Biological Modeling and Lower River Field Studies

Update for Summer 2003

The watershed assessment database for fish and invertebrates is nearly completed, with final 2003 fish data for remaining 11 sites currently being added. This gives us approximately 65 sites with both fish and invertebrate community data and 50 additional sites with just invertebrate data.† A variety of metrics to be used in assessment modeling have been computed and some preliminary basin wide assessments presented at the 2003 meeting of the International Association for Great Lakes Research (IAGLR).The database is prepared for implementation of Land Use Transformation data within landscape based biological models.Statewide regressions for July water temperatures have also been implemented for the entire watershed to estimate water temperature stress for aquatic biota.

 

Lower river site selection

The Lower Muskegon River contains four valley segments based on the MRI-VSEC classification.For this project each vsec unit was further divided into sub-units based on the influence of factors such as habitat and confluences with major tributaries.†In 2003 we are sampling multiple locations in 5 of the sub-units in the lower river as well as the major tributaries (Brooks Creek, Cedar Creek, Bigelow Creek and Mosquito Creek) .We selected 8 random sites within each sub-unit to sample for species and habitat distribution patterns.Random sampling points on the main river were chosen by dividing each subunit into 100 m segments on GIS and using a random number generator to select nine random locations within each sub-unit.These locations were then assessed in the field for access and ability to sample.One site was dropped in each VSEC sub-unit based on difficulty of field access.†† The remaining eight sites within each sub-unit are being quantitatively sampled for invertebrates (May and Aug), fish (May July-Aug, and Oct) and habitat (as water depth allows).

 

In addition to mainstem sites on the lower river, three sites on each major tributary are also being sampled.The major tributaries include the Cedar Creek, Mosquito Creek, Brooks Creek and Bigelow Creek.Sites were selected in the upper, middle and lower portion of these rivers typically based on road crossing access.The length of the sample reach for each tributary site was 15 times the width of the river at that point.

Biological sampling on Lower River

Spring fish sampling has been completed and the database is being developed. At each lower river site fish were sampled along 100 m of edge using two passes with a tow barge electroshock unit.Main channel fish were sampled over one week using a MDNR boom shocking boat and sampling for two 10-minute segments in each sub-unit.In the tributaries fish were collected using both tow barge and backpack electroshockers as necessary.†† Fish were identified and weighted with some stomachs saved for trophic analysis.In addition to the main river sub-units, fish were also sampled in unique habitats including riverine wetlands in the lower river (vsecís 15 and 16).The unique habitats include the large emergent wetland complex associated with the South Branch and viewed along US 131, wetland pockets located along the channel and channels that cross-over between the South Branch and the North Branch.Each unique habitat was mapped and located via GPS.Fish in these habitats were sampled by a variety of methods: Fyke nets, minnow traps and electroshocking.


Quantitative invertebrate samples were collected at each site using a variety of methods depending on water depth and velocity, habitat type and substrate.At each site at least three samples were taken, one each from mid-channel and left and right edges.Each lower river sub-unit sample consisted of two replicate Ponar collections or the equivalent at 3 or more transect positions.If additional unique habitat was identified then additional samples were collected.Typically sites were visited via boat and benthic samples were collected with a Ponar sampler using a boom from the boat.In other unique habitats where substrate was accessible other types of samples were taken such as rock clusters and wood/plant clusters.In the tributaries samples were collected using a Hess sampler, a hand Ponar, rock clusters or wood/plant clusters.†† Samples were elutriated in the field if necessary and then preserved for analysis in the laboratory.Some of the laboratory analysis has begun.

 

  Boom and ponar dredge sampling on the main channel Equipment for tributary sampling
 

 

 

 

Habitat Mapping and Assessment

Habitat mapping and analysis is in progress.Methodology and equipment has been refined for the lower river and 2 full sub-vsecs have been mapped.Mapping and analysis consist of boating up each sub-vsec with a differential GPS, Pulse Coherent Acoustic Doppler Profiler, on-board computer, underwater camera, video camera and depth sounder.Habitat segments are identified within each sub-vsec and unique habitats important for fish spawning, nursery and forage are mapped.Other habitat characteristics are quantified and mapped such as substrate size and % composition, bank condition, flow hydraulics and channel geomorphology.Through out the sub-vsec hydraulic profiles are taken using the Doppler unit.The profiles are stored in an on-board computer and then analyzed in the laboratory.The field data and flow profiles are being used to create detailed geo-referenced habitat maps for the entire lower river.

 

The habitat in all sub-vsecs that have been sampled for fish and invertebrates will be mapped during the summer of 2003.If possible, additional sub-vsecs can be completed during the summer and fall of 2003.Tributaries and the remaining lower river sub-vsecs will be mapped in 2004.


Boat mounted Pulse-Coherent Acoustic Doppler Profiler, computer and GPS unit used in habitat surveys