The Body Composition of Adult Perch, Perca fluviatilis in Windermere, with Reference to Seasonal Changes and Reproduction

The present paper describes the seasonal cycle of sexually mature fish in terms of their main body constituents (water, fat, protein and ash). The energy values of both the somatic and gonadic tissues have been determined for a 'standard' fish of each sex and predictive equations have been formulated. The importance of understanding body composition changes in growth and production studies has long been accepted. Much of the work in this field has been done under laboratory conditions (e.g. Gerking 1955; Brett, Shelbourn & Shoop 1969; Niimi 1972a; Jezierska 1974; Elliott 1976). Others have measured the chemical composition of various body components from wild populations and some of these have been related to seasonal and reproductive cycles. Many references to work on chemical composition of fish can be found in Love (1970). Studies on the perch (Percafluviatilis L.) in Windermere have been extensive and well documented (Bagenal 1970). Le Cren (1951) describes in detail the length-weight relationship and seasonal cycle in gonad weight and condition of this perch population. Iles (1974) referring to this work infers from it that 'maturation involved to some degree at least, the translocation of material previously stored in the body'. This study tests that inference and extends the work further.