Editorial: The puzzle of fish ladders
Roxanne, a miniature dachshund, tries to introduce herself to spring chinook salmon at the Winchester dam fish ladder on the North Umpqua River near Roseburg, Ore., on Wednesday, June 11, 2008. The salmon are migrating upriver. From June 1 to 10, 1,396 spring chinook were counted as they moved through the ladder. Roxanne is owned by Rick and Frankie Betz of Roseburg. (AP Photo/The News-Review, Robin Loznak) Purchase photo reprints »
Last week the Gazette ran an article under the headline, “Do fish ladders work?” With thousands of fish passages having been constructed in the U.S. over many decades — often with taxpayer money — it’s a question that should have an answer by now. But due to a lack of investment in fish passage research and analysis, uncertainty persists.
There needs to be an unequivocal answer to the question, especially as more fishways are planned for construction locally, nationally and internationally. We think politicians with sway over budgets and research spending should invest more in this field. The University of Massachusetts Amherst could also aid in this endeavor, for it is a leader in fishway research, providing one of the few places in the U.S. where graduate students can obtain an advanced degree in fishway engineering.
It was UMass research that led the Gazette to report once again on fishways last week. A recent study conducted by an international team of professors, including one from UMass, suggests that New England fishways are, for the most part, failing to get fish up and over dams to their spawning grounds, sometimes letting no fish pass at all.
The team surveyed 20 dams, some large, some small, that are connected with fishways on the Connecticut, Merrimack and Susquehanna rivers. They found migration over theses dams falls far short of goals. For example, the number of American shad that pass over the dams hovers around 2 percent of the target on the Merrimack River. Sturgeon aren’t getting through passages on the three rivers at all.
But not everyone agrees with these findings.
Critics have accused researchers of cherry picking data. Some say the study doesn’t take into account the most recent dam research or the importance of dams in saving water for droughts, preserving wetlands and filtering pollution from downstream waters.
The U.S. Fish and Wildlife Service acknowledges fishways aren’t living up to their promise, though it doesn’t see as dire a situation as the UMass research. According to Curtis Orvis, a fish ladder engineer with Fish and Wildlife’s Springfield office, fishways are about 28 percent effective. Yet, due to a lack of research, it isn’t clear why fishways aren’t producing better results.
It could be that some fishways are poorly designed. Predators may be staking out entrance points where fish gather to go up and over dams. Or fish may not be interested in entering concrete passageways, a foreign-looking path to many aquatic animals.
Meantime, the sheer number of dams and under-performing fishways is harming migratory fish populations. The UMass research suggests that with each dam fish have to pass, the number that get through decreases. When the diminished group makes it to the main-stem dam, few get across.
Not all fishways are failures. On the West Coast, massive fishways over hydropower dams have had good records of enabling fish passage. And in New England, rock-ramp or natural-looking fishways are among the most successful.
Orvis notes there is simply no money out there for fishway research. This needs to change. Methods need to be devised to improve their effectiveness. At stake are the dwindling but economically important populations of migrating fish such as the Atlantic salmon, shad and river herring and their overall impact on the greater aquatic ecosystem.