Evaluating the utility of effective breeding size estimates for monitoring sea lamprey spawning abundance

Sea lamprey (Petromyzon marinus) is an invasive species that is a significant source of mortality for populations of valued fish species across the North American Great Lakes. Large annual control programs are needed to reduce the species' impacts; however, the number of successfully spawning adults cannot currently be accurately assessed. In this study, effective breeding size (N_b) and the minimum number of spawning adults (N_s) were estimated for larval cohorts from 17 tributaries across all five Great Lakes using single nucleotide polymorphisms (SNP) genotyped via RAD-capture sequencing. Reconstructed larval pedigrees showed substantial variability in the size and number of full- and half-sibling groups, N_b (<1–367), and N_s (5–545) among streams. Generalized linear models examining the effects of stream environmental characteristics and aspects of sampling regimes on N_b and N_s estimates identified sample size, the number of sampling sites, and drainage area as important factors predicting N_b and N_s. Correlations between N_b, N_s, and capture–mark–recapture estimates of adult census size (N_c) increased when streams with small sample sizes (n < 50) were removed. Results collectively indicate that parameters estimated from genetic data can provide valuable information on spawning adults in a river system, especially if sampling regimes are standardized and physical stream covariates are included.