Akule aerial survey 2015 and 2017

The bigeye scad (Selar crumenophthalmus, locally known as akule) is an important food source for many Hawaiians and represents one of the most productive near-shore fisheries in Hawai'i. These fish occupy an intermediate trophic link between the coastal environment in which they feed and the pelagic environment of their predators. Akule are largely fished using surround nets deployed from a fishing boat. Boats frequently work in tandem with spotter planes to efficiently target the most advantageous 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 locate and estimate the biomass of akule schools surrounding the island of O'ahu for the 2015-2016 fishing season following a standardized schedule and protocol. The aerial survey data were then used to create fishery-independent indices of abundance at varying temporal and spatial scales to compare with indices generated from commercial catch and effort data. The data also allowed for a better understanding of akule spatial and temporal patterns around O'ahu. Trends among fishery-dependent and fishery-independent 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 three times. A clear temporal trend was also observed; indices increased from the lowest values during the beginning season (November – January) to the highest values during the peak season (May – July). The corresponding fishing operation was also monitored, and the average catch totaled 20% of the targeted school when using surround gill nets.

Estimate biomass of akule schools around Oahu using plane and spotter pilot to determine if index of fishery-independent biomass estimation differs from index from catch and effort data reported to DAR. Secondarily, to confirm that aerial estimates are accurate or at least to understand the bias associated with estimating school size.

Work done with the Council and Commercial Fisher through Cooperative Research Program.

Send written request to PIFSC and requires approval by the PIFSC data owner.

Requires signing a PIFSC non-disclosure statement for fisheries confidential data.

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