OBSERVATIONS ON THE DISTRIBUTION OF LEATHERJACKETS IN NORTHERN-IRELAND

A map of the geographic distribution of leather jackets across five counties of Northern Ireland was produced from annual survey data. Climatic data were used to develop a multiple regression model explaining variation in the mean annual survey population for the years 1970–1984. Predicted populations for 1985–1988 compared favourably with observed counts. Both negative binomial and Adès distributions were successfully fitted to the frequency distribution of leatherjacket field populations from 1969–1986. It is concluded that the distribution of populations in the Province is not random and factors influencing mean leatherjacket numbers differ from those reported for other regions. The multiple regression model is proposed as a substitute for an annual survey of leatherjacket populations in Northern Ireland and it is suggested that the Adès family of distributions may enable it to be extended to predict leatherjacket frequency distributions each year. Copyright © 1990, Wiley Blackwell. All rights reserved