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Atlantic Salmon Spawning Gravel Permeability Study

Permeability is the rate at which subsurface water flows through substrate. Salmon spawn in substrate ranging from gravel to cobble.  The female salmon excavate a hole in the substrate and deposit eggs while males simultaneously fertilize them.  The female then cover the eggs with substrate from immediately upstream.  The incubating embryos and larva require flow through the substrate to provide oxygen and carry away metabolic wastes.  Spawning substrates that have relatively high permeability result in high embryo and larva survival.  The Atlantic Salmon Commission is measuring the permeability of salmon spawning habitat and relating this to the survival of incubating salmon, as well as the frequency of use of different spawning locations.

In the 1980’s, Atlantic Salmon Commission staff measured permeability to 1) determine the effects of a siltation event in Chase Mill Stream in the East Machias drainage, and 2) evaluate the quality of 12 known spawning areas in the Machias drainage.  The Jonesboro staff is revisiting these locations to determine if permeabilites have changed markedly over the last two decades.  In addition, the Commission has begun an effort to sample additional known spawning habitat in the Downeast rivers.  In 2004, staff sampled 21 sites; seven sites each in the Narraguagus mainstem, Old Stream in the Machias drainage, and Chase Mill Stream.  The Commission plans to continue this project; targeting recently used spawning areas in most Maine salmon rivers.