Gunderson: Spatial patterns in the dynamics of slope rockfish stocks 
227 
the shallower extremes, and the 200-m contours are 
separated by only about 30 km. Nevertheless, the 
size and age composition in these two areas differed 
sharply (Gunderson et al., 1977). The composition of 
the parasite fauna on adult Pacific ocean perch in 
Moresby Gully has also been shown to differ signifi- 
cantly from that found on adult ocean perch in Goose 
Island Gully (immediately south of Mitchell’s) 
(Leaman and Kabata, 1987). It seems clear that, 
whereas spawner-recruit processes probably operate 
over broad geographic scales, adult migrations are 
limited, and changes in abundance and age compo- 
sition for this species in response to fishing are highly 
localized. 
The results of this study indicate that responses 
to fishing also occur over very small spatial scales 
off Oregon-southern Vancouver Island as well as in 
Queen Charlotte Sound, and that this is true for 
rougheye, splitnose, and darkblotched rockfish as 
well as for Pacific ocean perch. The index areas off 
the northern Washington coast were only 28 km 
south of the Canadian experimental overfishing zone 
(Fig. 1), yet rockfish stocks in this area appear to 
have experienced little change in abundance between 
1968 and 1992. Shortspine thornyhead abundance 
within the 219-366 m depth interval actually in- 
creased between 1968 and 1972, although these fish 
represent only the shallowest part of the range and 
the younger age groups in a stock that can extend to 
depths greater than 1,100 m (Ianelli et al. 4 ). 
Although the rockfish assemblage in the northern 
Washington index sites was not depleted to the same 
extent as its counterpart in Canadian waters during 
1970-92, it is far from being at pristine abundance. 
The effects of the overfishing during 1966-68 are still 
evident because the abundance of fish older than age 
15 is still much lower than that characteristic of 
lightly exploited stocks (Fig. 6). Pacific ocean perch 
stocks in the index areas appear to have undergone 
significant exploitation between 1970 and 1992 but 
have not declined to the same extent as those in 
Canadian waters to the north (Tables 1 and 4) or 
in U.S. waters to the south (Fig. 4). 
The size and age at maturity for Pacific ocean 
perch in the northern Washington index areas 
appear to have declined significantly between 1968 
and 1972 (Gunderson, 1977) and 1992. Length at 
50% maturity declined from 34.4 cm to 31.6 cm 
(Table 5), whereas age at 50% maturity declined 
from 10.1 years to 8.1 years. This shift in size and 
age at maturation should be viewed with some cau- 
tion, however, because most adult fish examined in 
1992 were still in the”maturing” stage. Only one of 
the 382 adults examined was in a more advanced 
4 Ianelli, J. N., R. Lauth, and L. D. Jacobson. 1994. Status 
of the thornyhead ( Sebastolobus sp. ) resource in 1994. App. 
D in Status of the Pacific coast groundfish fishery through 
1994, and recommended acceptable biological catches for 
1995. Pacific Manage. Council, Portland, OR, 58 p. 
Table 5 
Estimated length and age at maturity for female Pa- 
cific ocean perch off the northern Washington coast, 
1968-72 versus 1992. 
1968-1972 
1992 
a 
-29.0258 
-20.3196 
p 
0.8439 
0.6428 
l 05 (cm) 
34.40 
31.61 
Var tf 0 .6> 
0.0437 
0.1498 
Z-statistic' 
6.33 
Wyears^ 
10.1 
8.1 
1 See Gunderson (1977). 
