Angling pressure, yield and catch per effort of grayling, Thymallus thymallus (L)., and brown trout, Salmo trutta L., on the rivers Glomma and Rena, southeastern Norway

Postal questionnaires, interviews and accurate reports from anglers were used to study angling activity, yield and catch per effort of grayling, Thymallus thymallus (L.), and brown trout, Salmo trutta L., on three stretches of the regulated river Glomma and two stretches of its tributary, the river Rena in southeastern Norway. Angling activity was expressed as hours angling per kilometre of river and varied from 364 (CL 245–598) to 1337 (CL 912–1991) h km ‐1 . Grayling and brown trout dominated the catches. The catches were estimated between 476 (CL 334–659) and 753 (CL 517–1155) grayling and brown trout per kilometre river stretch. The mean weights were estimated between 216 and 353 g for grayling, and 260 and 395 g for brown trout. The yield of grayling and brown trout was estimated between 8.7 (CL 6.1–12.4) and 46.4 (CL 34.9–62.3) kg ha ‐1 yr ‐1 . The quotient grayling/brown trout in the catches varied between 0.41 and 5.1, and was found to be significantly negatively correlated with angling effort ( r = ‐ 0.838, P <0.05). Catch per effort was estimated between 132 (CL 82–218) and 382 (CL 287–513) g h ‐1 , and was also negatively correlated to angling effort, according to: Catch per effort (g h ‐1 ) = ‐ 0.210 × effort (h km ‐1 ) + 405 ( r = and 0.899, P <0.02). Angling activity in earlier years was determined from number of permits sold where data were available. On stretches where angling activity was moderate, there was a tendency towards increase, whereas on stretches where activity had been high for several years, the activity seemed to have stagnated, indicating that a saturation had been reached.