Northern Shrimp (Pandalus borealis) Recruitment in West Greenland Waters Part II. Lipid Classes and Fatty Acids in Pandalus Shrimp Larvae: Implications for Survival Expectations and Trophic Relationships

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.

Download Full-text

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

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2005.02.012 ◽

2005 ◽

Vol 62 (7) ◽

pp. 1454-1462 ◽

Cited By ~ 19

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.

Download Full-text