MIGRATORY SALMONIDS AS VECTORS OF CARBON, NITROGEN AND PHOSPHORUS BETWEEN MARINE AND FRESH-WATER ENVIRONMENTS IN NORTHEAST ENGLAND

This study provides estimates of fluxes between freshwater and marine environments of organic carbon (C), nitrogen (N) and phosphorus (P) tr ansported by migrating Atlantic salmon and sea trout. Mean annual valu es were assessed for a group of seven rivers in north-east England ove r a 7-year period (1989-1995). The total annual import to the rivers v ia adults of both species ranged between 48.5 and 156.8 t C, 10.5-34.1 t N and 1.7-5.3 t P. Total annual export by smelts and kelts ranged b etween 20.3 and 71.5 t C, 4.5-15.9 t N and 0.75-2.6 t P. The net flux of each of C, N and P by these fish represented only 0.09-0.24% of the total annual river loads. The net marine impart of each element repre sented approximately 75% of the gross adult import. Migratory fish pro vide the only direct source of such materials to the upper reaches of rivers. (C) 1998 Elsevier Science B.V.