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Fishery Bulletin 106(3) 
A Females — early March 
Immature 
17% 
Spent 
45% 
Prespawning 
11 % 
Spawning 
27% 
C Females — late March 
Immature 
6% 
Spent 
78% 
Prespawning 
3% 
Spawning 
13% 
B Males — early March 
Spent 
38% 
Immature 
24% 
Spawning 
Prespawning 
37% 
D Males — late March 
Immature 
12% 
Prespawning 
20 % 
Spent 
68% 
Spawning 
0% 
Figure 5 
Gonad maturity stages for Pacific cod ( Gadus macrocephalus) caught in March 2004. Fish were classified as immature, 
prespawning, spawning, or spent (immediately postspawning) based on visual inspection of the gonad. (A) females in 
randomly sampled catch from 15 through 22 March 2004, (B) males from this period, (C) females in randomly sampled 
catch from the same locations in 23-30 March 2004, and (D) males from this period. 
sex ratio indicate that the local population of Pacific cod 
in our study area was not a closed, static pool of fish 
but a shifting, dynamic mix. In fact, the tagging data 
indicate that the short-term movement scale for Pacific 
cod in this region is substantially larger than the 10 
nmi notrawl zone. Although fishing removal may have 
had an immediate localized effect on fish abundance, 
the effect was obscured by rapid fish movement (less 
than one week) over a geographic scale greater than 
that of the fishery removal. Thus, of the three localized 
depletion scenarios presented earlier (see Introduction), 
our results strongly disagree with conjecture one (sta- 
tionary localized depletion). Because the experiment 
was limited in scale, our results do not eliminate the 
possibility of conjectures two and three (regional ef- 
fects over larger spatial scales or displaced effects due 
to directed movement). Recent hydroacoustic studies of 
walleye pollock ( Theragra chalcogramma ) abundance 
in the same region (Barbeaux et al. 1 ) also indicated at- 
tenuation of fishery-removal effects by rapid fish move- 
ment. Barbeaux et al. saw a visible pattern in echo sign 
during fishing, but diurnal fish movements eliminated 
the pattern within 12-24 hours. 
The movement of Pacific cod, as qualitatively observed 
in the tagging data, could appear as a decline in catch 
rates for catch data measured on the same geographic 
scale. In a previous study of possible effects of commer- 
cial fishing on Pacific cod abundance (Fritz and Brown, 
2005), commercial catch-per-unit-of-effort (CPUE) data 
were collected from a large region of the southeast Ber- 
ing Sea, including our study area. Fritz and Brown 
interpreted a decreasing trend in fishery CPUE from 
1 Barbeaux, S. J., M. Dorn, J. Ianelli, and J. Horne. 2005. 
Visualizing Alaska pollock (Theragra chalcogramma) ag- 
gregation dynamics. ICES Council Meeting 2005/U:01. 
