Seasonal movements and distribution of Dungeness crabs Cancer magister in a glacial southeastern Alaska estuary

Abstract

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.

From earth and ocean: investigating the importance of cross‐ecosystem resource linkages to a mobile estuarine consumer

“…They are highly mobile, generalist consumers and cover broad depth ranges of benthic habitats thus making them well suited to benefit from a diverse resource base and periods of high resource availability (Stone and O'Clair 2001, Anderson et al 2008, Bȃnaru and Harmelin-Vivien 2009. The Dungeness crab is one of the largest, and most economically valuable invertebrates in estuaries of the northeastern Pacific (Jensen and Asplen 1998).…”

“…An extended larval period enables them to disperse substantial distances prior to settlement. Individuals can live for 8-10 years and adult movement can be extensive in open coastal areas but is thought to be more localized in fjord-type channels (Stone andO'Clair 2001, Hildenbrand et al 2011). Dungeness crabs are opportunistic omnivores, with ontogenetic diet shifts ranging from decomposing organic matter, microalgae, and diatoms to bivalves, shrimp, and fish as individuals mature (Stevens et al 1982, Jensen andAsplen 1998).…”

“…In addition, salmon spawning occurs prior to winter months when crabs migrate to deeper habitats and reduce activity (Stone and O'Clair 2001). Therefore any energetic benefits from salmon subsidies could be relegated to maintenance through dormant winter seasons, rather than growth.…”

Intertidal migration and habitat use by subadult Dungeness crab Cancer magister in a NE Pacific estuary

“…Naylor 1962, Stone & O'Clair 2001 or reproductive habitats (e.g. Hooper 1986, Stone & O'Clair 2001, Forward et al 2003. However, many species also undertake more frequent, albeit less conspicuous, migrations with circadian and/or circatidal periodicities (Gibson 2003).…”

“…Gonzalez Gurriaran et al 2002, Moksnes 2002 and/or seasonal movements to wintering grounds (e.g. Naylor 1962, Stone & O'Clair 2001 or reproductive habitats (e.g. Hooper 1986, Stone & O'Clair 2001, Forward et al 2003.…”