Preliminary Results from Visual Fish Surveys in the Main Hawaiian Islands Released

Figure 1.  Mean total fish biomass density observed at coral reef survey sites in the main Hawaiian Islands during the September 
               2012 cruise. Biomass at the surveyed sites on Oahu was generally less than at sites on other islands.
Figure 1. Mean total fish biomass density observed at coral reef survey sites in the main Hawaiian Islands during the September 2012 cruise. Biomass at the surveyed sites on Oahu was generally less than at sites on other islands.

PIFSC has published a preliminary summary of findings from recent visual surveys of coral reef fishes in the main Hawaiian Islands. The surveys were conducted in September 2012 by a team of biologists from the PIFSC Coral Reef Ecosystem Division working on the NOAA Ship Oscar Elton Sette. The team used the stationary-point-count method to survey 163 sites within selected intervals of coastline which the investigators were able to visit. As indicted in Figure 1, large stretches of coastline were excluded from the survey. Within the surveyed areas at each island, sampled sites were randomly selected taking into account the amount of coral reef habitat in designated depth zones. Surveys were conducted at depths of 0-30 m at Lanai (n = 29 sites), Maui (n = 49), Molokai (n = 50), Oahu (n = 35). The ultimate aim of the surveys is to cover all portions of the coastlines over multiple cruises.

Observed fish biomass was lower at survey sites on the north and west shores of Oahu than at survey sites in the other main Hawaiian Islands; this was true for all consumer groups and size classes of fish (Figs. 1-3).

Among fish consumer groups, primary consumers include herbivores (which feed on plants) and detritivores (which eat detritus on the seafloor). Secondary consumers consist largely of omnivores (which eat plants and animals) and invertivores (which eat invertebrates).

The preliminary results were issued as a 2-page PIFSC Data Report which was posted on the PIFSC website.

Further details on the surveys, part of the Pacific Reef Assessment and Monitoring Program, are available on the PIFSC CRED website.

Figure 2. Mean fish biomass (± standard error) per size class and island surveyed. Fishes were measured by total length (TL) 
               in centimeters (cm). Size classes shown here are 0–20, 20–50, and > 50 cm TL.
Figure 2. Mean fish biomass (± standard error) per size class and island surveyed. Fishes were measured by total length (TL) in centimeters (cm). Size classes shown here are 0–20, 20–50, and > 50 cm TL.
Figure 3. Mean fish biomass (± standard error) per consumer group and island surveyed.  Primary consumers are herbivores and 
               detritivores, and secondary consumers are omnivores and invertivores.
Figure 3. Mean fish biomass (± standard error) per consumer group and island surveyed. Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.