Zebra mussel densities, shell free dry mass and sample site information in Lake Winnipeg 2017-2019
At offshore sites, triplicate Ponar grabs (0.052 m-2) of sediment were collected from the M/V Namao. At nearshore sites, sediment samples were collected from a smaller workboat using a Petite Ponar grab (0.023 m-2) at the 3 m depth contour. Total sampling effort varied across the three years owing to time and logistical constraints (see Supplemental Table S1 for additional detail).
Additional samples were collected at up to 18 shoreline sites (depths ranging from 0.2 - 1.0 m) around the lake in 2019. Depending on the type of substrate present, different sampling approaches were employed. For silt to gravel sized substrates, three to five 1 m long benthic kick-net (Canadian Aquatic Biomonitoring Network; CABIN, 400 µm mesh) drags were utilized. For cobble to rock sized substrate, three to five 0.25 m2 quadrats were placed randomly on the lake bed and up to five individual rocks were removed. All live mussels were removed from the rocks (when present) using a paint scraper. A sheet of tinfoil (Handi-foil®; PN 51805, standard foil wrap) was placed over the surface area of the rock and excess foil trimmed away. The foil was carefully cleaned of debris, folded and placed in a Ziploc® bag for later weighing. The weight of foil for each sampled rock was determined gravimetrically (to nearest 0.01 g) using a laboratory balance and converted to surface area using the relationship FoilArea (cm2) = 305.73*FoilWeight(g) (r2 = 0.99, df = 8) derived from a model-II regression of foil mass and area measurements of foil squares cut from the same roll of foil in the laboratory. For boulder to bedrock size substrates, a 0.01 m2 wire quadrat was placed at up to five randomly selected locations and all mussels within the wire quadrat were removed. The percentage of hard substrate present at each site was determined to the nearest 10%, and the percent rock, rock surface area, and rock bottom area were used to normalize densities per m2 of lake-bottom, following Bailey et al. (1995).
- Publisher - Current Organization Name: Environment and Climate Change Canada
- Licence: Open Government Licence - Canada
Data and Resources
|Zebra mussel densities, shell free dry mass and sample site information in Lake Winnipeg 2017-2019|