Consistency in the life history traits of four invasive pseudorasbora parva populations in Southern England

Life history plasticity can be a strong predictor of the establishment and invasion success of introduced fishes. Here, the life-history traits of four P. parva populations in adjacent ponds in Southern England were measured throughout 2013 to determine the timing and length of their reproductive season and the extent of trait plasticity. The relative abundance of the populations (as catch per unit effort) was similar, with low variability in their traits relating to reproductive effort and somatic growth. All the populations were male dominated. Both sexes matured at small body sizes, with fish as small as 30 mm being mature in both sexes, with the age at maturity for both sexes being age 1+ years. The peak spawning period, characterised by female fish investing heavily in reproduction when their gonado-somatic index (GSI) values were highest and declined thereafter, occurred in May and June, and after a mean of 212 ± 24 degree-days >12 oC, and with water temperatures being 13.2 to 14.6 °C. There were no further peaks in GSI, despite the species being considered to have prolonged spawning periods across spring and summer. These results also suggest that whilst the expression of life-history traits of invasive fishes often vary with density, they can be highly consistent between populations at similar abundances and locations.