of Tacoma) had equal or higher population growth rates and birth rates, 
fewer premature births, and roughly equal neonatal deaths of pups as 
compared to their neighbors on the remote Smith and Protection Islands 
(reference areas) in the Strait of Juan de Fuca. Ten newly-born pups 
found dead at Smith Island had discolored or atrophied livers, whereas 
only two with these conditions were found elsewhere. Some dead pups at 
Smith Island had symptons of an influenza viral infection. There were no 
signs of severe degenerative tumors or similar internal disorders among 
animals examined from South Sound. However, more adult seals had skin 
lesions near their umbilicus at Gertrude Island than at Smith Island. The 
significance of these latter findings is not known, but it appears the 
population is generally doing well. 
Table 4. Synopsis of Biological Indicators of pollution measured in 
marine birds and mammals in Puget Sound. 
Biological Group 
Type of Measurement 
Where Observed 
Glaucous-winged 
gulls 
High liver:body 
weight ratios 
Colonies near the Duwamish 
Great blue herons 
Diminished eggshell 
thickness relative 
to 1947 
Samish Island, March Point, 
near the Duwamish, Nisqually 
Delta 
Harbor seals 
Premature births, 
influenza virus, 
discolored or 
atrophied livers 
among pups 
Smith Island 
(reference area) 
Population changes. 
Changes in the size of populations of various biota have been monitored 
through surveys in the field, analyses of catches and examination of 
harvest (landings) records. Populations sizes can be controlled by many 
powerful nature factors and, in the case of commercially important 
species, by market conditions and regulations. Nevertheless, the ultimate 
test of the health of a population of organisms is that of its size. Data 
for many species, especially those that are harvested, are available. 
Synopses for one harvested and four non-harvested species are listed in 
Table 5. 
Oysters. The Olympia oyster which was harvested in great numbers (up to 
1.6 mTTlion pounds in 1914) in the Sound is now grown in only two areas 
(Little Skookum and Totten Inlets). Less than 100,000 pounds per year are 
39 
