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Acoustic Telemetry Assessment of Hatchery-Reared Smolts in the Narraguagus River

Acoustic Telemetry Assessment of Hatchery-Reared Smolts in the Narraguagus River
Acoustic Telemetry Assessment of Hatchery-Reared Smolts in the Narraguagus River

Gill sample (foreground) of acoustic telemetry tagged age 1+ hatchery smolt. This sample will aid in identifying physiological condition (Na, K-ATPase) of study fish



Acoustic telemetry is a modern technology researchers employ to remotely monitor animals and help answer critical questions about species performance and survival. For over two decades the Northeast Fisheries Science Center has tagged and monitored Atlantic salmon smolts within several Maine Rivers to describe migration ecology through these systems and their coastal environments. From 1997 – 2005 biologists collected baseline data on naturally-reared smolts from the Narraguagus River.

Beyond natural production, extensive restoration efforts have occurred on the Narraguagus River, with Atlantic salmon fry and parr stocking. During the period of 2008-2012 an attempt to boost population numbers was implemented by stocking age 1+ smolts. Approximately 40,000 smolts were stocked annually during this period with limited success. One hundred and fifty-four 2SW adult returns were documented, which equates to 5.6 2SW adults per 10,000 smolts stocked. These results were below the efforts expectations and return rates observed within other systems.

Restoration stocking with smolts from 2016 – 2020 prompted us to conduct a two year study to evaluate these fish using acoustic telemetry.  The telemetry array monitors freshwater, estuarine, and the early marine environments. During the first year, we staggered three release dates within the late April to early May time frame. Our objectives are to determine if there are differences in survival and behavior of these groups and highlight any variables (stock date, temperature exposure – accumulated thermal units, discharge, physiological condition - Na,K-ATPase, etc) that may contribute to differences in results. In addition to migration performance, we will identify where (and when) bottlenecks (predation, environment, habitat, etc) occur, which will inform managers of areas to focus during future restoration efforts within the watershed. This assessment will benefit the priority management action of optimizing the number of post smolts that enter the Gulf of Maine.

Questions? Contact Jim Hawkes or Graham Goulette, NOAA NEFSC. 

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