1 Introduction: Redfish Rocks Longline Surveys
Longline (LL) sampling targets demersal fishes living on rocky reef habitats using catch and release methods. All fish caught are identified to species level and measured for length. Fish are caught using standardized longline gear for a fixed amount of time, providing data on effort.
Our LL sampling at Redfish Rocks grew out of a pilot study comparing hook and line sampling to longline sampling. This pilot study was based on observations of our local fishing captain that there were several species targeted by commercial fisheries in the area that were not well represented in hook and line catch (Huntington and Watson 2017). Sampling is conducted in the marine reserve and two comparison areas, Humbug and Orford Reef (see methods Appendix for additional information about comparison area selection). The pilot study occurred in 2015 and 2016, sampling continued in 2017 and 2019, providing four years of data for our analysis and inclusion in the synthesis report.
Data from longline monitoring efforts can be used to explore questions about fish abundance and size from a method that is similar to local commercial nearshore longline fishing efforts. We can also explore these data with questions about diversity and catch composition to compare across monitoring tools to understand tool bias or to validate trends seen across tools. This can further help us understand how the fish communities at these sites are similar or different. Data on abundance and size enable us to explore how fish catch, biomass, and size have changed over time; and whether these changes are similar both inside the reserve and outside in comparison areas. For all data our main focus is exploring trends by site and year.