Ice can be considered suspended lateral margin habitat, if you find it just as the channel has opened up, but along the edges, the ice still provides shelter for fish. Over-head cover!
However, the most common type of suspended lateral margin habitat consists of woody material and grasses. Moss can also be included, along with dead leaves and other plant materials. This habitat, when submerged along the water’s edge, is home to numerous aquatic invertebrates.
Caddis flies require the woody debris and grasses as shelter building material and they can use it for their armoured fortress that they carry with them on their daily travels, on the stream bottom of quieter waters. This is usually in amongst the submerged willow plant’s dead and living branches, along the stream bank.
Midge larva love to anchor onto submerged twigs and the stems of canary grass, to get good access to the best feeding areas. The constant flow of water brings all that they require to survive, until they are ready to transform into winged flight, above water.
Shrimp like Gammarus find detritus a friendly habitat for feeding and breeding. The baby shrimp can be seen swimming about in the dead leaf matter that collects in willow debris catchers.
Near my house runs a small trout stream which has been thru years of heavy silt build up and low flow conditions. When the stream bed gets silted in by tons of annual bed movements of silt, soil and clay, the only habitats for those underwater, gill breathing aquatic invertebrates, that need clean flows to live, move to new habitats. This is when they all congregate into suspended lateral margin habitats to find a new home.
When the stream is cleaned up by stream bank stabilization plantings and other riparian plantings, the stream becomes more productive for trout and also just an overall healthier trout stream with cleaner flowing waters.
In the Bow Valley Riparian Recovery and Enhancement Program, most of the plants were planted along the water’s edge, where they will produce the biggest bang for the buck, in creating new fish habitat. This includes aquatic invertebrate suspended lateral margin habitats.
Now, after six years of planting and tens of thousands of native willows and a few deciduous trees, the results are starting to come in. Any fisheries scientist worth his or her salt, should know that the creating of this type of habitat has wide ranging benefits for a trout stream! This means improved water quality and volume transported downstream, with reduced evaporation, so humans can also benefit by having cleaner water to tap into, downstream.
When planting, my spacing is usually approximately 1 metre between plants, so this is often observed on some of my planting sites right along the water’s edge, where only I plant willows, due to the liabilities of planting so close to the water’s edge with volunteers.
On some locations the survival is good and the spacing is easily recognized. Each willow plant is considered a single habitat unit in my own personal assessment methodology. The reason for this is because it is not just about the fish, the aquatic invertebrates must be factored into the equation for a successful stream restoration program, based on riparian planting.
The stream bank stabilization work is a bonus that really boosts the water quality in a trout stream. The annual reduction of tons of stream bed movement has resulted on very obvious stream bed clean up and an increase in the availably gravels, cobbles, boulders and exposed submerged woody debris.
All of the above is good stuff for a healthy trout stream, and if your objectives are fish habitat enhancement, you love to see all of this happen right before your eyes. This is why the photo and video coverage that I have done over the years will pay big dividends in the end. I can also happily report the good news back to the readers.