Date of Award

12-2005

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

James McCleave

Second Committee Member

Joan Trial

Third Committee Member

Michael Kinnison

Abstract

I examined migratory behaviors of Atlantic salmon, Salmo salar, by investigating the effects stocking practices and environmental variables have on migratory behavior and rate. To study stocking practices and their influence on salmon behavior, I monitored how individual salmon behaved when they reached the confluence of the Piscataquis River with the Penobscot River using PIT tag technology. This major tributary splits the drainage, serving as a natural "Y ", with smolts stocked in both upriver sections. Using criteria developed to describe salmon behavior at this fork, I observed behaviors that indicated strong homing in three of the four stocking groups. Between 50 and 100% of the marked Atlantic salmon exhibited homing behavior to their stocking location. Breakdown by age and release type showed little evidence that these factors change homing behavior. Tributary stocking sites had higher homing behavior than the mainstem sites for both the Piscataquis stocking sites and the Penobscot stocking sites. Tributary stocking sites had higher homing behavior than the mainstem sites for both the Piscataquis stocking sites and the Penobscot stocking sites. I also analyzed passage rates of adult Atlantic salmon through a series of six river segments divided by hydroelectric dams on the Penobscot River system in three different years. Median migration rates ranged from 3.73 to 20.26 km day-1. Fastest passage rates were recorded in the middle two segments of the river, with slowest median rates recorded in the first segment above the release site and through the two uppermost segments monitored. Passage rates were highly variable within and among years and segments. Passage rates slowed during summer months for each segment, and were slower in years with higher than normal flows during the migratory season. Passage rates were related to environmental variables using multiple regression analysis. Flow was negatively correlated with passage rates and temperature had a positive parabolic relationship with passage rate where as maximum temperature increased, passage rates increased until the temperature reached a threshold where the passage rate then began to decrease. Results suggest that flow and temperature had significant effects on passage speed through river corridors. The high variability observed with slow passage rates in each segment may be due to poor fishway attraction, fish seeking thermal refuges, or route searching behavior.

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