Proactively averting the collapse of Amazon fisheries based on three migratory flagship species

Abstract

Migratory species are the most important commercial fishes in the Amazon. They are also now the most threatened directly by some combination of overfishing, floodplain deforestation, and dam construction. Limited governmental monitoring and implemented regulations impede adequate management of the fisheries at adequate scale. We summarize the current stock status of the three most heavily exploited long-distance migratory species, which are two goliath catfishes (Brachyplatystoma rousseauxii and B. vaillantii) and the characiform Colossoma macropomum. In addition, we analyze impacts beyond overfishing on these species. Our results indicate: (i) the overfishing trends for these important species are either ominous or indicate the verge of collapse of the commercial fisheries based on them, and (ii) a dangerous synergy between overfishing, hydroelectric dams, and floodplain deforestation further challenge fisheries management of migratory species in the Amazon. We propose eight direct governmental actions as a proactive approach that addresses the main impacts on the fisheries. We consider that the most practical way to assess and manage overfishing of migratory species in the short run in an area as large as the main commercial fishing area in the Amazon is at market sites where enforced regulations can control fish catch. The management of the three species considered here has implications beyond just their sustainability. Their management would represent a paradigm shift where the governments assume their legal responsibilities in fishery management. These responsibilities include regulation enforcement, data collecting, inter-jurisdictional cooperation to protect migratory species at realistic life history scales, mitigation of the Madeira dams to assure goliath catfish passage to the largest western headwater region, and recognition of monitoring and managing wetland deforestation for the protection of fish and other aquatic and terrestrial biodiversity.

Identifying the current and future status of freshwater connectivity corridors in the Amazon Basin

“…The socio-ecological and economic impacts of such fragmentation and alteration of the flow regime can be expected to lead to declines in populations or losses of migratory species, declines in fisheries, changes to floodplain and riverine habitats due to inundation and flow alterations, and loss of sediment flows that feed downstream floodplains and delta habitats (Arantes et al, 2019;Constantine et al, 2014;Prestes et al, 2022). Many indigenous and riverine communities depend on migratory fish as a source of protein and livelihood with recorded consumption rates of freshwater fish by Amazonian riverine communities being among the highest recorded globally (e.g., Isaac et al, 2015).…”

“…Many indigenous and riverine communities depend on migratory fish as a source of protein and livelihood with recorded consumption rates of freshwater fish by Amazonian riverine communities being among the highest recorded globally (e.g., Isaac et al, 2015). Fragmentation of additional free‐flowing corridors would be expected to impact fish populations as has been documented in recent declines in fish populations and associated reductions in catch, particularly for migratory species (Lima et al, 2020; Prestes et al, 2022; Van Damme et al, 2019). An example of community‐level impacts comes from the decline in fisheries affecting the livelihoods of fishers in the vicinity of the Belo Monte hydroelectric dam following its construction (Castro‐Diaz et al, 2018).…”

“…For example, long stretches or entire rivers that are FCCs and that are important for multiple species such as the Amazon River and lower reaches of the Tapajós River, could be highlighted as “no‐go” zones for future dam development. Prestes et al (2022) similarly recommend trans‐national or interstate agreements for migratory fisheries management across jurisdictions, noting that while all Amazonian countries with the exception of Colombia are signatories to the Convention on Migratory Species, no Amazonian freshwater migratory species are listed within the Convention. Other models include the U.S. Wild and Scenic Rivers designation, Ramsar sites that protect entire free‐flowing river catchments (e.g., the Bita River Ramsar site in Colombia), the designation of water reserves that guarantee allocations of river flow for nature and specific human uses (Salinas‐Rodríguez et al, 2018), and a recent law that would protect “permanent preservation rivers” (“Rios de preservação permanente”) in the state of Minas Gerais in Brazil (Azevedo‐Santos et al, 2019).…”

The bycatch of piramutaba, Brachyplatystoma vaillantii industrial fishing in a salinity and depth gradient in the Amazon estuary, Brazil

“…This catfish is explored by artisanal fisheries using gillnets and long lines and industrial fisheries using pair or triple trawling (Barthem, and Goulding 1997;Ruffino 2003). The industrial fishery of the piramutaba began in 1971 with the use of adapted shrimp boats (Silva et al 2016), reached the largest landing (22,486 tonnes) in 1977, and occupied the ninth place on the list of exportation goods from Pará state, Brazil by 1980 (Dias-Neto et al 1985;Barthem 1990;Dias-Neto 1991;Prestes et al 2022). The piramutaba trawl fishery is limited to the Amazon estuary facing the Marajó Island and the coast of state of Amapá coast, Brazil (Prestes et al 2022), a region characterized by the extensive input of sediments by the Amazon River (Geyer et al 1996), with enormous oscillation in the discharge of the Amazon River, which, at its peak in May-June, more than doubles the minimum discharge, which occurs in November (Guimberteau et al 2012).…”

“…The industrial fishery of the piramutaba began in 1971 with the use of adapted shrimp boats (Silva et al 2016), reached the largest landing (22,486 tonnes) in 1977, and occupied the ninth place on the list of exportation goods from Pará state, Brazil by 1980 (Dias-Neto et al 1985;Barthem 1990;Dias-Neto 1991;Prestes et al 2022). The piramutaba trawl fishery is limited to the Amazon estuary facing the Marajó Island and the coast of state of Amapá coast, Brazil (Prestes et al 2022), a region characterized by the extensive input of sediments by the Amazon River (Geyer et al 1996), with enormous oscillation in the discharge of the Amazon River, which, at its peak in May-June, more than doubles the minimum discharge, which occurs in November (Guimberteau et al 2012). The region is located between the North Cape (01º42'S and 49º55'W) and the Maguari Cape (00º15'S and 48º25'W) (Figure 1), encompassing a 80-mile coastline stretch with a depth range between 3 and 20 m (Santos et al 1984;Dias-Neto et al 1985).…”