Reproductive Strategies of the Big Skate (Beringraja Binoculata) with Evidence of Multiple Paternity
Beringraja binoculata is a large skate species commonly caught, raised, and exhibited in public aquaria, especially along the Pacific coast of North America. It is one of only two species in the Rajidae family the other species being B. pulchra found in the western Pacific able to produce multiple embryos within an egg case. Although recent studies have suggested this species might be the most fecund elasmobranchs currently known, there has not been a detailed study on whether this species' novel reproductive strategy is influenced by location and different environments (e.g. captive vs. wild). Specifically, if the reproductive strategies differ in egg case sizes, embryo numbers, embryo sizes, and if offspring sex ratios (OSR) were present. Specimens collected from NOAA trawl surveys between 2008-2016 showed evidence that egg cases and embryo sizes were larger in the wild than in captivity; 3-4 embryos in an egg case were the most common in the wild, while 2 was the most common in captivity. OSR were not significantly different between in the two environments, but in this study, there were more female than male offspring in both captive and wild settings. At 42 º North latitude, egg case sizes and embryo numbers peaked, suggesting that the region is considered a suitable habitat to raise offspring due to strong upwelling conditions from the California current ecosystem. Captive B. binoculata egg cases were raised to hatching to improve the description of the developmental stage process done by Hitz (1964). A growth curve was calculated to determine the development of the embryos among four observed stages. Paternity tests were conducted using four microsatellites primer sets to find multiple paternity exists within this species and that females may store sperm for a minimum of three months in captivity, suggesting that B. binoculata possesses several reproductive strategies.