Fluctuations in Range and Abundance of Snow Crab (Chionoecetes Opilio) from the Eastern Bering Sea: What Role for Pacific Cod (Gadus Macrocephalus) Predation?

2013 ◽  
Vol 89 (1) ◽  
pp. 57-81 ◽  
Author(s):  
Julian Burgos ◽  
Billy Ernst ◽  
David Armstrong ◽  
Jm (Lobo) Orensanz
Keyword(s):  
Bering Sea ◽  
Snow Crab ◽  
Pacific Cod ◽  
Chionoecetes Opilio ◽  
Eastern Bering Sea ◽  
Gadus Macrocephalus

Catchability of snow crab (Chionoecetes opilio) by the eastern Bering Sea bottom trawl survey estimated using a catch comparison experiment

2013 ◽  
Vol 70 (12) ◽  
pp. 1699-1708 ◽  
Author(s):  
David A. Somerton ◽  
Kenneth L. Weinberg ◽  
Scott E. Goodman
Keyword(s):  
Experimental Data ◽  
Bering Sea ◽  
Weighted Average ◽  
Assessment Model ◽  
Bottom Trawl ◽  
Snow Crab ◽  
Trawl Survey ◽  
Chionoecetes Opilio ◽  
Bottom Trawl Survey ◽  
Eastern Bering Sea

Catchability of the eastern Bering Sea (EBS) bottom trawl survey for snow crab (Chionoecetes opilio) was estimated from experimental data to provide a constraint on the survey catchability parameters in the stock assessment model. The experiment utilized a second fishing vessel to conduct side-by-side trawling with each of two survey vessels at 92 stations using an experimental trawl assumed to capture all crabs in its path. Trawl efficiency, or the captured proportion of crabs in the trawl path, was estimated for the 83-112 Eastern otter trawl from experimental data using a nonparametric smooth function of carapace width, sediment size, and depth. Survey catchability was then estimated as the catch-weighted average of the predicted trawl efficiency at all 275 survey stations where snow crabs were captured. The fitted model indicated that trawl selectivity was greater in sand than mud and greater in shallow water than deep. At a carapace widths >95 mm, the minimum commercial size limit, the estimated survey catchability of males is considerably less than previously reported.

Life history schedule and periodic recruitment of female snow crab (Chionoecetes opilio) in the eastern Bering Sea

2012 ◽  
Vol 69 (3) ◽  
pp. 532-550 ◽  
Author(s):  
Billy Ernst ◽  
David A. Armstrong ◽  
Julián Burgos ◽  
J.M. (Lobo) Orensanz
Keyword(s):  
Bering Sea ◽  
Mature Female ◽  
Snow Crab ◽  
Age At Maturity ◽  
Eastern Canada ◽  
Chionoecetes Opilio ◽  
Frequency Distributions ◽  
Eastern Bering Sea ◽  
Crab Abundance ◽  
Mean Size

Snow crab ( Chionoecetes opilio ) populations have fluctuated cyclically in eastern Canada and the eastern Bering Sea, where recruitment to the mature female pool has occurred over a period of three decades (1978–2007) in pulses with a mean period of 7 years. It has been hypothesized that this was the result of a parent–offspring relation between sequentially linked strong cohorts of mature primiparous females, which requires that periodicity matches the time lapsed between egg extrusion by the maternal broodstock and the offspring reaching maturity. We show that female age at maturity (post-settlement) varies between 4.5 and 7.5 years, with most females maturing at 5.5–6.5 years (7–8 years after egg extrusion). Pulses of female recruitment to the mature population do not show a latitudinal trend, consistent with uniformity in age-at-maturity. Results of tracking crab abundance and size–frequency distributions in cod stomach and trawl samples between successive pulses of the cycle are consistent with the hypothesis of serial linkage among pulses. Periodicity is reflected in trends of clutch fullness and average shell condition and in the negative correlation between the strength of primiparous female cohorts and the mean size of their members.

