186 
NOAA 
National Marine 
Fisheries Service 
Abstract— Tidewater glacial fjords 
provide important habitat for breed- 
ing harbor seals (Plioca vitulina ) 
that rest, give birth, and nurse pups 
on icebergs. These fjords also attract 
tourist vessels that potentially dis- 
turb seals. In May and June dur- 
ing 2001-2006, we documented seal 
abundance, pupping phenology, and 
seal-vessel interactions in Tracy 
Arm, a glacial fjord in southeastern 
Alaska. We used randomized obser- 
vations to determine the frequency 
at which seals entered the water in 
the presence and absence of vessels, 
and we estimated the reaction dis- 
tances of seals to approaching ves- 
sels. Mean daily vessel counts var- 
ied from 10.2 (2001) to 2.0 (2006) 
(range: 1-33). Tour and power ves- 
sels were the most common types of 
vessels, but seals were most sensi- 
tive to cruise ships and kayaks. The 
odds of a seal entering the water 
were higher when vessels were pres- 
ent (>2 times) or within 100 m (3.7 
times), and when a pup was pres- 
ent (1.3 times). The baseline, un- 
disturbed, rate of seals entering the 
water was 0.06 (95% Cl: 0.05-0.08) 
per 10 min. Seal births occurred 
during 30 May-25 June and peaked 
(4-8 per day) during 7-13 June. The 
maximum pup count (408) was ob- 
served on 24 June. Harbor seal fit- 
ness in Tracy Arm may be reduced 
by vessel disturbances during breed- 
ing and pupping. 
Manuscript submitted 4 February 2015. 
Manuscript accepted 28 January 2016. 
Fish. Bull. 114:186-202 (2016). 
Online publication date: 3 March 2016. 
doi: 10.7755/FB.114.2.6 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Fishery Bulletin 
<%- established 1881 •<?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Haul-out patterns and effects of vessel 
disturbance on harbor seals ( Phoca vitulina ) 
on glacial ice in Tracy Arm, Alaska 
Elizabeth A. Mathews (contact author ) 1 
Lauri A. Jemison 2 
Grey W. Pendleton 2 
Karen M. Blejwas 1 - 2 
Kevin E. Hood 3 
Kimberly L. Raum-Suryan 4 
Email address for contact author: BethAnnMathews@gmall.com 
1 Department of Natural Sciences 
University of Alaska Southeast 
1 1 120 Glacier Hwy 
Juneau, Alaska 99801 
Present address: 1350-B Yulupa Avenue 
Santa Rosa, California 95405 
2 Division of Wildlife Conservation 
Alaska Department of Fish and Game 
P.O. Box 115525 
Juneau, Alaska 99811-5525 
3 Juneau Ranger District Wilderness Program 
U.S. Forest Service 
U.S. Department of Agriculture 
8510 Mendenhall Loop Road 
Juneau, Alaska 99801 
4 Sea Gypsy Research 
928 NW Cottage Street 
Newport, Oregon 97365-3337 
Harbor seals ( Phoca vitulina ) are 
widespread throughout the temper- 
ate and subarctic waters of the North 
Pacific and North Atlantic and pri- 
marily inhabit coastal waters where 
they haul out on land or ice to rest, 
give birth, and molt (Hoover, 1983). 
In Alaska, tidewater glacial fjords 
provide important habitat for pup- 
ping and molting harbor seals (Bish- 
op, 1967; Calambokidis et al., 1987; 
Mathews and Pendleton, 2006; Jan- 
sen et al., 2010; Hoover-Miller et al., 
2011). The number of harbor seals 
that use glacial ice increases in the 
late spring and summer, when they 
give birth and molt on drifting ice 
(Calambokidis et al., 1987; Mathews 
and Kelly, 1996; Herreman et al., 
2009; Blundell et al., 2011; Womble 
and Gende, 2013). Glacial ice may 
be preferable to terrestrial haul-out 
sites because of the reduced risk of 
terrestrial or marine predation and 
the availability of ice throughout the 
tidal cycle (Fay, 1974; Hoover, 1983; 
Calambokidis et al., 1987; Mathews 
and Adkison, 2010). Up to 73% of 
the several thousand seals in Glacier 
Bay National Park (GBNP), Alaska, 
use glacial habitat rather than land 
haul outs during breeding (Mathews 
and Pendleton, 2006). 
Glacial fjords in Alaska also at- 
tract substantial numbers of tour- 
ists, most of whom visit these sites 
by boat during the summer. These 
visits introduce the potential for the 
disturbance of seals and other wild- 
life in these fjords. With dramatic 
increases in tourism in Alaska and 
worldwide over the past 2 decades, 
and the coincident high use of glacial 
fjords during summer by both harbor 
seals and tourists, the possibility for 
unintended harassment of seals in- 
creases — harassment that is in vio- 
lation of the Marine Mammal Pro- 
