scholarly journals The Sperm Plug Is a Reliable Indicator of Mating Success in Female Dungeness Crabs, Cancer Magister

2004 ◽  
Vol 24 (2) ◽  
pp. 314-326 ◽  
Author(s):  
Shauna J. Oh ◽  
David G. Hankin
Keyword(s):  
Mating Success ◽  
Reliable Indicator ◽  
Cancer Magister ◽  
Dungeness Crabs

Does intense fishing on males impair mating success of female Dungeness crabs

1997 ◽  
Vol 54 (3) ◽  
pp. 655-669 ◽  
Author(s):  
D G Hankin ◽  
T H Butler ◽  
P W Wild ◽  
Q -L Xue
Keyword(s):  
Mating Success ◽  
Egg Production ◽  
Carapace Width ◽  
Minimum Size ◽  
Cancer Magister ◽  
Worst Case ◽  
Mature Adult ◽  
Commercial Harvest ◽  
Size Limits ◽  
Dungeness Crabs

Commercial capture of female Dungeness crabs, Cancer magister, is prohibited and minimum size limits for commercial harvest of male crabs are designed to allow most males to mate at least once before capture. Annual exploitation rates often exceed 90%, however, and the resulting scarcity of large males might reduce mating success among large females. We present new data regarding (i) sizes of male and female crabs collected in premating embraces, (ii) carapace width frequencies of female Dungeness crabs, (iii) presence of sperm plugs and sperm, and (iv) fecundity. Minimum carapace width of hard-shelled mating males typically exceeds postmolt carapace width of soft-shelled females (i), but female Dungeness crabs exceeding the minimum legal size of males usually account for less than 5% of mature adult female crabs (ii), and sublegal-sized males actively participate in mating (i). Remnants of sperm plugs, definitive indicators of mating, were found in 97.5% of recently molted large females (iii), suggesting that virtually all molting females mate regardless of size. On the basis of (ii) and (iv), hypothetical worst-case calculations, assuming that no large females could find mates, suggest that total egg production would be reduced by no more than 2-25% among molting female crabs.

scholarly journals Injury in trapped Dungeness crabs (Cancer magister)

2007 ◽  
Vol 64 (3) ◽  
pp. 464-472 ◽  
Author(s):  
Julie S. Barber ◽  
J. Stanley Cobb
Keyword(s):  
Laboratory Experiment ◽  
Mating Success ◽  
Injury Rate ◽  
Size Ratio ◽  
Crab Species ◽  
Target Species ◽  
Cancer Magister ◽  
Injury Rates ◽  
Crab Density ◽  
Dungeness Crabs

Abstract Barber J. S., and Cobb, J. S. 2007. Injury in trapped Dungeness crabs (Cancer magister). – ICES Journal of Marine Science, 64: 464–472. Although traps are the most effective fishing equipment used to capture crabs they can also result in indirect damage to target species. We examined the effect of trap-soak time, crab density, and the legal to sublegal size ratio on injury rates to male Dungeness crabs, Cancer magister. Our field results show that injuries increase significantly with increased trap-soak time, and as a consequence of different size ratios (crabs in traps with a greater ratio of sublegal crabs had more injuries). The injury rate was independent of density. In a laboratory experiment, injured crabs were as capable as intact crabs of obtaining, defending, and consuming food. However, studies on other crab species indicate that injury reduces growth, delays reproduction, decreases mating success, and increases mortality. If the costs of injury are similar for Dungeness crabs, this could diminish the rate of recruitment into the fishery.

scholarly journals Ventilation, Oxygen Uptake and Haemolymph Oxygen Transport, Following Enforced Exhausting Activity in the Dungeness Crab Cancer Magister

1979 ◽  
Vol 80 (1) ◽  
pp. 271-285 ◽  
Author(s):  
B. R. McMAHON ◽  
D. G. McDONALD ◽  
C. M. WOOD
Keyword(s):  
Cardiac Output ◽  
Oxygen Uptake ◽  
Oxygen Transport ◽  
Lactate Concentration ◽  
Fold Increase ◽  
Oxygen Extraction ◽  
Oxygen Release ◽  
Cancer Magister ◽  
Metabolic Scope ◽  
Dungeness Crabs

