Meeting Abstract
Skates, a specious group of cartilaginous fishes, lay egg cases in which embryos develop for months to years. These cases sit on the bottom of the seafloor and are subject to dislodgement by ocean currents and attack by predators. We investigated the factors that affect how well egg cases from 8 species, found in the North Pacific and Arctic Ocean, resisted being swept away by currents. To better understand the hydrodynamic principles that each species is capable of withstanding, before breaking away from the substrate, we quantified the maximum currents, friction, and turbulence using a flume and a tilt table. Further, we used scanning electron microscopy in order to visualize the variation in morphology of the microstructures covering egg cases and to determine if there was a relationship between egg case texture and attachment to the substrate. While egg cases exhibit an increased ability of attachment in certain orientations with regard to flow or friction (anterior, posterior, or lateral), we found that preferred orientations did not remain the same between species. Maximum flow speed and friction are dependent on species, as well as the individual, indicating that some species are better able to withstand a wide disparity of flow speeds, or stronger currents, and friction forces than others. We attribute this to the vast diversity of egg case microstructures found across species. Lastly, Reynold’s numbers were calculated for each egg case to determine laminar or turbulent flow in each orientation. Overall, this research has implications for predictive models of skate egg nursery habitats, locating new nesting site locations, and fisheries management models across the North Pacific Seas to include strategies for avoiding nursery grounds and areas where bycatch occurs.
