Quantifying how spatial resolution affects fish distribution model performance and prediction: A case study of Caspian Kutum, Rutilus frisii

Boosted regression trees Environmental predictors Habitat modelling Spatial scale

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December 25, 2024

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The present study aimed to investigate the effect of spatial resolution of data on distribution modelling performance for the Caspian Kutum, Rutilus frisii. A set of spatial resolutions (4, 8, 16, 32, and 64 km) were considered in the modelling analyses, using sea surface temperature, chlorophyll-a concentration, particulate organic carbon content, bottom slope, and depth as environmental predictors of fish catch-per-unit-of-effort (CPUE). The boosted regression trees (BRT) method was applied as the modelling technique. The results showed considerable reductions in data variability (coefficient of variation (%) and variance) with decreasing spatial resolution for most environmental variables and CPUEs. The model performance (adj-R2) was improved with decreasing resolutions, but the best prediction ability of the models was obtained with the BRTs fitted on the lowest resolutions (i.e. 4 and 8 km). While sea surface temperature was the main influencing predictor in the fitted BRTs at all resolutions, resolution-dependence differences were observed in the significance and response curves of other predictors of the models across the spatial resolutions. Overall, our findings indicated that using different levels of spatial resolution highly affects the modelling process, with more relevant explanations and higher prediction power using finer resolutions.