Long et al.: Effects of ghost fishing on the population of Paivlithodes camtschaticus in Womens Bay, Alaska 
107 
Logistic regression revealed that neither size nor sex 
affected the probability of a tagged crab being killed 
or caught in ghostfishing gear, although there was a 
nonsignificant trend (P=0.055; Table 4) for larger (>140 
mm CL) tagged crabs than for the smallest (40-60 mm 
CL) crabs to be killed in ghostfishing gear; however, 
this trend may be driven by the low number of crabs 
tagged in the smallest and largest size categories (Ta- 
ble 4, Fig. 4). Because we did not observe any ghostfish- 
ing mortality for crabs with CL <60 mm, we restrict 
our inference about the effect of ghost fishing at the 
population level to crabs with CL >60 mm. Although 
our data suggest that the ghostfishing mortality rate 
for the largest crabs (>140 mm CL; this size category 
includes legal-size crabs) is higher than our average 
rate for crabs of all sizes, we take the conservative 
approach by applying a constant rate of ghostfishing 
mortality to all crabs >60 mm CL because of our lower 
sample size for crabs in the largest size category. 
Discussion 
The 17-year data set used in our study allowed us to 
estimate the effect of ghost fishing on a local popula- 
tion of red king crab. The results of this study indicate 
that ghost fishing in Womens Bay was responsible for 
more mortality of red king crabs with CL >60 mm than 
any other single observed cause of mortality observed 
during our study. Indeed, our data provide evidence 
that the rate of mortality from ghost fishing may be 
almost double the rate from all other sources of mor- 
tality combined (for caveats to this assertion, see the 
discussion later in this section on mortality associated 
with molting). These results indicate that ghost fishing 
has a large, negative effect on the population of red 
king crab in Womens Bay and that changes in regu- 
lations designed to minimize ghost fishing or in their 
enforcement may be warranted. 
Although many studies have quantified the effects 
of ghost fishing, most estimate the number of animals 
killed per unit of time (e.g., Breen, 1987; Hebert et ah, 
2001), the number killed per pot per unit of time (e.g., 
Bullimore et al., 2001; Al-Masroori et ah, 2004; Camp- 
bell and Sumpton, 2009), or simply the number of crabs 
caught per pot (e.g., Stevens et ah, 2000; Havens et 
ah, 2008). These studies focus on following or recov- 
ering lost gear and examining catches and mortality 
over time on a local population. However, in scaling up 
to estimate effects on larger or commercially targeted 
populations, assumptions or estimates of the number 
of pots lost and the population size are required. By 
following the fates of individuals in the Womens Bay 
population, we could estimate with precision the ac- 
tual mortality rate at the population level, assuming 
tags do not alter crab behavior. A drawback of this ap- 
proach, however, is that it applies only to Womens Bay 
and is not easily extrapolated to other areas. Still, this 
problem is one shared by all studies of ghost fishing. 
0 50 100 150 200 250 300 350 
Time (days) 
Figure 3 
Predicted percent mortality over a year for red king 
crab (Paralithodes camtschaticus) in Womens Bay, Ko- 
diak Island, Alaska. “Overall mortality” is the total 
mortality from all sources and is the sum of ghostfish- 
ing mortality and other mortality. “Ghost fishing” is the 
percentage of crabs that are killed in ghostfishing gear. 
“Other mortality” includes all other sources of mortal- 
ity, including predation and fishing. (A) Conservative 
estimates of mortality; only crabs that died in ghost- 
fishing gear were included in estimates of ghostfishing 
mortality. (B) Upper estimates of mortality; all crabs 
caught in intact ghostfishing gear were included in 
these estimates of ghostfishing mortality. 
Our conservative estimate of ghostfishing mortal- 
ity is precise, and because of the narrow definition for 
crabs considered to have died in pots, it represents 
the absolute minimum effect that ghost fishing had on 
the population of red king crab in Womens Bay dur- 
ing our study. However, it is likely a large underesti- 
mate. Because this study was not originally intended 
to document the effects of ghost fishing, divers active- 
ly decreased the effects of ghost fishing by releasing 
trapped crabs and disabling ghost pots. How many of 
the crabs caught in pots would have died is difficult 
to determine. Although escape rates for red king crabs 
from intact commercial red king crab pots may be up 
