When fishers guide scientific exploration: Case study with ‘ōpelu in Hawai‘i

ABSTRACT Objective The Mackerel Scad Decapterus macarellus (hereafter, ‘ōpelu), a coastal pelagic carangid, is an important commercial, recreational, and cultural marine resource in Hawai‘i. Fishers often use ‘ōpelu as bait, for personal consumption, or to share or sell. ‘Ōpelu form aggregations at specific locations repeatedly, often referred to as ‘ōpelu ko‘a, which fishers observe and use as fishing locations. Consequently, fishers have a deep understanding of these aggregation sites and what makes these locations ideal for ‘ōpelu. To understand the environmental factors influencing ‘ōpelu aggregation behavior and catchability, we combined fisher knowledge and fishery-dependent data to create a model of ‘ōpelu catch. Methods We interviewed ‘ōpelu fishers in 2021 about environmental factors that influence ‘ōpelu aggregation behavior and catchability. We then applied the observations shared among the fishers to the ‘ōpelu commercial catch records (1997–2022) to test which factors predicted ‘ōpelu CPUE. Results Interviews of 11 fishers provided a variety of factors that influence ‘ōpelu aggregation and catchability, including lunar phase, season, and ocean temperature. We then merged available environmental data streams into the commercial catch records and conducted statistical analysis using a generalized additive model with catch as a response variable. The parsimonious model indicated significant partial effects of sea surface temperature, seasonality, El Niño–Southern Oscillation, Pacific Decadal Oscillation, and lunar phase. Conclusions Model results generally aligned with interviews, mutually enhancing their contextual understanding. The integration of interviews and modeling not only facilitated a more insightful analysis of ‘ōpelu aggregation and catchability but also allowed fishers to contribute their perspectives to the research conducted on their fishery.