Downeast Salmon Federation News

DSF Key Partner in Multi-Year pH Mitigation Study
 

In our continuing effort to identify and ultimately mitigate factors that are depressing freshwater- and early marine survival of juvenile Atlantic salmon, we at the DSF have been focusing more resources on assessment of the long-term impacts of acid rain and land use changes on the chemistry of the Downeast salmon rivers1. In cooperation with DSF, researchers from the University of Maine, the Maine Department of Environmental Protection, and the U.S. Department of the Interior, U.S. Geological Survey are conducting experiments to evaluate how the water quality of the Pleasant River may affect the health and development of young Atlantic salmon. While the water quality of the river is generally good, it does contain low but detectable levels of the blueberry pesticide, hexazinone, and in the spring and fall, high rainfall and snowmelt contribute to a rise in acidity which, in turn, causes the release of toxic aluminum from the river banks into the water. This combination, pesticide + acid + aluminum, creates a 'multiple stressor' environment for young salmon.

State and federal agencies charged with salmon management, the National Academy of Sciences review team, and many experts in the field have all concluded that the combination of episodic low pH, high aluminum (exchangeable form), and low calcium in these river systems may have a significant negative impact on Atlantic salmon in the Downeast rivers. However, there has been little consensus on how to proceed to either determine the cause and effect relationship or develop a mitigation strategy.

With shrinking state and federal budgets there has been less and less money available for the salmon restoration program in Maine, so when the DSF decided to take on a river chemistry research project we knew that we would have to do significant fund raising from private sources. Due to the generosity of The Bailey Wildlife Foundation, which has provided a significant amount of the funding, along with the C.F. Adams Charitable Trust, The Eastern Maine Conservation Initiative, the Maine Council of the Atlantic Salmon Federation, and the Maine Outdoor Heritage Fund, DSF renovated the Pleasant River hatchery and began the research phase of the project in early 2008.

In order to accommodate the multi-year research project, we divided the existing Pleasant River Hatchery facility in half. Half continues to be used to rear eggs to fry to be stocked into the Downeast rivers, as we have been doing for the past 16 years. The other half has been reconfigured to raise salmon from egg to smolt (the stage at which they leave the rivers and head to the ocean). We retained 7,000 fry at the hatchery for this experiment. Half of the fish are being reared in untreated river water (prone to episodic low pH events) the other half in water buffered with calcium carbonate (CaCO3 ). By buffering the pH we hope to control for several factors that may be negatively affecting salmon growth and survival in fresh water and in their early marine phase. The project also looks at the combined effects of the agricultural herbicide hexazinone (Velpar), used in the local blueberry industry, and low pH on salmon prey capture ability. This will help us determine if the combined stressors of low pH and pesticides impair feeding performance which has implications for long-term growth and survival.

In the summer of 2008, USGS researcher Adria Elskus is conducted preliminary experiments evaluating the ability of hatchery fry to capture 'prey', or feeding performance. She does this by placing fry, one at a time, into small 2 quart plastic buckets, adding 30 water fleas (Ceriodaphnia for you biology types!), and giving the fry 20 minutes to capture as many as he can. A fry whose health is compromised by multiple stressors is likely to capture less prey - perhaps due to poor eyesight, poor swimming ability, and/or poor reflexes. Adria will complete a similar experiment in the summer of 2009 on a sample of fish reared from fertilized eggs hatched in the Pleasant River facility. The success of this group, which has been exposed to Pleasant River ambient water since soon after fertilization, will be compared to that of the 2008 study group, which entered the study at the fry stage of development.

In addition to the prey-capture study, a portion of the study fish are sampled monthly for growth and every two months to measure their physiological response to the different treatments. This is a great opportunity for undergraduate students interested in Atlantic salmon restoration-University of Maine at Machias environmental studies student Kevin Flanagan assisted Jacob van de Sande, the DSF’s Hatchery Manager and Educator, with sample collection during the spring 2009 semester. Stephen McCormick, fisheries physiology researcher with the U.S. Department of the Interior, U.S.Geological Survey’s Conte Anadromous Fish Research Center in Turners Falls, MA conducts non-lethal sampling of gill tissue from a small sample of the fish to analyze levels of exchangeable aluminum and Na+/K+-ATPase, also known as the sodium-potassium pump. Found in all animal cells, this “pump” provides active transport of nutrients, sugars, and proteins, etc. across cell membranes. The culmination of the study will be a salt water challenge test where the smolts will be put into salt water tanks and their physiological responses measured. Upon completion of this study we should have a solid understanding of whether adding lime to the Pleasant River will have any benefits to the fresh and saltwater growth and survival of Pleasant River salmon. The study will conclude in 2011 with the release of the fish hatched in the spring of 2009.