Research Document - 2002/006

A new Traffic Light Assessment for northern shrimp (Pandalus borealis) on the eastern Scotian Shelf

By P. Koeller, M. Covey, M. King

Abstract

The DFO-industry survey index decreased in 2001 for the second consecutive year. The strong 1994 and 1995 year classes were nearly at the end of their life cycle in 2001 and recruitment to the fishery may be below average for the next 2 years, consequently the population appears to be declining from the historic high levels of the late 1990s. Environmental indicators, including temperatures and capelin abundance, appear to be unfavourable - increasing aggregation of shrimp on the grounds may be a response to these changing environmental conditions. Spawning stock biomass remains high, and the area with the lowest exploitation rate is experiencing declines similar to the more heavily fished areas, consequently the declines appear to be due more to environmental than fishing effects. However, increases in female exploitation, fewer larger females in the population due to removals by the fishery, increased fishing during the ovigerous period and decreases in the size at transition and maximum sizes may be impacting negatively on the population's reproductive capacity. The Traffic Light analysis for the eastern Scotian Shelf shrimp stock was revised and upgraded by extending the historical time series of many indicators to include the period of low abundances in the 1980s. The wider range of values during favourable and unfavourable conditions allowed the setting of definable and consistent (albeit arbitray) limits for the colours of individual indicators (0.66, 0.33 percentiles). The summary for both 2000 and 2001 was red, indicating a more severe intervention than the previous year. A population model was used to simulate a shrimp population subjected to the combined effects of fishing and unfavourable environmental conditions and the level of intervention needed to prevent the spawning stock biomass from decreasing below the lowest levels observed historically.

Complete document (PDF, 950 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.