Influence of hydrographical and meteorological factors on catch and recruitment strength of the sprat stock in western Norway

Abstract

The dependence of recruitment strength on hydrographical conditions has been studied, i. e., possible relationship between the transport of sprat larvae from the Skagerak to the stock in western Norway and the thickness of Skagerak water in the coastal current. The material consists of data from 23 years of hydrographical observations and catch statistics. A correlation analysis gave the correlation coefficient r=0.4713 (P≈0.02). which means that good catches seem to be conditioned by a great thickness of Skagerak water the previous year. The validity of the material is discussed, especially the use of catch statistics as numerical expression of recruitment strength. An analysis of the influence of prevailing winds on the hydrographical conditions and on the catch distribution has been carried out. Weak northerly winds during summer seem to give the southernmost county in western Norway a greater proportion of the total sprat catch the following year. The results of this investigation indicate that the majority of the sprat in western Norway originate from spawning in the Skagerak and the Kattegat.