UVM Theses and Dissertations
Format:
Print
Author:
Simonin, Paul W.
Dept./Program:
Natural Resources
Year:
2010
Degree:
MS
Abstract:
Nonnative species have been a powerful driver of ecological change in recent decades, and can complicate management, inflict economic costs, and threaten biodiversity. Rainbow smelt (Osmerus mordax) and alewife (Alosa pseudoharengus) are cannibalistic, pelagic fish species native to coastal regions of northeastem North America and elsewhere. Rainbow smelt are presumed to be native to Lake Champlain as well, and have been the main forage species supporting higher organisms, including the salmonid and walleye (Sander vitreus) sport fisheries in the lake. However, alewife have recently become established here, and thus have the potential to dramatically alter the Lake Champlain ecosystem.
Previous work in this lake focused on adult rainbow smelt, and found cannibalism is a function of fish distribution. In light of this, and alewife invasion, our study quantifies adult and particularly young-of-year (YOY) rainbow smelt and alewife distribution and abundance temporally in relation to their physical environment. We used hydroacoustic equipment, trawls, and gill nets to observe fish over inshore-to-offshore transects during day and night. Each trip we also collected temperature, dissolved oxygen, pH, conductivity, and light data throughout the water column, and recorded continuous surface light levels. Surveys were conducted every two to three weeks from June to October of 2007 and 2008.
In the main lake, YOY rainbow smelt were first observed June, whereas YOY alewife not until late July. In this region, YOY rainbow smelt were most abundant in mid-July, and YOY alewife in early-August, while Malletts Bay populations peaked earlier. Daily mortality rates were higher for earlier hatching fish. YOY alewife growth rates were faster than those of YOY rainbow smelt, and both species recruited to the adult population by October. We found YOY and adult alewife in shallower water than their rainbow smelt counterparts. YOY rainbow smelt distribution overlapped with adult rainbow smelt and YOY alewife, but adult alewife were shallower.
Using a modeling appraach with information criteria, we found YOY and adult rainbow smelt distributions were related to temperature, temperature gradients, and light, whereas YOY alewife distribution was related to temperature and light. Our study expands the current knowledge base in several ways by providing a uniquely comprehensive description of seasonal and diel dynamics of interacting cannibalistic populations in relation to physical habitat gradients. This explicit understanding of physical-biotic connections and species behavior clarifies our understanding of fish population dynamics and informs decisions regarding Lake Champlain and other systems.
Previous work in this lake focused on adult rainbow smelt, and found cannibalism is a function of fish distribution. In light of this, and alewife invasion, our study quantifies adult and particularly young-of-year (YOY) rainbow smelt and alewife distribution and abundance temporally in relation to their physical environment. We used hydroacoustic equipment, trawls, and gill nets to observe fish over inshore-to-offshore transects during day and night. Each trip we also collected temperature, dissolved oxygen, pH, conductivity, and light data throughout the water column, and recorded continuous surface light levels. Surveys were conducted every two to three weeks from June to October of 2007 and 2008.
In the main lake, YOY rainbow smelt were first observed June, whereas YOY alewife not until late July. In this region, YOY rainbow smelt were most abundant in mid-July, and YOY alewife in early-August, while Malletts Bay populations peaked earlier. Daily mortality rates were higher for earlier hatching fish. YOY alewife growth rates were faster than those of YOY rainbow smelt, and both species recruited to the adult population by October. We found YOY and adult alewife in shallower water than their rainbow smelt counterparts. YOY rainbow smelt distribution overlapped with adult rainbow smelt and YOY alewife, but adult alewife were shallower.
Using a modeling appraach with information criteria, we found YOY and adult rainbow smelt distributions were related to temperature, temperature gradients, and light, whereas YOY alewife distribution was related to temperature and light. Our study expands the current knowledge base in several ways by providing a uniquely comprehensive description of seasonal and diel dynamics of interacting cannibalistic populations in relation to physical habitat gradients. This explicit understanding of physical-biotic connections and species behavior clarifies our understanding of fish population dynamics and informs decisions regarding Lake Champlain and other systems.