Ralph and Miller 



Chapter 33 



Offshore Population Estimates in California 



INTENSIVE SURVEY AREA 



DISTANCE 

 FROM 



aQBEM 



COASTAL 

 SEGMENT 



. TRANSECT 

 LINE 



100m . f SURVEY 

 loom J_| STRIP 



SHORELINE 





Figure 1 Diagram of intensive survey areas used to determine distribution of Marbled Murrelets from the 

 shoreline outward to 6,000 m. 



1989 through 1993 at three survey areas: two in Del Norte 

 County (Pebble Beach and Crescent Beach) and one in 

 Humboldt County (South Jetty) (fig. 2). We chose areas that 

 were accessible from nearby harbors and based on previous 

 Marbled Murrelet sightings consistently had murrelets 

 present. We used two open-decked boats with center consoles 

 and without visual obstructions (Boston Whalers, 5.5 m and 

 7 m lengths). Boat speeds ranged from 8 to 12 knots, 

 depending upon sea conditions, with slower speeds in higher 

 seas. Surveys began in the morning, as soon after sunrise as 

 sea and fog conditions allowed. Surveys ended usually by 

 mid-day, as sea conditions deteriorated. 



Surveys consisted of travelling along a series of 6-8 km 

 long transect lines parallel to shore and, in general, following 

 the depth contours of the ocean floor. The transect lines 

 were positioned offshore from the shoreline at 400 m, 800 

 m, 1400 m, 2000 m, 3000 m, and 5000 m (fig. 1). Due to 

 inshore rocks or surf, the 400 m distance was only possible 

 at the protected Crescent Beach site. 



Each year we completed one to four surveys per month 

 at each intensive survey area, as weather and sea conditions 

 permitted. On each survey day we attempted to complete all 



transects; however, a change in conditions sometimes resulted 

 in partial surveys. Subsequent surveys would begin with 

 those transects not completed on the previous survey. 



Extensive Surveys 



We surveyed the coastline of northern and central 

 California from the Oregon border to Point Lobos, south of 

 Monterey Bay (fig. 2). The sampled area was divided into 

 26 coastal sections with varying numbers of 2-km segments, 

 totalling 393 segments or 786 km (table 7, fig. 2). The 

 length of each coastal section, and therefore the number of 

 2-km segments, was determined by topography and access 

 from harbors. Depending on availability of boats and harbors, 

 the different sections of coast were sampled with different 

 intensity. Areas with easy access to harbors were sampled 

 most frequently. 



Each coastal section was surveyed at two distances 

 from the shoreline, 800 m and 1,400 m. The transects were 

 parallel to the shoreline and observations were recorded in 

 2-km segments. As with the intensive surveys, the area 

 surveyed by each 2-km segment was 200 m wide by 2,000 

 m long, or 0.4 km 2 . 



354 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



