Hydrological controls of fisheries production in a major Amazonian tributary

Abstract

Amazonian rivers are characterized by a strongly seasonal flood pulse, which is being altered by ongoing and planned hydropower development across the basin. Changes in hydrology have a cascade of physical, ecological, and social effects, and some ecohydrological changes in the Amazon are expected to be irreversible. To better understand these linkages, we investigated shared trends and causal factors driving fish catch in a major Amazonian tributary before dam construction to derive relationships between catch and natural hydrologic dynamics that can be used to assess likely post‐dam fisheries impacts. We applied a time series‐based dimension reduction technique (dynamic factor analysis) to investigate dynamics in fish catch across 10 commercially important species using daily fish landings and hydrological data. We found a 4‐trend dynamic factor model to best fit the observed data, with fitted trends exhibiting variation representative of seasonal and longer‐term hydrologic variation. We next considered 11 candidate explanatory time series and found the best dynamic factor model used 4 explanatory variables: maximum water level, flooding duration, previous year's flow, and rate of change in flow; however, each species showed a unique response to this set of hydrological variables. Species‐specific responses suggested that future dam operating rules need to closely mimic the natural hydrologic regime in order to maintain the biological dynamics of this and similarly diverse systems. In particular, high flows associated with increased catch the following year are important to maintain, but may be difficult to achieve in the context of reservoir regulation and energy production goals.

<b>Jatuarana fishing dynamics <i>Brycon amazonicus</i> (Spix & Agassiz, 1829) of the upper and middle Madeira River Basin

“…The higher yield years (1993 and 1997) may have been influenced by higher hydrological measurements in previous years (1992 and 1996), which reflects on the catches of subsequent years (Doria et al, 2012). Corroborating with Lima, Kaplan, and Doria (2017) evaluated models that correlated the fishery production of some species caught in the Madeira River and hydrological variables, verified that the number of flooded days showed a significant and positive correlation for a subset of species, including jatuarana.…”

FISHING PRODUCTION OF <i>Pinirampus pirinampu</i> AND <i>Brachyplatystoma platynemum</i> CATFISH HAS BEEN AFFECTED BY LARGE DAMS OF THE MADEIRA RIVER (BRAZILIAN AMAZON)

“…Fisheries in the Madeira River region are classified as small-scale artisanal fishing and present traits common to fishing activities conducted in other areas of the Amazon basin, such as being multi-species, multi-equipment and seasonal (Doria et al, 2012). Hydrological seasonality interferes with the total production and catch composition of fish species, since fish stocks are synchronized with river water level variations due to their migratory reproduction and dispersal processes (Garcez et al, 2017;Lima et al, 2017). Meanwhile, fishers demonstrate knowledge of the fishing environment and adapt to these variations to succeed in their livelihood (Isaac et al, 2015;Garcez et al, 2017).…”

“…The construction of hydroelectric dams has caused widely recognized impacts on geomorphology, thermal regime, flow regime and other physicochemical and biological characteristics that shape local aquatic ecosystems, and drive fish diversity, composition, distribution and abundance (Agostinho et al, 2008;Kirchherr and Charles, 2016). In the Madeira River, the natural water level variations determine the life cycle of commercially important fish species, thus affecting artisanal fishing, as such, the anthropic interference of hydroelectric power generators that can threaten fish production and consequently livelihoods (Isaac et al, 2016;Lima et al, 2017;Almeida et al, 2020). Among these species are two migratory catfish, the "barba chata" catfish (Pinirampus pirinampu, Spix & Agassiz 1829) and the "babão" catfish (Brachyplatystoma platynemum, Boulenger 1898).…”

Checklist of the fishes from Jamari River basin, in areas under influence of dams, Rondônia, Brazil

“…This ecosystem is mainly affected by the pollution from the use of mercury by mining, construction of dams, deforestation and overexploitation of several natural resources (Castello et al 2013). Amazonian rivers have a lowly exploited hydroelectric potential in comparison to other Neotropical basins (Lima et al 2017). Meanwhile, in this region, some 175 large hydroelectric plants are already in operation or under construction and 277 are planned for the coming years (Castello & Macedo 2016).…”