Examining the influence of depth and tidal current on nearshore fish communities using scientific and citizen science data




Campbell, Jillian

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Learning about marine ecosystems is challenging; organisms move, abiotic conditions change, underwater environments are difficult to sample, and in BC, the coastline is lengthy and largely remote. This thesis explores two ways to address these challenges, first through developing surrogates and second through using citizen science data. Physical aspects of the environment are relatively easy to sample and can be used to explain observed changes or differences in biodiversity, which are often difficult to sample. Characteristics of marine biodiversity can then be inferred based on the intensity or extent of the abiotic surrogate and habitats critical for commercially important or endangered species, or habitats that support increased biodiversity or ecosystem services can be identified. Still, information about taxa distribution and abundance are required to determine the success of these abiotic surrogates in explaining biodiversity. Gathering abundance data on wide temporal and spatial scales is expensive and difficult to achieve with small scientific diving crews. However, the recreational SCUBA diving community is well-positioned to aid in filling biological data gaps. In this study, depth and current speed are evaluated for their effectiveness at explaining fish community biodiversity using a scientifically collected data set. We found depth to be a suitable abiotic surrogate for fish species richness and abundance, but tidal current speed was ineffective at determining trends in fish biodiversity. Citizen science data were examined to demonstrate how robust these data are for use in scientific studies through the exploration of two case studies. The first case study explored how lingcod (Ophiodon elongatus) abundances changed over time due to fishery management efforts, and the second case study examined how current speed, as identified by citizen science surveyors, could be used as an abiotic surrogate for fish biodiversity.



marine ecosystem, abiotic surrogate, tidal current, depth, marine fish, citizen science, lingcod (Ophiodon elongatus), marine spatial planning, nearshore benthic fish, fish community composition