scholarly journals The Uncertainty of an Assessment Procedure for the West Greenland Stock of Northern Shrimp, Pandalus borealis (Krøyer)

2000 ◽  
Vol 27 ◽  
pp. 183-192 ◽  
Author(s):  
C Hvingel ◽  
M C S Kingsley
Keyword(s):  
Assessment Procedure ◽  
The West ◽  
Pandalus Borealis ◽  
West Greenland ◽  
Northern Shrimp

scholarly journals Calibration of bottom trawls for northern shrimp

2008 ◽  
Vol 65 (6) ◽  
pp. 873-881 ◽  
Author(s):  
Michael C. S. Kingsley ◽  
Kai Wieland ◽  
Bo Bergström ◽  
Michael Rosing
Keyword(s):  
Density Dependence ◽  
Bayesian Methods ◽  
The Other ◽  
Bottom Trawl ◽  
Trawl Survey ◽  
Low Density ◽  
The West ◽  
Pandalus Borealis ◽  
Northern Shrimp ◽  
Data Calibration

Abstract Kingsley, M. C. S., Wieland, K., Bergström, B., and Rosing, M. 2008. Calibration of bottom trawls for northern shrimp. – ICES Journal of Marine Science, 65: 873–881. The Skjervøy 3000 trawl used since 1988 in the West Greenland bottom-trawl survey has been replaced by a Cosmos 2000. To be able to compare old data on the northern shrimp (Pandalus borealis) with new data, calibration experiments were carried out by trawling twice consecutively along the same track, using either the same gear twice or the two different gears in one order or the other. Catch models were fitted to the shrimp data—both size-aggregated catch weights and size-specific counts—by likelihood and Bayesian methods. The catch in the second haul relative to that in the first depended not only on the gear used in the two hauls, but also on density, the second catches being a smaller proportion of first catches when densities were high, and often larger than the first catches at low-density stations. This density-dependence of the catch ratio was larger for small shrimp than for big ones. The Cosmos trawl was estimated to fish with ∼87% of the catchability of the Skjervøy trawl after correction for its greater wingspread. Catchability ratio varied with the size of shrimp caught, but the differences were not statistically significant.

scholarly journals Improving the West Greenland Trawl Survey for Shrimp (Pandalus borealis)

2000 ◽  
Vol 27 ◽  
pp. 151-160 ◽  
Author(s):  
D Carlsson ◽  
P Kanneworff ◽  
O Folmer ◽  
M Kingsley ◽  
M Pennington
Keyword(s):  
Trawl Survey ◽  
The West ◽  
Pandalus Borealis ◽  
West Greenland

scholarly journals Buffered random sampling: a sequential inhibited spatial point process applied to sampling in a trawl survey for northern shrimp Pandalus borealis in West Greenland waters

2004 ◽  
Vol 61 (1) ◽  
pp. 12-24 ◽  
Author(s):  
M.C.S. Kingsley ◽  
P. Kanneworff ◽  
D.M. Carlsson
Keyword(s):  
Random Sampling ◽  
Sampling Method ◽  
Sample Survey ◽  
Standard Errors ◽  
Trawl Survey ◽  
Pandalus Borealis ◽  
West Greenland ◽  
Northern Shrimp ◽  
Manual Adjustment ◽  
Statistical Effects

Abstract A stratified random sample survey has been carried out since 1988 as a component of the assessment of the stock of northern shrimp Pandalus borealis in offshore West Greenland waters. In 1999, the placing of stations independently and randomly was replaced by buffered random sampling, in which stations were randomly placed but prevented from being closer together than a prescribed limit. Buffered random sampling gave a more even distribution of stations within strata, and nearest-neighbour distances were on average increased by 50%. The statistical effects were difficult to determine, but did not appear to be large, and the estimated standard errors did not change much from previous years. However, the buffered sampling method generated designs in which stations were evenly distributed over the strata, and did away with the need for subjective manual adjustment of the positions of stations which independent random sampling sometimes placed too close to another station.

scholarly journals Changes in recruitment, growth, and stock size of northern shrimp (Pandalus borealis) at West Greenland: temperature and density-dependent effects at released predation pressure

2005 ◽  
Vol 62 (7) ◽  
pp. 1454-1462 ◽  
Author(s):  
Kai Wieland
Keyword(s):  
Predation Pressure ◽  
Moderate Increase ◽  
Bottom Temperature ◽  
Pandalus Borealis ◽  
Stock Size ◽  
Density Dependent ◽  
West Greenland ◽  
Northern Shrimp ◽  
Northern Regions ◽  
Survey Estimates

Abstract Stock size of northern shrimp (Pandalus borealis) in West Greenland waters has been fairly stable from the late 1980s to the mid-1990s. Thereafter, survey estimates of biomass increased substantially, and the exploitation rate declined slightly in the most recent years. The present analysis was carried out on a spatially disaggregated basis in order to account for the latitudinal differences in bottom temperature and shrimp density. Changes in recruitment and, with a lag of 2 years, in stock biomass were most pronounced in the northern part of its distributional range, while bottom temperature increased in all survey regions since the mid-1990s. Length-at-age was positively correlated with temperature in general, but a trend towards slower growth was observed in areas with the highest stock densities in the most recent years. It is concluded that the moderate increase in temperature above a lower threshold of the optimal range in the northern regions has extended the distributional area that is most favourable for northern shrimp. This, together with a decreasing rate of exploitation and a continuous low predation pressure, resulted in an increase of the stock to a level at which density-dependent effects have become prominent in parts of study area.

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