Semiautomated Process for Enumeration of Fishes from Recreational-Grade Side-Scan Sonar Imagery

The use of hydroacoustic techniques is increasing as scientists search for less invasive ways to monitor fish populations, and using recreational side-scan sonar (SSS) imagery for monitoring has become more common in aquatic resource management over the last 15 years due in part to its low cost and user-friendly interface. The time-consuming nature of manually counting fish targets has limited the use of the data that is collected by these systems in research or management contexts. To reduce the time and effort that is required to enumerate acoustic targets that are presumed to be fish, we developed a semiautomated process that rapidly quantifies targets from recreational SSS imagery by using an open-source image processing software. Perceived fish targets were enumerated using a set of macroinstructions that performed similarly to manual enumeration by three experienced assessors. This method reduced variation that arises from individual assessors and eliminated the prohibitive time constraints that are associated with manual processing. Herein, we describe how our semiautomated process could be used in fisheries management contexts after further research and development of sampling methods. Future research will focus on field validation, quantifying relative abundance, testing across a broader range of environmental conditions, and exploring other applications for fisheries management.