40 
Abstract — We compared the capture 
efficiency and catch dynamics of col- 
lapsible square and conical pots used 
in resource assessment and harvest- 
ing of red king crabs ( Paralithod.es 
camtschaticus [Tilesius, 1815]) in the 
Barents Sea. After two days of soak- 
ing, square pots caught three times 
as many crabs as conical pots, and 
their catches consisted of a higher pro- 
portion of male crabs and male crabs 
larger than 160 mm carapace length 
compared to the catches in the coni- 
cal pots. Catches in the square pots 
did not increase as soak times were 
increased beyond two days, which 
indicates equilibrium between the 
rate of entries into and the rate of 
exits from the pots. Catches in conical 
pots, however, increased with increas- 
ing soak times up to eight days, the 
longest soak time examined in this 
study. These findings demonstrate 
the higher efficiency of square pots 
and the importance of understanding 
catch dynamics when making popu- 
lation assessments based on catch- 
per-unit-of-effort data. The favorable 
catch characteristics and handling 
properties of the collapsible square 
pot may make this pot design suitable 
for other crab fisheries, as well. 
Manuscript submitted: 16 January 2007. 
Manuscript accepted 3 August 2007. 
Fish. Bull. 106:40-46(2008). 
The views and opinions expressed or 
implied in this article are those of the 
author and do not necessarily reflect 
the position of the National Marine 
Fisheries Service, NOAA. 
Efficiency and catch dynamics of collapsible square 
and conical crab pots used in the red king crab 
( Paralithodes camtschaticus ) fishery 
Stian Stiansen 1 ' 2 
Anders Ferno 1 - 2 -* 
Dag Furevik 1 * 
Terje Jergensen (contact author) 1 * 
Svein Lokkeborg 1 * 
Email address forT. Jorgensen: ter|ej@imr.no 
1 Institute of Marine Research 
PO Box 1870 Nordnes 
NO-5817 Bergen, Norway 
2 Department of Biology 
University of Bergen 
NO-5020 Bergen, Norway 
The introduction of red king crab 
(Paralithodes camtschaticus [Tilesius, 
1815]) (RKC) in the Barents Sea in 
the 1960s led to a commercial pot fish- 
ery in this area. In Norwegian waters, 
surveys conducted with conical pots 
in order to estimate population abun- 
dance on the basis of catch-per-unit-of- 
effort (CPUE) data began in 1993. In 
2002, the first licenses for commercial 
fishing of RKC were issued. To har- 
vest this new resource, an efficient, 
selective, and habitat-friendly fishing 
gear is required. Only small coastal 
fishing vessels (< 15 m) are licensed 
in the Norwegian RKC fishery and 
these vessels are too small to effec- 
tively operate large rigid pots. Ini- 
tially, conical pots were used because 
they have been used in the Russian 
and Japanese fishery for king crabs 
(Ivanov, 2002). Preliminary studies 
with a modified square, collapsible 
cod pot showed higher catches, and 
according to the fishermen, the square 
pot had better handling properties 
than the conical pot. The industry 
therefore requested adoption of this 
modified square pot design in the 
RKC fishery. 
The introduction of new fishing 
gear in the commercial fishery, and 
subsequently in population assess- 
ments, requires a knowledge of its 
catching properties in order to ensure 
sustainable harvesting practices and 
to interpret changes in CPUE data 
(Hilborn and Walters, 1992; Nizyaev 
and Bukin, 2002). Thus, before the 
collapsible square pot was adopted, 
fishing trials had to be carried out to 
compare the catching efficiency and 
selection characteristics of the square 
pot with those of the conical pot. 
Fishing with pots without escape- 
preventing devices (e.g., triggers or 
soft-eyed entrances) is a dynamic 
process, in which the ratio of crabs 
entering the pot to those escaping the 
pot usually decreases as soak time 
increases (Zhou and Shirley, 1997a; 
Watanabe and Yamasaki, 1999). Our 
fishing trials were therefore carried 
out with soak time as an explanatory 
variable. 
The objectives of the experiment 
were to compare the two different pot 
designs with regard to 1) catch effi- 
ciency, 2) size distribution and sex 
ratio of the catch, and 3) the degree 
to which these characteristics (catch 
efficiency, size distribution, and sex 
ratio) are affected by soak time. Such 
* signifies equal authorship. 
