Figure 4. The 2011 eastern Bering Sea bottom trawl survey commercial crab species distribution at each station.
In 2011, commercially important crab were caught at all but 23 of the standard stations (Fig. 4). Biomass estimates in metric tons of Bristol Bay legal male red king crab (Paralithodes camtschaticus) have decreased over the last 4 years from 33,541 metric tons (t) in 2007 to 15,412 t in 2011; mature males decreased from 30,248 t in 2010 to 19,599 t in 2011. Mature females in Bristol Bay decreased between 2010 and 2011 from 40,797 to 37,486 t. Estimates for legal males in the Pribilof District increased between 2010 (2,881 t) and 2011 (3,751 t); mature males also increased during this time from 3,107 t to 3,834 t, and mature female estimates increased from 468 t in 2010 to 814 t in 2011. The 2011 coefficients of variance (CV) of Bristol Bay mature male and female red king crab biomass estimates ranged from 15% to 25%; the Pribilof District mature male and female red king crab CVs ranged from 64% to 73%.
From 2010 to 2011, the estimated biomass of legal male blue king crab (P. platypus) in the Pribilof District increased from 202 to 399 t, and mature males increased from 322 to 461 t, with a CV for mature and legal males of 84%–88%. In the St. Matthew Island Section of the Northern District, both mature and legal-sized males increased from 2010 estimates of 8,141 and 4,317 t to 9,516 and 5,701 t, respectively, above the average estimates from the previous 20 years. The CV for the St. Matthew Island Section mature male biomass was 55%.
Mature male Tanner crab (Chionoecetes bairdi) abundance increased between 2010 and 2011 from 27,949 to 33,810 t; mature females also increased from 5,922 to 8,457 t. Abundance estimate of legal males increased from 7,955 to 14,229 t. The CVs for mature female and male biomass ranged from 8% to 26%.
Estimated biomass of legal male snow crab (C. opilio) increased from 136,140 to 146,275 t between 2010 and 2011 with a CV of 11%. Mature female biomass also increased from 132,166 t in 2010 to 236,886 t in 2011, with a CV of 18%.
The 2011 biomass estimates reported in metric tons (t) and pounds (lbs) with 95% confidence intervals (+ 1.96 SE) for legal-sized males of commercial crab stocks in the eastern Bering Sea were as follows:
Commercial Crab Species
2011 Legal-sized Male Biomass (+ 95% CI)
Bristol Bay District red king crab (Paralithodes camtschaticus)
15,412 (5,238) t
33,977,299.61 (11,547,788.81) lbs
Pribilof District red king crab (P. camtschaticus)
3,751 (4,787) t
8,269,046.58 (10,554,038.49) lbs
Pribilof District blue king crab (P. platypus)
399 (693) t
879,573.20 (1,528,179.24) lbs
St. Matthew Island Section blue king crab (P. platypus)
5,788 (5,555) t
12,759,351.83 (12,246,469.72) lbs
Southern Tanner crab (Chionoecetes bairdi), east 166° W
10,207 (5,880) t
22,503,103.69 (12,964,143.55) lbs
Southern Tanner crab, east 166° W, > 5.5 inches
5,356 (4,344) t
11,807,249.93 (10,109,706.61) lbs
Southern Tanner crab, west 166° W
23,278 (16,729) t
51,319,174.78 (36,880,898.03) lbs
Southern Tanner crab, west 166° W, > 5.0 inches
15,676 (13,672) t
34,560,932.62 (35,029,759.51) lbs
Snow crab (C. opilio), all districts
146,297 (32,652) t
322,525,931.00 (71,984,466.52) lbs
Snow crab, all Districts, > 4.0 inches
94,763 (22,025) t
208,915,452.54 (48,556,399.29) lbs
Due to the delaying effects of colder than average water temperatures on the red king crab reproductive cycle, the Aldebaran and Alaska Knight returned to Bristol Bay to resample 20 predetermined stations between 25 and 31 July. Stock assessment models rely on growth increments and mating success, and only 52% of the 450 mature females sampled during the standard survey had extruded a new clutch of uneyed embryos.
Among resurveyed female crab in late July, 93% were mature females and of these, 94% were in new hardshell condition with newly extruded uneyed embryos. These new hardshell females had molted and mated over the 6-week period between the first sampling event in early June and the resample in late July.
Crab Special Projects – In addition to the standard data collection, several special projects were carried out during the survey, including the collection of live red king crab females sent to the AFSC's Kodiak Laboratory to study the effects of ocean acidification on reproductive success as well as larval condition and survival. Stomach samples from over 200 male and female Chionoecetes spp. were collected to investigate the diet of Tanner and snow crab. One hundred male snow crab were collected to study the effect of cold temperatures on crab metabolism and reflexes. Hemolymph samples from Paralithodes, Hyas, Pagurus, and Elassochirus spp., and Erimacrus isenbeckii were collected at randomly selected stations to monitor bitter crab syndrome and for population genetics studies; photographic and genetic data were collected from Chionoecetes hybrid crab.
Nine survey stations were added to the standard survey design to assess adult and juvenile red king crab distribution in the nearshore waters of Bristol Bay.
