Underwater Stereo-Camera Survey Methodology for Estimating Density and Size of Northern Abalone (Haliotis kamtschatkana)
2021
Rooper, Christopher N. | MacNeill, Shaun | Lee, Lynn | McNeill, Dan | Yamanaka, Kae Lynne | Towler, Richard | Williams, Kresimir
Northern abalone are an important component of the intertidal and subtidal ecosystems of the Pacific Coast. This research was carried out to test the feasibility of utilizing underwater stereo-camera technology to conduct surveys to estimate the abundance and size structure of northern abalone populations. Consistent with other studies, depth and substrate both impacted the density and length of northern abalone, and provided a basis for implementing stratification strategies for density estimation. The average deployment took about 18 min and resulted in 47 useable image quadrats. The estimated time to analyze each frame was about 3 min, translating into ∼2.5 h of processing time per deployment. The precision of the resulting density estimates was high (relative error ∼0.22–0.37 depending on the method used for stratification) and could be improved by increasing the number of study sites to 35 or greater. The pooled density of northern abalone was estimated as 1.07 individuals/ m–² (SE = 0.21) and the mean length of northern abalone across the study sites was 67.7 mm (SE = 0.08). Future stereo-camera surveys could be used as a cost-effective supplement to self-contained underwater breathing apparatus diver surveys to increase the precision of abundance and size estimates of northern abalone populations.
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