236 
Fishery Bulletin 106(3) 
Table 1 
Data from reported embryonic developmental periods and developmental temperatures for oviparous elasmobranch species from 
previously published st udies worldwide. Values are the arithmetic means of the reported values. 
Common name 
Scientific name 
Mean developmental 
period (days) 
Mean developmental 
temperature (°C) 
Source 
Thorny skate 
Raja radiata 
912 
4.6 
Berestovskii, 1994 
Little skate 
Leucoraja erinacea 
279 
10 
Steele et al., 2004 
Clearnose skate 
Raja eglanteria 
63 
24 
Libby and Gilbert, 1960 
Clearnose skate 
Raja eglanteria 
82 
21 
Luer and Gilbert, 1985 
Clearnose skate 
Raja eglanteria 
85 
20 
Luer et al., 2007 
Clearnose skate 
Raja eglanteria 
368 
9.1 
Perkins, 1965 
Big skate 
Raja binoculata 
277 
11.5 
Hitz and Reid, 1968* 
Spiny rasp skate 
Okamejei kenojei 
137 
14.6 
Ishihara et al., 2002 
Thornback skate 
Raja clavata 
139 
14.9 
Ellis and Shackley, 1995 
Thornback skate 
Raja clavata 
137 
15.38 
Clark, 1922 
Thornback skate 
Raja clavata 
170 
14.31 
Clark, 1922 
Small-eyed ray 
Raja microcellata 
217 
14.66 
Clark, 1922 
Blonde skate 
Raja brachyura 
217 
14.13 
Clark, 1922 
Spotted skate 
Raja montagui 
155 
15.93 
Clark, 1922 
Cuckoo skate 
Leucoraja naevus 
248 
13.17 
Clark, 1922 
Chain catshark 
Scyliorhinus retifer 
256 
12.25 
Castro et al., 1988 
Small spotted catshark 
Scyliorhinus canicula 
165 
13.3 
Ellis and Shackley, 1995 
Small spotted catshark 
Scyliorhinus canicula 
334 
10 
Thomason et al., 1996 
Small spotted catshark 
Scyliorhinus canicula 
205 
16 
Thomason et al., 1996 
Small spotted catshark 
Scyliorhinus canicula 
160 
16 
Ballard et al., 1993 
Spotted ratfish 
Hydrolagus colliei 
300 
12.75 
Dean, 1906 
Alaska skate 
Bathyraja parmifera 
1290 
4.4 
Hoff (this study) 
* Indicates an unpublished study for which the author has the original data. 
Results 
Sampling of nursery site 
The nursery site was relatively small in area, covering 
approximately 2 km 2 for the highest egg case densities 
areas. During the initial July-August 2004 nursery 
investigation, 21 hauls were conducted and egg case 
densities ranged between 362 and 148,957 eggs/km 2 
(mean=19,470 ±36,030 eggs/km 2 ). A single trawl con- 
taining 148,957 eggs/km' 2 possessed >70% viable eggs 
and was designated as an index site for subsequent 
seasonal trawl sampling (Fig. 1). The seasonal trawl 
samples contained between 45,418 and 549,843 eggs/km 2 
(mean =199,683 ±181,467 eggs/km 2 ) from the index site 
and 53-84% of the eggs per tow were viable. The Alaska 
skate and the Bering skate ( Bathyraja interrupta) were 
both found during most sampling periods. The Alaska 
skate predominated in abundance (96%) and in egg 
case composition (99.6%). Although the Bering skate 
accounted for about 4% of the skates found at the site, 
their egg cases contributed only 0.4%, indicating that 
this was mainly a single species nursery site for the 
Alaska skate. The most abundant fish species encoun- 
tered throughout the sampling period included walleye 
pollock, arrowtooth flounder ( Atheresthes stomias), flat- 
head sole ( Hippoglossoides elassodon), rex sole ( Glypto - 
cephalus zachirus ), and Pacific cod. The most abundant 
invertebrate species (from summer 2004 trawls) were 
Tanner crab ( Chionoecetes bairdi), tentacle-shedding 
anemone ( Liponema brevicornis), and Oregon triton 
( Fusitriton oregonensis). 
Biological sampling 
The size composition of Alaska skate, for all samples 
combined, indicated that males and females of mature 
sizes and reproductive state used the nursery nearly 
exclusively of other posthatching stages; immature and 
newly hatched juvenile skates were rarely found (Fig. 2). 
Gonad examination revealed developed ovaries and 
egg cases in the uterus of female Alaska skates, and 
fully developed claspers and testes in males during all 
seasons examined, indicating sexual maturity and that 
skates were in actively reproducing states. Recent stud- 
ies have provided evidence that the eastern Bering sea 
populations of Alaska skate reach a mature state around 
93 cm TL for both sexes (Matta and Gunderson, 2007); 
thus nearly all individuals found within the nursery site 
of the present study were of reproductive size. 
Seasonal nursery use was evident from trawl samples 
collected at the index site. The Alaska skate showed 
