Publication Abstract

Title: Does coexistence affect the growth and condition of native crucian carp Carassius carassius and introduced goldfish C. auratus in small ponds?

Publication Abstract: Despite its long history of introductions in Europe, and its demonstrate adverse genetic impact on native crucian carp Carassius carassius, the Asiatic cyprinid, goldfish Carassius auratus, has been little studied where introduced and its ecological impacts remain unknown. To address this, we examined growth in crucian carp and goldfish in quasi-natural ponds of Epping Forest (London, England), both in sympatry and allopatry. The growth trajectories in allopatry and sympatry revealed much faster growth of goldfish in sympatry than allopatry. Crucian carp growth trajectories were similar in allopatry and sympatry but in sympatry crucian body condition values were significantly higher (t-test, P <0.001) than in allopatry. These results may simply reflect differences among ponds in food availability, with goldfish-only ponds coincidentally having greater resources, or alternatively that co-existence incites these congeners to maximize growth potential, with associated ramifications for reproductive output. The implications for crucian carp conservation are discussed.