12 



The lower boundaries of eelgrass beds could not be identified in 

 some instances on any photographs and were estimated from bathymetry and 

 typical depth of eelgrass growth for that area. These beds are listed 

 in the results. 



Eelgrass beds are rarely continuous patches of vegetation; instead 

 there are bare areas within these beds of varying size. Some of these 

 bare areas are apparent on photographs to the unaided eye, some become 

 apparent when a photograph image is magnified, others are below the 

 limit of resolution of a photograph and can only be measured in the 

 field or on small scale aerial surveys. Alternatively, eelgrass may 

 occur as numerous discrete patches too small and numerous to digitize. 

 In all these cases, a perimeter was drawn around eelgrass beds or 

 clusters of eelgrass beds on photographs, and the percent cover of this 

 outlined "bed" — as viewed on a photograph with the unaided eye — was 

 estimated using a percent cover scale chart (Fig. 2, c.f. Orth and 

 Moore, 1983a). 



The accuracy of visually estimating percent cover was tested by 

 placing a photograph under a dissecting scope with cross-hairs, and 

 randomly moving the photograph between 50 and 100 times. The actual 

 percent cover was calculated by dividing the number of times the cross- 

 hair landed on eelgrass by the total number of observations. In 

 general, visual estimates of large scale percent cover were accurate 

 within 15% of this random count method. 



