Abstract

With increases to the number of species and populations impacted by human activities, the need for human involvement in their maintenance and/or conservation has grown in turn. This involvement increasingly takes the form of re-introductions, relocations, or supplementation of populations in decline or that have been lost. As a result, reintroduction biology has become a quickly growing field of research that attempts to answer the many questions related to reintroductions and translocations. When and how to release individuals into the wild, at what age should they be released, and in what situations is the introduction of new individuals sufficient to establish new populations.
To advance our understanding of species reintroductions and address some of these questions in situ, adaptive management experiments and new techniques were developed for the Atlantic salmon reintroduction program in the Lake Champlain basin. These experiments assessed the suitability of commonly used methods in salmonid reintroduction and supplementation for re-establishing or strengthening self-sustaining populations and meta-population structure through direct comparisons of long-term survival, spawning returns, and dispersal rates. Concurrently, to address how changes in the species composition of Lake Champlain have affected the ability of reintroduced salmon to establish themselves, radio telemetry was employed to monitor spawning migrations through a challenging, high velocity section of the Boquet River, a tributary to Lake Champlain. In doing so, new, transferrable radio telemetric techniques for continuous fine scale monitoring were developed.
In comparing alternative rearing/release techniques to the standard method of producing large 1+ parr through the use of elevated rearing temperatures, several significant trends were apparent. First, while fry (age 0+) are commonly held to exhibit reduced survival to adulthood relative to 1+ parr, once natural mortality during the first year was accounted for, fry returns exceeded those of standard production parr while their dispersal rates were more consistent with Atlantic salmon meta-populations. Second, all three alternative parr rearing/release methods reduced straying rates relative to standard methods. Third, while advancing release dates lowered parr-to-adult survival relative to standard procedures, using seasonal water temperatures prior to release significantly improved both survival and spawning returns.
Once released, growing salmon fed on alewife, an invasive prey species containing thiaminase, which lowered thiamine levels among mature adults, potentially impacting energy levels and swimming performance. At a challenging, high velocity section of the Boquet River, we detected a significant effect of this thiamine deficiency on downstream movement rates from both high and low flow sections of the river as well as an effect of thiamine supplementation, particularly among male salmon. To confirm this, however, a new telemetric technique was required. We therefore developed a technique that successfully estimated the location of tagged salmon to within several meters using readily available equipment and statistical models.
Overall, these results will assist the reintroduction efforts in Lake Champlain and their implications are highly transferrable to the reintroduction/supplementation of other at-risk or extirpated populations. The methods developed below are readily implementable and provide positive returns on investment, both over the short- and long-term, while representing a step forward for the reintroduction of species of high economic, cultural, and ecological importance.