Evaluation of the occurrence of multiple paternity in Squalus acanthias in the South Atlantic region using nuclear markers

Abstract Understanding shark reproductive modes is crucial for conservation, as these K-strategist species are vulnerable to overexploitation. The spiny dogfish (Squalus acanthias), a small shark listed as ‘vulnerable’ by the IUCN, has a 22-month gestation period and a reproductive output ranging from 1 to 21 pups per litter. This study aimed to investigate multiple paternity in S. acanthias using Single Nucleotide Polymorphism (SNP) markers. Samples from six litters, comprising 40 individuals collected in Argentina, were analyzed using a ddRADseq library. SNP markers were screened with the STACKS pipeline, and kinship and paternity were analyzed using COANCESTRY and COLONY software. Results revealed 1,021 to 1,620 SNPs per litter, with multiple paternity detected in all litters. The number of sires per litter ranged from 2 to 4. No correlation was found between litter size and multiple paternity, suggesting this behavior may enhance genetic diversity. The species’ size and sex segregation, coupled with females in shallower waters, increase their vulnerability to fishing pressure. Overfishing and bycatch exacerbate the reduction in sexually mature individuals, threatening population recovery. This study highlights the need for management policies that incorporate reproductive strategies, especially for species like S. acanthias with complex life histories and low recovery rates.