242 
NOAA 
National Marine 
Fisheries Service 
Fishery Bulletin 
& established 1881 •<?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Temporal changes in abundance of harbor 
porpoise iPhocoena phocoena ) inhabiting the 
inland waters of Southeast Alaska 
Email address for contact author: marilyn.dahlheim@noaa.gov 
Abstract— Abundance of harbor por- 
poise ( Phocoena phocoena) was es- 
timated from data collected during 
vessel surveys conducted through- 
out the inland waters of Southeast 
Alaska. Line-transect methods were 
used during 18 seasonal surveys 
spanning 22 years (1991-2012). Es- 
timates were derived from summer 
surveys only because of the broader 
spatial coverage and greater number 
of surveys during this season than 
during other seasons. Porpoise abun- 
dance varied when different periods 
were compared (i.e., 1991-1993, 
2006-2007, and 2010-2012); how- 
ever, persistent areas of high por- 
poise densities occurred in Glacier 
Bay and Icy Strait, and off the town 
of Wrangell and Zarembo Island. 
Overall abundance of harbor por- 
poise significantly declined from the 
early 1990s (A/=1076, 95% confidence 
interval [CI]=910— 1272) to the mid- 
2000s (A=604, 95% CI=468-780). 
This downward trend was followed 
by a significant increase in the early 
2010s (N= 975, 95% CI=857-1109) 
when abundance rose to levels simi- 
lar to those observed 20 years ear- 
lier. Potential factors that could con- 
tribute to the downward trend were 
examined. The 2 regions with high 
densities of harbor porpoise (i.e., 
Glacier Bay and Icy Strait as well as 
Wrangell and Zarembo islands), that 
were consistently occupied by this 
species, and the different trend val- 
ues of these 2 regions indicate that 
some fine-scale population structur- 
ing may exist for harbor porpoise in- 
habiting the inland waters of South- 
east Alaska. 
Manuscript submitted 14 May 2014. 
Manuscript accepted 25 March 2015. 
Fish. Bull 113:242-255 (2015). 
Online publication date: 14 April 2015. 
doi: 10. 7755/FB. 113.3.2 
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. 
Marilyn E. Dahiheim (contact author ) 1 
Alexandre N. Zerbini 1 ' 2 
Janice M. Waite 1 
Amy S. Kennedy 1 
1 National Marine Mammal Laboratory 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE 
Seattle, Washington 98115-6349 
2 Cascadia Research Collective 
218/4 West Fourth Avenue 
Olympia, Washington 98501 
Harbor porpoise (Phocoena phocoena) 
are distributed throughout Alaska 
waters (Fiscus et al. 1 ; Leatherwood 
and Reeves, 1978; Leatherwood et al. 2 ; 
Lowry et al. 3 ' 4 ; Dahiheim et al., 2000, 
2009; Hobbs and Waite, 2010), com- 
monly inhabiting waters less than 
100 m deep (Barlow, 1988; Carretta 
et al., 2001; Hobbs and Waite, 2010). 
Currently, 3 stocks of harbor por- 
poise are recognized in Alaska: 1) 
1 Fiscus, C. H„ H. W. Braham, R. W. Mer- 
cer, R. D. Everitt, B. D. Krogman, P. D. 
McQuire, C. E. Peterson, R. M. Sonntag, 
and D. Withrow. 1976. Seasonal dis- 
tribution and relative abundance of ma- 
rine mammals in the Gulf of Alaska, 238 
p. Northwest Fish. Sci. Cent. Processed 
Rep., [Available from Alaska Fish. Sci. 
Cent., Natl. Mar. Fish. Serv., 7600 Sand 
Point Way NE., Seattle, WA 98115.] 
2 Leatherwood, S., A. E. -Bowles, and R. 
R. Reeves. 1983. Endangered whales 
of the eastern Bering Sea and Shelikof 
Strait, Alaska. Results of aerial surveys 
April 1982 through April 1983 with notes 
on other marine mammals seen. Hubbs 
Sea World Research Institute Technical 
Report No. 83-159, 315 p. [Available 
from the Natl. Mar. Mamm. Lab., Alas- 
ka Fish. Sci. Cent. ,7600 Sand Point Way 
NE., Seattle, WA 98115.] 
the Southeast Alaska stock — occur- 
ring from Dixon Entrance (54°30'N; 
134°00'W) to Cape Suckling (60°00'N; 
144°00'W), 2) the Gulf of Alaska 
stock — occurring from Cape Suck- 
ling to Unimak Pass, and 3) the Ber- 
ing Sea stock — occurring throughout 
the Aleutian Islands and all waters 
north of Unimak Pass (Allen and An- 
gliss, 2012). The boundaries of these 
3 stocks are based on geography and 
3 Lowry, L. F., K. J. Frost, and J. J. Burns. 
1982. Investigations of marine mam- 
mals in the coastal zone of western Alas- 
ka during summer and autumn. Annu- 
al report on contract NA 81 RAC0050, 
submitted to NOAA, Outer Continental 
Shelf Environmental Assessment Pro- 
gram, Juneau, Alaska, 37 p. [Available 
from the Natl Mar. Mamm. Lab., Alaska 
Fish. Sci. Cent. ,7600 Sand Point Way 
NE., Seattle, WA 98115.] 
4 Lowry, L. F., K. J. Frost, D. G. Calkins, 
G. L. Swartzman, and S. Hills. 1982. 
Feeding habits, food requirements, and 
status of Bering Sea marine mam- 
mals. Vol. 1. Final report submitted 
to the North Pacific Fishery Manage- 
ment Council, Anchorage, Alaska, 292 p. 
[Available from the Natl. Mar. Mamm. 
Lab., Alaska Fish. Sci. Cent. ,7600 Sand 
Point Way NE., Seattle, WA 98115.] 
