López González, Leysa

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    Comparison of handline, underwater visual census (UVC), and remote underwater video (RUV) used by fisheries-independent programs to assess reef fish abundance and biomass
    (2022-08-08) López González, Leysa; Cruz Motta, Juan J.; College of Arts and Sciences - Sciences; Rosario, Aida; Appeldoorn, Richard S.; Department of Marine Sciences; Huérfano Moreno, Víctor A.
    Concerning declines in fish populations have ecological and socio-economic implications, jeopardizing the source of income and food security of millions of families. The purpose of fisheries independent programs is to implement cost-effective robust monitoring approaches necessary to assess spatiotemporal changes in fish structure and composition to help policymakers create appropriate management plans. Several methods have been employed by these programs resulting in different conclusions. We compared four different methods: two methods based on visual censuses (UVC: transect and roving), one method based on remote underwater videos (RUV), and handline (HL) to determine differences among the methods and establish whether the differences are complementary. All methods were simultaneously performed in a total of 13 sites on the east (Fajardo) for a total of 26 observations and 9 on the southwest (La Parguera Natural Reserve, LPNR) of Puerto Rico with a total of 42 observations. Multivariate analysis revealed that there are significant dissimilarities between the methods evidenced by the higher species diversity, abundances, and biomass observed in UVC and RUV. Higher spatiotemporal variability was associated with HL than with UVC and RUV, which were similar to each other. The method with the highest number of unique species was UVC (31) followed by HL (4) and RUV (3). Differences were also observed in fish groups assessed with HL detecting fewer species consisting mainly of the family Serranidae, while other important fish groups, such as individuals from families Scaridae and Acanthuridae, were observed in UVC and RUV. Univariate analysis for commercially important species also showed that UVC and RUV methods are more precise and time efficient than HL. A complementary association between that transect and roving was observed with the latter increasing the diversity observed during surveys. As a result, a multi-gear approach is recommended depending on the aims of the studies. UVC and RUV serve to gauge a broader range of fish structure and composition, while HL should be implemented in cases where age and sex data are necessary.