scholarly journals The contribution of fecundity and embryo quality to reproductive potential of eastern Bering Sea snow crab (Chionoecetes opilio)

2016 ◽  
Vol 73 (12) ◽  
pp. 1800-1814 ◽  
Author(s):  
Joel B. Webb ◽  
Laura M. Slater ◽  
Ginny L. Eckert ◽  
Gordon H. Kruse
Keyword(s):  
Bering Sea ◽  
Embryo Quality ◽  
Stock Assessment ◽  
Reproductive Potential ◽  
Large Male ◽  
Reference Points ◽  
Snow Crab ◽  
Eastern Canada ◽  
Chionoecetes Opilio ◽  
Eastern Bering Sea

Development of refined indices of female reproductive potential is needed for estimation of alternative biological reference points for the eastern Bering Sea (EBS) snow crab (Chionoecetes opilio) fishery, which is managed with large male-only harvest regulations. Females were collected from 2007 to 2009 to investigate seasonal and interannual variation in fecundity with maternal size, shell condition (a proxy for age after maturity), and recent mating and again in 2010 to examine biochemical measures (carbon, hydrogen, and nitrogen) of embryo quality. Mean model-adjusted fecundity was highest for primiparous and young multiparous females and declined with advancing shell condition, presumably from senescence. This pattern was also found for clutch fullness indices evaluated from 20 years of stock assessment survey data. Indicators of low female sperm reserves were associated with decreased (∼10%) fecundity for multiparous females. Seasonal comparison of size–fecundity relationships suggested that embryo loss during brooding was minimal, and embryo quality analyses suggested that strong variation with maternal characteristics was unlikely. Finally, fecundity-at-size of EBS females may be lower than that of conspecifics in Japan and eastern Canada.

scholarly journals Distributional patterns of 0-group Pacific cod (Gadus macrocephalus) in the eastern Bering Sea under variable recruitment and thermal conditions

2012 ◽  
Vol 69 (2) ◽  
pp. 163-174 ◽  
Author(s):  
Thomas P. Hurst ◽  
Jamal H. Moss ◽  
Jessica A. Miller
Keyword(s):  
Bering Sea ◽  
Thermal Conditions ◽  
Pacific Cod ◽  
Eastern Bering Sea ◽  
Pacific Cod Gadus Macrocephalus ◽  
Gadus Macrocephalus ◽  
Basin Scale ◽  
Distributional Patterns ◽  
Variable Recruitment ◽  
The Bering Sea

Abstract Hurst, T. P., Moss, J. H., and Miller, J. A. 2012. Distributional patterns of 0-group Pacific cod (Gadus macrocephalus) in the eastern Bering Sea under variable recruitment and thermal conditions. – ICES Journal of Marine Science, 69: 163–174. Despite the importance of Pacific cod in Bering Sea fisheries and foodwebs, little is known about the habitat use and the distribution of early life stages. We analysed 6 years of catch data for 0-group Pacific cod in fishery-independent surveys of the Bering Sea shelf. Juvenile cod were most commonly captured on the middle shelf over depths of 50–80 m and were rarely captured north of 58°N. Consistently high catches were observed east of the Pribilof Islands and north of Port Moller along the Alaska Peninsula. There was evidence of density-dependent habitat selection at the local scale as the frequency of occurrence increased with regional catch per unit effort. At the basin scale, the southerly distribution of the weak 2009 cohort suggested the possibility of a range contraction for small cohorts. There was no consistent shift in the distribution of juvenile Pacific cod in response to interannual climate variability. These results for Pacific cod contrast with those observed for walleye pollock, which appears to exhibit greater variance in distribution, but are similar to patterns observed for juvenile Atlantic cod. Future work should focus on distribution in nearshore habitats and examine the patterns of dispersal and the connectivity of the Bering Sea and Gulf of Alaska populations.

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