Environmental Conservation

Papers

Assessing the importance of fishing impacts on Hawaiian coral reef fish assemblages along regional-scale human population gradients

I. D. WILLIAMSa1a2 c1, W. J. WALSHa2, R. E. SCHROEDERa3, A. M. FRIEDLANDERa4, B. L. RICHARDSa3 and K. A. STAMOULISa2

a1 Hawaii Cooperative Fishery Research Unit, Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA

a2 Hawaii Division of Aquatic Resources, Honokohau Marina, 74-380B Kealakehe Parkway, Kailua-Kona, Hawaii 96740, USA

a3 Joint Institute for Marine and Atmospheric Research (JIMAR), University of Hawaii and Coral Reef Ecosystems Division (CRED) NOAA, National Marine Fisheries Service, Pacific Islands Fisheries Science Center, 1125B Ala Moana Boulevard, Honolulu, HI 96822, USA

a4 NOAA/NOS/NCCOS/CCMA- Biogeography Branch and The Oceanic Institute, Makapuu Point/41-202 Kalanianaole Highway, Waimanalo, Hawaii 96795, USA

SUMMARY

Humans can impact coral reef fishes directly by fishing, or indirectly through anthropogenic degradation of habitat. Uncertainty about the relative importance of those can make it difficult to develop and build consensus for appropriate remedial management. Relationships between fish assemblages and human population density were assessed using data from 18 locations widely spread throughout the Main Hawaiian Islands (MHI) to evaluate the significance of fishing as a factor potentially driving fish trends on a regional scale. Fish biomass in several groups was negatively correlated with local human population density and a number of lines of evidence indicate that fishing was the prime driver of those trends. First, declines were consistently evident among fish groups targeted by fishers, but not among lightly fished or non-target groupings, which indicates that declines in target groups were not simply indicative of a general decline in habitat quality along human population gradients. Second, proximity to high human populations was not associated with low fish biomass where shoreline structure prevented ready access by fishers. Relatively remote and inaccessible locations within the MHI had 2.1–4.2 times the biomass of target fishes compared to accessible and populous locations, and may therefore function as partial refugia. However, stocks in those areas were clearly far from pristine, as biomass of large predators was more than an order of magnitude lower than at more intact ecosystems elsewhere in the Pacific.

(Received January 29 2008)

(Accepted May 26 2008)

(Online publication August 29 2008)

Correspondence

c1 Correspondence: Dr Ivor Williams Tel: +1 808 327 6231 Fax: +1 808 327 6229 e-mail: ivor@hawaii.edu