Why Erosion and Sedimention Control is Important: A Fish s Point of View Fisheries Protection Program Department of Fisheries and Oceans June 6, 2014
Basic definition: Sediment is defined as soil particles deposited into lakes and streams through the process of erosion. What is Sediment?
What is Sediment? Sediment can be classified based on its size and composition
What is Sedimentation? Sedimentation and erosion are natural processes that occur with flowing water But too much sediment can cause problems for fish
Common Misconception SEDIMENTATION Refers to the deposition of all particle sizes of sediment on the bottom of a waterbody. SILTATION Refers to the input of fine sized particles (i.e. < 0.063 mm) to the waterbody. These fine particles typically remain in suspension and contribute to the turbidity (water clarity).
Sources of Sedimentation LAND DISTURBING ACTIVITIES EXPOSED SOILS
Exposed Soils
Fisheries Act Definition Fish habitat means: Spawning grounds and any other areas, including nursery, rearing, food supply and migration areas, on which fish depend directly or indirectly in order to carry out their life processes.
Freshwater Fish Habitat Requirements
How Does Sediment Effect Fish and Fish Habitat? Excessive sediment, in suspension or deposited, can have damaging impacts on all life stages of fish, particularly salmonids
Life Cycle of Salmonids
Spawning In the fall, a redd, is constructed by the female consists of a series of pockets in the gravel where the eggs are deposited fertilized by the male. Spawning sites are usually located at the head of a riffle where stream flow can percolate through the bottom substrate.
Eggs Normally hatch the following spring (April or May) - depending on water temperature). Clean gravels of different sizes are required to ensure percolation of well-oxygenated water during embryo development.
Alevins Following hatching, the alevins (sac fry) live within the spaces of the spawning gravels surviving totally on their yolk sacs and clean oxygenated water.
Fry Once the yolk sac has been used up alevins = fry Fry emerge from the gravels and begin their first year of growth in nursery areas adjacent the spawning sites.
Parr Over 1 year old Parr marks - camoflage Remain in their stream of birth usually between 2 to 4 years before they are large enough to go to sea.
How Does Sediment Effect Fish and Fish Habitat? Depends on the exposure: 1. Duration How long? 2. Extent How far? 3. Intensity How much? Suspended vs. deposited
Habitat Effects (changes to spawning habitat) Redd Degrades spawning habitat and redds: Adults avoid spawning beds smoothered Clog spaces between gravels restrict water circulation reduced oxygen reduced egg survival Natural flushing is reduced prevents removal of harmful wastes excreted by the embryos
Habitat Effects (changes to nursery habitat) Smothers eggs and fry: Delayed fry emergence trapped in spaces between the gravels Low oxygen: premature hatching smaller/poor quality fry
Physiological Effects (stressors on physical health) Mortality Relationship between sediment and direct mortality is complex Depends on life stage, time of year, size of fish, sediment composition Also depends on the exposure (duration, extent, and intensity)
Gill trauma: Physiological Effects (stressors on physical health) Fish gills are delicate and easily damaged by abrasive sediment particles. Infection = death Other trauma: Increased levels of deformities, fin erosion, lesions, tumours, gill flaring and coughing,
Trophic Effects (Feeding) Alter foraging/feeding Salmonids are sight feeders Become the prey!!!
Trophic Effects (Feeding) Can affect aquatic insects ie: fish food!! Smothers aquatic insects Dislodges insects from attachments Clog aquatic insects gills or feeding structures Eliminates aquatic insect habitat
Indirect Impacts (ecosystem-wide effects) Reduces primary production Suspended solids = Reduced water clarity Reduced water clarity = Reduced light penetration Reduced light penetration = Unhappy plants Unhappy plants = Less oxygen produced for fish
Indirect Impacts (ecosystem-wide effects) Changes to river morphology
Summary of Impacts
What Can you do to Help? Have a plan = erosion and sedimentation control to minimize the risk of sedimentation of the waterbody during ALL phases of the project: Implement before starting work to prevent sediment from entering the water body Maintain until: all disturbed ground has been permanently stabilized suspended sediment has resettled runoff water is clear Decommission once site is stabilized.
Why Protect Fish Habitat?
To Report Sedimentation Events Fisheries Protection Program - Triage Monday to Friday (709) 772-4140 FPP-NL@dfo-mpo.gc.ca Canadian Coast Guard - Regional Ops Center 24/7 (709) 772-2083 1-800-563-2444
Questions??