126 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
a* established in 1881 
Spencer F. Baird 
First U S Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
A comparison of laboratory-holding and tag- 
return methods for evaluating delayed mortality 
of Dungeness crab (Cancer magister) discarded in 
Oregon fisheries 
Email address for contact author: noelle.yochum@noaa.gov 
1 Department of Fisheries and Wildlife and 
Coastal Oregon Marine Experiment Station 
Oregon State University 
2030 SE Marine Science Drive 
Newport, Oregon 97365 
Present address for contact author: Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE 
Seattle, Washington 98115 
2 Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2030 SE Marine Science Drive 
Newport, Oregon 97365 
3 Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE 
Seattle, Washington 98115 
Abstract— -The delayed mortality 
rate of crab discarded during fishing 
operations can be under- or over¬ 
estimated in laboratory holding ex¬ 
periments, given the unnatural con¬ 
ditions and the short-term duration 
of these experiments. To evaluate 
the extent to which a method af¬ 
fects accuracy in these estimations, 
we compared mortality rates estab¬ 
lished through laboratory holding 
with mortality inferred from a year- 
and-a-half long tag-return study of 
Dungeness crab (Cancer magister) 
discarded in Oregon crab fisheries. 
The reflex action mortality predic¬ 
tor (RAMP) approach, which relates 
reflex impairment to probability of 
mortality, was applied in both stud¬ 
ies. Similar patterns in mortality- 
and tag return- rates with respect 
to fishery, sex, reflex impairment, 
shell hardness, and injury from the 
2 studies lends support to the reli¬ 
ability of the laboratory-generated 
mortality rates. However, results 
suggest that mortality rates deter¬ 
mined in captivity are likely under¬ 
estimated when crab are dropped a 
distance of greater than 6 m (and 
potentially less) back to water. This 
underscores the importance of de¬ 
termining the contribution to mor¬ 
tality of variables in the capture, 
handling, and discard process that 
are not incorporated in a study to 
estimate mortality of discarded ani¬ 
mals. Both studies also highlighted 
the significance of sample size when 
applying the RAMP approach to 
a fishery with low rates of discard 
mortality. 
Manuscript submitted 1 June 2017. 
Manuscript accepted 13 December 2017. 
Fish. Bull. 116:126-141 (2018). 
Online publication date: 26 January 2018. 
doi: 10.7755/FB.116.1.2 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Noelle Yochum (contact author) 1 
Allan W. Stoner 2 
David B. Sampson 1 
Craig Rose 3 
Mortality can result from the fish¬ 
ing, handling, and discard process 
for nontarget animals, either imme¬ 
diately after capture or after a delay 
(Benaka et ah, 2014). To evaluate 
the mortality of discarded animals 
(henceforth termed “delayed discard 
mortality”), a variety of methods 
have been employed. These include 
the following: 1) captive-holding 
methods (Kennelly et al., 1990; 
Bergmann et ah, 2001; Parker et 
ah, 2003); 2) mark-recapture meth¬ 
ods (Kruse et ah, 1994; Watson and 
Pengilly 1 ; Trumble et ah, 2000); and 
Batson, L. J., and D. Pengilly. 1994. 
Effects of release method on recovery 
rates of tagged red king crabs Paral- 
ithodes camtschaticus in the 1993 Bris- 
3) results from telemetric studies, in¬ 
cluding that use radio- (Raby et ah, 
2012; Nguyen et ah, 2014), acoustic- 
(Pepperell and Davis, 1999; Donald¬ 
son et ah, 2012; Yergey et ah, 2012), 
and satellite-tracking tags (Gallagh¬ 
er et ah, 2014). Also used are 4) in 
situ net pens or cages (Diamond and 
Campbell, 2009; Brownscombe et ah, 
2015; Bower et ah, 2016); and 5) in 
situ visual monitoring (Campbell et 
ah, 2010; Hochhalter, 2012; Brown¬ 
scombe et ah, 2014; Danylchuk et 
ah, 2014). 
In conjunction with methods to 
determine mortality, the reflex action 
tol Bay commercial fishery. Reg. Inf. 
Rep. 4K94-40, 21 p. Alaska Dep. Fish 
Game, Kodiak, AK. 
