240
12. Kelp, Urchins, and Otters in the California Coastal Region
1: Urchins05
II
2: Urchin 610
3: Urchin 1115
4: Urchins 1620
5: Urchins 2125
rzsoooo.oo
11 875= 00 0I-+ --4---='r--+- - - - - - +-- - - - - + - - - - - ---1
II
0.00 of0.00
-+
15.00
30.00
Months
-
45.00
2==3.... 4..... 5
60.00
FIGURE 12.6
seen in Figures 12.6 to 12.8. Cohorts of 0-5, 21-25 , 26-30, 31-35 , and 36-40
millimeters all exhibit smooth, somewhat bell-shaped curves. There is a
time lag between each of the peaks of these cohorts . These successive
peaks show a particular group of urchins moving through the cohorts . The
eventual drop in population of these cohorts can be directly related to otter
predation. Specifically, otters tend to consume the very urchins that constiII
1: Urchins 2630
2: Urchins3135
3: Urchin 3640
4: Urchins 4145
5: Urchins 4650
sooooo.oo
11--.
00
II
0.00 of0.00
-+
15.00
30.00
Months
.... 4..... 5
1..... 2..... 3.... 4..... 5
45.00
60.00
F,GURE 12.7