Determination of gonad reproductive state using non-lethal ultrasonography in endangered black (Haliotis cracherodii) and white abalone (H. sorenseni)

Abstract

IntroductionBlack (H. cracherodii) and white abalone (H. sorenseni) are federally listed as endangered species in the United States. Conservation efforts include captive breeding programs; however, determination of the reproductive state of individual abalone is notoriously difficult using traditional visual assessments. Ultrasonography is a well-recognized technology used to assess gonad reproductive condition accurately and nonlethally in cultured and wild fish, and more recently cultured red abalone (H. rufescens). Here, we implemented the use of ultrasound imaging technology to monitor the gonad condition of endangered black and white abalone.MethodsRepeated ultrasound assessments of the gonad were used to assess seasonal changes in reproductive development in wild black (n=20), and captive white abalone (n=25).ResultsA modified ultrasound gonad index score was developed to incorporate multiple species of abalone. The ultrasound index scores ranged from one to five, with an index score of one being the lowest (gonad margin is thinly wrapped around the digestive gland or not present) and an index score of five being the highest (gonad margin is thick and significantly compressing the digestive gland).ConclusionWe show that non-lethal ultrasound imaging technology is useful for tracking cyclical changes in the gonad reproductive condition as well as a more precise selection of individuals that are in peak reproductive condition for captive breeding programs.

Temperature-induced variations in dulse (Devaleraea mollis) nutrition provide indirect benefits on juvenile red abalone (Haliotis rufescens) Growth

“…As part of a broader conservation effort to mitigate the impact of climate change on endangered abalone populations (National Marine Fisheries Service, 2008, we sought to investigate the direct and indirect effects of temperature on dulse and juvenile abalone physiology respectively. Our results contribute to a comprehensive exploration of the effects of ocean warming on abalone physiology, including adult reproductive health, with consequences for hatchery management and juvenile abalone recruitment (Boles et al, 2022(Boles et al, , 2023. Concurrent efforts by Neylan et al (2023), revealed slower growth, delays in fecundity, and decreased gonad tissue thickness on adult abalone when exposed to elevated ocean acidification conditions at 14°C.…”