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Fishery Bulletin 108(2) 
0 10 20 30 40 
Age (years) 
Figure 7 
Comparison of published spiny dogfish ( Squalus acanthias) female growth 
models from sources listed in Table 4. (A) Growth models published for Pacific 
Ocean spiny dogfish: “Alaska” includes the Gulf of Alaska (GOA) model from 
this study and a Prince William Sound (PWS) model (Vega, 2006); “British 
Columbia inshore” includes three models for dogfish sampled within the 
Strait of Georgia and Hecate Strait (Ketchen, 1975; Saunders and McFar- 
lane, 1993); “Puget Sound inshore” covers models based on samples collected 
within the Puget Sound area south off British Columbia and east of the 
Washington coast (Vega, 2006); “Pacific Coast South” includes four models 
based on samples collected off Oregon and California (Vega, 2006); “Pacific 
Coast North” includes models based on samples collected off of Washington 
and the west coast of Vancouver Island (Ketchen, 1975; Jones and Geen, 
1977; Vega, 2006); (B) The growth models from the Atlantic Ocean, North 
Sea. and Black Sea (Holden and Meadows, 1962; Sosinski 1978; Nammack et 
al., 1985; Fahy, 1989; Avsar, 2001; Henderson et al., 2002; Soldat [footnote 1 
in Table 6]). Note the different x-axis scales. 
each species, and a complete sample 
of the size range may lead to a more 
conclusive determination as to which 
species exhibit two-phase growth. 
Disregarding the two-phase mod- 
els, the best-fit model was model 2 
for males and model 5c for females. 
In this situation, given the lack of 
data and difficulties with the two- 
phase models, it may be more ap- 
propriate to select the best model 
not based on the AIC criteria alone, 
but to also consider the biological 
soundness of the models. Model 2 
(males) and model 5c (females) are 
the statistical best fit of the more 
biologically reasonable models. Both 
of these best-fit models require L 0 as 
an input, not as an estimated pa- 
rameter. The lack of data for spiny 
dogfish <50 cm TLext likely causes 
the models that estimate L 0 to have 
difficulty fitting the data and as a 
result estimate L 0 to be larger than 
would be expected. 
In the majority of published stud- 
ies on spiny dogfish age and growth 
the traditional von Bertalanffy 
model is used. To facilitate a broad- 
er comparison of our results with 
growth parameter estimates for oth- 
er regions of the geographic distri- 
bution of spiny dogfish, we compared 
parameters estimated from model 1 
(Table 4) with growth curves fitted 
by using the traditional vB formula- 
tion, as reported in published stud- 
ies (Table 5, Fig. 7). Clear differ- 
ences in spiny dogfish growth exist 
between the North Pacific and North 
Atlantic oceans. For instance, we 
found that male and female dogfish 
reach larger asymptotic sizes (87.2 
and 112.2 cm TL ext , respectively) in 
the GOA than off the northeastern 
United States (82.5 and 100.5 cm 
TL gxt , respectively; Nammack et al., 
1985). Indeed, virtually all stud- 
ies have found large differences in 
growth of spiny dogfish between 
the North Pacific and North Atlan- 
tic (Table 5, Fig. 7). Fish from the 
North Atlantic tend to grow more 
rapidly, achieve smaller asymptotic 
sizes, and have shorter life spans 
than those from the Pacific. Differ- 
ences in growth also exist within 
the Pacific (Table 5, Fig. 7). For ex- 
ample, our GOA growth estimates 
are similar to those for spiny dog- 
