|Document Type:||Journal Article|
|Title:||Size at maturity for grooved Tanner crab (Chionoecetes tanneri) along the U.S. west coast (Washington to California)|
|Author:||Aimee Keller, J. C. Buchanan, Erin Steiner, Douglas Draper, Aaron Chappell, Peter H. Frey, Melissa A. Head|
|Keywords:||grooved Tanner crab,US west coast,maturity,growth,depth,size,|
We conducted a multiyear study to examine interannual variability in mean size (carapace width, mm), maturity size (mm), and depth (m) for grooved Tanner crab (Chionoecetes tanneri Rathbun, 1893) along the U.S. west coast. An additional goal was to provide updated, estimates of carapace width (mm) at 50% maturity (W50) for male and female grooved Tanner crab and assess changes over time. Randomly selected samples came from trawl surveys undertaken annually by the Northwest Fisheries Science Center at depths of 55 to 1280 m. We used allometric relationships between carapace width and either abdominal width (females) or chela length (males) to determine functional maturity by sex. We evaluated maturity by fitting logistic regression models to proportion mature. W50 varied significantly between males (125.2 mm) and females (89.1 mm) but interannual differences were slight. Annual mean carapace widths (CW) were greater for mature males (139.9 – 143.4 mm) relative to females (98.8 – 100.4 mm). Average sizes of immature grooved Tanner crab varied between sexes with males (75.7 – 84.6 mm) larger than females (66.7 – 71.9 mm). Size frequency distributions indicated little overlap in size of mature male and female grooved Tanner crab but considerable overlap between immature grooved Tanner crab. The best model expressing complexity in growth incorporated width, sex, and maturity stage. Depth ranged from 195 – 1254 m with the average depth of mature grooved Tanner crab (females, 737 m; males, 767 m) significantly shallower than immature (females, 949 m; males, 918 m) grooved Tanner crab.
Our randomly selected samples came from fisheries independent bottom trawl surveys undertaken annually by the Northwest Fisheries Science Center at depths of 55 to 1280 m. We used allometric relationships between carapace width and either abdominal width (females) or chela length (males) to determine functional maturity for each sex. We subsequently evaluated maturity by fitting logistic regression models to the proportion mature.
|Theme:||Ecosystem approach to improve management of marine resources|
Assess ecosystem status and trends.