The evaluation of a rake method to quantify submersed vegetation in the Upper Mississippi River

Abstract

A long-handled, double-headed garden rake was used to collect submersed aquatic vegetation (SAV) and compared to in-boat visual inspection to record species presence at 67 individual sites. Six rake subsamples were taken at each site and a rake density rating was given to each species collected in the subsamples. Presence at the site, frequency of occurrence in the six rake samples, and additive density rating (the sum of the six rake density ratings) were quantified for each species at each site. The validity of the indices was tested against biomass data collected by clipping all remaining vegetation from the 67 sites. In the turbid water of the Mississippi River, visual inspection of SAV from boats was ineffective with only 27% of the species detected, while raking retrieved on average 70% of the total number of submersed species in the 67 sites. Presence of species at individual sites was correlated with biomass from Stuckenia pectinata, while frequency of occurrence and additive density rating were correlated with biomass for species with greater than 21 g of total biomass from all sites. The efficiency of the rake to collect biomass varied among species; only 18% of total biomass was captured via raking the site six times. Additive density rating as an index of abundance can be used to detect temporal changes in the same water body; however, cross-species comparison is not encouraged unless the efficiency of the rake has been determined for each species being compared.

Measuring submerged macrophyte standing crop in shallow rivers: A test of methodology

“…Percentage cover, percentage volume, and dry weight 8 biomass co-varied in accordance with our first hypothesis, concordant with previous studies which had reported positive relationships (O'Hare et al, 2010b;Yin et al, 2011). However, a 1:1 relationship was not found for any relationship.…”

“…There is some limited evidence to suggest a positive relationship between cover and biomass (Dawson, 1978;O'Hare et al, 2010b;Yin et al, 2011).…”

Influences of Availability on Parameter Estimates From Site Occupancy Models With Application to Submersed Aquatic Vegetation

“…Hence, an occupancy estimator for SAV rake data for all ϕ —heterogeneous ϕ settings may ultimately require alternative occupancy models or looking beyond modeling solutions to alternative sampling designs. Alternative models include one that assumes latent associations between detection probabilities and abundance (Royle and Nichols []); such associations appear reasonable for a number of species (Yin and Kreiling []). Another model that has been poorly explored but which appears promising for use with clustered SAV rake data is the estimation of species occupancy at the survey rather than site scale (cf.…”

Aquatic Vegetation and Invertebrate Communities of Big Stone National Wildlife Refuge

“…We also documented, but did not quantify, any vegetation taxa observed outside of the subsampling areas, but within the 2-m ring. Additionally, we collected vegetation from each subsampling area to determine vegetation composition and density using a 35-cm-wide double-headed rake sampler (Deppe and Lathrop 1992;Yin et al 2000;Kenow et al 2007;Yin and Kreiling 2011). The rake had fourteen 5-cm-long teeth per head, and each tooth was divided into 5 equal segments with alternating black and white markings.…”

“…Vegetation and water quality. For vegetation collected with the rake sampler, we calculated an additive density rating (ADR) value for each sample site by summing the overall (i.e., all taxa combined) and taxon-specific density ratings from each of the six subsampling areas (Yin and Kreiling 2011). Similarly, we calculated the frequency of occurrence by summing the presence or absence (1 or 0) values from the six subsampling areas.…”