Release of critically endangered crocodiles: Development and application of a food web approach to determine suitability of release habitat

• Published in: Aquatic conservation 2019-11, Vol.29 (11), p.1849-1862
• Main Authors: McInerney, Paul J., Shackleton, Michael E., Rees, Gavin N., Frechette, Jackson L., Sam, Han, Hor, Leng
• Format: Article
• Language: English
• Subjects: Aquatic reptiles; Biology; Biomass; Cambodia; Cardamom Mountains; Catch per unit effort; Communities; Community composition; Composition; Conservation; Crocodiles; Crocodylus siamensis; Density; DNA barcodes; Dynamics; Ecological monitoring; Endangered species; Endemic species; Fish; Fishing; Fishing effort; Fishing pressure; Food chains; Food webs; Genera; Interrogation; Juveniles; Mountains; Polls & surveys; Pressure; Rivers; Siamese crocodile; species composition; Surveying
• ISSN: 1052-7613; 1099-0755
• DOI: 10.1002/aqc.3159

The Siamese Crocodile (Crocodylus siamensis) is a critically endangered medium‐size crocodilian endemic to Southeast Asia. Extirpated from much of its natural range, conservation efforts in the Cardamom Mountains of Cambodia include the release of captive‐reared juveniles and sub‐adults into river reaches known to support adult C. siamensis populations. Despite conservation concerns, the biology of wild C. siamensis is not well studied and the ecology of ecosystems at release locations is poorly understood. Fish are thought to comprise a major component of the diet of C. siamensis. Here, the aim was to characterize fish communities within three potential C. siamensis release locations, focusing on community composition, density, size class structure and food web dynamics. The survey sites varied in both C. siamensis density and human fishing pressure, and the results are interpreted in light of these drivers. Genomic interrogation of fishes of the Cardamom Mountains distinguished 13 distinct fish species, contributing to genetic databases and adding to the documented taxon list for the region. The presence of two previously unconfirmed fish genera in the region is confirmed. The first estimates of fish density, biomass and size class distribution for three rivers in the Cardamom Mountains are provided. The three potential C. siamensis release reaches that were sampled showed clear differences in fish community composition, structural and trophic dynamics. Fish density and biomass were highest in the high‐density C. siamensis survey reach and lowest in the high human fishing pressure reach. Survey reaches with food webs that were more reliant on autochonously driven food webs supported higher densities and biomass of fish. These results have important implications for future C. siamensis conservation efforts in Cambodia and contribute valuable ecological information on a relatively unexplored region.