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Document Type
Oral Presentation
Department
Environmental Science and Policy
Faculty Mentor
Karen Wilson
Keywords
River Herring, Alewife, Dams, Smallmouth Bass, Otolith
Abstract
The purpose of this research is to determine how the growth rates of top fish predators, such as Smallmouth Bass (Micropterus dolomieu), are affected by access to high quality prey like sea-run fish (spend parts of their life in freshwater and the sea), including Alewife (Alosa pseudoharengus). Several studies have documented marine derived nutrients in freshwater fish predators, but few have investigated how freshwater fish predator growth is affected by the presence of marine derived nutrients transported into the ecosystem by Atlantic sea-run fish. Otoliths (bone-like structures in ears) form daily and annual growth rings which can be used to determine fish age and growth rate. Stable isotope analysis of fish muscle tissue can provide insight into diet over the scale of weeks to months - and can infer marine derived nutrient use.
To determine growth in the presence of sea-run Alewife in the Penobscot River watershed, sagittal otoliths from Smallmouth Bass were aged whole and were then sectioned and aged again in order to determine the relative accuracy of each aging method. The otolith sections were imaged and the rings were measured in the software ImageJ, using the ObjectJ application. From ObjectJ, inferred annual growth rates were determined as well as a back-calculated length at age. Annual growth rates were compared between sites using comparisons of means tests such as t-tests and ANOVA. Average annual growth rates were paired with stable isotope analysis data (δ13C, δ15N) from fish muscle tissue. Ages and annual growth rates were paired with stable isotope data from the same fish. We expect the results will show variation in the growth rates of the resident fish between cohort years and between lower mainstem and tributary sites, and that older fish of a larger body size will show more marine derived nutrients in their tissues. Results from this study may help us better understand the role of marine derived nutrients in driving freshwater productivity of resident piscivores.
Growth of Smallmouth Bass in rivers with a restoring river herring run
The purpose of this research is to determine how the growth rates of top fish predators, such as Smallmouth Bass (Micropterus dolomieu), are affected by access to high quality prey like sea-run fish (spend parts of their life in freshwater and the sea), including Alewife (Alosa pseudoharengus). Several studies have documented marine derived nutrients in freshwater fish predators, but few have investigated how freshwater fish predator growth is affected by the presence of marine derived nutrients transported into the ecosystem by Atlantic sea-run fish. Otoliths (bone-like structures in ears) form daily and annual growth rings which can be used to determine fish age and growth rate. Stable isotope analysis of fish muscle tissue can provide insight into diet over the scale of weeks to months - and can infer marine derived nutrient use.
To determine growth in the presence of sea-run Alewife in the Penobscot River watershed, sagittal otoliths from Smallmouth Bass were aged whole and were then sectioned and aged again in order to determine the relative accuracy of each aging method. The otolith sections were imaged and the rings were measured in the software ImageJ, using the ObjectJ application. From ObjectJ, inferred annual growth rates were determined as well as a back-calculated length at age. Annual growth rates were compared between sites using comparisons of means tests such as t-tests and ANOVA. Average annual growth rates were paired with stable isotope analysis data (δ13C, δ15N) from fish muscle tissue. Ages and annual growth rates were paired with stable isotope data from the same fish. We expect the results will show variation in the growth rates of the resident fish between cohort years and between lower mainstem and tributary sites, and that older fish of a larger body size will show more marine derived nutrients in their tissues. Results from this study may help us better understand the role of marine derived nutrients in driving freshwater productivity of resident piscivores.
