Flood pulse effects on multispecies fishery yields in the Lower Amazon

Abstract

Seasonally fluctuating water levels, known as ‘flood pulses’, control the productivity of large river fisheries, but the extent and mechanisms through which flood pulses affect fishery yields are poorly understood. To quantify and better understand flood pulse effects on fishery yields, this study applied regression techniques to a hydrological and fishery record (years 1993–2004) for 42 species of the Amazon River floodplains. Models based on indices of fishing effort, high waters and low waters explained most of the interannual variability in yields (R2=0.8). The results indicated that high and low waters in any given year affected fishery yields two and three years later through changes in fish biomass available for harvesting, contributing 18% of the explained variability in yields. Fishing effort appeared to amplify high and low water effects by changing in direct proportion to changes in fish biomass available for harvesting, contributing 62% of the explained variability in yields. Although high waters are generally expected to have greater relative influence on fishery yields than low waters, high and low waters exerted equal forcing on these Amazonian river-floodplain fishery yields. These findings highlight the complex dynamics of river-floodplain fisheries in relation to interannual variability in flood pulses.

Population recovery, seasonal site fidelity, and daily activity of pirarucu (Arapaima spp.) in an Amazonian floodplain mosaic

“…The water level oscillation induces stark changes in the landscape, flooding extensive terrestrial habitats, modifying aquatic habitat availability, creating seasonal refuges, connecting populations, and influencing the accessibility and impact of commercial fisheries (Junk et al., ). As a result, the flood pulse clearly affects fish behaviour and ecology in multiple ways, with subsequent effects on fisheries yields (Castello, Isaac, & Thapa, ; Endo, Peres, & Haugaasen, ; Fernandes, ). Pirarucu have been used as a model taxon to elucidate fish responses to the prolonged flood pulse phenomenon (Araripe, do Rêgo, Queiroz, Sampaio, & Schneider, ; Castello, ).…”

Fishery yields vary with land cover on the Amazon River floodplain

“…C 3 plants and algae have been found to support trophic pathways to river fishes of the Mekong basin in Asia (Ou & Winemiller, ), the Paraná and Amazon basins in South America (Forsberg et al., ; Hoeinghaus, Winemiller, & Agostinho, ; Oliveira, Soares, Martinelli, & Moreira, ) and the Brazos River in North America (Zeug & Winemiller, ). Accordingly, inundatable floodplain area is generally positively related to fish biomass and associated fishery yields (Castello, Isaac et al., ; Welcomme, ).…”

Hydrological controls of fisheries production in a major Amazonian tributary

“…The magnitude and timing of flow in Amazonian river systems and their associated lakes and wetlands are characterized by a strongly seasonal flood pulse (Junk, Bayley, & Sparks, ). Many studies have elucidated how the flood pulse promotes high primary and secondary production in the Amazon and other tropical rivers, with some of the most important effects observed in the dynamics of fish stocks and fishing yields (Bayley, ; Castello, Isaac, & Thapa, ; Fearnside, ; Górski et al, ; Halls & Welcomme, ; Isaac, Castello, Santos, & Ruffino, ; Mérona & Gascuel, ; Moses, ; Petesse & Petrere, ). Beyond the scientific community, fishermen also recognize important associations between hydrological dynamics, fishing efficiency, and economic earnings (Doria, Lima, & Neto, ; Gonçalves & Batista, ; Isaac & Cerdeira, ).…”

“…Following from its role in structuring fish reproduction, migration, and growth, the flood pulse has also been shown to play a major role in the dynamics of fishing yields (Bayley, ; Castello et al, ; Fearnside, ; Halls & Welcomme, ; Petesse & Petrere, ). In addition to directly affecting fish abundance, seasonal changes in water level and fish habitat also affect catchability and fishing effort (Isaac et al, ).…”

“…Other studies have stressed the maintenance of channel‐floodplain connectivity as a major factor controlling the diversity and resilience of migratory and nonmigratory fish species (Welcomme, ). Castello et al (, ) modelled the connections between fisheries, flooding, and effort, concluding that the magnitude and timing of low‐ and high‐water periods, when combined with fishing effort, explained most of the observed interannual variability in fisheries yields. In a recent study, Isaac et al () expanded upon these insights by also considering fishing gear and catchability to show how fishermen alternate habitats and species to optimize their economic and biomass returns; this study also identified important water level lag effects, indicating that extremely wet years led to increased fisheries recruitment in later months and years.…”