. 1985. Re- 
action of harbor seals ( Phoca vitulina) to boats in Glacier 
Bay, Alaska, 23 p. [Unpubl. report.] Cascadia Research 
Collective, Olympia, WA. 
2 Allen, S. 1991. Harbor seal habitat restoration at Straw- 
berry Spit, San Francisco Bay, 44 p. Final report for U.S. 
Marine Mammal Commission contract MM2910890-9, NTIS 
PB91-212332, Marine Mammal Commission, Bethesda, MD. 
3 Nuka Research and Planning Group. 2012. Southeast 
Alaska vessel traffic study, 21 p. Nuka Research and Plan- 
ning Group, Seldovia, AK. [Available at website.] 
4 Hoover-Miller, A. A. 1994. Harbor seals (Phoca vitulina): 
biology and management in Alaska, 45 p. Report to the Ma- 
rine Mammal Commission, Washington, D.C. 
Steep declines in harbor seal counts have been doc- 
umented at 2 glacial sites in Alaska (Hoover-Miller 4 ; 
Mathews and Pendleton, 2006; Womble et al., 2010; 
Hoover-Miller, 2011), highlighting the need for a better 
understanding of 1) the basic ecology of seals that use 
glacial habitat and 2) the potential benefits and costs of 
using glacial ice to give birth, breed, or molt (Blundell 
et al., 2011). In the 1980s, GBNP began partial and 
complete vessel closures in John Hopkins Inlet, a tide- 
water glacial fjord, in response to concerns about the 
disturbance of harbor seal pups (Calambokidis et al. 1 ); 
those regulations remain in place (Glacier, 2006). 
Research on harbor seals in glacial fjords in Alaska 
has been concentrated in GBNP (Streveler 5 ; Calam- 
bokidis et al. 1 ; Mathews and Kelly, 1996; Mathews 
and Pendleton, 2006; Young, 2009; Womble et al., 2010; 
Blundell et al., 2011; Womble and Gende, 2013), Kenai 
Fjords National Park (KFNP) (Hoover, 1983; Jezierski, 
2009; Hoover-Miller et al., 2011, 2013), and Disen- 
chantment Bay (Jansen et al., 2010, 2015). Tracy Arm 
is a glacial fjord that is used by more than 1000 har- 
bor seals during the summer and that has high tourist 
visitation. However, other than aerial population as- 
sessment surveys and preliminary telemetry tagging 
(results not available), there has been no research be- 
fore this study on harbor seals in Tracy Arm (Withrow 
and Jansen 6 ). Blundell and Pendleton (2015) studied 
haul-out patterns by tracking harbor seals equipped 
with VHF-transmitters in Tracy Arm and neighboring 
Endicott Arm, but that study was conducted after the 
collection of data for this study. 
The objectives of this study were 1) to determine 
the patterns of abundance of nonpup and pup harbor 
seals during the pupping season and investigate the 
potential effects of environmental factors and number 
of vessels on seal counts, 2) to document vessel traf- 
fic (numbers and type) in Tracy Arm during early-mid 
summer, and 3) to determine the effects of the pres- 
ence, type (e.g., cruise ship, tour vessel), proximity of 
vessels, and environmental variables on the probability 
that hauled-out seals would enter the water. 
Materials and methods 
Study area 
Tracy Arm-Fords Terror Wilderness within the Ton- 
gass National Forest comprises 2 deep and narrow 
fjords: Tracy Arm and Endicott Arm (Fig. 1; each fjord 
is >48 km long). The Sawyer and South Sawyer gla- 
ciers, located at the end of Tracy Arm, flow into tide- 
water, which creates icebergs; both glaciers are rapidly 
5 Streveler, G. R 1979. Distribution, population ecology and 
impact susceptibility of the harbor seal in Glacier Bay, Alas- 
ka, 49 p. [Available from Glacier Bay National Park and 
Preserve, PO. Box 140, Gustavus, AK.] 
6 Withrow, D. E., and J. K. Jansen. 2015. Personal com- 
mun. Natl. Mar. Mamm. Lab., Alaska Fish. Sci. Cent., Natl. 
Mar. Fish. Serv., NOAA, Seattle, WA 98115-6349. 
