World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 47 of fingerlings has enabled the University of Miami Aquaculture Program to begin developing protocols for nursery and grow-out stages of red snapper. Results from recent research trials show lowmortality and an FCR of ~1.4 on commercial pelletized feed for fish cultured in research systems up to ~300 g. Such results, when coupled with similar outcomes obtained in private grow-out facilities, further reinforces the suitability of the species for culture in a multitude of grow-out conditions. OliveFlounder One of the most promising species for development of land-based marine aquaculture in the US is the olive flounder or Japanese flounder, also known as hirame in Asia and other high-value markets. In November 2015, an illegal shipment of 35 olive flounder broodfish was apprehended on the West Coast by the US Fish andWildlife Service, held under the care of the American Association of Zoo Keepers and then transferred from their curators (Shedd Aquarium in Chicago) to the University of Miami. Broodfish were acclimated, held in quarantine and given prophylaxis before stocking in a maturation tanks with controlled environmental conditions (light, temperature and filtered seawater). Since then, these broodfish, as well as selected F1 offspring, once mature, have been volitionally spawning at the UMEH year-round, generating numerous opportunities for conducting a variety of studies at all developmental stages, from embryos to adults – enabling us to successfully close their life cycle. UMEH broodstock olive flounder have been spawning throughout the year at controlled temperature averaging 17 C, ranging from 13 to 22 C. Fish are kept in a 20-m 3 fiberglass tank provided with aeration and pure oxygen to maintain dissolved oxygen levels at or above saturation levels (8-10 mg/L). Fish have been fed cut fish, squid and a vitamin/mineral gel mix daily to satiation, corresponding to approximately 10 percent of their total biomass in the tank. The number of broodfish maintained in the tank ranges from 18 to 24, ranging in size from 2 to 8 kg each. Estimated biomass in the tank has been approximately 60 kg (3 kg/ m 3 ), with a sex ratio of approximately 1:1. Over the last five years, we have also achieved a number of notable production goals with the species. Survival rates during larval rearing consistently range from 30 to 50 percent, Survival rates during the nursery and grow-out stages exceed 90 percent. Growth rate and feed conversion have also been remarkable. Even at stocking densities as high as 50 kg/m 3 , olive flounder grow to 0.5- 1 kg in 12 months with FCRs as low as 1.2. Working with Beaver Street Fisheries and local distributors, we have been test marking this product in local restaurants. Current work with this species is aimed at developing economically-viable land-based marine aquaculture in the US using RAS production techniques for flounder grow-out, with important emphasis on implementing flounder aquaculture in the Atlantic states region. Spawning, larval rearing, nursery and growout activities at the UMEH clearly indicate that, in properly managed systems, the olive flounder can be successfully produced at commercial level in the US and elsewhere. This corroborates the commercial-scale culture of this species in Asian countries, mainly Japan and South Korea but also China. This is a top-choice species for land-based aquaculture. NassauGrouper The Nassau grouper is another demersal species with promising production characteristics. In the fall of 2013, the UMAquaculture Program, in collaboration with the seafood distribution company Beaver Street Fisheries, Inc. and their sister company, Tropic Seafood in Nassau, Bahamas, decided to revisit this iconic Caribbean species. The collaboration began with the permitted capture of adult grouper broodstock near New Providence Island in the Bahamas, which were stocked into indoor maturation tanks at Tropic Seafood. During their natural spawning period in late January 2015, groupers were sampled to determine oocyte stages in females and milt production in males for potential spawning readiness. Selected fish were implanted with slow release gonadotropin-releasing hormone (GnRH-a) pellets obtained through a collaboration with the University of Maryland IMET, resulting in a successful spawn of fertilized eggs that were shipped to the UMEH. Eggs hatched within 24-28 hours and were subsequently stocked into larval rearing tanks and managed following our standard larval husbandry protocols. Survival was very low and only ~100 fingerlings reached the post settlement phase at 45 days post hatch, when they are considered early juveniles. The primary goal of the research transitioned to rearing this F1 cohort as future broodstock, aimed at closing the life cycle in captivity of this iconic species. Since then, considerable research has been conducted on aspects of bioenergetics and growth of these fish, as well as on their reproductive physiology. Periodic sampling has been conducted to determine sexual maturity and evaluate their potential for volitional or induced spawning so as to close the cycle with the F1 captive- reared generation. During this period, the cohort has been fed a natural diet of frozen sardines, mackerel, herring and squid, with weekly supplementation of vitamins and minerals used for broodfish maintenance. Consumption and growth were minimal during winter (20-24 C) and maximal during summer (28-32 C). The greatest individual growth observed was approximately 400 g weight and 275 mm total length in 12 months. At 5 years from egg, the average weight was 5.7 kg and 61 cmwith some individuals approaching 8 kg and 68 cm in total length. Other Species The hogfish is the third species being investigated as part of an ongoing NOAA-Florida Sea Grant-funded research project (with Nassau grouper and red snapper being the other two). This species is a highly regarded foodfish found throughout the southern US and Caribbean Sea area. The UMEH began working with this species in early 2017 to learn more about its life history and to explore the viability of commercial production. Although there have been limited volitional spawns of this species at UMEH, as measured by spawning frequency and number of viable eggs, nonetheless these are the first reported spawns of hogfish in captivity. Research work continues at UMEH aimed at developing aquaculture techniques for this species. The UMAquaculture Program is recently engaged in new initiatives aimed at developing environmentally sustainable and economically viable production of almaco jacks and yellowtail snapper. Additionally, research is underway as part of a collaborative effort to establish monosex production of mahi-mahi. The UM Aquaculture Program, as part of larger collaborative research efforts, ( C O N T I N U E D O N P A G E 4 8 )