Aerial survey as a tool for understanding bigeye scad (Selar crumenophthalmus) dynamics around the island of O'ahu, Hawai’i

Abstract

The bigeye scad (Selar crumenophthalmus) supports one of the most productive near-shore fisheries in Hawai'i. Fishing boats frequently work in tandem with spotter planes to efficiently target bigeye scad schools. These spotter planes provide the means for a fishery-independent estimate of abundance based on direct observation, which may prove more sensitive to population trends than traditional estimates based on reported commercial catch and effort. An experienced spotter pilot was utilized to survey the biomass of bigeye scad schools surrounding the island of O'ahu for the 2015–2016 fishing season. The survey data were then used to create fishery-independent indices of apparent abundance at varying spatial and temporal scales to compare with fishery-dependent indices generated from commercial catch and effort data from net gears. The survey data also allowed for a better understanding of bigeye scad spatial and temporal patterns around O'ahu. Trends between fishery-independent and fishery-dependent indices of abundance were similar. The western region of O'ahu has the highest index value, exceeding each of the other three regions by two to five times. A clear temporal trend was also observed; indices increased from the lowest values during the beginning of the fishing season (November–January) to the highest values during the peak season (May–July). Our findings suggest that commercial catch and effort data are adequate to track trends in abundance of bigeye scad and inform management decisions.