Growth and smolting in lower-mode Atlantic Salmon stocked into the Penobscot River, Maine

North American Journal of Fisheries Management
By: , and 

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Abstract

Restoration of Atlantic Salmon Salmo salar in Maine has relied on hatchery-produced fry and smolts for critical stocking strategies. Stocking fry minimizes domestication selection, but these fish have poor survival. Conversely, stocked smolts have little freshwater experience but provide higher adult returns. Lower-mode (LM) fish, those not growing fast enough to ensure smolting by the time of stocking, are a by-product of the smolt program and are an intermediate hatchery product. From 2002 to 2009, between 70,000 and 170,000 marked LM Atlantic Salmon were stocked into the Pleasant River (a tributary in the Penobscot River drainage, Maine) in late September to early October. These fish were recaptured as actively migrating smolts (screw trapping), as nonmigrants (electrofishing), and as returning adults to the Penobscot River (Veazie Dam trap). Fork length (FL) was measured and a scale sample was taken to retrospectively estimate FL at winter annulus one (FW1) using the intercept-corrected direct proportion model. The LM fish were observed to migrate as age-1, age-2, and infrequently as age-3 smolts. Those migrating as age-1 smolts had a distinctly larger estimated FL at FW1 (>112 mm) than those that remained in the river for at least one additional year. At the time of migration, age-2 and age-3 smolts were substantially larger than age-1 smolts. Returning adult Atlantic Salmon of LM origin had estimated FLs at FW1 that corresponded to smolt age (greater FL for age 1 than age 2). The LM product produces both age-1 and age-2 smolts that have greater freshwater experience than hatchery smolts and may have growth and fitness advantages. The data from this study will allow managers to better assess the probability of smolting age and manipulate hatchery growth rates to produce a targeted-size LM product.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Growth and smolting in lower-mode Atlantic Salmon stocked into the Penobscot River, Maine
Series title North American Journal of Fisheries Management
DOI 10.1080/02755947.2013.866996
Volume 34
Issue 1
Year Published 2014
Language English
Publisher Taylor & Francis
Contributing office(s) Coop Res Unit Leetown
Description 12 p.
First page 147
Last page 158
Country United States
State Maine
Other Geospatial Penobscot River
Online Only (Y/N) N
Additional Online Files (Y/N) N
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