Age and growth in a newly-established invasive population of topmouth gudgeon

Specimens of invasive topmouth gudgeon, Pseudorasbora parva, from Šúr Pond (Bratislava, Slovakia) were examined to assess age and growth, and to determine whether this recently-established invasive population employs a less specialized ontogenetic trajectory than the specialized form typical of native and/or long-time established populations. Samples were collected in October 2004 (n=143). Standard length (SL) ranged from 18.16 mm to 67.57 mm (mean 32.56 mm), and eviscerated body weight ranged from 0.10 to 5.02 g (mean 0.63 g). Scale caudal diameter ranged from 0.52 to 2.42 mm (mean 1.08 mm). SL at which the scales started to form was estimated to be 1.58 mm. The population was represented with 5 age groups, from 0+ to 4+. Relative to other populations for which comparable data are available the recently-established population of topmouth gudgeon was found to mature at smaller size and at a younger age compared to native and/or long-time established populations (all specimens bigger than 25.0 mm SL, and 94% of specimens from the age group I were already mature).