World Aquacluture Magazine - September 2020

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2020 31 sized native piscivore ( Cephalopholis fulva ) and is accompanied by a reduction in species richness of native fish on patch reefs (Albins 2013). On a larger temporal and spatial scale, increases in lionfish abundance have coincided with 65 percent reduction in the biomass of the lionfish’s native prey fishes on large natural reefs in just two years (Green et al . 2012). Similar negative impact of the lionfish inva- sion have been documented by others (Benkwit 2015, Ingeman 2016, Palmer et al . 2016). More serious repercussions could be the cascade of chain effects ensuing from lionfish predation. The decrease in the density of prey herbivorous fishes could result in overgrowth of macroalgae which could contribute to the degradation of reefs (Albins and Hixon 2008, Albins and Hixon 2013, Côté et al . 2013). Now attention is turning to lionfish management and how to mitigate the adverse impact of lionfish invasion on the coral-reef ecosystem (Frazer et al . 2012, Côté et al . 2013, Côté et al . 2014, Dahl et al . 2016, Malpica-Cruz et al . 2017, Usseglio et al . 2017). Sabah Grouper as an Invasive Species Nowwhat about the hybrid Sabah grouper? Is it going to become an invasive species like the lionfish? At the moment, there is a dearth of information to be able to determine the ecological impact of the introduction of this non-native species into Hong Kong waters. Research on the reproductive biology of the Sabah grouper, feeding ecology and growth rate is needed before their potential threat to native fish communities can be measured. Further, to assess the total impact of the invader, Parker et al . (1999) recommends investigations along three dimensions – range, abundance and per-capita or per- biomass effect of the invader – as well as measurement of the impact at five levels: 1) Effects on individuals (including demographic rates such as mortality and growth), 2) Genetic effects (including hybridization), 3) Population dynamic effects (abundance, population growth), 4) Community effects (species richness, diversity, trophic structure), and 5) Effects on ecosystem processes (nutrient availability, primary productivity). At the moment, what can be said from a marine biology perspective is the following: According to a study by the Eco- Education and Resources Center, wet markets in Hong Kong sell Sabah groupers that are 20-40 cm in length (Kao 2018a) but hybrid Sabah groupers only reproduce at 80-95 cm in length (Ching et al . 2018, Luin et al . 2013). The specific growth rate of the hybrid Sabah grouper is optimal between 26-30 C (0.8-0.9 percent BM/d; De et al . 2016). At lower and higher temperatures (22 C and 34 C), the specific growth rate falls to 0.6 percent BM/d and 0.7 percent BM/d, respectively. Growth of hybrid Sabah groupers would therefore be optimum from June to October when the average sea temperature in Hong Kong ranges from 26 to 30 C. Thus, if individuals of 20-40 cm in length were introduced into the wild as mercy releases, it would take several years before they would reach a size when they would be reproductively active. However, before the Sabah grouper could establish breeding populations, it seems likely that they would be caught by recreational anglers (Kao 2018a) and by other fishermen. To the economist, the result is simply the old story of the tragedy of the commons, in this case with good news for the ecologist. Big fish could end up in the ocean food chain. So, are the Green groups correct? That is where an understanding of property rights econom- ics comes in. The Green groups should not worry too much. That is because, as soon as cultured Sabah groupers becomes common property upon release to the sea, fishermen will target them because they are big, marketable and free. The fish will swiftly become vic- tims of the tragedy of the commons, as explained at the beginning of this article. Of course, in the meantime, and depending on the quantity of fish released, the practice of releasing Sabah groupers for religious purposes could well cause some ecological disturbance or even damage. So, instead of mercy releases, a wise friend of the environment should welcome the Sabah grouper to his dinner plate as it reduces consumption of wild groupers and other coral reef fish. Conclusion The hybrid fish Sabah grouper has displaced many wild coral reef fish in the Hong Kong fish market. Its wholesale and retail prices are more stable and lower than the leopard coral grouper. If the salmon is a good textbook example for fish culture as a means to overcome the tragedy of the commons in temperate seas, the Sabah grouper could be the best real-world example for the subtropical Pacific Rim. Notes Professor Lawrence W.C. Lai (B.Soc.Sc. (Econ), M.T.C.P., M.Soc.Sc (Econ), LL.B, Ph.D, former member of AEM) wclai@hku.hk Dr. Rosita Ong Che (B.Sc. Bio; MSc. Bio. Ph.D Zoology, formerly with Swire Marine Lab, HKU) rongchehk@yahoo.com.hk Chair Professor KWChau (B.Bldg, Ph.D) hrrbckw@hku.hk Ronald Coase Centre for Property Rights Research University of Hong Kong References Adler, J.H. 2002. Legal obstacles to private ordering in marine fisheries. Roger Williams University Law Review 8:9-42. Agnello, R.J. and L.P. Donnelley. 1975. Property rights and efficiency in the oyster industry. Journal of Law and Economics 18:521-533. Albins, M.A. 2013. Effects of invasive Pacific red lionfish Pterois volitans vs. a native predator on Bahamian coral-reef fish communities. Biological Invasions 15:29-43. Albins, M.A. and M.A. Hixon. 2008. Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes. Marine Ecology Progress Series 367: 233-238. Albins, M.A. and M.A. Hixon. 2013. Worst case scenario: potential long-term effects of invasive predatory lionfish ( Pterois volitans ) on Atlantic and Caribbean coral-reef communities. Environmental Biology of Fishes 96:1151-1157. Anderson, E.E. 1988. Factors affecting welfare gains from fishing gear restrictions. Northeastern Journal of Agricultural and Resource Economics 17:156-166. Baltz, D.M. 1991. Introduced fishes in marine systems and inland seas. Biological Conservation 56:151-177. Benkwitt, C.E. 2015. Non-linear effects of invasive lionfish density on native coral-reef fish communities. Biological Invasions 17:1383-1395. ( C O N T I N U E D O N P A G E 3 2 )