110 
Fishery Bulletin 113(2) 
Table 2 
Best-fit semivariogram models and parameters for the spatial distribu- 
tion of spiny dogfish ( Squalus acanthias) catch per unit of effort (CPUE) 
for the sink gillnet (SGN) and otter trawl (OT) fisheries and in the North- 
east Fisheries Science Center bottom trawl survey (Survey) between 1989 
and 2009 during autumn and spring in the northeast U.S. shelf large 
marine ecosystem. Semivariogram parameters included the sill (C s ), the 
nugget (Co), and the range (a). Anisotropy parameters included the ratio 
of the minor to major lengths (Ratio) and the angle for the principal di- 
rection of continuity (Angle). Models include exponential (Exp), Gaussian 
(Gau), and spherical (Sph). 
Gear 
Model 
c s 
c 0 
a (km) 
Ratio 
Angle (°) 
Autumn 
SGN 
Exp 
6.74 
0.00 
0.10 
0.93 
54 
OT 
Gau 
4.94 
6.16 
1.79 
0.93 
141 
Survey 
Exp 
3.45 
4.94 
1.57 
0.91 
130 
Spring 
SGN 
Gau 
2.30 
1.90 
1.31 
0.73 
30 
OT 
Exp 
12.02 
4.80 
20.19 
0.98 
39 
Survey 
Sph 
4.37 
4.76 
1.38 
0.76 
37 
For the OT fishery, the magnitude of SOq was rela- 
tively similar between seasons but differed in trend 
(Fig. 4, C and D). During autumn, a period of relatively 
low SOq (42% [SD 11.5]) was observed in 1990-1997 
and higher SOq was seen in 1998 and thereafter (68% 
[SD 12.2] (Fig. 4C). In contrast, no pattern was evident 
during spring (Fig. 4D). Predicted spatial distributions 
of spiny dogfish estimated with interpolation methods 
for the OT fishery revealed reasonable mean predic- 
tion and 100-fold cross-validation errors (Table 3). For 
this fishery, trends between SOq and SO\ were similar 
during autumn but more variable during spring. Dur- 
ing autumn, lower SOj values were identified through- 
out the mid-1990s (Fig. 4C). During spring, SOj values 
were consistently larger than SO q estimates; however, 
a marked reduction was observed during the early to 
mid-2000s (Fig. 4D). 
Availability to fishery 
Aggregated spiny dogfish The percentage of the spiny 
dogfish stock available to both fisheries was gener- 
ally higher during autumn than during spring (Fig. 
5A), indicating that a greater portion of the popula- 
tion was available to each commercial fishery during 
this season. In general, availability to the SGN fishery 
remained below 30% with the exception of availability 
in the mid- to late 2000s (Fig. 5A). Although a similar 
pattern was observed for the OT fishery during spring, 
availability to this fishery during autumn increased 
abruptly in 2001 and remained high (Fig. 5A). 
Stage-dependent availability The availability of each 
life-history stage of spiny dogfish was highly vari- 
able for fisheries and seasons (Fig. 5). Sporadic sur- 
vey catches of neonates, particularly during autumn, 
resulted in erratic (and potentially unreliable) trends 
for both seasons and fisheries (Fig. 5B). Patterns in 
availability of immature males were also relatively in- 
consistent throughout the time series, although analy- 
ses indicated recent increases for the OT fishery during 
both seasons (Fig. 5C). Availability of mature males, 
immature females, and mature females revealed simi- 
lar trends, namely recent increases and higher avail- 
ability during autumn than during spring for both fish- 
eries (Fig. 5, D-F). 
Abundance of mature female spiny dogfish from the 
bottom trawl survey was related significantly to avail- 
ability of mature female spiny dogfish to the OT fish- 
ery during autumn (availability=22.269 log e [CPUE] + 
10.954, coefficient of multiple determination [i? 2 ]=0.48, 
P=0.0005) and to the SGN fishery during spring (avail- 
ability=-7.867 log e [CPUE]+24.217, P 2 =0.24, P=0.0236) 
(Fig. 6). As abundance increased during autumn, the 
percentage of mature females available to the OT fish- 
ery increased significantly (Fig. 6A). The relationship 
between survey abundance and availability to the SGN 
fishery revealed an opposite but significant trend dur- 
ing spring. As abundance of mature females increased, 
the percentage available to the SGN fishery decreased 
significantly (Fig. 6B). 
Correlation between fisheries and survey catch data 
Spiny dogfish distribution was not highly correlat- 
ed with commercial fishery effort for either fishery 
(r<0.23, r sp <0.43). Although most correlations between 
spiny dogfish distribution and fishery catch (SOq, SO{) 
