Project Report PR-98-01
An Analysis of the Fish Communities Along the Barbers Point Ocean Outfall, Ewa Beach, Oahu, Hawaii, Using Remote Video, 1997 Data
Richard E. Brock
Because the diffuser of the Barbers Point Ocean Outfall lies below safe diving depths, a remotely controlled video camera system was used to determine the status of the marine fish communities and selected diurnally exposed macroinvertebrate species residing on the diffuser. Video reconnaissance was completed over the entire 534-m length. Three visual “transects,” which “sampled” approximately 31% of the total diffuser length, were established on the diffuser pipe. Video sampling of the diffuser fish communities was carried out in January of 1992 through 1995, in March of 1996, and in April of 1997. The results of the six annual surveys indicate that the diffuser fish communities are dominated by species that are either small as adults or juveniles of larger species, probably as a result of the presence of only small-scale shelter created by small armor rock and gravel used in constructing the discharge pipe. Because of poor camera resolution, differing angles of the camera, small fish sizes, and the fishesº nature to flee from the approaching camera, the fish census Data are highly variable and should be viewed as more qualitative than quantitative in nature. Despite this variability from transect to transect and year to year, only one parameter showed any statistical change over the six annual survey years. This parameter was the mean size of the area sampled to find an individual fish using the nonparametric Kruskal – Wallis analysis of variance. The statistical difference is related to the lower number of individual fish and macroinvertebrates encountered during the 1997 survey, which is related to the ability to see fish due to poor visibility, camera resolution, and camera angle. Little significance should be attached to any change noted in the fish or macrobenthic communities residing on the Barbers Point diffuser because of the variable quality of the Data generated by use of the remotely controlled video system.