Detection of predation on Australian native fishes by Gambusia holbrooki

Clearing and staining of Gambusia holbrooki facilitated identification of juvenile fishes among the gut contents, and a feeding trial with captive Gambusia allowed assessment of gut transit time and degradation of melanotaeniid larvae. Regurgitated fishes and eggs in fixative solutions were also investigated. These techniques, extending to 12 h the post-feeding interval in which fishes may be found and differentiated among Gambusia gut contents, were tested on 631 wild-caught Gambusia collected in eastern Australia; an ingested native fish could be identified in the gut of 18 Gambusia, and a cannibalized fish in the gut of three.