Stable isotope-based tools to understand the effect of trawling ban on crustacean community in coastal waters of Hong Kong

Abstract

Our results showed that there was a greater trophic niche diversity in four studied crustacean communities three years after the trawl-ban, when compared to those of 2012 (before the trawling ban). Using Bayesian standard ellipse areas, we further compared the niche width of target crustacean species representing known functional groups (carnivore and omnivore) before and after the trawl-ban. Only two carnivorous species, namely Charybdis feriata and Oratosquilla oratoria, changed their niche width after the trawling ban, showing an expansion in dietary composition of Charybdis feriata. Such changes were likely linked to ecosystem recovery within the southeast waters, waters around Lamma and outer estuary, while the dietary composition of Oratosquilla oratoria only expanded within inner estuary after the trawl-ban. Further analyses are currently being conducted to assess whether the mean trophic level of carnivorous crustacean communities increases after the trawl-ban. The variation of isotopic signatures in the consumers before and after the trawling ban will be discussed in light of their life history traits (e.g. size), food sources, and substratum heterogeneity.