Movements of Adult Female Dungeness Crabs (Cancer magister) In Northern California Based on Tag Recoveries

1985 ◽  
Vol 42 (5) ◽  
pp. 919-926 ◽  
Author(s):  
Nancy Diamond ◽  
David G. Hankin
Keyword(s):  
Adult Female ◽  
Fishing Effort ◽  
Nonparametric Tests ◽  
Northern California ◽  
Cancer Magister ◽  
Directed Movement ◽  
Location Data ◽  
Movement Data ◽  
Large Numbers ◽  
Dungeness Crabs

Of 11072 adult female Dungeness crabs (Cancer magister) tagged and released in northern California, 463 were recovered with useful location data that could be used for analyses of crab movement patterns. Although qualitative analyses of movement data suggested possible directed northward movement during winter months, application of two nonparametric tests of movement directionality (the Rayleigh test and Moore's test) failed to support significant directed movement during winter. Large numbers of tagged crabs were recovered inshore of release in shallow sandy areas during spring months, but valid statistical analyses of spring movement data were ruled out by concentration of fishing effort in shallow waters during spring. Nevertheless, recovery of large numbers of tagged females in inshore areas during spring is entirely consistent with an hypothesis of spring inshore movement of females for molting, mating, and later extrusion of egg masses. This hypothesis can be constructed on the basis of information independent of tag recovery data. The most striking finding was that 46% of all recovered crabs were recaptured within 2 km of original release sites; many of these crabs had been at large more than 1 yr. Adult female Dungeness crabs appear to constitute extremely localized stocks in northern California.

Effort Dynamics of the Northern California Dungeness Crab (Cancer magister) Fishery

1983 ◽  
Vol 40 (3) ◽  
pp. 337-346 ◽  
Author(s):  
Louis W. Botsford ◽  
Richard D. Methot Jr. ◽  
Warren E. Johnston
Keyword(s):  
Population Dynamics ◽  
Time Lag ◽  
Substantial Effect ◽  
Fishing Effort ◽  
Northern California ◽  
Dungeness Crab ◽  
Cancer Magister ◽  
Harvest Rate ◽  
Predator Prey ◽  
Market Expansion

Knowledge of the dynamic response of fishing effort to abundance is essential to a complete understanding of the cycles in catch in the northern California Dungeness crab fishery. In this fishery there is a lagged response of harvest rate to changes in abundance that is caused either by a time lag in fishermen entering and leaving the fishery following changes in abundance, a lag in market expansion and contraction following changes in abundance, or a combination of both. The time lag in this response appears to have decreased over the past 30 yr. This lagged response is a potential cause of the cycles. However, neither of the two potential cyclic mechanisms examined here, a predator–prey mechanism (with man as the predator) and a price-dependent escapement mechanism (with price dependent on past catch), is a cause of these cycles. Although time-varying effort does not cause the cycles, it does have a substantial effect on the resulting catch record and population dynamics. If there is a density-dependent recruitment mechanism in this population as proposed earlier, the presence of this lagged response would cause the period of observed cycles to be longer than would be expected on the basis of population dynamics alone. Hence, previous estimates of the expected period of cycles from various population mechanisms are low. Removal of this response is a potential means of stabilizing this fishery.Key words: effort, Dungeness crab, harvest rate, predator–prey, price, stability, age, cycles

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 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.

scholarly journals Distinguishing technology from biology: a critical review of the use of GPS telemetry data in ecology

2010 ◽  
Vol 365 (1550) ◽  
pp. 2303-2312 ◽  
Author(s):  
Mark Hebblewhite ◽  
Daniel T. Haydon
Keyword(s):  
Animal Ecology ◽  
Animal Movement ◽  
Gps Telemetry ◽  
Long Distance ◽  
Location Data ◽  
The Past ◽  
Movement Data ◽  
Migratory Songbirds ◽  
Spatio Temporal ◽  
Gps Devices

In the past decade, ecologists have witnessed vast improvements in our ability to collect animal movement data through animal-borne technology, such as through GPS or ARGOS systems. However, more data does not necessarily yield greater knowledge in understanding animal ecology and conservation. In this paper, we provide a review of the major benefits, problems and potential misuses of GPS/Argos technology to animal ecology and conservation. Benefits are obvious, and include the ability to collect fine-scale spatio-temporal location data on many previously impossible to study animals, such as ocean-going fish, migratory songbirds and long-distance migratory mammals. These benefits come with significant problems, however, imposed by frequent collar failures and high cost, which often results in weaker study design, reduced sample sizes and poorer statistical inference. In addition, we see the divorcing of biologists from a field-based understanding of animal ecology to be a growing problem. Despite these difficulties, GPS devices have provided significant benefits, particularly in the conservation and ecology of wide-ranging species. We conclude by offering suggestions for ecologists on which kinds of ecological questions would currently benefit the most from GPS/Argos technology, and where the technology has been potentially misused. Significant conceptual challenges remain, however, including the links between movement and behaviour, and movement and population dynamics.

scholarly journals Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

2012 ◽  
Vol 90 (5) ◽  
pp. 663-676 ◽  
Author(s):  
A.M. Pagano ◽  
G.M. Durner ◽  
S.C. Amstrup ◽  
K.S. Simac ◽  
G.S. York
Keyword(s):  
Sea Ice ◽  
Adult Female ◽  
Open Water ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Long Distance ◽  
Gps Collars ◽  
Movement Data ◽  
Global Positioning ◽  
Ice Conditions

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004–2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

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.”

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