Ground Truth and Site Assessment of Model Predicted Fish Spawning Habitats in the St. Clair-Detroit River System

Large scale predictive modeling of potential fish spawning areas in the St. Clair-Detroit River System (SCDRS) was completed in 2011, which identified several potential spawning areas. We used side-scan sonar and underwater video to assess the physical habitat properties and to develop substrate classification maps at model-selected sites. Egg mats were used to assess the extent of spawning activity and to ground truth model outputs. Several areas were identified as suitable for restoration activities that do not appear to be active spawning sites or contain characteristics that would detract from using the site for restoration activities. However, ground truth of the sonar identified over 700 other targets of interest, ranging in size from a few, to tens of square meters, scattered throughout the sites. These targets were primarily debris fields, but also consisted of natural rock piles. It appears that these small patches of debris and rock substrate contribute greatly to fish habitat, providing structure, potential food sources, and relief from the current. Assessments will continue in 2014 to continue validation of model results, quantify physical properties, and assess use by spawning fishes. These data will help identify suitable sites for construction of rock-rubble fish spawning reef restoration sites.