Scaphognathite and heart-pumping frequencies, ventilation volume, cardiac output, oxygen uptake and oxygen transport by haemolymph have been studied in unrestrained Dungeness crabs (Cancer magister) before, immediately after, and during recovery from 20 min of enforced exhausting activity. Exercise increased oxygen uptake 4-fold. This increase was achieved by more than 2-fold elevation of both ventilation volume and cardiac output and by greater participation of haemocyanin in oxygen delivery. The elevated ventilation volume resulted entirely from an increase in scaphognathite pumping frequency, while the rise in cardiac output resulted largely from increase in stroke volume. Prior to exercise haemocyanin accounts for less than 50% of the oxygen delivered to the tissues. Following exercise this increases to over 80%, the additional oxygen release being mediated by a depression of prebranchial oxygen tension and a substantial Bohr effect resulting from build up of lactate ion in the haemolymph and subsequent fall in pH. These changes allowed % oxygen extraction from branchial water to be maintained at 28% despite a 2-fold increase in ventilation volume, and allowed an increase in %. oxygen extraction by the tissues. Despite these changes oxygen supply fell below demand during exercise, and considerable anaerobic metabolism resulted, as evidenced by a 9-fold increase in haemolymph lactate concentration. The resulting oxygen debt required 8–24 h for repayment. Aerobic metabolic scope, and mechanisms of increasing oxygen uptake and transport in this crab are compared with those of a range of fish species.

Heat-Pasteurization Process for Inactivation of Nonproteolytic Types of Clostridium botulinum in Picked Dungeness Crabmeat

1997 ◽  
Vol 60 (8) ◽  
pp. 928-934 ◽  
Author(s):  
M. E. PETERSON ◽  
G. A. PELROY ◽  
F. T. POYSKY ◽  
R. N. PARANJPYE ◽  
F. M. DONG ◽  
...  
Keyword(s):  
Clostridium Botulinum ◽  
Temperature Treatment ◽  
Heat Processing ◽  
Type B ◽  
Cancer Magister ◽  
Enrichment Medium ◽  
Heat Resistant ◽  
Heat Pasteurization ◽  
D Values ◽  
Dungeness Crabs

Development of a heat-pasteurization process is described for picked meat of Dungeness crabs (Cancer magister) contained in oxygen-impermeable flexible pouches, For each time-temperature treatment, 30 samples, each inoculated with an equal mixture of three strains of C. botulinum nonproteolytic type B, for a total of 107 spores, provided the basis for calculation of the thermal resistance (a 7D process). Following heat processing, the crabmeat was removed from the pouches and transferred to enrichment medium where it was incubated anaerobically for 150 days. Endpoints at which spores survived were determined by the presence of toxin in the enrichment medium. Process times ranged from 90 min at 88.9°C to 20.3 min at 94.4°C. D values (the time at each temperature required to reduce the inoculum by 1 log) ranged from 12.9 for the 88.9°C process to 2.9 for the 94.4°C process. The relative sterilization value, F0 was .054 and the pasteurization value, , was 240. This pasteurization process safely extends refrigerated shelf life by inactivating spores of Clostridium botulinum nonproteolytic types B, E, and F and also non-spore-forming pathogens such as Listeria monocytogenes. The process does not, however, inactivate the heat-resistant proteolytic strains of C. botulinum or other more heat-resistant spore-formers. The packages and master cartons of the pasteurized product, therefore, should be labeled “Keep refrigerated—Continuous refrigeration below 38°F (3.3°C) required.”

A ciliate infection (Paranophrys sp.) in laboratory-held Dungeness crabs, Cancer magister

1981 ◽  
Vol 37 (2) ◽  
pp. 201-209 ◽  
Author(s):  
David A. Armstrong ◽  
Eugene M. Burreson ◽  
Albert K. Sparks
Keyword(s):  
Cancer Magister ◽  
Dungeness Crabs
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