Maschner et al.: A 4500-year time series of Gadus macrocephalus size and abundance 
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165°0'0"W 160°0'0”W 
The North Pacific and the western Gulf of Alaska region showing Alaska and the location 
of Sanak Island where bones were collected at archeological sites to determine whether 
a change in fish size was evident over the 4500 archeological record. 
The Sanak Pacific cod fishery now includes mostly 
fishermen of Aleut-Scandinavian descent who use jigs, 
pots, and longlines in nearshore waters, but the fishery 
has deep, prehistoric roots (Tews, 2005). Archaeological 
data indicate that Aleuts have occupied Sanak Island 
for over 6000-7000 years and Pacific cod bones domi- 
nate the matrices of all preserved midden deposits from 
over 120 prehistoric village sites found on the island. 
These remains provide a novel laboratory for construct- 
ing long-term time series of Pacific cod populations. 
The goal of this study was to compare archeological 
data with modern fisheries data to assess whether in- 
dustrialized fishing has changed the size of Pacific cod 
in the North Pacific Ocean and to investigate whether 
or not Pacific cod size and abundance may be influenced 
by climate change. Pacific cod are among the most 
heavily exploited and consumed species of fish in the 
Northern Hemisphere and have declined significantly 
in most parts of the world in the past 30-40 years. In 
eastern Canada, fishing resulted in Atlantic cod ( Gadus 
morhua) becoming smaller and reaching sexual maturi- 
ty at younger ages as fisheries reduced the populations 
by more than 90% (Fanning et ah, 2003; Hutchings, 
2005; Lilly et al., 2005). Evolutionary reductions in 
body size caused by fishing have also been reported for 
Baltic cod ( Gadus morhua callarias) (Andersen et al., 
2007). In the Gulf of Alaska, Pacific cod are generally 
thought to be fished at sustainable levels, but there is 
a limited time series to assess whether fisheries have 
changed the size of fish caught over the past 50 years 
(Thompson et al., 2006). It is, however, possible to use 
paleofisheries data to assess whether the lengths and, 
by correlation, average fecundity of fish caught today 
are comparable to those caught thousands of years ago 
before the advent of industrialized fisheries, and to 
use lengths and frequencies of Pacific cod harvested in 
prehistory to assess the role of climate in the structure 
of Pacific cod populations. 
Materials and methods 
All of the samples used to estimate the sizes of fish 
over the prehistoric time sequence were derived from 
shell-midden deposits that were excavated by trowel and 
sieved through 6-mm mesh, an appropriate sieve size 
given specimen sizes in the region (e.g., see Discussion 
in Cannon, 1999), and our results were substantiated 
by direct comparisons with bulk samples processed with 
3-mm mesh). In our analysis, we controlled for possible 
