Secchi Disk / Water Clarity Measurements

Secchi Disk

Secchi Disk

I recently built a Secchi disk (see link for instructions) for water clarity measurements. A Secchi disk has four quadrants painted black and white and is 20 cm (freshwater model) in diameter. The disk is lowered into the water using a line marked in feet or meters and the point that the disk disappears from view is called the Secchi depth. Measurements should be taken between 9 am and 3 pm on the shaded side of the boat (to avoid glare off the surface of the water). If you roughly double the reading from the Secchi disk you get a good idea on the extent of light penetration. Generally, plants will only have a enough light to grow at double the Secchi disk measurement (in full sun). The attenuation (or extinction) coefficient can also be obtained (Secchi depth in meters/1.7).

I’m taking readings in an attempt to see if I can find patterns correlating water clarity/water colour/water temperature with baits that preformed well that day/trip. I’ll keep a running log below for now.

  • Grand River, April, a few inches only, 49 F, catfish using cutbait
  • Lake St. Clair, July, 13-14 ft, 65 F?, smallmouth bass with perch coloured lures
  • Fanshawe Lake, June 4-5 ft, 70 F, walleye with live bait (minnows); late July, 84 F 2-3 ft, largemouth and smallmouth, whacky worms (multiple colours), drop shots, crayfish on shakyhead
  • Conestogo Lake, June, 8-9 ft leeward shore and 12-13 ft windward shore, ~ 70-75 F, pike and smallmouth bass with live bait (minnows); September, 2.5-3ft, 67.5 F – pike and smallmouth bass on perch coloured crankbaits
  • Lake Nippissing (West Arm), July, 8-10 ft, tea stained water, ~75 F, pike on fire tiger coloured Blue Fox #4
  • Flack Lake (Elliot Lake area), July, 20-21 ft, 67-70 F, lake trout down rigging at 30 to 60 ft of depth – silver spoons (e.g. Williams Quicksilver) on sunny days, black/purple and white on overcast days, smallmouth bass on smoke coloured tube baits, Strike King KVD Caffeine Shad, Berkley Gulp minnows (black and white), pumpkinseed wacky worms
  • Lake Manitou, 14-15 ft, 70 F, smallmouth bass on smoke and brown coloured tube baits, perch coloured crankbaits, nothing on white tubes on white jigs
  • Lady Evelyn Lake, 13ft, tea stained, 65-67 F, walleye on leeches, Berkley Gulp 4″ grey/white minnow or white twister tail with fluorescent yellow/green jig heads, pike on #4 fire tiger Blue Fox spinners, orange J11 Rapala
  • Wildwood Lake, October, 1.5-2 ft (green coloured), 74 F, smallmouth and largemouth (and a number of pike) on emerald shiner Berkley Gulp Alive (drop shot rig with 1/8 oz weight in 11 – 15 ft of water). (Note: Tournament, this setup worked ok but others did better, not sure on what); May 5-6 ft, 67 F, pike on crankbaits and jerkbaits (minnow coloured); September, 1 ft (green coloured), 70 F, crawfish red and citrus shad crankbaits, smallmouth, largemouth, pike (also on perch DT-6)

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