We report the results of a survey of the fishes of Kāne‘ohe Bay, O‘ahu, conducted in 2017 as part of the Smithsonian Institution MarineGEO Hawaii bioassessment. We recorded 109 species in 43 families. The most speciose families were Acanthuridae (11 species), Gobiidae (11 species), Pomacentridae (10) and Chaetodontidae (9 species). Nine of the species that we collected are known or suspected to be introduced to the Hawaiian Islands. Specimens were identified, measured and photographed. All specimen vouchers were fixed in formalin and ultimately transferred to 75% ethanol for long-term storage. For nearly all species, we took multiple tissue samples from specimen vouchers prior to formalin-fixation; we preserved tissues in 95% ethanol and then stored them at −80°C. The 5′-end of the mitochondrial cytochrome oxidase I gene (mtCOI) was sequenced for 94 species to confirm their taxonomic identification. Using these barcode sequences, we also measured genetic distances between collected individuals and their conspecifics from other localities outside Hawaii to verify the hypothesis that Hawaiian populations of species broadly distributed throughout the Indo-Pacific may be genetically distinct. We present select case studies to demonstrate the potential for undiscovered endemism in the Hawaiian fish biota.

Susceptibility to infestation by a gnathiid isopod (Gnathia marleyi: Crustacea: Isopoda) was examined among 16 species from 9 families and 3 orders of common Caribbean reef fishes off St. John, United States Virgin Islands. Fish were placed in cages during times of peak gnathiid activity. Individuals from most (n=14) species were compared against a single species (French Grunt, Haemulon flavolineatum) that served as a standard and effectively controlled for the effects of habitat and variation in gnathiid abundance on exposure to and the likelihood and intensity of host infestation by gnathiids. All species were susceptible to infestation by gnathiids, with individual hosts harbouring up to 368 gnathiids. However, there was significant variation in levels of infestation among the 14 comparison species. Controlling for body size, nocturnal species from the families Haemulidae and Lutjanidae had the highest gnathiid infestation. Our finding that haemulids and lutjanids are particularly susceptible has important implications for the role of gnathiids in Caribbean reef food webs, given the role members of these families play in trophic connectivity between reefs and associated habitats. To our knowledge this is the first manipulative field study to examine variation among potential hosts in susceptibility to an ectoparasite in any terrestrial or aquatic system and is the greatest number of teleost hosts documented for any gnathiid species.

The application of no-take marine reserve status to an area is expected to increase abundance and average size of individuals of species targeted by fisheries. The majority of the evidence supporting such expectations still involves comparisons of abundance at the one time of sites with and without marine reserve protection. Very few studies have data on the abundance and size structure of species targeted by fisheries in an area before reserve status is applied. Quantitative estimates of density and biomass of coral trout, Plectropomus spp., the major target of the hook and line fisheries on the Great Barrier Reef (GBR), Australia, on inshore fringing reefs of the Palm and Whitsunday Island groups, central GBR, are provided for 3–4 years before (1983–1984), and 12–13 years after (1999–2000) the establishment of no-take reserves in 1987. Quantitative estimates of density and biomass of coral trout in areas open to fishing were also collected in 1999–2000 at these two island groups. Density and biomass of coral trout increased significantly (by factors of 5.9 and 6.3 in the Palm Islands, and 4.0 and 6.2 in the Whitsunday Islands) in the reserve sites, but not the fished sites, between 1983–1984 and 1999–2000. In 1999–2000, density and biomass of coral trout and a secondary target of the fisheries, Lutjanus carponotatus, were significantly higher in the protected zones than in the fished zones at both island groups. The density and biomass of non-target fish species (Labridae, Siganidae and Chaetodontidae) did not differ significantly between reserve and fished zones at either island group. This is the most convincing data to date that the management zoning of the world's largest marine park has been effective, at least for coral trout on inshore reefs.

What are the effects of no-take marine reserves on trophic relationships of coral reef fish? Previous studies often have lacked detailed dietary information on major predators, and have often been confounded by differences in habitat complexity between reserve and fished sites. This study investigates the effects of marine reserve protection on predator-prey interactions of coral reef fish on the inshore islands of the Great Barrier Reef (GBR). The abundance of species of prey fish of Plectropomus leopardus (Serranidae), a piscivore and the major target of the hook and line fisheries on the GBR, were estimated in protected and fished zones. These prey species were identified from previous detailed studies of the diet of P. leopardus. Fish populations and habitat characteristics were surveyed by underwater visual census. Previous studies had determined that the biomass of P. leopardus was 3–4 times higher in protected than fished zones in the Whitsunday and Palm Islands, central GBR, after 14 years of protection. Eight of the nine prey species had a higher density within fished zones than protected zones, six significantly so. The density of all prey fish was twice that in the fished than the protected zone (p < 0.001). There were no significant differences in availability of different sized refuge holes, structural complexity or live coral cover between zones. Thus, important attributes of habitat complexity did not confound the comparisons between reserve and fished zones. Finally, a significant negative correlation (r = 0.46) between coral trout biomass and summed prey fish biomass suggested that predation may be an important structuring process in this system. The results have implications for the conservation of fishery targets and their prey. The study highlights the potential ecosystem implications of the use of no-take marine reserves as conservation and fisheries management tools.