harvested now. The considerable decrease was attributed to the discharges 
from pulp mills along with severe winter weather in the early 1900s. The 
population is now making a gradual recovery. 
Table 5. Synopsis 
of selected population changes in Puget Sound biota. 
Biological Group 
Type of Measurement 
Where Observed 
Olympia (native) 
oysters 
Harvests reduced from 1.6 
million Ib./yr. in 1914 to 
about 100,000 Ib./yr in 
1984 
Historically near pulp 
mill discharges 
Glaucous-winged 
gulls 
Numbers of nesting pairs 
increased 25x to 600x in 
past 40 years vs. 4x at 
Smith Island in past 20 
Elliott Bay, Commence¬ 
ment Bay colonies 
years 
Harbor seals 
Population near Tacoma 
increased from 150 in 
1965 to 500 in 1984 
Gertrude Island 
Harbor porpoise 
Population has disappeared 
Sound-wide 
Killer whale 
(Orca) 
Reduced birth rate, high 
percent mortality, high 
percent population change 
(decrease) relative to 
other pods 
Transient southern pod 
that frequents Puget 
Sound 
Gulls . The populations of gulls in the Sound have increased dramatically, 
probably in response to the availability of refuse near the urban areas. 
Populations of many other marine bird species have fluctuated with varying 
patterns; none showing signs of any dramatic decreases. 
Harbor seals . The size of the harbor seal and sea lion populations have 
increased rapidly over the past 20 years. Estimates of the harbor seal 
population at an important haul-out site, Gertrude Island, near Tacoma, 
reflect this overall trend of increasing numbers of pinnipeds in the Sound 
(Figure 4). The recent rate of increase at Gertrude Island exceeds the 
biological reproductive capacity of the population there, indicating that 
recruitment through emigration has occurred. 
Harbor porpoise . The population of harbor porpoise that historically 
frequented the Sound has disappeared. This species is intolerant of 
disturbance and probably now avoids the urbanized areas of the Central 
Basin. 
40 
