26 SEPTEMBER 2024 • WORLD AQUACULTURE • WWW.WAS.ORG early-juveniles do not require green water conditions, since the retinal green sensitivity disappears, and their vision begins to mirror that of adults, becoming more adaptive to feeding in lower-light conditions (Loew et al. 2002, Margulies et al. 2016). Aquaculture-applied Research Simulated air shipments of live YFT eggs and larvae were successfully conducted at the Achotines Laboratory, as part of a joint IATTCUniversity of Miami workshop (Margulies et al. 2016). After encouraging results, several air shipments were conducted from the Achotines Laboratory to the United States, as part of joint projects with Hubbs Sea World Research Institute (HSWRI), in San Diego, California, and the University of Maryland Baltimore County (UMBC), Institute of Marine and Environmental Technology. Survival rates of larvae transported for about 24 h ranged from 24-80 percent, demonstrating that international air shipment of early life stages of YFT is feasible. A study testing the effect of different rotifer enrichment diets on growth and survival of PBF, conducted by the ELHG in Japan (Stein et al. 2018), helped to confirm the efficacy of enrichment protocols for live feed commonly used over the years in YFT larval rearing trials. In this study, the commercial diets tested in rotifer enrichment (the standard enrichment used by the IATTC for YFT culture and the standard used by KU for PBF larvae) appeared to be nutritionally efficient for PBF larvae, and the fatty acid composition and proximate composition analysis of enriched rotifers were provided. Genetics Studies Studies on Mendelian inheritance and variation of ribosomal protein genes and microsatellite DNA markers (Chow et al. 2001, Takagi et al. 2003), and variation in RNA, DNA and protein content were studied in laboratoryreared YFT (Tanaka et al. 2019). Moreover, studies designed to genetically monitor the captive population of YFT at the Achotines Laboratory utilizing the long fragment of the mtDNA D-loop region, and DNA extraction and PCR amplification methods (Niwa et al. 2003, Cusatti et al. 2022) were effective in identifying individual spawning females, enabling possible extension of this type of analysis to investigations of population structure in the wild (Margulies et al. 2016). Multiple YFT females participated in single spawning events, and individual females spawned constantly for 18-26 months in the main broodstock tank, supporting empirical observations that YFT females in captivity are capable of spawning continuously for long periods of time. Tunas are highly sensitive to handling in captivity and determining the sex of the broodstock population in T1 has always been done postmortem. Now, the Achotines research team is exploring the possibility of using genetic techniques to determine the sex of broodstock and their offspring in real time using new methodologies developed for PBF (Agawa et al. 2015), and also via immunochemical analysis. Climate Change Studies The effects on marine biodiversity caused by climate change, including ocean warming, ice-melting, marine heatwaves, and ocean acidification, currently affects an estimated 680 million people living in low-lying coastal areas, almost 2 billion who live in coastal megacities, nearly half of the world’s population that depends on fish for protein, and almost 60 million who work in fisheries and aquaculture sectors worldwide (UN 2024). Studying the effects of climate change on various aspects of tuna life history has been a very important part of the research developed by the IATTC at the Achotines Laboratory. The effect of water temperature on YFT spawning occurrence, FIGURE 7. Effects of ocean acidification studied on YFT larvae at the Achotines Laboratory. Predicted relationship between mean pCO2 and YFT larval survival after seven days of growth. Trial 1: black line, Trial 2: red dots. FIGURE 8. Biodegradable FADs being tested in the sea-cage off Achotines Bay. A study testing the effect of different rotifer enrichment diets on growth and survival of PBF, conducted by the ELHG in Japan (Stein et al. 2018), helped to confirm the efficacy of enrichment protocols for live feed commonly used over the years in YFT larval rearing trials.
RkJQdWJsaXNoZXIy MjExNDY=