Eyes on the Eel: Level 2

Level 2. Quantitative Transects (QT)

We have carried out these transects along 8 river reaches during months of July and September 2015, and plan to do them at the same reaches June, July, and September 2016. They differ from Swat Team assessments in only 4 ways. The QT effort takes one day per site (to do 6 cross sections each on a tributary and on the mainstem confluence upstream and downstream). Also, there is initial site preparation (mapping, bench-marking.

  1. First, each cross-stream transect (one in upstream riffle, two in receiving pool) is benchmarked on both sides of the river (with nails and tree tags, or long 6” to 9” nails driven into the ground. We should not use rebar (at least without using a cap on stakes), because they might injure people or animals. Benchmarked transects will allow us to compare changes at the same sites over time more precisely, but they require time to set up so they can be found again, and they require stringing a meter-tape across the channel during measurement.
  2. Second, we install temperature loggers (iButtons or Hobos) to these sites to track temperatures, and we should roughly map substrate facies (patches of of bed sediments of given sizes) and map flow velocity cores (often visible as a tongue of white water penetrating from the upstream riffle into the downstream pool) through the reach.
  3. Third, we will bring measure densities of important, slow moving animals (e.g. caddisflies like Dicosmoecus, Glossosoma, Neophylax) in quadrats placed systematically across the channel with respect to the x-stream site locations.
  4. Fourth, we will choose 5 representative cobbles per site, role them quickly into submerged fine-mesh aquarium nets, lift them into a white bucket, and gently but thoroughly rinse or brush off all attached invertebrates. These will be poured into a flat white tray and visually inspected, to count major taxa (estimating length of individuals, perhaps in batches if abundant). Invertebrates can be released if ID’d, or preserved in vials (70 % EtOH) or photographed if ID’s are needed. We should probably only put time into identifying taxa that are common but unknown, or seem important for other reasons (possible exotics, etc.).

Proceed with depth, substrate, flow velocity, algal taxa/height/density/condition, and notes on animals as described for Swat Team assessments, but choosing the cross-stream sites to be precisely under the 1.0 or 0.5 intervals on the tape which spans the channel while a given transect is being documented.

Gear needed

  • Meter tape (30-m often enough, but for lower mainstem sites, 100-m tapes may be handy.)
  • Nails (and labelled tree tags or flagging) to mark permanent cross-stream locators for a given transect. Hammers to drive nails into trees or ground substrates. Should be able to string or wrap meter tape along these nails repeatedly—over 25 years, my nails have required occasional repair or re-installation.
  • Rite-in-the-Rain waterproof or water resistant notebook or this type of paper on a clip board.
  • A waterproof digital camera
  • A wading rod marked in 10-cm increments (mep uses a ski pole, great for saving you from falls and pushing aside poison oak, as well). Meter sticks are pretty flimsy for wading and in fast currents.
  • A 15 cm (6”) plastic ruler if you’re learning how to visually estimate rock particle sizes in the Wentworth series.
  • Laminated site maps with acetate sheet overlays for substrate and velocity mapping.
  • Negatively-weighted quadrats (0.5 m x 0.5 m = 0.25 m2 )—these can be made of ½” PVC with right angle corners, filled with sand or water to subdue bouyancy before corners are connected.
  • Whirl paks, old film containers, or vials for samples, with a plastic bottle of 70% EtOH for preservative.
  • 5 gal buckets
  • white plastic trays
  • tweezers or teaspoons for picking up bugs.

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