Hybrid grouper fish, released into Hong Kong’s coastal waters as part of a religious ritual, could be wreaking havoc on local biodiversity. By exploiting unique ecological niches and asserting themselves as dominant predators, the hybrid giants have the potential to outcompete their native, non-hybrid counterparts and threaten the balance of marine ecosystems.
Known as the Sabah grouper, or the Tiger Grouper-Giant Grouper hybrid (TGGG), the hybrid species is bred through aquaculture by interbreeding the Tiger Grouper (Epinephelus fuscoguttatus) with the Giant Grouper (E. lanceolatus).
They commonly appear in Hong Kong’s fish markets, where they’re revered for their ability to grow to huge sizes rapidly. These qualities also make it a popular choice for local mercy releases, a Buddhist and Taoist practice where animals are released into the wild.
The symbolic act is well-intentioned, but could it be hurting local ecosystems? A team of ecologists at the University of Hong Kong recently investigated.
Using DNA metabarcoding, the researchers were able to analyze the genetic material found within the groupers’ stomach contents to get a clear idea of what prey they were eating. This revealed that the Sabah grouper hybrid has a unique appetite, chowing down on various species that aren’t usually eaten by native species, including fish, crustaceans, and even squid.
The researchers took samples from Port Shelter Bay, south of Sai Kung Peninsula in Hong Kong.
Image credit: seaonweb/Shutterstock.com
By filling these untapped ecological roles, it has carved out a thriving existence in coastal waters. In addition, its impressive size, resilience, and lack of natural predators position it as a formidable contender for apex predator status.
“Our findings show that the TGGG is not just another introduced species, it has the potential to significantly disrupt trophic dynamics and reshape coastal ecosystems,” Professor Celia Schunter, lead investigator of the study from the University of Hong Kong, said in a statement.
Hybridization is surprisingly common in the natural world and it can be a powerful force for change. Occasionally, the offspring of two different species outperform their non-hybrid relatives due to hybrid vigor, aka heterosis, where the hybrid inherits advantageous traits from both parent species.
A clear example of this is the hybrid pythons that are currently taking over the Everglades. Combining the traits of both parent species – Burmese pythons (Python bivittatus) and Indian pythons (P. molurus) – the hybrid population has skyrocketed in recent decades, causing a collapse of the region’s small mammals.
Just like Hong Kong’s problem with the Sabah grouper, the Florida hybrid pythons are ultimately the product of animals being released into the wild by humans. As for the hybrid fish, however, their unchecked spread acts as a living lesson on how even well-meaning actions, like mercy releases, can ripple into ecological chaos, reminding us that nature often pays the price for human oversight.
“This study underscores the need for careful monitoring and management to mitigate the unintended impacts of human activities on biodiversity,” explained Dr Arthur Chung, postdoctoral fellow at the University of Hong Kong and co-author of the study.
The new study is published in the journal Reviews in Fish Biology and Fisheries.
