In Dr. Stokesbury's lab, we get the opportunity to participate in numerous fish tracking projects with some of our collaborators. One such project deals with improving connectivity and fish passage on several Bay of Fundy coastal river systems. Dams and other man-made barriers pose a global threat to fishes by altering habitat, hindering migrations, changing river flow, and blocking off spawning grounds, which can collapse fish stocks and even lead to extirpation in certain areas. To minimize the threats, these barrages are often fitted with fishways such as ladders that facilitate upstream passage. However, the effectiveness of most fishways remains understudied. In order to address this question, Ducks Unlimited Canada has partnered with Irving Oil, Acadia University, DFO, Canadian Wildlife Service and the Mi'Kmaw Conservation Group in order to quantify passage of upstream migrating alewife through fishway on each of three rivers - LaPlanche, Missaquash, and LaCoupe - bordering the Maritime provinces of New Brunswick and Nova Scotia on the Isthmus of Chignecto. The project aims to improve fish passage design to benefit a wide range of species, including Atlantic salmon, gaspereau, blueback herring and American eel. Research is based out of the Beaubassin Research Station, located among the Beausejour Marshes and maintained by Ducks Unlimited, Irving Oil and Acadia University. The original house located on the property has been restored to a research facility, while the surrounding freshwater and salt marshes are the sites of numerous research project. I had the pleasure of spending several days at the research station last summer, and have come back again this year to assist with the Alewife tracking! Beaubassin was the first place I encountered Alewife, and participation in PIT tagging allowed me to gain valuable skills in fish handling, which have come in very handy when working on my own project!
Alewife movements through fishways is quantified using passive integrated transponder (PIT) tags (read more about the different kinds of tags here). The signals are picked up by antennas mounted on baffles or weirs upstream and downstream of the passage, which provides information on whether or not an individual fish was able to make it up the fishway. Fish are captured, tagged and released throughout the duration of the run, resulting in very large sample sizes. In order to then assess the data, passage rate is quantified as the number of individuals successfully passing, divided by the total number of individuals entering the fishway.
So far, the findings suggest Denils are more efficient for fish passage than the pool‐and‐weir fishways. Size and sex also appear to play a role; larger individuals have a higher passage success, and males pass more efficiently compared to females of a similar size. It is, however, important to remember that this work is still under progress, and numerous factors, including effects of tagging, might be combined to influence fish passage. Continuing to research fish movement, particularly around man-made structures, is important for the maintenance of healthy fish stocks 🐟
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AuthorLiza is a marine biologist, artist and photographer with a passion for ocean conservation. Archives |