392 
Fishery Bulletin 106(4) 
The archaeological record in the western North Atlan- 
tic shows that the average length of Pacific cod caught 
today by commercial fisheries is at least 40 cm smaller 
than that of prehistoric times, and indicates that the 
Pacific cod populations have been impacted by modern 
fisheries (Kenchington and Kenchington, 1993; Jackson 
et ah, 2001). Similar shifts have been discovered in 
the central North Atlantic where Amorosi et al. (1994) 
demonstrated significant differences in the length dis- 
tributions of Pacific cod between the Medieval period 
and the modern era. In contrast, we found that the 
minimum difference in the average length of Pacific 
cod taken by longline fisheries was only 3-4 cm larger 
than the smallest prehistoric mean size fish caught 
by the ancient Aleuts using jigs. The implications of 
these regional differences are intriguing given the dif- 
ferent historical trajectories in commercialization of 
the groundfish fisheries in these two regions, namely 
a different emphasis on harvesting technologies (i.e., 
a much higher proportion of the North Pacific catch is 
taken with cod pots, compared to the North Atlantic, 
where cod pots have seen minimal use). The North 
Pacific cod pot fishery, in particular, reduces the catch 
of juvenile fish. 
This study points to ways in which ancient archaeo- 
logical deposits can be used to significantly extend the 
time-depth of fish population studies and can provide 
important insights into long-term sustainability. Such 
palaeofisheries research is important for placing modern 
decadal population trends within a longer-term perspec- 
tive. In the case of Pacific cod, the paleoecological re- 
cords indicate that today’s Pacific cod are comparable in 
size to fish that inhabited the Gulf of Alaska thousands 
of years ago. This finding indicates that modern fisher- 
ies have not altered the average length distributions of 
Pacific cod in the Gulf of Alaska when measured over 
long time scales. 
The fact that modern Pacific cod length distributions 
are within the range of precommercial variability in- 
dicates that the current commercial Pacific cod fishery 
has sustained the length structure (and therefore aver- 
age fecundity structure) of the prehistoric (noncommer- 
cial) Gulf of Alaska Pacific cod population. Compared 
to the North Atlantic, the changes we observed in fish 
length between the prehistoric and modern eras in the 
Gulf of Alaska are more consistent with natural fluctua- 
tions than with harvesting pressure. The fact that the 
present-day size-structure of Gulf of Alaska Pacific cod 
stocks is consistent with a sustainable fishery (Thomp- 
son et al., 2006) and that the current size-structure is 
comparable to that of pre-industrially fished populations 
indicates that current Pacific cod fisheries management 
policies and harvesting techniques in the western Gulf 
of Alaska are working. That is, management practices 
and harvests are maintaining a natural Pacific cod 
population structure based on mean size as a compara- 
tive metric of sustainability. However, we caution that 
global warming may become a complicating factor for 
modern management practices given that Pacific cod 
populations may be vulnerable to pressures caused by 
increasing oceanic temperatures, as appear to have oc- 
curred circa AD 1000-1300. 
Acknowledgments 
This research was funded by the National Science 
Foundation under awards NSF OPP 0326584 and NSF 
BE/CNH 0508101. L. Ford, Interim Vice President of 
Research at Idaho State University, provided gener- 
ous postdoctoral support for this project. We are also 
grateful for the support provided to A.W. Trites by the 
North Pacific Marine Science Foundation through the 
North Pacific Universities Marine Mammal Research 
Consortium. We thank G. Thompson and four anony- 
mous reviewers for their valuable comments, and grate- 
fully acknowledge the student laboratory assistants 
who sorted nearly 100,000 fish bones. The fieldwork 
on Sanak Island was done with the permission of the 
Sanak Corporation and in cooperation with the Pauloff 
Harbor Tribe. 
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