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

Abstract 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 (Nb) and the minimum number of spawning adults (Ns) 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, Nb (<1–367), and Ns (5–545) among streams. Generalized linear models examining the effects of stream environmental characteristics and aspects of sampling regimes on Nb and Ns estimates identified sample size, the number of sampling sites, and drainage area as important factors predicting Nb and Ns. Correlations between Nb, Ns, and capture–mark–recapture estimates of adult census size (Nc) 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