Size selection of adult Atlantic salmon at fish passage facilities on the Penobscot River, Maine George Maynard 1, Joseph Zydlewski 2,1 1.University of Maine, Dept. of Wildlife Ecology, Orono, ME U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME 04469

Acknowledgements Oliver Cox Bill Halteman Doug Sigourney Dimitry Gorsky Ed Hughes Andrew O’Malley Dan Stich Ken Beland

Introduction Fishways have existed on the Penobscot River since the mid 1800s Not all fishways are created equal Many factors influence how well salmon are able to pass through fishways

Introduction Water temperature Adapted from Jonsson et al Maine DMR 2012

Introduction Water temperature Water flow

Introduction Water temperature Water flow Time of year

Introduction Water temperature River level Time of year Interannual variation

Introduction Water temperature River level Time of year Interannual variation Salmon size

Salmon Size Maximum swim speed is inversely related to size (Katopodis 1999) Larger Atlantic salmon – require more attraction flow (Laine et al. 2002) – experience longer migratory delays (Jonsson et al. 2007)

Study Sites Penobscot River system Six hydropower dams Monitored using PIT arrays

Methods: Data Collection Water temperatures from Maine DMR at the Veazie fishway River height from USGS West Enfield gauge Fork length measured during tagging at Veazie

Methods: PIT Arrays PIT Receiver Downstream Upstream Antenna 1 Antenna 2

Results: Overview Fish Length (cm) But is it significant? Relationships tested using Bayesian logistic regression.

Results Four dams exhibited some size selection – Great Works – Milford – West Enfield – Mattaceunk (Weldon)

Results: Veazie ΔDIC = 3 n = 409 Time of year and temperature FactorSignificance Fork Length QC Height QC Temp-0.466*** QC OrdinalDate0.581*** Year0.267**

Results: Great Works ΔDIC = 2 n = 1471 Fork length was the most important predictor of success FactorSignificance Fork Length-0.221*** QC Height-0.114** QC Temp-0.156*** QC OrdinalDate0.027-

Results: Milford ΔDIC = 5 n = 1609 Fork length was the most important predictor of success FactorSignificance Fork Length-0.345*** QC Height-0.151** QC Temp QC OrdinalDate-0.148** Year0.156***

Results: Howland ΔDIC = 32 n = 1241 Annual Changes Pike jump FactorSignificance Fork Length QC Height QC Temp-0.333*** QC OrdinalDate-0.145** Year-0.616***

Results: West Enfield ΔDIC = 29 n = 2444 Annual impacts Fork length still significant FactorSignificance Fork Length-0.147** QC Height QC Temp-0.25*** QC OrdinalDate0.258*** Year-1.12***

Results: Mattaceunk (Weldon) ΔDIC = 36 n = 587 Annual Changes Fork length still significant FactorSignificance Fork Length-0.248*** QC Height0.224** QC Temp-0.412*** QC OrdinalDate0.546*** Year-0.703***

Discussion Small dataset at VZ and HD Influence of Year at WE and HD Average fish size at HD Upstream influence of delays Strongest selection at lowermost dams

Why care? Size may be indicative of a more successful individual – Feeding – Lifespan Larger individuals can invest more energy into gamete production Long term population impacts

Summary Current changes in river management will benefit adult salmon Construction of new Milford fishway Removal of downstream dams and bypass at Howland Further monitoring of fishways

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