Non-native fish as glochidial sinks: elucidating disruption pathways for Echyridella menziesii recruitment

Abstract

A potential mechanism of global decline in freshwater mussel (Unionida: Bivalvia) abundance and diversity is disruption of their obligate parasitic life-cycle by non-native fish species, which may introduce novel interaction pathways that threaten unionid recruitment. We assessed three non-native fish (brown bullhead catfish, Ameiurus nebulosus; rudd, Scardinius erythrophthalmus; and goldfish, Carassius auratus) as glochidial hosts for the New Zealand freshwater mussel Echyridella menziesii to test the hypotheses that (i) non-native fish will have lower glochidial attachment rates than a native fish (the common bully Gobiomorphus cotidianus), and (ii) encystment rate will be lower on non-native species. We found that the non-native fish had significantly lower total glochidial attachment than the native control fish after infestation and did not produce ecologically significant quantities of juvenile mussels. This research supports the general assumption that non-native species are less suitable hosts of native freshwater mussels. However, confirming our findings in the field will indicate if removing non-native fish or enhancing native fish populations is recommended for conservation of E. menziesii populations in New Zealand.