294 
Fishery Bulletin 99(2) 
There are substantial seasonal changes in the habitat, 
particularly those associated with variable coastal up- 
welling (Bakun, 1973; Hobson and Chess, 1988). From 
late spring through fall, beds of bull kelp, Nereocystis 
leutkeana, form canopies at the sea’s surface in many plac- 
es, but most are swept away by storm seas during the sub- 
sequent winter. We began our study there in 1975, and the 
area, along with its flora and fauna, had become familiar 
to us by the time data presented in this report had been 
collected. 
Measures of juvenile abundance 
We had noted interannual variation in numbers of first- 
year Sebastes spp. as an incidental adjunct to more than 15 
years of study in California’s nearshore habitats, but were 
prompted to begin annual assessments of their abundance 
only after exceptionally large numbers settled along the 
north coast during 1977. At the outset, time available for 
this work was limited by other projects; therefore through 
1982 our effort was directed mainly at developing means 
for identifying species. Features now used to distinguish 
Sebastes juveniles were at that time largely unknown, and 
of the three dominant forms settling in Mendocino habi- 
tats, only S. mystinus could be recognized at the outset. 
The other two juveniles — S. flavidus and S. melanops — 
remained indistinguishable until diagnostic features were 
determined by Laroche and Richardson (1980). 
Despite the uncertain identities involved, one of us 
(ESH) estimated the relative abundance of YOY Sebastes 
present each year from 1978 to 1982 as a percentage 
of large total abundance in 1977. These estimates were 
made during the course of other projects and without con- 
sideration of publication, but nevertheless were recorded 
in field notes. Each annual estimate during these years 
represented a consensus based on repeated assessments 
(about weekly) between June and October, and although 
they lacked precision, they represented the only measures 
of YOY abundance for years that produced much of the 
data on predation. Some readers will dismiss these esti- 
mates as overly subjective, but others will appreciate the 
opportunity of considering all available evidence. 
The annual assessments of YOY abundance became a 
major activity in 1983. By then, virtually all YOY Sebastes 
spp. seen underwater at the study sites could be identified, 
and we had developed standard procedures to assess their 
abundance. From that year on, YOY were counted during 
midday (1000 to 1400 h) at four sites within the study ar- 
ea. We attempted to make counts at least once each week 
but found that our ability to do so was determined largely 
by weather conditions The first counts each year were 
made shortly after the initial settlement of YOY, which 
occurred some time during late spring or early summer. 
The counts then continued through October, when it be- 
came evident that YOY of one major species — S. flavidus — 
were leaving the area. 
During each assessment one to three of us swam at con- 
stant speeds close to the seabed, making frequent changes 
in direction. We counted the YOY Sebastes within 3 m of 
varied tract lines that traversed all major habitats rep- 
resented at the sites. Because the highly variable tur- 
bidity and turbulence characteristic of this area strongly 
influenced our ability to see the fish, counts were made 
only when horizontal visibility exceeded 4 m and turbu- 
lence was not excessive. This limitation precluded a fixed 
schedule because counts were aborted more often than 
completed. 
Assessments were made at widespread sites along the 
coast of northern California, from Mendocino southward 
to Marin; however, only data from Mendocino were used 
in this report because that is where the predators were 
sampled. Similarly, although juveniles counted in the en- 
vironment were identified to species, our report refers to 
all as Sebastes spp. because they were compared with ju- 
veniles recovered from gut contents, which too often were 
damaged beyond recognition as species. 
The study of trophic relations in S. mystinus included 
YOY, and although food habits of these lack relevance 
here, sizes of individuals sampled from June through Oc- 
tober provide a measure of sizes available to predators 
during the first five months after settlement. This infor- 
mation has broad implications, because growth in S. mys- 
tinus is similar to growth in the vast majority of Sebastes 
YOY that settle in this habitat (except S. paucispinnus, 
which was not included). 
Food habits of predators 
The predators were sampled with scuba and hand-held 
spears throughout the 11 years of overlap between the 
two investigations. Only specimens with identifiable gut 
contents were used in this report. They were collected 
during midday (1000 and 1400 h), and all months were 
represented (Fig. 2). Specimens representing each species 
ranged upward in size from the smallest found with a YOY 
Sebastes among its gut contents. This eliminated from 
consideration the many specimens that were too small 
to include YOY among their prey. Each specimen was 
observed in its natural setting before capture, and many 
were collected as part of comprehensive assessments of 
the biota. Both of these circumstances contributed to inter- 
pretations of the gut contents. 
Following capture, specimens were measured (standard 
length), and their digestive tracts were removed and pre- 
served in 10% formalin. During later examination in the 
laboratory, the gut contents were removed and studied un- 
der magnification. Food items were identified to species 
when feasible, and the record of each prey taxon included 
number, size, stage of digestion, and percent contributed to 
the total diet. Much of this information is of limited interest 
here, but the last variable listed (labeled “percentage of di- 
et” in the figures) was used to show the relative importance 
of each prey category as food. This measure was obtained 
by grouping elements of the various prey categories as they 
lay spread out in a petri dish, and then visually estimating 
the percentage that each category represented of the entire 
sample. Generally, values presented are means calculated 
from individual diets in specified groups of predators. 
Juveniles of the highly distinctive Sebastes jordani were 
exceptions to the generalization that YOY Sebastes recov- 
