Fishery yields vary with land cover on the Amazon River floodplain

Abstract

Inland fisheries underpin food security in many tropical countries. The most productive inland fisheries in tropical and subtropical developing countries occur in large river–floodplain systems that are often impacted by land cover changes. However, few studies to date have assessed the effects of changes in floodplain land cover on fishery yields. Here, we integrated fisheries and satellite‐mapped habitat data to evaluate the effects of floodplain deforestation on fishery yields in 68 floodplain lake systems of the lower Amazon River, representing a wide range in relative amounts of woody, herbaceous and non‐vegetated land cover. We modelled relative fish yields (fish capture per unit effort [CPUE]) in the floodplain lakes as a function of the relative amounts of forest, shrub, aquatic macrophyte and bare/herbaceous habitats surrounding them. We found that forest amount was positively related (p = .0003) to multispecies CPUE. The validity of these findings was supported by rejection of plausible alternative causative mechanisms involving habitat‐related differences in amount of piscivores, fishing effort, lake area, and habitat effects on CPUE of the nine taxa dominating multispecies yields. Our results provide support to the idea that removal of floodplain forests reduces fishery yields per unit effort. Increased protection of floodplain forests is necessary to maintain the food, income and livelihood security services provided by large river–floodplain fisheries.

Ecosystem‐based management of Amazon fisheries and wetlands

“…The correlation between flooded forest areas and their river types across the Amazon was less clear. Experimental gillnet studies and commercial fish landing analyses in different areas of the Amazon reported that fish abundance and/or diversity was most associated with flooded forest area (Arantes et al., ; Castello et al., ; Lobón‐Cerviá, Hess, Melack, & Araujo‐Lima, ). An experimental gillnet investigation of 15 floodplain lakes of the Central Amazon floodplain correlated fish species richness with the extent of shrub vegetation during the high water period and the extent of aquatic herbaceous communities and open waters during the low water season (Freitas et al., ).…”

“…The species‐specific regression results for three of the flagship characiform taxa, however, do not reflect the relative collinearity of floodplain lake and flooded forest area in the western Amazon because the large floodplain lake area of the eastern Amazon is not linearly correlated with fisheries production (Figure ). A more local study that focused on the eastern subregion indicated that floodplain forest cover was more correlated with fish yield than aquatic macrophytes associated with lakes (Castello et al., ).…”

“…The lower Amazon River floodplain undoubtedly has important nurseries, and wetland deforestation may in part be responsible for the drastic decline in some species, such as the highly frugivorous tambaqui (Isaac & Ruffino, ), which was once the most important commercial species. Importantly, however, the remaining forest is still critical to fish production (Castello et al., ). The blackwater and clearwater sub‐basin areas (446,320 km 2 ) upstream of the main commercial fishing area, to which many species migrate partially or permanently after reaching large subadult stages, have suffered relatively little deforestation.…”

Size‐structured habitat selection by arapaima in floodplain lakes of the Lower Amazon

“…Unfortunately, present legislation offers only scant protection for these floodplains. In Brazil, for example, floodplain protection is mostly based on the Forest Code, which only protects a maximum of 500 m of floodplain adjacent to river channels even though Amazonian floodplains often extend for tens of kilometres (Castello et al, ). Increased levels of protection for the land cover of floodplains may be needed to decrease the vulnerability of floodplain fishes, and this topic warrants further study.…”

“…Tropical river floodplain ecosystems are home to myriads of fish species, but they have been under growing human pressures (Junk, ; Tockner & Stanford, ). Large expanses of tropical floodplains have undergone land cover changes, especially deforestation (Renó, Novo, Suemitsu, Rennó, & Silva, ), which are linked to fish population declines (Castello et al, ; Arantes et al, 2018). In addition, fishing activities have overfished and depleted several floodplain fish populations (Castello et al, ; Coomes, Takasaki, Abizaid, & Barham, ).…”