Revealing trends in densities of juvenile Atlantic salmon, Salmo salar L.,in the subarctic River Teno using cluster analysis on long-term sampling data
E. Niemela et al., Revealing trends in densities of juvenile Atlantic salmon, Salmo salar L.,in the subarctic River Teno using cluster analysis on long-term sampling data, FISH MA EC, 6(3), 1999, pp. 207-220
The density of juvenile Atlantic salmon, Salmo salar L., was monitored at 5
7 sites representing different habitats in the River Teno and two of its ma
jor tributaries from 1979 to 1995. Cluster analyses were used to combine si
tes with similar densities and to study trends in densities within clusters
. It was found that management measures have played an important role in ma
intaining salmon stocks and there was some evidence of increasing juvenile
salmon densities. Parr densities decreased significantly in one cluster con
taining 45% of the sites studied in the River Utsjoki, whereas densities in
creased significantly in one cluster in the River Teno and in one cluster i
n the River Inarijoki containing 38% of the sites in these rivers. Fry dens
ities increased significantly in two clusters containing 16% of all the sit
es studied in the three rivers. In general, the mean densities in successiv
e years in the clusters were independent. The results demonstrate the value
of long-term monitoring in ecological investigations.