NOTE Love et at: A rocky reef nursery for Raja rhina in the southern California Bight 
473 
Table 1 
Expected and actual (observed) longnose skate (Raja 
rhina) egg numbers by habitat type. Observations were 
made from the Delta submersible, eastern Santa Barbara 
Channel, October 2006. Habitat types were rock ridge 
(R), boulder (B), cobble (C), and sand (S). A two-character 
code was assigned each time a distinct change in substra- 
tum type was noted. The first character of the code rep- 
resents the substratum that accounted for at least 50% 
of the survey patch, and the second character represents 
the substratum accounting for at least 20% of the patch. 
Expected numbers were calculated by assuming that 
the density of skate eggs was not different across habi- 
tat types. Expected numbers were rounded to the near- 
est integer. Habitats are ordered from most to least area 
surveyed (m 2 ). 
Habitat 
Area surveyed 
(m 2 ) 
Expected 
egg numbers 
Actual 
egg numbers 
RR 
2219.0 
1513 
1721 
RC 
208.6 
142 
13 
RB 
76.1 
52 
2 
RS 
37.6 
26 
4 
CR 
10.4 
7 
0 
of decreasing particle size, these substrata were the 
following: rock ridge (R), boulder (B), cobble (C), and 
sand (S). A two-character code was assigned each time 
a distinct change in substratum type was noted. The 
first character of the code represented the substratum 
that accounted for at least 50% of the survey patch, 
and the second character represented the substratum 
accounting for at least 20% of the patch. Thus, RB rep- 
resented a patch composed of at least 50% rock ridge 
and at least 20% boulders. 
Results 
In the nursery area, we surveyed 2551.8 m 2 of sea floor 
in waters between 125 and 151 m depth (average depth 
139 m) and with bottom temperatures ranging from 
9.1° to 10.1°C (Fig. 1). The study site was primarily 
composed of high-relief rocky ridge (RR), along with 
lesser amounts of rock-cobble (RC), rock-boulder (RB), 
rock-sand (RS), and cobble-rock (CR) (Table 1). 
We observed 1740 eggs, of which 238 were character- 
ized as intact. As far as we could ascertain, all of the 
eggs observed were those of the longnose skate (Raja 
rhina Jordan & Gilbert, 1880) (Fig. 2). We observed a 
range of egg states, from those that appeared to be new- 
ly deposited to ones that had almost disintegrated. The 
eggs did not appear to have been randomly laid over the 
substrata because significantly more eggs were observed 
over the highest relief areas (habitat RR) than over the 
other habitats (chi-square=13.1, df=4, P=0.01) (Table 1). 
Eggs also appeared to be clumped in their distributions. 
Although many of the eggs were deposited singly, we 
Table 2 
Number of observations (from the Delta submersible) of 
each size of longnose skate ( Raja rhina) egg cluster (no. of 
eggs in cluster) in the nursery ground on the edge of Hue- 
neme Submarine Canyon, October 2006, categorized by 
habitat type. Habitat types were rock ridge (R), boulder 
(B), cobble (C), and sand (S). A two-character code was 
assigned each time a distinct change in substratum type 
was noted. The first character of the code represents the 
substratum that accounted for at least 50% of the patch, 
and the second character represents the substratum 
accounting for at least 20% of the patch. 
Number of 
eggs in cluster 
Number of observations 
RB 
RC 
RR 
RS 
1 
0 
13 
145 
4 
2 
1 
1 
38 
0 
3 
0 
0 
23 
0 
4 
0 
0 
9 
0 
5 
0 
0 
6 
0 
6 
0 
0 
4 
0 
8 
0 
0 
1 
0 
10 
0 
0 
6 
0 
12 
0 
0 
1 
0 
20 
0 
0 
3 
0 
24 
0 
0 
1 
0 
25 
0 
0 
1 
0 
30 
0 
0 
4 
0 
40 
0 
0 
2 
0 
>50 
0 
0 
8 
0 
Total 
1 
14 
1722 
4 
observed several aggregations with 300 or more eggs 
(Table 2). Most of the eggs were laid on rocks and rela- 
tively few on such invertebrates as sponges, deep-water 
corals, and sea anemones (Table 3). However, the eggs 
that were laid on invertebrates were significantly more 
likely to be intact than were those on rocks (intact on 
invertebrates = 95%, 95% confidence interval, 83-99%; 
intact on rock=12%, 95% confidence intervals 10-13%; 
chi-square=225, df=l, PcO.0001). 
We estimated the total number both of all eggs and 
only those that were intact. We assumed that our sur- 
vey transect path demarcated the outer perimeter of the 
nursery grounds because we noted eggs all along the 
transect path. Using densities of both all eggs (0.68183/ 
m 2 ) and only intact ones (0.093 eggs/m 2 ) and the area 
bounded by our transects (27,878 m 2 ), we estimated 
that there were 19,008 eggs in the nursery grounds, of 
which 2593 were intact. 
Discussion 
According to our many years of visual observations, 
skate nursery grounds are uncommon in southern 
