Hobson et al.: Predation on first-year Sebastes spp. 
293 
tors attacked the recently settled Sebastes 
only during years when these were more 
numerous. 
Among predators drawn to YOY abun- 
dances were three of the region’s most 
prominent species: the black rockfish ( Se- 
bastes melanops ), the blue rockfish ( Se- 
bastes mystinus ), and the kelp greenling 
( Hexagrammos decagrammus) (Fig. 1 ). The 
attacks by S. melanops might have been 
expected because this predator is known 
to prey regularly on a variety of fishes 
(Moulton, 1977; Rosenthal et al., 1988), 
but S. mystinus ordinarily feeds mainly 
on pelagic invertebrates (Gotshall et al., 
1965; Hobson and Chess, 1988), and H. 
decagrammus, a benthivore with more var- 
ied food habits, feeds mainly on Crustacea 
(particularly crabs), polychaetes, and mol- 
lusks (Moulton, 1977; Simenstead et al 1 ). 
Our objective was to determine when 
these varied predators attack YOY Se- 
bastes spp., how this predation relates to 
changes in YOY abundance, and to iden- 
tify implications for management. 
Materials and methods 
All of our studies on California’s north 
coast involved using scuba to investigate 
organisms in their natural settings. Under 
these circumstances, we routinely noted 
events like settlement of juvenile Sebastes 
even when our attention was directed else- 
where. This feature of our work was impor- 
tant in enabling us to integrate elements of 
disparate studies in preparing this report. 
Study area 
The area of study was in 5-15 m of water 
within 300 m of shore, about 2 km north 
and south of Albion, in Mendocino County 
(lat. 39°13'N; long. 123°14'W ). Because this 
coast is fully exposed to north Pacific seas, 
strong surge and turbulence prevailed 
most of the time. The ocean floor there 
consists mainly of irregular rock pave- 
ment and boulders (some 5-15 m in dia- 
meter) and isolated patches of sand. 
1 Simenstead, C. A., B. S. Miller, C. F. Nyblade, 
K. Thornburg, and L. J. Bledsoe. 1980. Food 
web relationships of northern Puget Sound 
and Straight of Juan De Fuca. Report to 
Marine Ecosystem Analysis (MESA), Puget 
Sound Project. U.S. Environmental Protec- 
tion Agency, Washington, D.C. 20460, 335 p. 
Figure 1 
(A) Black rockfish, Sebastes melanops. (B) Blue rockfish, Sebastes mystinus. 
(C) Kelp greenling, Hexagrammos decagrammus. The black rockfish, with a 
larger mouth and a body form more conducive to speed, is morphologically 
better adapted than the other two species for running down and capturing 
elusive prey above the sea bed. The more oval shape of the blue rockfish sug- 
gests less need for speed in capturing its regular prey, whereas its smaller 
mouth and shorter snout (which increases an ability to simultaneously train 
both eyes on small targets close ahead) are more typical of planktivores than 
piseivores. Both rockfishes have a lower jaw that extends beyond the upper, 
which is consistent with attacking prey that are above the seabed, whereas 
the kelp greenling has an upper jaw that extends beyond the lower, for attack- 
ing prey that are on the seabed. Also, the kelp greenling’s elongate body func- 
tions better swimming among, rather than above, the rocks. 
