By Vladislava Sukhanovskaya
Bundle tree trunks, dump them into the water, add rocks and here you go – a habitat for fish to hide from predators and have fun.
It sounds simple, but habitat restoration can cost hundreds of thousands of dollars, years of time and the collaborative effort of engineers, scientists and designers. It may be better to just start from scratch.
Canadian scientists from the Great Lakes Laboratory for Fisheries and Aquatic Sciences and the University of Alberta recently evaluated the effectiveness of helping freshwater fish reproduce by creating habitat, restoring habitat or by adding fish and nutrients to a lake or stream.
The salmonid species include coho salmon, chum salmon, chinook salmon, steelhead and brook trout. They all like habitats created from scratch, according to a study published in Environmental Management Journal last August.
Those habitats are in channels, ponds and floodplains. Creating them is the most expensive, but the most effective way to help salmonids reproduce, said Sebastian Theis, the leading author of the study and a postdoctoral researcher at the Toronto and Region Conservation Authority.
There are two arguments why habitat creation works so well. It can be very targeted when fish need an essential habitat – we can create specific habitat for spawning, Theis said.
“Since we are losing a lot of habitat, creating habitat adds something that was not there before,” Theis said.
The effectiveness still depends on the case, he said. For example, if the fish can’t migrate because of a dam, creation of habitat will be less effective than habitat restoration. The best decision in this case will be removing the dam and restoring connectivity, Theis said.
Habitat restoration is cheaper than habitat creation. It can take many forms such as submerging woody debris, restoring connections between different habitats, adding substrate and planting trees along banks, the study says. Materials for habitat restoration should be biodegradable and sustainable, Theis said.
“You chop down trees and you bundle them into a really big wood bundle,” he said. “You anchor those down and you put them in the shallow areas.”
Wood is a perfect place for algae and little vertebrates, Theis said.
Another way is to bundle trees into a V-shape, he said. It’s more stable and it creates shelter.
It’s important to design fish habitats not to be washed away by storms and high lake levels, said Ralph Toninger, associate director and the restoration and resource manager at the Toronto and Region Conservation Authority.
“We don’t usually design for a single species in mind,” said Rick Portiss, senior manager of Environmental Monitoring and Data Management at Toronto and Region Conservation Authority.
“When we’re working on habitat restoration projects we are looking from a holistic view,” he said. “We design for the entire fisheries community.”
Design and engineering are one of the most expensive parts of any habitat project, said Toninger.
“Our restoration sites look like construction sites,” he said. “We have bulldozers and excavators, dump trucks. That equipment is expensive to run.
“That kind of work can be “as cheap as $2,000 per hectare in inexpensive cases and we are talking about millions of dollars per hectare” in other cases, Toninger said.
The less effective way to help fish reproduce is biological manipulation such as stocking or adding nutrients into the water, said Theis.
Behavioral and genetic differences do not allow some stocked fish to survive, he added.