A tale of two species: Vermilion and sunset rockfish in the Southern California Bight

The vermilion rockfish complex consists of two distinct species, vermilion rockfish (Sebastes miniatus) and sunset rockfish (S. crocotulus) with clear haplotypic differences. Due to a one-way mitochondrial introgression from vermilion into sunset rockfish a high proportion (20–30%) of fish with a vermilion haplotype are characterized as sunset based on nuclear genotype (introgressed sunset, hereafter, introgressed). Here we examined differences in the distribution and biological attributes of vermilion and sunset rockfish (including introgressed individuals) collected during a fisheries independent groundfish survey conducted with hook and line gear in the Southern California Bight in 2014. We saw significant differences in spatial distribution (latitude, depth, and distance from the nearest port and mainland) and biological characteristics (average size, size frequency distribution, weight-length and size-depth relationships) between vermilion rockfish and both introgressed and sunset rockfish but no differences between sunset and introgressed fish. Our analyses established that introgressed and sunset rockfishes shared similar biological and geographic characteristics, with no significant differences based on the features we examined. Consequently, we explored the relationship between the catch of vermilion rockfish collected per site, relative to the combined presence of vermilion, introgressed and sunset rockfishes, and a suite of co-located environmental and geographic variables using binomial generalized additive models (GAMS). The best model explained 95.0% of the deviance, indicating that the occurrence of vermilion, introgressed, and sunset rockfishes depended on latitude, longitude, depth, dissolved oxygen, temperature and distance from port.