Genomic evidence for fisheries-induced evolution in Eastern Baltic cod

Overfishing is one human-driven perturbation driving major evolutionary pressure on marine populations. Fishing is often highly selective for particular traits and elicits marked phenotypic changes, while the evolutionary basis of such trait change remains unresolved. Here, we used a unique time series of the overexploited Eastern Baltic cod (Gadus morhua) to investigate growth trends during 25 years of heavy fishing along with hypothesized genetic changes at the full genome level. A growth analysis demonstrated a 48% decrease in asymptotic body length from 1996 to 2019 while a genome-wide association analysis revealed outlier loci and gene candidates linked to growth performance. The contributing loci showed signals of directional selection with high autocovariance of allele frequency change and significant overlap with regions of high genetic differentiation. Our findings suggest a genomic basis of fisheries-driven growth impairment and underscore implications for conservation policy regarding the adaptive potential of marine populations.