Present-day African analogue of a pre-European Amazonian floodplain fishery shows convergence in cultural niche construction

Abstract

Erickson [Erickson CL (2000) Nature 408 (6809) :190-193] interpreted features in seasonal floodplains in Bolivia's Beni savannas as vestiges of pre-European earthen fish weirs, postulating that they supported a productive, sustainable fishery that warranted cooperation in the construction and maintenance of perennial structures. His inferences were bold, because no close ethnographic analogues were known. A similar present-day Zambian fishery, documented here, appears strikingly convergent. The Zambian fishery supports Erickson's key inferences about the pre-European fishery: It allows sustained high harvest levels; weir construction and operation require cooperation; and weirs are inherited across generations. However, our comparison suggests that the pre-European system may not have entailed intensive management, as Erickson postulated. The Zambian fishery's sustainability is based on exploiting an assemblage dominated by species with life histories combining high fecundity, multiple reproductive cycles, and seasonal use of floodplains. As water rises, adults migrate from permanent watercourses into floodplains, through gaps in weirs, to feed and spawn. Juveniles grow and then migrate back to dryseason refuges as water falls. At that moment fishermen set traps in the gaps, harvesting large numbers of fish, mostly juveniles. In nature, most juveniles die during the first dry season, so that their harvest just before migration has limited impact on future populations, facilitating sustainability and the adoption of a fishery based on inherited perennial structures. South American floodplain fishes with similar life histories were the likely targets of the pre-European fishery. Convergence in floodplain fish strategies in these two regions in turn drove convergence in cultural niche construction. convergent evolution | cultural evolution | earthworks | historical ecology | tropical stream ecology F ifteen years ago, in his studies of human-modified landscapes in the Beni savannas of Bolivia, Erickson (1) identified a particular form of zigzag earthwork in a 525-km 2 area of seasonal floodplain in the Baures region as vestiges of fish weirs. "A fishweir is . . . any structure constructed in water and acting as a funnel or barrier to direct fish into a trap or enclosure or to entrap fish behind it, where they can be easily harvested" (2, p. 5). Fish weirs are ". . . usually built in a flowing stream to funnel fish into a trap or built in a tidal flat to trap fish behind it as the tide goes out" (2, p. xv). The structures Erickson identified as vestiges of fish weirs are linear ridges of raised earth (now 1-2 m wide and 20-50 cm tall) that cross savanna floodplains from one forest island to another for distances up to 3.5 km, changing direction every 10-30 m. Erickson stated that "funnel-like openings, 1-3 m long and 1-2 m wide, are present where the structures form a sharp angle." Erickson identified these gaps as passages where fish-catching devices were placed. Erickson's conclusions, based on the form of these ...

Balanced harvest: concept, policies, evidence, and management implications

“…The Bangweulu swamps in Northern Zambia are a vast oligotrophic wetland that support the second most important fishery of the country (Kolding et al , 2016c. The fishing pattern and methods have evolved into a flexible and dynamic combination of gillnets, weirs, longlines and traps, and have not changed much in recorded history, and probably centuries (McKey et al 2016). Most of the species and sizes caught are small with a high biological turnover, but larger species are still being relatively more heavily exploited (Fig.…”

Variability of hydrological connectivity and fish dynamics in a wide subtropical–temperate floodplain

“…Many fish species from densely vegetated floodplain habitats are constrained to move back to permanent water bodies (Fernandez, ), using the river channel as a dry‐season refuge (Junk et al, ; Ward, ). In response to lateral migrations in mass from floodplains back to the main channels, some predators develop specific hunting strategies (mainly birds and fish and also humans), staying at strategic places (e.g., mouth of floodplain lakes) and preying on the fish rush (McKey et al, ; Wantzen et al, ). Fish movements combined with trophic interactions (feeding, refuge, or breeding migrations and predation processes) result therefore in the ultimate transfer of a significant fraction of the annual production of seasonal floodplain habitats to the food web of permanent water bodies (Junk & Wantzen, ; Winemiller & Jepsen, ).…”

First record of epizootic ulcerative syndrome from the Upper Congo catchment: An outbreak in the Bangweulu swamps, Zambia

“…The Bangweulu floodplain and swamp supports one of the largest artisanal fisheries in Zambia (Musumali, Heck, Husken, & Wishart, ). Fish are harvested seasonally through an extensive and unique network of fish weirs that cover some 7,000 km 2 (Huchzermeyer, ; Kolding et al., ; McKey et al., ). This provides the main source of livelihood for an estimated 5,000 fishing families within Bangweulu Wetlands, generating income of approximately $6 million annually (C. F. Huchzermeyer, unpublished report 2013).…”

“…The Bangweulu floodplain and swamp supports one of the largest artisanal fisheries in Zambia (Musumali, Heck, Husken, & Wishart, 2009). Fish are harvested seasonally through an extensive and unique network of fish weirs that cover some 7,000 km 2 (Huchzermeyer, 2013;Kolding et al, 2003;McKey et al, 2016). This Wetlands, Chikuni, Zambia 2017).…”