Habitat Utilization and Early Life History Characteristics of Larval, Young-of-Year, and Juvenile Lake Sturgeon (Acipenser fulvescens) in the Great Lakes Connecting Channels

Abstract

I used field surveys, geospatial modeling, and cross-system comparisons to determine if dispersal of larval Lake Sturgeon (Acipenser fulvescens) differed in small and large river systems and resulted in a corresponding difference in habitat use for age 0–2 individuals. Most species – environmental relationships have been described based on interactions observed during an animal’s most dominant life history stage, or extrapolated from systems where animal behavior is better understood. As a result, knowledge of habitat use during early development of a species is often poorly understood, or assumed to be consistent throughout the animal’s range. Using field surveys in North Channel (NC) and Middle Channel (MC) of the St. Clair River, Michigan, I assessed movement patterns of larval Lake Sturgeon and found significantly higher catch per unit effort (CPUE; No. larvae / hour) in 3 locations 0.5–5 km downstream from their natal reefs. Further, I found variation in larval lengths and yolk sac stages from individuals collected in single nets at each of these sites. This suggests larvae of variable ages remained in the river and that suitable nursery habitat existed there and was being utilized by young sturgeon. I then developed a novel habitat suitability model (HSM) to evaluate the quantity, quality, and spatial distribution of riverine nursery habitat for larval, young-of-year (YOY), and juvenile (< 500 mm) Lake Sturgeon in NC. This HSM was developed using georeferenced information on substrate, invertebrate densities, benthic current velocities, and depth. Of the 283 larval Lake Sturgeon collected, the majority were found in high quality habitat (81%) and clustered in three locations (91.2% of total catch). Nine out of 11 YOY and juveniles collected in NC were also in high quality habitat, suggesting suitable habitat also exists for young Lake Sturgeon in NC. Cross-system comparisons of the HSM developed for NC were undertaken for MC and Fighting Island Channel (FIC) of the Detroit River. Model outputs indicated a significantly higher abundance of high quality habitat present in NC (29.1%) than MC and FIC (16.9% and 15.7%, respectively). HSM modeled output for NC indicated an abundance of suitable habitat first occurred < 0.5 km downstream from a known spawning location. Larval, YOY, and juvenile Lake Sturgeon were found in high densities at three distinct locations of high quality habitat and appeared to utilize similar riverine habitat throughout early development. In MC, larvae also concentrated in three distinct locations of high quality habitat. However, this habitat was less abundant and did not occur until 4.5 km downstream from MC reef. Larval collections in MC decreased as sampling progressed downstream, suggesting increased drift distance to suitable habitat resulted in increased larval mortality or alternative dispersal behavior. In FIC, high quality habitat was less common, larval Lake Sturgeon abundance was low, and larvae were not observed in high concentrations. This suggests that newly emerged larvae did not utilize available habitat in FIC, but instead drifted into the main channel of the Detroit River. My dissertation showed that dispersal of larval Lake Sturgeon in the GLCCs is strongly associated with location and abundance of suitable nursery habitat downstream from natal spawning reefs. Further, results indicated variation in habitat conditions downstream of natal reefs resulted in variable dispersal patterns of young Lake Sturgeon and should be taken into account for the planning of future restoration efforts.