NOTE Love et al. : A rocky reef nursery for Ra/a rhina in the southern California Bight 
475 
available to at least some predators than eggs lying on 
low substrata. 
Skate reproduction, with its emphasis on highly spa- 
tially restricted nursery grounds, appears to be an 
example of “predator swamping” (Van Montfrans et ah, 
1995). In addition, the observation that intact skate 
eggs are more likely to be found on sponges than on 
bare rocks may reflect an antipredator strategy by 
adult skates. Boring snails, including those in the fam- 
ilies Muricidae, Naticidae, and likely Ranellidae, are 
major predators on skate eggs and predation rates in 
nursery grounds can reach 40% or more (Lucifora and 
Garcia, 2004; Hoff, 2007). Snails of all of these families 
are found in southern California waters (McLean and 
Gosliner, 1993). Although they could not identify them 
in their trawl-based study, Lucifora and Garcia (2004) 
speculate that microhabitat differences in egg place- 
ment could lead to variable protection from predators. 
It is possible that sponges, with their spicule-rich skel- 
etons and potent chemical defenses, may deter snails 
or other egg predators. 
The Bering Sea skate nursery ground that Hoff 
(2007) investigated was notable for having 1) high 
currents and productivity and 2) the presence of only 
mature fish. The nursery site of our study was com- 
posed of high-relief rocks situated on the edge of a 
submarine canyon. Because of the relative absence of 
fine particulates on the substrata and the presence of 
unusually high densities of sponges, gorgonians, and 
other structure-forming invertebrates, we surmised 
that this nursery ground is bathed by high currents 
and is likely quite productive. In addition, we observed 
no juvenile or adult skates, providing additional evi- 
dence for Hoff’s (2007) hypothesis that newly hatched 
skates quickly leave their nursery grounds. 
In the context of this nursery ground much about 
longnose skate reproduction remains unknown. For 
instance, we do not know when the eggs are laid, their 
incubation period, nor the fate of the juveniles. We do 
not know how many skates use this habitat and how 
they migrate. Lastly we note that the extent to which 
female skates seek out sponges is unknown. However, 
if skate eggs deposited on sponges are at a competitive 
advantage, damage to these invertebrate communities 
(i.e., through destructive fishing practices) and the 
subsequent increase in egg predation, would have a 
detrimental effect on skate reproductive success. 
Acknowledgments 
D. Ebert identified the skate eggs and J. Hoff provided 
a great deal of useful background information on skate 
nursery grounds and provided us with a copy of his 
Ph.D. thesis. Also very useful were the discussions with 
D. Cadien on sponge and snail ecology. We thank the 
pilots of the research submersible Delta, J. Lilly and 
C. Ijames, and the crew of the research vessel Velero for 
support in the field. 
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