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Fishery Bulletin 113(3) 
— , ) — 
136°W 132°W 
Figure 1 
Map of study area in Southeast Alaska, with regions (strata), identified by 
numbers, where line-transect surveys of harbor porpoise (Phocoena phocoena ) 
were conducted from vessels in inland waters over the periodsl991-1993, 2006- 
2007, and 2010-2012. 
of reticles to the sighting, radar distance (in nauti- 
cal miles) to the shoreline at the same angle of the 
sighting, the species sighted, the number of individu- 
als seen (best, high, and low counts), and the direc- 
tion of travel of the animal(s). The sighting angle 
was obtained from peloruses mounted on the port 
and starboard bridge. To obtain distance to a sight- 
ing, Fujinon binoculars equipped with internal reti- 
cles were used. The top reticle was placed on the ho- 
rizon or shoreline, and the number of reticles down 
to the location of the sighting was counted to the 
nearest tenth of a reticle. The reticle binoculars were 
calibrated with the ship’s radar to objects of known 
distances. 
Field methods (2006, 2007, and 2010-2012) 
When line-transect surveys resumed in 2006 and 2007 
aboard the John N. Cobb, it was recognized that there 
was considerable patchiness in the distribution and 
variation in density of harbor porpoise throughout the 
inland waters of Southeast Alaska, such that assigning 
a single density estimate to the whole study area was 
not appropriate. Consequently, smaller regions (strata) 
were established that were characterized by different 
geographic features: bays; inlets; deepwater channels, 
such as Icy Strait and Chatham Strait; and large areas 
of exposed waters, such as Frederick Sound. Allocation 
of stratum-specific effort by region was based on harbor 
