3 years ago

Evaluating flood pulse relationships with fish catch in river‐floodplains of the central Amazon

Jesse E.B. Olsen, Leandro Castello, Yan Jiao, Vandick S. Batista, Nidia N. Fabré

Abstract

The seasonality of water levels in large river‐floodplain ecosystems, known as flood pulses, influence the dynamics of fish populations and associated catches. Various flood pulse variables (e.g. maximum stage) have been correlated to catches of river‐floodplain fishes, but no study to date has assessed the effects of various flood pulse variables and interannual lags on catch of a range of taxa in order to determine general patterns of flood pulse influence on fish catch. Interannual flood pulse effects are important because they infer changes on fish biomass. This study assessed which flood pulse variables and interannual lags have the strongest relationships with catches of 22 river‐floodplain fish taxa in river‐floodplain of the central Amazon Basin. Using data from 15,540 fishing trips, we modeled catch of each of the 22 taxa as a function of flood pulse variables one, two, and three years prior while accounting for the effects of fishing effort, gear, and flooding season in the same year. Our assessment was based on the difference between RMSE of the models with and without each individual flood pulse variable and respective lags. We found that low water flood pulse variables had the strongest relationships with catches but they were only slightly stronger than those of high water variables. Flood pulse variables with two‐year lags had the strongest relationship with catches, followed by three‐year and then one‐year lags. These results support the notion that high water levels increase fish biomass available for harvesting, leading to larger‐than‐normal catches in subsequent years, whereas low water levels decrease fish biomass, leading to smaller‐than‐normal catches. These findings allow to better manage and restore floodplain fisheries and river hydrology.

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