The hybrid grouper TGGG, a lab-made crossbreed between Tiger grouper (Epinephelus fuscoguttatus) and Giant grouper (E. lanceolatus) has recently become a popular food fish and choice for mercy release in Asia. Considering that the hybrid TGGG is a carnivorous generalist and known to be very fast growing, it is speculated this introduced species could already have established its own population and alter the local ecosystem. However, these claims remain unclear as currently there is little scientific knowledge on their distribution and ecological impact. Hence, we performed a citizen science survey on observations of the presence of hybrid TGGG in the wild. As we found large numbers of these groupers living in the wild, we collected specimen and employed a metabarcoding approach to study the diet of this hybrid in Hong Kong to compare with that of other local Epinephelus spp.. With this approach we are able to provide a comprehensive evaluation on the diet and potential dietary niche overlap or partition between species. We hypothesize that the diet of hybrid TGGG will show high variation between individuals due to process of diet transition, which lead to a broad range of dietary niche that overlap with other local Epinephelus spp. We describe the ecological niche of an artificial species in the wild, and provide valuable data to evaluate the ecological impact of carnivorous introduced species in the marine ecosystem.

Keywords: gut content analysis, mercy release, ecological niche