Deepwater marine protected areas of the main Hawaiian Islands: Establishing baselines for commercially valuable bottomfish populations

Abstract

This study provides the first comprehensive fishery-independent baseline assessment of commercially important deepwater bottomfish populations across the main Hawaiian Islands. Differences in bottomfish relative abundance and size distribution were evaluated for 6 deepwater Bottomfish Restricted Fishing Areas (BRFAs). While no differences were detected in species relative abundance, evaluation of size-frequency distributions found the 2 most commercially valuable species (Etelis coruscans and Pristipomoides filamentosus) to be significantly larger inside the BRFA at Ni'ihau, located off the most remote of the main Hawaiian Islands. This BRFA is 1 of 2 ongoing BRFAs offering 10 yr of protection. This result highlighted the time it may take a long-lived and slow-growing species to show a detectable response to protection and that size distribution analyses can detect these more subtle changes. No positive effects of protection were detected for the second ongoing BRFA located off Hawai'i. Instead, 2 species (P. filamentosus and P. sieboldii) were significantly larger outside the BRFA. In contrast to Ni'ihau, the second BRFA established in 1998 originally included less preferred habitat and is next to the second largest port in Hawai'i, offering greater access, higher population pressure and more problematic enforcement. This study demonstrates that biological, sociological and environmental context must also be considered when interpreting the effectiveness of marine protected areas.