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"O'Clair, Robert"
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Seasonal movements and distribution of Dungeness crabs Cancer magister in a glacial southeastern Alaska estuary
The movements of 10 female and 8 male adult Dungeness crabs, Cancer magister (Dana, 1852), were monitored biweekly to monthly with ultrasonic biotelemetry for periods ranging from 73 to 555 d. Female and male crabs had different seasonal patterns of habitat use, depth distribution, and activity. The general pattern for female crabs was: (1) a relatively inactive period between November and mid-April at depths below 20 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) abrupt movement into shallow water (<8 m) in late April and residence there until early June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; (3) increased activity beginning in July with movement back to deeper water, presumably to forage. Females that molted prior to oviposition did so in June and July. Male crabs occupied deep water (>40 m) from November to April, then concentrated in shallow water (<25 m), segregated from females, until late July. Males were most active in late summer and moved into deeper water (>30 m) near the mouth of the cove in fall. The range of depths were -0.5 to -61.3 m for females and +0.1 to -89.0 m for males. Female crabs showed fidelity to the head of the cove and typically ranged only 1.5 km from there. Male crabs, however, moved up to 7.2 km from the head of the cove, but did not move close to the nearest established population of Dungeness crabs 9.6 km distant. The discrete population of adult Dungeness crabs in Fritz Cove may be representative of most Dungeness crab populations inhabiting shallow embayments of the coastal fjord system of southeastern Alaska.
Journal Article
Behavior of Female Dungeness Crabs, Cancer Magister, in a Glacial Southeast Alaska Estuary: Homing, Brooding-Site Fidelity, Seasonal Movements, and Habitat Use
Abstract
Aspects of the behavior of ovigerous Dungeness crabs (Cancer magister) were studied in Fritz Cove, Alaska. To test fidelity and homing ability of crabs to their brooding site, we ultrasonically tagged eight ovigerous crabs and transplanted them 1.4 km from their brooding site. Eight ultrasonically tagged control crabs were returned to the brooding site. Crab movements were subsequently monitored weekly from late February to October to determine activity patterns and seasonal shifts in depth distribution and habitat use. Seven females transplanted away from the brooding site homed back to that site within 13 to 20 d. Ovigerous female crabs showed fidelity to the head of the cove and ranged a maximum of 3.4 km. Crabs had distinct seasonal patterns of depth distribution, habitat use, and activity which were related to reproductive status. The general pattern for female crabs was: (1) a relatively inactive period during winter and early spring at depths greater than −16 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) an abrupt movement into shallow water (less than −10 m) during mid-April and residence there until late June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; and (3) increased activity beginning in July with movement back to deeper water presumably to forage. Females that molted prior to oviposition did so between late May and September. Females occupied depths between +1.6 and −107.3 m. Home ranges were small (< 4% of the total cove habitat) and varied with crab size; smaller crabs had larger home ranges. Ovigerous females brooded embryos in a small, discrete area of unconsolidated, homogeneous, fine sand. These sediments were also highly permeable. Annual use of the main brooding area was documented for a 12-year period and emphasizes the importance of this essential habitat.
Journal Article
Seasonal movements and distribution of Dungeness crabsCancer magisterin a glacial southeastern Alaska estuary
The movements of 10 female and 8 male adult Dungeness crabs,Cancer magister(Dana, 1852), were monitored biweekly to monthly with ultrasonic biotelemetry for periods ranging from 73 to 555 d. Female and male crabs had different seasonal patterns of habitat use, depth distribution, and activity. The general pattern for female crabs was: (1) a relatively inactive period between November and mid-April at depths below 20 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) abrupt movement into shallow water (<8 m) in late April and residence there until early June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; (3) increased activity beginning in July with movement back to deeper water, presumably to forage. Females that molted prior to oviposition did so in June and July. Male crabs occupied deep water (>40 m) from November to April, then concentrated in shallow water (<25 m), segregated from females, until late July. Males were most active in late summer and moved into deeper water (>30 m) near the mouth of the cove in fall. The range of depths were –0.5 to –61.3 m for females and +0.1 to –89.0 m for males. Female crabs showed fidelity to the head of the cove and typically ranged only 1.5 km from there. Male crabs, however, moved up to 7.2 km from the head of the cove, but did not move close to the nearest established population of Dungeness crabs 9.6 km distant. The discrete population of adult Dungeness crabs in Fritz Cove may be representative of most Dungeness crab populations inhabiting shallow embayments of the coastal fjord system of southeastern Alaska.
