200 
Fishery Bulletin 1 14(2) 
turbance swath as boats traversed the inlet. The differ- 
ence in response distance in our study and the distanc- 
es at other study sites with less vessel traffic, wider 
fjords, or both, could, therefore, result from higher lev- 
els of seal habituation to vessels. Alternatively, seals 
less tolerant of vessels might have left Tracy Arm for 
sites with less disturbance, leaving more tolerant seals 
or those seals incapable of dispersing (e.g., in poor con- 
dition) (Gill et al., 2001; Frid and Dill, 2002; Bejder 
et al. 2009). Individual habituation and selection for 
disturbance-tolerant individuals could yield similar 
patterns of lower levels of seal responses to vessels in 
Tracy Arm compared with other areas with less vessel 
traffic. Additional research, however, would be needed 
to address whether habituation or tolerance is more 
likely in glacial Ijords with higher vessel traffic. 
Harbor seal pups in Tracy Arm 
The seasonal summer increase in vessel activity in 
Tracy Arm (Nuka Research and Planning Group 3 ) co- 
incides with the harbor seal pupping and nursing pe- 
riods (late May-mid-July). The timing of harbor seal 
births in Tracy Arm (peak births occurred during 7-13 
June and the maximum pup count occurred in late 
June) was similar to patterns in other glacial fjords in 
Alaska (Muir Inlet, Calambokidis et al., 1987; Johns 
Hopkins Inlet, Mathews and Pendleton, 2006; Aialik 
Bay Hoover-Miller et al., 2011). 
Our analyses of observations of vessels approaching 
hauled-out seals showed that seal groups on icebergs 
that included a pup (and presumably its mother) were 
1.6 times more likely to have at least 1 seal enter the 
water in response to the approach of a vessel than a 
seal in a group that did not include a pup (Fig. 6). The 
first seal, however, to enter the water usually was not a 
pup, which also was noted by Calambokidis et al. 1 and 
is consistent with observations of harbor seal mother- 
pup pairs at a terrestrial site (Renouf et al., 1983). 
Similarly, Suryan and Harvey (1999) and Henry and 
Hammill (2001) found that seal groups at a haul out 
with the highest proportion of pups were significantly 
more likely to show disturbance reactions to boats than 
seals hauled out at 2 other sites with lower proportions 
of pups. 
Disturbances that do not cause permanent separa- 
tion of the mother and her pup can have negative con- 
sequences for pup survival. Harbor seals have short lac- 
tation periods (Muelbert and Bowen, 1993; Thompson 
and Wheeler, 2008), and repeated disruption of nursing 
bouts could reduce pup growth and, consequently, pup 
survival (Harding et al., 2005). Repeated disturbances 
that increase the amount of time a young pup remains 
in cold glacial waters can increase its metabolism (Jan- 
sen et at., 2010), presumably having a negative impact 
on pup fitness. In addition, oxytocin, an endocrine 
hormone released during and shortly after birth, has 
been linked to maternal behavior in mothers (Pedersen 
and Prange, 1979; Pedersen et al., 1982; Keverne and 
Kendrick, 1992) and identified as an indicator of ma- 
ternal success in phocid seals (Robinson, 2014). Gray 
seal females displaying abnormal maternal behavior 
were found to have lower plasma oxytocin concentra- 
tions than successful mothers that raised their pups 
to weaning age, and it is hypothesized that one cause 
of low oxytocin concentrations is disturbance of the 
mother-pup pair shortly after birth (Robinson, 2014). 
Because dependent pups are present in Tracy Arm dur- 
ing the summer tourist season, the potential exists for 
reduced pup fitness. 
In 1996, the National Marine Fisheries Service 
(NMFS 10 ), NOAA, published voluntary guidelines for 
viewing marine mammals in Alaska. These guidelines 
recommended that viewers stay at least 91 m (100 
yards) from pinniped haul-out locations. In 2012, in- 
creasing concerns about disturbance to harbor seals 
in glacial fjords, including specific concerns about 
high levels of vessel traffic in Tracy Arm, led NMFS 
to consider regulations that would limit vessel distur- 
bance of seals that use glacial sites (Federal Register, 
2013). Because of public comment and other relevant 
information, NMFS decided to publish new volun- 
tary guidelines that recommend that vessels stay 457 
m (500 yards) from seals (NMFS 11 ) and to distrib- 
ute educational materials to vessel operators in 2015 
(NMFS 12 ). 
Limiting access to these glacial habitats during the 
most critical life history stages of pup birth and nurs- 
ing could reduce disturbance during critical mother- 
pup bonding, but it also could make seals more sen- 
sitive after closures are lifted because of potentially 
reduced habituation to vessel traffic. Better education 
of vessel operators could also help reduce seal distur- 
bance, but the narrow configuration of Tracy Arm and 
the desire by vessel operators to closely approach the 
glacier face, and hence the seals, are problematic, espe- 
cially in regard to the documented increase in marine- 
mammal-related tourism and the inevitable effect that 
such tourism will have on seal behavior. 
Acknowledgments 
This project was supported by NMFS grants to the 
Alaska Department of Fish and Game and by a Na- 
tional Science Foundation Research Experiences for 
Undergraduates Grant to the University of Alaska, 
Southeast. Logistical support was provided by the U.S. 
Forest Service (USFS), Juneau Ranger District, and by 
the captains of the MV Keet. B. Nielsen (Alaska De- 
partment of Fish and Game), T. Lydon and J. Neary 
10 National Marine Fisheries Service (NMFS). 2000 NOAA 
Fisheries proposes extra protection for humpback whale. 
[News release available at website, accessed January 2016] 
n National Marine Fisheries Service (NMFS). 2015. NOAA 
Fisheries revises approach guidelines for vessels in Alaska glacial 
fjords, accessed January 2016. 
12 National Marine Fisheries Service (NMFS). 2015. Alaska 
harbor seal: approach guidelines in glacial fjords. [Available 
at website.] 
