234 
Fishery Bulletin 111(3) 
The subjects of this study were snow crab ( Chionoece - 
tes opilio) and southern Tanner crab (C. bairdi). Both 
species are heavily fished along the continental shelf 
of the Bering Sea and the Sea of Okhtosk of the Rus- 
sian Federation. Snow and southern Tanner crabs are 
shallow-water species. They generally live from subtidal 
areas to a depth of -450 m, although snow crab has also 
been found in much deeper water (Jadamec et ah, 1999; 
Mihailov et ah, 2003; Slizkin, 2010). In Russian waters, 
the snow crab inhabits environments with a tempera- 
ture range from -1.8°C to 7°C. The southern Tanner 
crab is usually found in temperatures of 2-3°C, avoiding 
bottom areas where a cold intermediate layer persists 
for a long time (Slizkin et ah, 2001; Slizkin, 2010). In 
the area of overlap where the 2 species occur together, 
the abundance ratio of these crabs is strongly variable. 
Unlike many other crustaceans, snow and southern 
Tanner crabs undergo a terminal molt before they be- 
come mature adults (Conan and Comeau, 1986; Comeau 
and Conan, 1992; Sainte-Marie et ah, 1995). After their 
terminal molt, adult males of these species are avail- 
able to pot fishing for only 0. 5-3.0 years because their 
carapaces become progressively fouled and ultimately 
deteriorate. Also after their terminal molt, crabs can 
no longer grow and regenerate lost limbs. Adult males 
that lack a limb are returned to the sea after a catch is 
sorted and because discarded crabs may be re-injured, 
the number of individuals that lack limbs increases in 
heavily fished populations. High-density aggregations 
of female snow and southern Tanner crabs are found 
to occur in different areas from those where males are 
caught. Therefore, female snow and southern Tanner 
crabs are rarely encountered in catches. The percent- 
age of undersize males (carapace width <100 mm) usu- 
ally does not exceed 5-10% of the total catch because of 
selectivity characteristics of trap gear. Therefore, dam- 
aged and “dirty” male snow and southern Tanner crabs 
may often compose a significant portion of the discards 
that occur in pot fishing. Although these crabs do not 
have market value, they may be involved in reproduc- 
tion. It is probable that these crabs may be recaptured 
multiple times throughout their life and, therefore, 
may be exposed potentially to cumulative effects of 
fishing procedures. 
This study was designed to investigate the effects 
of decompression and other stressors associated with 
pot hauling on the physical condition of adult male 
snow and southern Tanner crabs that had completed 
a terminal molt between 1.5 years and a few months 
previously. We conducted our experiments in the field. 
Crabs taken from the commercial catch were placed in 
commercial pots. The pots were then sunk and hauled 
back to the surface at different frequencies. With this 
approach, multiple factors in addition to decompression 
can affect the survivability of animals. These other fac- 
tors include significant changes in environmental condi- 
tions during hauls, interaction of crabs with the gear, 
and exposure to the air. Therefore, to specifically assess 
the effects of decompression on crab physical condi- 
tion, histopathological changes in organs and tissues 
of crab caused by air-bubble disease were studied. Our 
approach was derived from the histological evidence of 
Johnson (1976), who found that the gills, heart, and an- 
tennal gland were the organs of blue crab ( Callinectes 
sapidus) most severely affected by exposure to water 
supersaturated with air to simulate decompression ef- 
fects. Bubbles persisted in the gills longer (more than a 
month) than in other organs of blue crab. We assumed 
that gill dysfunction caused by decompression would 
greatly affect the survivability of crabs after their re- 
lease. Because of the logistical constraints of direct ex- 
perimental research on gill function in the field, we in- 
vestigated physiological parameters that could be used 
to estimate gill function disorders. 
We selected hemocyanin (He) as the indicator for the 
assessment of the effects of pot fishing on the physical 
condition of the snow crab and southern Tanner crab. 
He is a copper-containing respiratory pigment that in- 
creases solubility of oxygen (O 2 ) by a factor of 2-4 and 
accounts for from 70% to more than 90% of the total 
protein concentration in the hemolymph of crustaceans 
(Truchot, 1992). Structural and functional variability 
of crustacean He has been shown to be of great impor- 
tance for the adaptive condition of these organisms in 
response to metabolic changes and environmental stim- 
uli (Bridges, 2001; Giomi and Beltramini, 2007). There- 
fore, we hypothesized that physiological alterations 
caused by impairment of respiratory function of the gills 
of snow and southern Tanner crabs could be correlated 
with changes in the structure and concentration of He. 
Plasma ion concentrations — for sodium ion (Na + ), potas- 
sium ion (K + ), chlorine ion (Cl - ), calcium ion (Ca 2+ ), and 
magnesium ion (Mg 2+ ) — also were measured to examine 
ionoregulatory changes at the gills of affected crabs. 
During our experiments, factors other than decompres- 
sion had an effect on crabs, including starvation and air 
exposure. Therefore, we also conducted experiments to 
assess the separate effects of starvation and air expo- 
sure on He. 
We had the following objectives: 1) the investiga- 
tion of histopathological deterioration of organs and tis- 
sues in snow and southern Tanner crabs subjected to 
pot hauling; 2) an analysis of the relationship between 
hauling intensity (the number and frequency of hauling 
events) and animal stress responses, including changes 
in behavior and biochemical parameters of hemolymph; 
and 3) an analysis of the utility of biochemical assays 
of He for prediction of survivability of snow and south- 
ern Tanner crabs subjected to hauling and discarding 
processes. 
Materials and methods 
Study areas 
Snow crab and southern Tanner crab were collected 
during 5 fishing voyages in 2006, 2008, and 2010 in 