Journal Article
Behavior of Female Dungeness Crabs, Cancer Magister, in a Glacial Southeast Alaska Estuary: Homing, Brooding-Site Fidelity, Seasonal Movements, and Habitat Use
Abstract
Aspects of the behavior of ovigerous Dungeness crabs (Cancer magister) were studied in Fritz Cove, Alaska. To test fidelity and homing ability of crabs to their brooding site, we ultrasonically tagged eight ovigerous crabs and transplanted them 1.4 km from their brooding site. Eight ultrasonically tagged control crabs were returned to the brooding site. Crab movements were subsequently monitored weekly from late February to October to determine activity patterns and seasonal shifts in depth distribution and habitat use. Seven females transplanted away from the brooding site homed back to that site within 13 to 20 d. Ovigerous female crabs showed fidelity to the head of the cove and ranged a maximum of 3.4 km. Crabs had distinct seasonal patterns of depth distribution, habitat use, and activity which were related to reproductive status. The general pattern for female crabs was: (1) a relatively inactive period during winter and early spring at depths greater than −16 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) an abrupt movement into shallow water (less than −10 m) during mid-April and residence there until late June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; and (3) increased activity beginning in July with movement back to deeper water presumably to forage. Females that molted prior to oviposition did so between late May and September. Females occupied depths between +1.6 and −107.3 m. Home ranges were small (< 4% of the total cove habitat) and varied with crab size; smaller crabs had larger home ranges. Ovigerous females brooded embryos in a small, discrete area of unconsolidated, homogeneous, fine sand. These sediments were also highly permeable. Annual use of the main brooding area was documented for a 12-year period and emphasizes the importance of this essential habitat.
Journal Article
BEHAVIOR OF FEMALE DUNGENESS CRABS, CANCER MAGISTER, IN A GLACIAL SOUTHEAST ALASKA ESTUARY: HOMING, BROODING-SITE FIDELITY, SEASONAL MOVEMENTS, AND HABITAT USE
Aspects of the behavior of ovigerous Dungeness crabs (Cancer magister) were studied in Fritz Cove, Alaska. To test fidelity and homing ability of crabs to their brooding site, we ultrasonically tagged eight ovigerous crabs and transplanted them 1.4 km from their brooding site. Eight ultrasonically tagged control crabs were returned to the brooding site. Crab movements were subsequently monitored weekly from late February to October to determine activity patterns and seasonal shifts in depth distribution and habitat use. Seven females transplanted away from the brooding site homed back to that site within 13 to 20 d. Ovigerous female crabs showed fidelity to the head of the cove and ranged a maximum of 3.4 km. Crabs had distinct seasonal patterns of depth distribution, habitat use, and activity which were related to reproductive status. The general pattern for female crabs was: (1) a relatively inactive period during winter and early spring at depths greater than −16 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) an abrupt movement into shallow water (less than −10 m) during mid-April and residence there until late June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; and (3) increased activity beginning in July with movement back to deeper water presumably to forage. Females that molted prior to oviposition did so between late May and September. Females occupied depths between +1.6 and −107.3 m. Home ranges were small (< 4% of the total cove habitat) and varied with crab size; smaller crabs had larger home ranges. Ovigerous females brooded embryos in a small, discrete area of unconsolidated, homogeneous, fine sand. These sediments were also highly permeable. Annual use of the main brooding area was documented for a 12-year period and emphasizes the importance of this essential habitat.
Journal Article
SEASONAL MIGRATION AND DISTRIBUTION OF FEMALE RED KING CRABS IN A SOUTHEAST ALASKAN ESTUARY
ABSTRACT
Seasonal movements and distribution of primiparous and multiparous red king crabs (Paralithodes camtschaticus) were monitored with ultrasonic biotelemetry approximately weekly for 1 year in Auke Bay, Alaska. Migration was associated with life-history events and may have occurred in response to spatial and temporal variations in environmental conditions and resources. All crabs displayed distinct shifts in depth and habitat use and followed a general pattern of seasonal movement as follows: (1) gradual movement to deep water in spring after mating and egg extrusion, and residence there through early November; (2) abrupt, synchronous movement into shallow-water areas in November, and residence there through late February or early March; and (3) gradual, synchronous movement to intermediate depths followed by movement into shallow water to molt and mate between late March and late May. The behavior of primiparous crabs was more variable than that of multiparous crabs. The differences in behavior may result from ontogenetic shifts in movements, and habitat selection. The annual range of primiparous crabs (x = 11.9 km2) exceeded that of multiparous crabs x( = 3.6 km2). Mean depth was directly correlated with photoperiod, and the sudden, synchronous movement of crabs between habitats coincided with thermohaline mixing. Females displayed a highly aggregated distribution, especially during winter in shallow water, where podding behavior of adult crabs was documented for the first time.
Journal Article