254 
Fishery Bulletin 113(3) 
Alaska waters, it is likely that several other regional 
and subregional populations exist within the 3 current- 
ly designated stocks. 
In summary, the results of our analysis with data 
from surveys conducted between the years 1991 and 
2010 led us to believe that numbers of harbor porpoise 
within the inland waters of Southeast Alaska declined 
significantly, highlighting a potentially important con- 
servation issue. With the inclusion of data from sur- 
veys conducted in 2011 and 2012, our analysis indi- 
cates that if a decline occurred, then the population 
may be recovering. It is not clear whether the observed 
decline and subsequent increase in abundance repre- 
sent a true decline in the population or a reflection of 
variable local abundance related to interannual differ- 
ences in prey availability, habitat suitability, or other 
factors. 
The overall changes in abundance of harbor porpoise 
observed in this study could have remained undetected 
were it not for the long time series of this research, 
clearly demonstrating both the value and need for 
multiyear studies on long-lived mammals, such as ce- 
taceans. Understanding the distribution, abundance, 
and population trends of a given species is essential for 
conservation efforts to be effective. On the basis of our 
study, we hypothesize that harbor porpoise populations 
within the inland waters of Southeast Alaska contain 
structure. Although this structure is currently unclear, 
we suggest that different stocks probably exist within 
this region. A proper assessment of the status of the 
harbor porpoise stock or stocks in Southeast Alaska re- 
quires a combination of research approaches, i.e., con- 
ducting coastal and inland surveys at the same time to 
evaluate stock abundance, exploring correction factors 
for this species (e.g., g[0] experiments), performing ge- 
netic studies (to fully define stock structure), and using 
satellite telemetry (to understand porpoise movements 
within or across current stock boundaries). 
Acknowledgments 
Our appreciation is extended to the various captains 
and crew of the John N. Cobb and of the FV Steller, 
FV Northwest Explorer, RV Medeia, and RV Aquila. We 
thank numerous observers for their many hours of sur- 
vey effort. This manuscript was improved by the criti- 
cal reviews of B. Taylor and J. Laake (Southwest Fish- 
eries Science Center, La Jolla, California). We thank 
H. Braham, D. DeMaster, S. Moore, P. Wade, and P. 
Clapham for their continued support of this research 
over a 22-year period. 
Literature cited 
Allen, B. M., and R. P. Angliss. 
2012. Alaska marine mammal stock assessments, 
2011. NOAA Tech. Memo. NMFS-AFSC-234, 288 p. 
Barlow, J. 
1988. Harbor porpoise, Phocoena phocoena, abundance 
estimation for California, Oregon, and Washington: I. 
Ship surveys. Fish. Bull. 86:417-432. 
2006. Cetacean abundance in Hawaiian waters estimat- 
ed from a summer/fall survey in 2002. Mar. Mamm. 
Sci. 22:446-464. 
Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 
1995. U.S. marine mammal stock assessments: guide- 
lines for preparation, background, and a summary of 
the 1995 assessments. NOAA Tech. Memo. NMFS- 
OPR-6, 73 p. 
Buckland, S. T., D. R. Anderson, K. P. Burnham, J. L. Laake, 
D. L. Borchers, and L. Thomas. 
2001. Introduction to distance sampling: estimating 
abundance of biological populations, 432 p. Oxford 
Univ. Press, Oxford, UK. 
Burnham, K. P., and D. R. Anderson. 
2002. Model selection and multi-model inference: a 
practical information-theoretic approach, 2 nd ed., 488 p. 
Springer- Verlag, New York. 
Calambokidis, J. and J. Barlow. 
1991. Chlorinated hydrocarbon concentrations and their 
use for describing population discreteness in harbor 
porpoises from Washington, Oregon, and California. In 
Marine mammal strandings in the United Sates: pro- 
ceedings of the second marine mammal stranding work- 
shop; Miami, 3-5 December 1987 (J. E. Reynolds III, 
and D. K. Odell, eds.), p. 101-110. NOAA Tech. Rep. 
NMFS 98. 
Carretta, J. V., B. L. Taylor, and S. J. Chivers. 
2001. Abundance and depth distribution of harbor por- 
poise ( Phocoena phocoena) in northern California deter- 
mined from a 1995 ship survey. Fish. Bull. 99:29-39. 
Chivers, S. J., A. E. Dizon, P. J. Gearin, and K. M. Robertson. 
2002. Small-scale population structure of eastern North 
Pacific harbour porpoises (Phocoena phocoena ) indicated 
by molecular genetic analyses. J. Cetacean Res. Man- 
age. 4:111-122. 
Dahlheim, M. E., and P. A. White. 
2010. Ecological aspects of transient killer whales Orci- 
nus orca as predators in southeastern Alaska. Wildl. 
Biol. 16:308-322. 
Dahlheim, M., A. York, R. Towell, J. Waite J., and J. Breiwick. 
2000. Harbor porpoise (Phocoena phocoena) abundance 
in Alaska: Bristol Bay to Southeast Alaska, 1991- 
1993. Mar. Mamm. Sci. 16:28-45. 
Dahlheim, M. E., P. A. White, and J. M. Waite. 
2009. Cetaceans of Southeast Alaska: distribution and 
seasonal occurrence. J. Biogeogr. 36:410-426. 
Gaskin, D. E. 
1984. The harbor porpoise Phocoena phocoena (L) region- 
al populations, status, and information on direct and 
indirect catches. Rep. Int. Whaling Comm. 34:569-586. 
Hammond, P. S., P. Berggren, H. Benke, D. L. Borchers, A. 
Collet, M. P. Heide-Jprgensen, S. Heimlich, A. R. Hiby, M. F. 
Leopold, and N. 0ien. 
2002. Abundance of harbour porpoise and other ceta- 
ceans in the North Sea and adjacent waters. J. Appl. 
Ecol. 39:361-376. 
Hobbs, R. C., and J. M. Waite. 
2010. Abundance of harbor porpoise (Phocoena phocoena) 
in three Alaskan regions, corrected for observer errors 
due to perception bias and species misidentification, 
and corrected for animals submerged from view. Fish. 
Bull. 108:251-267. 
