Age and growth of channel catfish Ictalurus punctatus in Lake Kitaura, Ibaraki Prefecture, Japan

Age and growth rates of the invasive exotic catfish Ictalurus punctatus were assessed by examination of otolith sections of 937 specimens (3.8-57.2 cm in standard length, SL) collected in Lake Kitaura, Ibaraki Prefecture, Japan. An opaque zone on the otolith margin, formed once a year from May to June, coincided with the peak spawning season. Von Bertalanffy growth equations differed significantly between sexes, being SLt = 63.5{1? exp[?0.120(t +0.416)]} for males and SLt= 56.5{1-exp[-0.134(t +0.437)]} for females [SLt is SL (cm) att (year)]. The estimated maximum ages for males and females were 14 and 13 years, respectively. An age-length key for converting length frequencies into age frequencies was established, and is a useful tool for assessing the population status of the species and the development of effective management strategies.