Fishery resources in Hong Kong have been over-exploited since the 1970s. In 2010, there were still around 400 trawlers operating in local waters. These trawlers non-selectively catch marine organisms of all sizes, while exerting severe physical damage to the benthic ecosystem. To mitigate the associated impacts of overfishing and trawling, the Government of the Hong Kong Special Administrative Region has imposed a territory-wide trawling ban across local marine waters since 31 December 2012. This study aims to investigate if the trawl-ban policy is effective to facilitate recovery of demersal fish resources, in terms of species diversity, abundance and biomass, in Hong Kong. Under an approved scientific permit, trawl surveys were conducted using a commercial shrimp trawler in eastern (including outer (EO) and inner Tolo (EI)), southern (waters in southeast (SE) and around Lamma (SL)) and western waters (outer (WO) and inner estuary (WI)) of Hong Kong. The fish communities between 2004, 2007 and 2012 (pre trawl-ban) and 2013 to 2015 (post trawl-ban) were compared.
Results/Conclusions
The results revealed that the demersal fish community at WI had significant increase in total biomass in 2015 when compared to that before the trawl-ban. The fish communities at SE, SL and WO, however, showed negative recovery trends. The species diversity (expressed by Hill’s N1) of SE in 2015 was significantly lower than that in 2012 and 2013. The same pattern was observed in the total biomass and species diversity of SL. Significantly lower species diversity of WO was also recorded in 2014 and 2015 when compared to 2013. The negative signs of recovery were partly due to illegal trawling activities as a result of poor enforcement and patrolling, increase of fishing pressure from other non-trawling fishing methods, coastal development and deterioration of marine water quality. Trophic levels and population dynamics of selected fish species will be studied to countercheck if the trawl ban is able to provide opportunity for the heavily impacted fish populations to recover.