Long et al.: Effects of ghost fishing on the population of Parahthodes camtschaticus in Womens Bay, Alaska 
105 
?’GF = r PGF’ 
where r^p = the rate of crab loss due to ghost fishing; 
r = the overall loss rate calculated above; and 
PGF - the proportion of crabs in this study that 
died from ghost fishing. 
We assumed that tagged crabs with a condition clas- 
sified as “unknown” had either died from causes other 
than ghost fishing (e.g., fishing mortality and poaching) 
or had molted. Additionally, we assumed that crab with 
tags classified as “derelict” had died from causes other 
than ghost fishing, had molted, or had been killed in 
ghostfishing gear. Therefore, we divided the crabs with 
unknown conditions or derelict tags into categories on 
the basis of the relative observed frequency of each 
cause of mortality. Tags classified as lost were kept as 
a separate category because no data on what happened 
to the tag were available. 
Divers found 20 tagged crabs and hundreds of 
closely aggregated crabs alive in intact ghost pots and 
released them. In most cases, it was not possible to 
record the numbers of untagged live crabs released by 
divers because of the large numbers of those crabs and 
because visibility was greatly limited by silt disturbed 
from pot handling; therefore, only rough estimates 
were made. Two of the tagged crabs that were released 
later died in another crab pot. Given the length of time 
the crabs were likely in the pots, it is unlikely that 
many of these crabs would have escaped alive (High 
and Worlund, 1979). 
To estimate an upper and lower limit for the mor- 
tality rate of crabs from ghost fishing in the absence 
of diver interference, we calculated the loss rates with 
the assumption that none of the crabs released from 
pots would have died (conservative estimate) and with 
the assumption that all of them would have died (up- 
per estimate). For the conservative estimate, we used 
the date the crab died, molted, or was lost after having 
been released as the date of the final condition. For the 
upper estimate, we classified the crab as a “ghostfish- 
ing mortality” and used the date the crab was released 
from the pot as the date of the final condition of the 
crab, as if the crab had been found dead in the pot. We 
performed a logistic regression, using sex as a factor 
and CL as a covariate, to examine whether size or sex 
of a crab made it more likely that it would be caught 
or killed in ghostfishing gear. 
Results 
The size of tagged crabs ranged from 42 to 162 mm CL 
(mean=100 mm CL). Of the 192 crabs tagged over the 
course of multiple studies, 90 were female and 102 were 
male. The number of crabs tagged each year ranged 
from 2 (in 2007 and 2008) to 20 (in 1996) and averaged 
1 1 crabs per year. Crabs were tracked for an average 
of 147 days and a maximum of 468. The total number 
of observations on tagged crabs was 3300. Molting was 
Table 1 
Final conditions determined in this study for the 192 
red king crabs ( Paralithodes camtschaticus) or their 
tags that were tracked by acoustic tagging in associa- 
tion with other projects over the period of 1991-2008 
in Womens Bay, Kodiak Island, Alaska. “Molted” means 
the tagged crab molted. “Unknown” means the tag was 
recovered by divers but it could not be determined if the 
tagged crab had molted or died. “Lost” means the tag 
could not be located from the surface. “Derelict” means 
the tagged crab either molted or died as evidenced by 
the fact the tag stopped moving but the condition was 
not determined by diving. “Other mortality” means the 
tagged crab died from a cause other than ghost fishing. 
“Ghostfishing mortality” means the tagged crab died 
in ghostfishing gear. “Handling mortality” means the 
tagged crab died as a result of the tagging process. “Tag 
failure” means the tag failed to adhere to the tagged 
crab’s carapace. 
Final condition 
Number 
Percentage 
Molted 
76 
39.6 
Unknown 
48 
25.0 
Lost 
22 
11.5 
Derelict 
16 
8.3 
Other mortality 
13 
6.8 
Ghostfishing mortality 
13 
6.8 
Handling mortality 
3 
1.6 
Tag failure 
1 
0.5 
the most common final condition of a tagged crab, fol- 
lowed by unknown condition (Table 1). Three crabs mi- 
grated out of Womens Bay during the project, but they 
were tracked and their final condition was determined 
as was done for all other tagged crabs. Thirteen crabs 
died in ghostfishing gear, and 13 more crabs had other 
sources of mortality. 
Known sources of mortality included predation by 
sea otters (3 crabs) and an octopus (1 crab) and likely 
poaching by humans (the tags of 2 crabs below the 
legal-size limit were returned to researchers with im- 
plausible stories about how the tags were obtained). 
Legal fishing did not account for a single mortality of 
a tagged crab during this study. Of the 13 crabs that 
died in ghostfishing gear, 12 crabs were caught in ghost 
pots and 1 crab was found in a ghost gill net. As for 
all the crabs caught in ghostfishing gear and released 
alive by divers, they all were found in the same type 
of gear: ghost pot. 
Crabs that died in ghostfishing gear ranged from 
69 to 160 mm CL and included 4 ovigerous females. 
Crabs caught and released by divers ranged from 66 
to 141 mm CL and included 5 ovigerous females. One 
difference between the crabs that died and the crabs 
that were released was the number of days between 
the time when the crab was caught in the trap (as es- 
timated from surface tracking) and the time when a 
