Diverse Early Life-History Strategies in Migratory Amazonian Catfish: Implications for Conservation and Management

Abstract

Animal migrations provide important ecological functions and can allow for increased biodiversity through habitat and niche diversification. However, aquatic migrations in general, and those of the world’s largest fish in particular, are imperiled worldwide and are often poorly understood. Several species of large Amazonian catfish carry out some of the longest freshwater fish migrations in the world, travelling from the Amazon River estuary to the Andes foothills. These species are important apex predators in the main stem rivers of the Amazon Basin and make up the region’s largest fishery. They are also the only species to utilize the entire Amazon Basin to complete their life cycle. Studies indicate both that the fisheries may be declining due to overfishing, and that the proposed and completed dams in their upstream range threaten spawning migrations. Despite this, surprisingly little is known about the details of these species’ migrations, or their life history. Otolith microchemistry has been an effective method for quantifying and reconstructing fish migrations worldwide across multiple spatial scales and may provide a powerful tool to understand the movements of Amazonian migratory catfish. Our objective was to describe the migratory behaviors of the three most populous and commercially important migratory catfish species, Dourada (Brachyplatystoma rousseauxii), Piramutaba (Brachyplatystoma vaillantii), and Piraíba (Brachyplatystoma filamentosum). We collected fish from the mouth of the Amazon River and the Central Amazon and used strontium isotope signatures (87Sr/86Sr) recorded in their otoliths to determine the location of early rearing and subsequent. Fish location was determined through discriminant function classification, using water chemistry data from the literature as a training set. Where water chemistry data was unavailable, we successfully in predicted 87Sr/86Sr isotope values using a regression-based approach that related the geology of the upstream watershed to the Sr isotope ratio. Our results provide the first reported otolith microchemical reconstruction of Brachyplatystoma migratory movements in the Amazon Basin. Our results indicate that juveniles exhibit diverse rearing strategies, rearing in both upstream and estuary environments. This contrasts with the prevailing understanding that juveniles rear in the estuary before migrating upstream; however, it is supported by some fisheries data that has indicated the presence of alternate spawning and rearing life-histories. The presence of alternate juvenile rearing strategies may have important implications for conservation and management of the fisheries in the region.

Migration and brackish environment use of Prochilodus lineatus (Characiformes: Prochilodontidae) inferred by Sr:Ca ratio transects of otolith

“…Here, we have to emphasize the need to link the obtained results with current resource management actions in order to contribute to their sustainability. We highlight the importance of intensifying this type of studies including other markers such as stable isotopes of Sr, which would allow to track the movements of the specimens in freshwater throughout the basin (Hegg et al, 2015).…”

“…Several algorithms have been used to facilitate the interpretation of fish movement patterns and to quantify the number of habitat changes during their life history (Hedger et al, 2008;Walther et al, 2011;Killick, Eckley, 2014;Freshwater et al, 2015;Hegg et al, 2015;Wynne et al, 2015). In this work we used Change-Point analysis (CPA) to facilitate the classification of individuals and quantify the number of changes in otolith elemental ratio (Shrimpton et al, 2014;Hegg et al, 2015).…”

“…In this work we used Change-Point analysis (CPA) to facilitate the classification of individuals and quantify the number of changes in otolith elemental ratio (Shrimpton et al, 2014;Hegg et al, 2015). We assumed that significant changes in the transect corresponded with habitat changes due to chemical composition of the water (Freshwater et al, 2015;Hegg et al, 2015;Wynne et al, 2015). CPA determined whether there had been a change in the underlying process that generated the sequence of events and identified where the change occurred.…”

Identification of nurseries areas of juvenile Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) by scale and otolith morphometry and microchemistry

“…In relation to monitoring and use of otolith microchemistry, analyzing the geochemical origin of different studied elements, as well as the incorporation of isotopical relations could generate other markers of origin to study even adult individuals (Ashford & Jones, 2007;Walther & Thorrold, 2009;Niklitschek et al, 2010;Hegg et al, 2013Hegg et al, , 2015Garcez et al, 2015).…”

Ecosystem‐based management of Amazon fisheries and wetlands

“…catfishes undertake the only known continental-scale migrations in the Amazon. The migrations of dourada, piramutaba, babão (Brachyplatystoma platynemum, Pimelodidae) and zebra catfish (Brachyplatystoma juruense, Pimelodidae) involve movements from the eastern or central Amazon where nurseries are located,to the western Amazon where spawning occurs in river channelsCañas & Pine, 2011;Hegg et al, 2015;Hermann et al, 2016). Continental-scale migrations span at least 75% of the length of the Amazon Basin and, in the case of dourada, at least 90% of the length of the basin stretching from the Andes to the Amazon River estuary and plume (Figure 6).…”