Detection of predation on Australian native fishes by Gambusia holbrooki.
Clearing and staining of the introduced larvivorous fish G. 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 the upper Orara River, New South Wales, Australia (between October 1997 and January 1998). An ingested native fish (melanotaeniids and pseudomugilids) could be identified in the gut of 18 Gambusia, and a cannibalized fish in the gut of 3.