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

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

Luiza Prestes et al. PLoS One. .

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.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Area and fishery production of long-distance migratory catfishes.

The Amazon region, highlighting the countries, departments (Bolivia, Peru, Colombia) or states (Brazil), and fish markets (black dots) where data have been collected, and the main fish landing cities (red points).

Fig 2
Fig 2. Fishing B. rousseauxii across the Amazon Basin.

(A) A young B. rousseauxii captured in the eastern Amazon River at about the size (50 cm fork length) when the species first begins to migrate upstream in the Amazon River; (B) adult fish in the western Amazon near the Andes that were ready to spawn.

Fig 3
Fig 3. Industrial trawl fishery for B. vaillantii.

Trawl fisheries in the open waters of the Amazon estuary adjacent to the mouth of the Amazon River account for most of the B. vaillantii catch.

Fig 4
Fig 4. Colossoma macropomum in the Central Amazon.

Adult C. macropomum are now rare in fisheries because of decades of overexploitation of both mature and immature fish. Floodplain deforestation along the lower Amazon River has also impacted the species.

Fig 5
Fig 5. The goliath catfish fishery region and overfishing in the Amazon River estuary.

(A) The industrial trawl fishing zone and the restricted fishing area based on legislation in force. (B) Annual catches (tons) of the B. vaillantii bottom pair-trawler fishing fleet in the Amazon estuary (yellow bars) available for the 1972–2006 period, combined with the Maximum Sustainable Yield proxies (tons) with 95% confidence limits (black line) and the F/FMSY ratio (triangle).

Fig 6
Fig 6. Historical trends in the capture of C. macropomum and B. rousseauxii.

(A) Negative exponential trend adjusted to C. macropomum landings in Manaus (tau = -0.809; p<0.05); (B) Linear trend adjusted to C. macropomum landing in Tefé (tau = -0.032; p>0.05); (C) Linear trend adjusted to two periods of B. rousseauxii landings in Porto Velho (tau = -0.039; p<0.05).

Fig 7
Fig 7. Main states or departments and cities associated with overfishing.

Production in percentage categories. The highlighted cities are responsible for at least 50% of the production. Overfishing of the flagship species considered here needs to be controlled from the major urban ports that account for most of the landings.

References

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