Comparing angling, underwater visual census, and video sampling methods to refine [fishery independent] long-term monitoring of a reef fish assemblage in a temperate marine reserve

Robust marine reserve assessment requires managers to understand the biases of their sampling methods. As marine reserve managers, we investigated the comparability of fish assemblage data collected using hook and line (HnL) angling, unbaited remote underwater video (RUV), and diver-based underwater visual censuses (UVC) to optimize long-term monitoring within Redfish Rocks Marine Reserve, a temperate no-take reserve in Oregon. Sequential surveys were performed at the same spatial locations to compare (1) species richness and frequency of occurrence, (2) community composition, and (3) size structure of temperate reef fishes among methods. We also evaluated sampling efficiency (i.e. sample size, and cost) to detect change. The occurrence of common species was similar among the three methods while less common, solitary species exhibited differences in encounter rates among methods. HnL observed the highest proportion of commercially important species and most diverse assemblage. The least abundant and diverse fish assemblage was observed by RUV, likely due to poor detection of cryptic species and low encounter rates of solitary species. For the dominant schooling rockfish taxa (Sebastes melanops and Sebastes mystinus/diaconus) frequency of occurrence was lower for HnL compared to UVC, likely due to spatial sampling extent, and hook selectivity reducing observations of these small mouthed taxa. Larger individuals were also observed using HnL compared to UVC, likely due to hook selectivity limiting the catch of smaller individuals. While there were differences in mean size, the length-frequency distribution shape did not differ between methods for many species, suggesting data could be integrated across methods with a correction factor. HnL approaches were more cost-effective and time-efficient to detect significant change in community and species-specific abundances, though for select species, UVC offered an efficient alternative to HnL. Therefore, we suggest discontinuing RUV surveys from future long-term monitoring efforts at Redfish Rocks Marine Reserve. Instead, we propose using available resources to increase the sample size of both the Hook and Line and UVC surveys to increase the statistical power to detect changes over time in this marine reserve.prepared by Jessica L. Watson, Brittany E. Huntington.Title from PDF title page (viewed on March 31, 2022).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references (pages 25-29).Mode of access: Internet from the Oregon Government Publications Collection.Text in English