41241c3ae9377de90c55f271ceb9f9f5 fishes-10-00495.pdf 85215d6d6a80fff26d3674333540cef3e9433744 fishes-10-00495.pdf 9ce2bd6497ab410bbac1d874d8feea0225580d3d8644a4747f2bfac5759e3001 fishes-10-00495.pdf Title: Ecology of River Dolphins and Fish at Confluence Aggregations in the Peruvian Amazon Subject: Amazon River dolphins often form multi-species aggregations at water confluences. This study used a multi-year data set to examine dolphins, fish, and geomorphology at dolphin aggregations. Methods included dolphin transect surveys, dolphin point counts, net and line fish captures, side-scan sonar, and eDNA analyses at five dolphin aggregations and two control sites. Amazon River dolphins (Inia geoffrensis and Sotalia fluviatlis) are typically found at aggregation sites that occur at water confluences that have greater dolphin numbers than control sites. The confluences had riverbed depressions averaging six metres in depth where fish were concentrated. Pink river dolphins preferred to form aggregations in flooded forest tributaries and large rivers, while grey river dolphins preferred the larger rivers. There were eighty-nine fish species at the confluences within the size of fish consumed by dolphins, and a higher abundance of fish occurred in and around the aggregation sites compared to control sites. The number of dolphins present at the aggregation sites correlated with fish abundance. Dolphin life history, such as fishing, resting, raising calves, and social interactions, occur at the aggregation sites. The aggregation sites are important conservation areas of the endangered pink and grey river dolphins, and through their folklore, Indigenous people living at confluence sites assist in the conservation of the aggregations and have lived with dolphins at confluences for thousands of years, contributing to their survival. Keywords: pink river dolphin; grey river dolphin; Amazon fish; dolphin aggregations; river confluences Author: Richard Bodmer, Peter Henderson, Claire Spence, Tara A. O. Garraty, Kimberlyn Chota, Paola Uraco, Miguel Antunez, Tula Fang, Jack Butcher, Jake E. Bicknell, Osnar Pizuri and Pedro Mayor Creator: LaTeX with hyperref Producer: pdfTeX-1.40.25; modified using OpenPDF 1.4.2 CreationDate: Thu Oct 2 11:33:08 2025 CEST ModDate: Thu Oct 2 11:37:26 2025 CEST Custom Metadata: yes Metadata Stream: no Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 19 Encrypted: no Page size: 595.276 x 841.89 pts (A4) Page rot: 0 File size: 2118917 bytes Optimized: no PDF version: 1.7 name type encoding emb sub uni object ID ------------------------------------ ----------------- ---------------- --- --- --- --------- IMAEHO+VnURWPalladioL Type 1 Custom yes yes yes 139 0 WFZVZC+URWPalladioL-Ital Type 1 Custom yes yes yes 140 0 CHIAVT+URWPalladioL-Bold Type 1 Custom yes yes yes 141 0 RZOILQ+URWPalladioL-Roma Type 1 Custom yes yes yes 142 0 KHCGJH+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 218 0 KHCGJF+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 219 0 KHCGID+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 220 0 WBVKDJ+URWPalladioL-BoldItal Type 1 Custom yes yes yes 268 0 GHKNOH+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 285 0 GHKNMG+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 286 0 GHKNNH+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 287 0 GHKNOJ+PalatinoLinotype-Bold TrueType WinAnsi yes yes no 295 0 GHKNOH+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 296 0 GHKNMG+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 297 0 GHKNNH+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 298 0 GHKNOH+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 364 0 GHKNMG+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 365 0 GHKNNH+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 366 0 IOOFIG+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 353 0 IOOFHE+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 354 0 IOOFGD+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 355 0 GHKNOH+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 409 0 GHKNMG+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 410 0 GHKNNH+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 411 0 Jhove (Rel. 1.28.0, 2023-05-18) Date: 2025-12-19 05:11:23 CET RepresentationInformation: fishes-10-00495.pdf ReportingModule: PDF-hul, Rel. 1.12.4 (2023-03-16) LastModified: 2025-12-18 10:05:11 CET Size: 2118917 Format: PDF Version: 1.7 Status: Well-Formed and valid SignatureMatches: PDF-hul MIMEtype: application/pdf PDFMetadata: Objects: 562 FreeObjects: 1 IncrementalUpdates: 0 DocumentCatalog: ViewerPreferences: HideToolbar: false HideMenubar: false HideWindowUI: false FitWindow: true CenterWindow: false DisplayDocTitle: false NonFullScreenPageMode: UseNone Direction: L2R ViewArea: CropBox ViewClip: CropBox PrintArea: CropBox PageClip: CropBox PageLayout: SinglePage PageMode: UseNone Outlines: Item: Title: Introduction Item: Title: Materials and Methods Children: Item: Title: Study Area Item: Title: Dolphin Surveys Item: Title: Fish Catch per Unit Effort Surveys Item: Title: Side-Scan Sonar Surveys Item: Title: eDNA Item: Title: Statistical Analysis Item: Title: Results Children: Item: Title: Dolphin Aggregations Item: Title: Pink River Dolphin Item: Title: Grey River Dolphin Item: Title: Dolphin Behaviour at Aggregations Item: Title: Seasonal Differences in Site Usage Item: Title: Channel Geomorphology of the Riverbed at Dolphin Aggregations Item: Title: Fish Numbers Item: Title: Fish Species and Abundance Item: Title: Dolphin–Fish Correlation Item: Title: Dolphin Demographics at Aggregations Item: Title: Discussion Item: Title: Conclusions Item: Title: References Info: Title: Ecology of River Dolphins and Fish at Confluence Aggregations in the Peruvian Amazon Author: Richard Bodmer, Peter Henderson, Claire Spence, Tara A. O. Garraty, Kimberlyn Chota, Paola Uraco, Miguel Antunez, Tula Fang, Jack Butcher, Jake E. Bicknell, Osnar Pizuri and Pedro Mayor Subject: Amazon River dolphins often form multi-species aggregations at water confluences. This study used a multi-year data set to examine dolphins, fish, and geomorphology at dolphin aggregations. Methods included dolphin transect surveys, dolphin point counts, net and line fish captures, side-scan sonar, and eDNA analyses at five dolphin aggregations and two control sites. Amazon River dolphins (Inia geoffrensis and Sotalia fluviatlis) are typically found at aggregation sites that occur at water confluences that have greater dolphin numbers than control sites. The confluences had riverbed depressions averaging six metres in depth where fish were concentrated. Pink river dolphins preferred to form aggregations in flooded forest tributaries and large rivers, while grey river dolphins preferred the larger rivers. There were eighty-nine fish species at the confluences within the size of fish consumed by dolphins, and a higher abundance of fish occurred in and around the aggregation sites compared to control sites. The number of dolphins present at the aggregation sites correlated with fish abundance. Dolphin life history, such as fishing, resting, raising calves, and social interactions, occur at the aggregation sites. The aggregation sites are important conservation areas of the endangered pink and grey river dolphins, and through their folklore, Indigenous people living at confluence sites assist in the conservation of the aggregations and have lived with dolphins at confluences for thousands of years, contributing to their survival. 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