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The trout ( Salmo trutta ) population of the Afon Cwm, a small tributary of the Afon Dyfi, mid‐Wales
Author(s) -
Crisp D. T.,
Beaumont W. R. C.
Publication year - 1995
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1995.tb01105.x
Subject(s) - salmo , trout , brown trout , biology , tributary , fishery , population , zoology , fish <actinopterygii> , demography , geography , cartography , sociology
Data are presented from a 10‐year (1984 to 1993) study of a Salmo trutta population in the Afon Cwm, a small tributary of the Afon Dyfi, mid‐Wales. The stream is a spawning and nursery area for sea trout. Growth of trout within the stream can be summarized by a von Bertalanffy growth coefficient ( K ) of 0·310, with asymptotic length (1∞) 21·6 cm and with length at age 1 of 7·6 cm. Mean population density in the whole stream varied from year to year between 0·05 and 0·60 0‐group trout m −2 and between 0·05 and 0·70 older trout m −2 . Mean biomass varied, between years, from 0·1 to 3·5 g m −2 for 0‐group and from 1·3 to 10·4g m −2 for older trout. Loss between 3 and 5 months of age appeared to be proportionate at about 50 to 60% and instantaneous loss rate from 5 to 53 months of age varied from 0·04 to 0·10 month −1 and was positively correlated with cohort number at 3 months of age. Production between 3 and 53 months of age varied between cohorts from 3 to 8 g m −2 live weight.