Evaluating the Effects of Barriers on Slimy Sculpin Movement and Population Connectivity Using Novel Sibship‐based and Traditional Genetic Metrics

Abstract

Population genetics‐based approaches can provide robust and cost‐effective ways to assess the effects of potential barriers, including dams and road‐stream crossings, on the passage and population connectivity of aquatic organisms. Determining the best way to apply and modify genetic tools for different species and situations is essential for making these genetics‐based approaches broadly applicable to fisheries and aquatic habitat management. Here, we used multiple genetic approaches to assess the movement and population structure of Slimy Sculpin Cottus cognatus at two road‐stream crossings in Michigan and one dam in Massachusetts, USA. We captured and genotyped individual sculpin and assessed movement and population connectivity by using (1) a sibship‐based approach, where the presence and proportional distribution of siblings on either side of a barrier indicates population connectivity and the possible direction of movement (i.e., presumed movement from higher to lower proportions), and (2) two Bayesian genetic assignment approaches (STRUCTURE and BayesAss) to identify migrants across potential barriers based on individual population assignment probabilities. We also used traditional genetic metrics to assess within‐population genetic variation and among‐population genetic divergence. At all three locations, we found evidence for sculpin movement across the potential barrier based on sibship reconstruction, but small family sizes limited the ability of this approach to provide robust estimates of the rate and direction of movement. At two sites, a lack of genetic differentiation between above‐ and below‐barrier populations limited the effectiveness of the genetic assignment methods for identifying possible migrants. At the third site, reduced upstream allelic diversity and effective number of breeders resulted in high genetic differentiation (FST) between above‐ and below‐barrier populations, and both sibship and genetic assignment methods provided strong evidence of limited connectivity and bias against upstream movement. Overall, combining approaches and metrics may help overcome the limitations of any one method and maximize the value of datasets for genetics‐based monitoring and assessment.

Diets, Condition, and Reproductive Fitness of Slimy Sculpin (Uranidea cognata) after Catastrophic Flooding in Trout Streams in Southeastern Minnesota, USA

“…Powerful flooding in Garvin Brook and Trout Run produced severe channel scouring and displacement of boulders >40 cm in diameter, simultaneously destroying sculpin habitat and food resources. The presence of sculpin in Gilmore Creek and Garvin Brook only 2 weeks post-flood suggests that either fish were able to find refuges [5,8] that enabled them to survive mass bedload rearrangement, or they were able to quickly recolonize stream reaches from nearby, less-impacted systems [43,44]. Although slimy sculpin are often considered sedentary and unlikely to exhibit more than small-scale movements [29], there is increasing evidence that they are capable of both rapid and long-range movements, especially when recolonizing defaunated stream reaches [43][44][45].…”

“…The presence of sculpin in Gilmore Creek and Garvin Brook only 2 weeks post-flood suggests that either fish were able to find refuges [5,8] that enabled them to survive mass bedload rearrangement, or they were able to quickly recolonize stream reaches from nearby, less-impacted systems [43,44]. Although slimy sculpin are often considered sedentary and unlikely to exhibit more than small-scale movements [29], there is increasing evidence that they are capable of both rapid and long-range movements, especially when recolonizing defaunated stream reaches [43][44][45]. An apparent lack of less-impacted reaches in Garvin Brook (severe flooding affected the entire stream, extending from headwater springs downstream to the confluence with the Mississippi River) suggests that survival in refuges was most likely, especially since even young-of-year sculpin were large enough by August to significantly reduce their vulnerability to elevated current velocities [5,22].…”

Distinguishing and Employing Two Species of Fish in Assessment of Stream Quality

“…The tendency of different species to hybridize with one another (Strauss, 1986; Rudolfsen et al, 2019) and the proclivity to form new species in individual river systems (Lemoine et al, 2014) adds to challenges in identification of different sculpin species. Slimy Sculpin have also shown ability to overcome both upstream and downstream barriers to movement (Weinstein et al, 2019), which could increase their overlap with Mottled Sculpin. At sites where sculpin were present, overlapping distribution of sculpin species identified a region of sympatry in the upper Manistee River at 5 of the 12 electrofished sites, but our accuracy in differentiating Mottled Sculpin and Slimy Sculpin using either morphological or genetic characteristics was high.…”

“…An alternative to individual species is the use of closely related species. Species relatedness can be an advantage in environmental assessment because both inter-specific competition and differences in habitat quality could affect presence and abundance (Weinstein et al, 2019). Sculpin ( Cottus spp.)…”

Recovery of a Population of Slimy Sculpin (Uranidea cognata) after an Autumn Fish Kill in the Headwaters of a Minnesota Trout Stream

“…Due to its wide geographic range, sensitivity to a variety of anthropogenic disturbances, relatively high abundance, short life span, high reproductive output, and easy to measure biological parameters, the species has been recommended for use as a sentinel species for monitoring studies throughout the northern regions of North America [19,25]. Although generally considered as non-migratory with low mobility and strong site fidelity [18], slimy sculpin can display long-range movements under certain conditions [26,27].…”