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.

Regional Variation in the Size of Maturity of Two Species of Tanner Crab (Chionoecetes bairdi and C. opilio) in the Eastern Bering Sea, and Its Use in Defining Management Subareas

1981 ◽  
Vol 38 (2) ◽  
pp. 163-174 ◽  
Author(s):  
David A. Somerton
Keyword(s):  
Bering Sea ◽  
Regional Variation ◽  
Carapace Width ◽  
Minimum Size ◽  
Computer Technique ◽  
Eastern Bering Sea ◽  
Commercial Harvest ◽  
Tanner Crab ◽  
Size Limits ◽  
Chionoecetes Bairdi

Minimum size limits for the commercial harvest of tanner crab (Chionoecetes bairdi and C. opilio) are based on the sizes of sexual maturity. Establishing such size limits in the eastern Bering Sea is complicated by a large regional variation in the size of maturity. A computer technique was developed which partitioned the eastern Bering Sea into subareas that were relatively homogeneous with respect to the size of maturity. The best partitioning for C. bairdi was a separation of the eastern Bering Sea into two subareas along 167°15′N longitude. No acceptable partitioning could be found for C. opilio. The size of 50% maturity for male C. bairdi was estimated to be 108.9 mm carapace width in the western subarea and 117.0 mm in the eastern subarea. The size of maturity upon which the current minimum size for C. bairdi is based is nearly the same as the size estimated for the western subarea but significantly less than the size estimated for the eastern subarea.Key words: crabs, size of maturity, Chionoecetes bairdi, Chionoecetes opilio, tanner crab, eastern Bering Sea

Mating Success of Female Dungeness Crabs (Cancer magister) in Oregon Coastal Waters

2012 ◽  
Vol 31 (3) ◽  
pp. 835-839 ◽  
Author(s):  
Paul H. Dunn ◽  
Alan L. Shanks
Keyword(s):  
Mating Success ◽  
Coastal Waters ◽  
Cancer Magister ◽  
Dungeness Crabs

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

Exploitation and Mortality of Male Dungeness Crabs (Cancer magister) Near Tofino, British Colombia

1989 ◽  
Vol 46 (9) ◽  
pp. 1609-1614 ◽  
Author(s):  
Barry D. Smith ◽  
Glen S. Jamieson
Keyword(s):  
Frequency Analysis ◽  
Carapace Width ◽  
Fishing Mortality ◽  
Cancer Magister ◽  
Commercial Catch ◽  
Small Component ◽  
Size Frequency ◽  
British Colombia ◽  
Intense Exploitation ◽  
Dungeness Crabs

Male Dungeness crabs (Cancer magister) were sampled by traps and monitored by tagging as they moulted and entered the fishery near Tofino, British Columbia, from April 1985 until March 1987. Males first recruited to the fishery after moulting from the μ = 129-mm CW (carapace width) to the μ = 156-mm CW normal instar. Sublegalsized males (< 154 mm notch-to-notch CW) in the μ = 156-mm CW instar (≈ 42% of this instar) were found to have a high annual natural mortality (M = 2.9–4.5), with < 10% surviving to legal size. Legal-sized males experienced high annual fishing mortality (F = 5.1–6.9), so consequently a small component of the commercial catch consisted of males in larger instars. Size frequency analysis, which measured the percent exploitation of the μ = 156-mm CW instar, indicated that legal-sized males remained in relatively low abundance during this year-round fishery because of intense exploitation. Mark–recovery data and size frequency analysis also indicated this intense fishery was sustained throughout most of the year by a protracted moulting season. Consequently, we observed prolonged periods with a high percentage of less desirable soft-shelled males in the commercial catch.

Estimation of Size-Specific Molting Probabilities in Adult Decapod Crustaceans Based on Postmolt Indicator Data

1989 ◽  
Vol 46 (10) ◽  
pp. 1819-1830 ◽  
Author(s):  
Michael S. Mohr ◽  
David G. Hankin
Keyword(s):  
Adult Female ◽  
Binary Classification ◽  
Carapace Width ◽  
Estimation Procedure ◽  
Survival Ratio ◽  
Cancer Magister ◽  
Constant Variance ◽  
Indicator Data ◽  
Dungeness Crabs

