2020-07-07 P&E Agenda - Item 3 - Attachment 1 - TNC Project Management Plan

Annex 3: Monitoring methods: Ecological

An overview of monitoring methods deployed in the TNC’s shellfish restoration program is provided below
together with the associated key performance indicators. The monitoring methods described here are adapted
from the Shellfish Habitat Restoration Monitoring and Assessment Handbook 26. Some methods may be adapted,
or omitted, as practically and efficiency demands.

Mapping restoration sites and monitoring sampling sites

Method: Multi-beam sonar
To map the dimensions, bathymetry monitoring area of subtidal shellfish restoration sites,
multibeam sonar is often used. Using this method, a multibeam sonar ‘towfish’ is deployed
from a vessel and transects are run in a grid pattern over the potential, or pre-determined restoration site/s. Echo
soundings using multibeam sonar is are accurate to 0.1 m. The survey grid is provided in ASCII format to Chart
Datum at both 5 m and 25 m grid spacings, or is determined using one of the following formulas:

                             Side-scan Sonar Lane width = Range – (Altitude + Overlap)

Altitude is the altitude (height) of the ‘towfish’ scanning unit above the seafloor (this would be a value equal to
10% of the range), and overlap is the desired overlap between lanes (overlap of 10%).

                             Multi-beam Sonar Lane width = Total Range – Overlap

The total range is determined by the frequency used (generally 3 times the water depth but check manufacturer’s
specifications) and desired overlap is ideally 10 percent of the total swath width).

The results of the scans are then presented for interpretation.

Method: aerial/satellite imagery/GPS
For mapping the total area and monitoring areas of shallow-subtidal and intertidal restoration sites, multi-beam
sonar is not a practical survey method. Instead, aerial/satellite imagery or drones and a GIS are employed.
Alternately, for intertidal/shallow subtidal sites, the edge of the reef can be walked around using a handheld GPS
logging the track and the area can be calculated by the internal area of the track.

Determining shellfish restoration impact by area

Method: Physical measurement
The vertical growth of the shellfish ecosystem can be measured by periodically placing a ruler (or meter stick or
graduated rod) vertically on the site, with careful contact at the sediment surface, and then using another ruler
(or other thin, flat, rigid object) to lie horizontally on top of the shell and against the stick to make the height
observation. The average of these measurements is taken to determine the mean height.

Key Performance Indicators

i1. Total area of restoration substrate deployed (m3) – Total area of patches/rows of substrate, with and without
live oysters, deployed within the project footprint.

i2. Total restoration footprint (m3) – Total area of seafloor encompassing all substrates deployed in a given
restoration site and/or all sites throught the estuary.

i3. Total restoration substrate deployed (t) or (m3) – As deterined by the quantity of substrate, usually rubble/rock
+ dried oyster shell + spat on shell + adult oysters (or combinations thereof) that is deployed from the vessel, or
set on the seabed at a given restoration site, or deployed across all restoration sites.


26
     The Nature Conservancy et al, Oyster Habitat Restoration Monitoring and Assessment Handbook


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