From a historic perspective the cod in the Barents Sea-Svalbard region has been the most productive gadoid stock in the Atlantic. Variation in catches has always been large, but during the last 10-15 years catches and stock abundance have reached the lowest level on record. Three major causes of variation have been discussed; stock reduction through exploitation, environmental influences on recruitment, and species interaction effects on maturation, growth and mortality. In addition, interactions between these three sources might be important. The influence of each specific factor is difficult to evaluate from incidental observations and short-term time series. In that respect, the time series on catches and on biological and environmental information of this stock, which partly goes back to the 19th century assumes a unique position in comparison with data on most other stocks.
In this paper fluctuations in catches and stock abundance will be compared with changes in recruitment, size/age composition and growth. This information is discussed in view of historic variation in ecological and environmental parameters. The stock has been under particularly high exploitation pressure since the mid-seventies. Further, large changes in growth rates and poor recruitment to the commercially exploited stock have characteristic for the end of the 1980s and the 1990s. The analysis here shows that substantial long-term variation might underlie short-term variability, and, more importantly, that long-term changes roughly coincide with similar fluctuations in the environment. Consequently, it is suggested that inserting on a steady-state perspective on the population dynamics of this stock may lead to mismanagement and to a reduction of long-term yield.
Download Info
To download:
If you experience problems downloading a file, check if you have the
proper application to
view it first. Information about this may be contained
in the File-Format links below. In case of further problems read
the IDEAS help
page. Note that these files are not on the IDEAS
site. Please be patient as the files may be large.
Publisher Info
Paper provided by International Institute for Applied Systems Analysis in its series Working Papers with number
ir00023.
Cited by: (explanations, Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.)