Evaluation of Gonad Reproductive Condition Using Non-invasive Ultrasonography in Red Abalone (Haliotis rufescens)

Abstract

The reproductive status in abalone (Haliotis spp.) can be difficult to discern using traditional visual inspection methods and may therefore rely on lethal histological analyses for a definitive determination. With endangered species of abalone, lethal histological examinations are strictly prohibited due to their imperiled status. This research investigated the effectiveness of using non-invasive ultrasound technology as an alternate means of identifying the reproductive status of abalone rather than through invasive biopsies or lethal histological methods. Twelve abalone were randomly selected from cultured red abalone broodstock cohort (n = 200) produced at The Cultured Abalone Farm (Goleta, CA) to initially test these methods. Following initial gonad ultrasound determination, a subset of another cohort of 5 year-old (n = 62) red abalone produced at the UC Davis Bodega Marine Laboratory were monitored using ultrasonography to detect seasonal changes in gonad size for 7 weeks. Following the 7-week assessment period, the full cohort of 5-year old abalone (n = 122) were then spawned and gonads were also evaluated using ultrasound technology before and immediately after spawning. Ultrasound imaging technology accurately differentiated between digestive and reproductive tissues, allowing for the characterization of an ultrasound gonad index score for rapid assessment. Mean gonad thickness determined via ultrasound imaging was categorized on a scale of 1–5, with an index of 1 being the lowest (gonad tissue thin or absent) and an index of 5 being the highest (gonad margin has increased and is compressing the digestive gland) for red abalone. Ultrasound imaging technology was successful in rendering a gonad index score that can be used to track gonad maturation over time in cultured or captive species. Tracking ultrasound gonad scores over time is a useful tool for improving abalone culture production, and increasing animal welfare by reducing handling stress associated with gonad assessments. Individual abalone that are empirically determined ready to be spawned can then be selected for broodstock. Non-invasive ultrasound technology has the potential for broad applications within abalone aquaculture to enhance both food and conservation aquaculture 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.…”

Within‐ and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival

“…We used a Sonosite Edge II Ultrasound System with a HFL50 6‐15 MHz probe (Mechanical Index = 0.7; Thermal Index = 0.1; Read Depth = 6; Exam type = breast) (FUJIFILM Sonosite, Bothell, WA) to examine and measure the gonadal tissue of adult abalone prior to spawning (Boles et al., 2022). We took ultrasound images prior to spawning on the morning of April 2, 2021.…”

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

“…Abalone reproductive anatomy was imaged with a SonoSite Edge II Ultrasound System (FUJIFILM SonoSite Bothell, Washington) using a HFL50 15-6-MHz transducer probe (Mechanical Index=0.7; Thermal Index=0.1; Read Depth=6; exam type: breast). To reduce handling stress, ultrasound examinations were conducted by immersing abalone in seawater affixed to transparency copier film (3M #PP2950, Austin, Texas) shell side down to expose the muscular foot and categorically ranked using established methods (Boles et al, 2022). Abalone gonadal tissue wraps around the outer portion of the cone-shaped digestive gland and is located between the shell and the foot on the right-hand side of the mantle cavity (Figure 1).…”

“…Ultrasound technology has been used by biologists for decades as a non-lethal technique to assess the reproductive health in finfish conservation (Evans et al, 2004;Swanson et al, 2008;Chiotti et al, 2016;Brizendine et al, 2018;Carim et al, 2021) and for commercial aquaculture purposes (Bonar et al, 1989;Blythe et al, 1994;Colombo et al, 2004;Naeve et al, 2018). While ultrasonography had previously been used in paūa (H. iris) to identify shell lesions that diminish the ability of the adductor muscle to properly adhere to the shell, leading to increased mortality (Nollens et al, 2002), only recently has ultrasound technology been successfully used to characterize abalone reproductive state, specifically red abalone gonad condition (Boles et al, 2022). The goal of this study is to assess the use of non-lethal ultrasonography as a technique to monitor the reproductive condition of endangered black and white abalone and to evaluate the applicability of the technology for use in conservation programs.…”