Size at maturity for grooved Tanner crab (Chionoecetes tanneri) along the U.S. west coast (Washington to California)

Abstract

We conducted a multiyear study to examine interannual variability in the 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 (W 50 ) 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 (CW) and either abdominal width (AW) (females) or chela length (CL) (males) to determine functional maturity by sex. We evaluated maturity by fitting logistic regression models to proportion mature grooved Tanner crab. W 50 varied significantly between males (125.2 mm) and females (89.1 mm) but interannual differences were slight. The annual mean CW were greater for mature males (139.9-143.4 mm) relative to females (98.8-100.4 mm). The 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 the 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 a mature grooved Tanner crab (females, 737 m; males, 767 m) significantly shallower than an immature (females, 949 m; males, 918 m) grooved Tanner crab.

Flipping for Food: The Use of a Methane Seep by Tanner Crabs (Chionoecetes tanneri)

“…Behavioral observations also indicate a link between C. tanneri and the seep habitat that suggest our findings based on a few specimens are likely common within the species. The persistent dense population of C. tanneri at Clayoquot Slope contrasts with the highly migratory nature of this species (Keller et al, 2012(Keller et al, , 2016 and provides an additional indication that C. tanneri use the seep habitat. In addition, C. tanneri are normally separated geographically by size classes and sex yet there were multiple size classes and both sexes present at Clayoquot Slope (Supplementary Table 2).…”

“…A false discovery rate (0.05) correction was applied to correct for multiple comparisons. There was a significant difference in the bulk 13 C of mature vs. juvenile C. tanneri (determined from carapace width; <8.5 and >8.5 cm; t-test, p = 0.044; Supplementary Table 2; Keller et al, 2016). Clayoquot Slope and Barkley Canyon sediment δ 13 C values averaged −22.1 ± 0.1 and −22.3 ± 0.2‰, respectively, and Cascadia Basin δ 13 C values averaged −21.6 ± 0.2‰.…”

“…The observations of active foraging behavior by the C. tanneri specimen suggested that they may be using the seep as a source of trophic support. Chionoecetes tanneri are a commercially harvested species in the NE Pacific (Somerton and Donaldson, 1996;Kruse et al, 2005;Keller et al, 2012) that migrate across the margin (Keller et al, 2012(Keller et al, , 2016. As a result, if they are harvesting seep production they could be exporting it to non-seep ecosystems and potentially to humans.…”

Interannual Variation in the Population Dynamics of Juveniles of the Deep-Sea Crab Chionoecetes tanneri

“…The next two cohorts were smaller than indicated by the literature, at 4.3 instead of 4.9 cm and 5.8 instead of 6.5 cm. Because of the low abundance of individuals with CW >5 cm, the three last modes were grouped into a single cohort 7 of subadults [immature crabs with carapace widths between 4.0 and 10.0 cm (Workman et al, 2002;Keller et al, 2016)] (Table 4).…”

“…The genus Chionoecetes includes four species from the Gulf of Alaska to northern Mexico (Rathbun, 1925;Pereyra, 1966;Hart, 1982): Chionoecetes bairdi and C. opilio, which occur in waters shallower than 450 m and C. tanneri and C. angulatus found from 458 to 1784 m and from 1069 to 3000 m, respectively (Rathbun, 1925;Pereyra, 1966;Hart, 1982;Workman et al, 2001). Stages of maturity are depth-segregated, with adults living from 600 to 900 m depth (Pereyra, 1966;Workman et al, 2002;Gillespie et al, 2004;Keller et al, 2012Keller et al, , 2016, and juveniles and subadults (immature with carapace width <10 cm; Keller et al, 2016) deeper than 900 m (1200 m for C. angulatus). Reproduction also impacts crab distribution through aggregating behaviors of adults in late winter (Pereyra, 1966;Workman et al, 2001).…”