For crustaceans that exhibit a well-defined molting season, postmolt indicator methods may be used to classify a sample of animals collected after the molting season into those that have molted and those that have failed to molt. This binary classification of a sample may be used to estimate size-specific molting probabilities. We derive maximum likelihood estimators for these molting probabilities, and for the variances of estimated molting probabilities, based on such postmolt indicator data. Estimators assume that the premolt–postmolt relation is linear with an additive and normally distributed error term of constant variance and, in their simplest form, assume that the ratio (Ri) of size-specific survival probabilities through the molting season for molting as compared with nonmolting individuals is known. For the more likely situation in which only a plausible range for Ri is specifiable, an estimation procedure is proposed which minimizes the maximum possible error (mean square error) of the molting probability estimator over this range. We illustrate application of estimators using shell condition data collected from the northern California population of adult female Dungeness crabs (Cancer magister). Estimated annual molting probabilities for adult female Dungeness crabs were greater than 0.90 for crabs less than 135 mm carapace width, but then declined rapidly until they were near zero for crabs exceeding 160 mm carapace width. This conclusion was not substantively affected by choices of a survival ratio ranging from 0.4 to 1.0.

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.

Comparing size-limit and quota policies to increase economic yield in a lobster fishery

2015 ◽  
Vol 72 (9) ◽  
pp. 1292-1305 ◽  
Author(s):  
Richard McGarvey ◽  
André E. Punt ◽  
Janet M. Matthews ◽  
John E. Feenstra ◽  
Caleb Gardner ◽  
...  
Keyword(s):  
Egg Production ◽  
Maximum Size ◽  
Catch Rate ◽  
Minimum Size ◽  
Control Rule ◽  
Exploitation Rate ◽  
Harvest Control Rule ◽  
Lobster Fishery ◽  
Size Limits ◽  
Rule Setting

To advance economic and sustainability objectives in a lobster fishery, four broadly different management policies were evaluated: minimum and maximum size limits, constant catch quotas, and quota set yearly in proportion to the previous year’s catch per unit effort (CPUE). The performance of each policy was evaluated based on its discounted economic yield, together with egg production, catch, and catch stability. Maximum size limits performed poorly for all indicators. Raising the minimum size increased economic yield by improving yield-per-recruit. Output controls, both constant and dynamic, uniformly outperformed size limits, leading to substantially higher economic yield and egg production. A dynamic harvest control rule, setting quota in proportion to the previous year’s catch rate, achieved the highest economic yield, catch, and egg production over 20 years. The optimal (30%) exploitation rate under this policy produced a 182% improvement in economic yield compared with a baseline strategy of only minimum size, but led to a mean year-to-year change in quota of 11.5% in response to yearly variable recruitment. This quota-setting management regime is straightforward to implement, using only catch rate as input. When absolute exploitation rate estimates are not available, this quota-setting harvest control rule can be constructed using only a target level of effort.

Diel Activity of an Estuarine Population of Dungeness Crabs, Cancer Magister, in Relation to Feeding and Environmental Factors

1984 ◽  
Vol 4 (3) ◽  
pp. 390-403 ◽  
Author(s):  
Bradley G. Stevens ◽  
David A. Armstrong ◽  
James C. Hoeman
Keyword(s):  
Environmental Factors ◽  
Diel Activity ◽  
Cancer Magister ◽  
Dungeness Crabs

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.

Growth of the edible crab (Cancer pagurusL.) off south-west England

1974 ◽  
Vol 54 (4) ◽  
pp. 803-823 ◽  
Author(s):  
D. B. Bennett
Keyword(s):  
Egg Production ◽  
Carapace Width ◽  
Large Male ◽  
Annual Growth ◽  
Published Data ◽  
North East ◽  
South West ◽  
Males And Females ◽  
Moulting Cycle ◽  
South West England

Moult increments, annual moult frequency and hence annual growth were determined from suture-tagged edible crabs (Cancer pagurusL.) released and recaptured off Devon, Cornwall, and Dorset.The average moult increments of males and females at a premoult carapace width of 100 mm were similar; at larger sizes the average moult increment of females was considerably less than that of males. Annual moult frequency ofC. pagurusin south-west England decreased with increase in size, females more so than males.As a result of the smaller moult increments and lower moult frequency of females, their annual growth is considerably less than that of males. This appears to be the result of three aspects of sex and reproduction: (1) reduction in moult increments, probably as a result of competition for nutritive resources between egg production and body growth; (2) the interruption of the moulting cycle by successive annual spawnings from a single impregnation at the previous moult; and (3) accentuation of the larger increments in weight at moulting of male crabs due to the allometric growth of their chelae. A consequence of the higher growth rate of males is the presence of very large male crabs – a distinctive feature of the population structure of the stock off south-west England.The growth of C.pagurusin south-west England was compared with published data for stocks off the east and north-east coast. Moult increments were similar for both areas, but there were considerable differences in the moult frequencies. In the south-west, males moult more frequently than females; the opposite is the case for the east and north-east crab stocks. A valid reason for this difference has not yet been established.

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