Using the Randomized Response Technique to Investigate Illegal Fishing and Contribute to Abalone Management in Northern California

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 the Northern California recreational red abalone (Haliotis rufescens) fishery. Using an anonymous paper-based compliance and sociodemographic survey of recreational fishers in Sonoma and Mendocino Counties, I estimate 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 and among the general population. No significant relationship between the socio-demographic variables gathered (age, income, county of residence, fishing experience) and RRT survey responses indicates that no clear profile can be ascertained to help identify potential violators. However, visitors have higher non-compliance estimates for all regulations except daily take limits, for which an estimated 72% of locals violate vs. only 18% of visitors. These rule-specific violation estimates allow for the development of efficient management priorities, as managers may target specific measures or user groups. Further research should develop quantitative RRT estimates of illegal take, and explore violation drivers operating within the fisher population.