Sperm characteristics in perch Perca fluviatilis L.

Sperm densities in perch Perca fluviatilis males showed a positive correlation with the amount of stripped milt. Sperm flagellum length did not correlate with body mass, but a significant correlation between flagellum length and the total number of sperm produced was found. # 2006 The Fisheries Society of the British Isles Key words: flagellum length; Perca fluviatilis; perch; sperm density; sperm limitation. Sperm production is a crucial factor for the potential reproductive success of males in many species (Nakatsuru & Kramer, 1982). Especially under strong sperm competition, higher sperm numbers in the ejaculates are likely to increase a male’s chance of fertilization (Parker et al., 1996). But sperm produc-tion is limited by physiological constraints, e.g. by testis size, which often de-pends on the body size of a male (Schärer & Robertson, 1999). In many fish species, large males produce a multiple of the sperm number of small males (Petersen & Warner, 1998). Moreover, sperm allocation tactics can vary according to the size and status of a male or its amount of available sperm (Kazakov, 1981; Gross, 1996; Taborsky, 1998). Allometries in sperm production and gonad characteristics between small and large males have been described in several species, e.g. small males having relatively larger testes or higher sperm densities in the seminal fluid or differences in hormone production (Gage et al., 1995; Leach & Montgomerie, 2000; Uglem et al., 2002). Sperm flagellum length, motility or longevity can also depend on the size and status of a mal