The randomized response technique as a tool for estimating non-compliance rates in fisheries: a case study of illegal red abalone (Haliotis rufescens) fishing in Northern California

SUMMARY Illegal fishing has detrimental environmental and social impacts, but these effects are difficult to mitigate without reliable estimates of fisher non-compliance. Methods used by fisheries managers to estimate illegal fishing often require indirect estimation of poaching using biological, economic or sociological indicators. This study presents a unique application of the randomized response technique (RRT) for direct estimation of non-compliance in fisheries to the Northern California recreational red abalone (Haliotis rufescens) fishery. An anonymous paper-based compliance and sociodemographic survey of recreational fishers in Sonoma and Mendocino Counties estimated 29% non-compliance with the daily take limit, 23% with the minimum size limit, 19% with licensing laws and 15% with the annual take limit. RRT results also indicated how different sociodemographic characteristics related to non-compliance. Visitors had higher non-compliance rates than local fishers for all regulations except daily take limits, which an estimated 72% of locals violated versus 18% of visitors. High fisher awareness of regulations, fisher age, income and fishing experience did not appear to influence illegal take. RRT is a powerful tool which can aid conservation managers in prioritizing action.