Live reef food fish trade causes rapid declines in abundance of squaretail coralgrouper (Plectropomus areolatus) at a spawning aggregation site in Manus, Papua New Guinea

Abstract

Overfishing by the live reef food fish trade (LRFFT) is recognised as being one of the greatest threats to fish spawning aggregations (FSA) of coral reef fish (Johannes and Riepen 1995; Sadovy and Vincent 2002; Sadovy et al. 2003; Warren-Rhodes et al. 2003). However, direct evidence of FSA loss or decline as a result of LRFFT activities is negligible in the IndoPacific (Rhodes and Warren-Rhodes 2005), with the majority of documented accounts being based on the local knowledge of fishers (Johannes et al. 1999; Hamilton et al. 2005a; Sadovy 2005; Sadovy and Domeier 2005). In this paper we present evidence from Melanesia that quantitatively demonstrates the impact of the LRFFT on the FSA of the squaretail coralgrouper (Plectropomus areolatus). We do this by compiling underwater visual census (UVC) data that were collected from three grouper FSA sites located on the south coast of Manus, in Papua New Guinea. Two of the three monitored sites (Sites 29 and 33)3 have never been opened to the LRFFT, while the third site (Site 35) was exploited to supply the LRFFT between July and December 2005. Our preliminary results show that relative to the two unfished “control” sites, Plectropomus areolatus abundances and densities at Site 35 declined very rapidly following the commencement of the LRFFT. The UVC survey results also show that peak FSA of P. areolatus formed at Sites 29 and 33 between March and June 2006, as was predicted by local fishers. During the same period, no clearly defined peak season was detected at Site 35.