WWW.WA S .ORG • WORLD AQUACULTURE • MARCH 2022 23 ( C O N T I N U E D O N P A G E 2 4 ) Disinfection methods to prevent the development of harmful or beneficial microorganisms can further reduce microbial populations in laboratory cultures. Pacific lamprey Entosphenus tridentatus are reared at Confederated Tribes of the Umatilla Indian Reservation facilities, typically in monoculture (Fig. 5). Because larval lamprey are closely associated with the sediment in their natural environment, they may have an important ecological relationship with the benthic microbial community. We hypothesized that rearing larval lamprey with other species would improve lamprey growth and survival in a culture setting. We conducted a polyculture experiment in which speckled dace Rhinichthys osculus were held in the same recirculating system with larval lamprey. After 274 days, the size increase of larval lamprey in polyculture (20.5 ± 3.3 mm growth) was significantly greater (p < 0.05) than those in monoculture (16.6 ± 1.3 mm growth; Fig. 6). Survival was not enhanced in polyculture; however, the addition of a filter mat to rearing tanks resulted in increased survival relative to previous cultures without the mat. The filter mat and polyculture with dace likely promoted the development of a more abundant or stable microbial community compared to the monoculture system. Improvements in growth and survival support the idea that microbial interactions are important for these benthic, filterfeeding larvae. This work furthers our understanding of rearing requirements for this culturally important species and highlights the importance of ecological community linkages in aquaculture. Development of Larviculture Protocols for Rearing the Ecologically Important Long-spined Sea Urchin within a Novel Recirculating System Aaron Pilnick, Keri O’Neil, Matthew DiMaggio and Joshua Patterson The University of Florida and The Florida Aquarium have been working in partnership to develop aquaculture protocols for the ecologically important long-spined sea urchin Diadema antillarum for coral reef restoration. Once an abundant reef-grazing herbivore throughout the Caribbean, this keystone species is responsible for consuming fleshy macro- and turf algae that competes with reefbuilding corals (Hughes et al. 2010). In 1983-1984, an unidentified disease caused 93-100 percent mortality of long-spined sea urchin populations throughout its native range, resulting in a sudden lack of herbivory and contributing to an ecological phase shift from hard coral to macroalgae-dominated reef ecosystems (Lessios 2016). This species has not recovered substantially and the loss of functional herbivory has strongly contributed to ongoing Caribbean coral reef declines (Miller et al. 2003). Reef restoration practitioners are therefore greatly interested in augmenting reef herbivory by restoring populations to pre-mortality densities. These objectives would benefit from scalable methods to sexually propagate this species from gametes and restock to the wild (Fig. 7). Development of long-spined sea urchin aquaculture has realized limited success FIGURE 6. Mean lengths (mm) of larval Pacific lamprey in monoculture and polyculture treatments during the study. FIGURE 7. Conceptual model illustrating D. antillarum restocking via hatchery produced animals. Stages include in situ broodstock collection from wild populations, ex situ broodstock maintenance, larval development within scalable hatchery production settings, settlement and juvenile grow-out, and in situ restocking on targeted coral reefs. Arrow colors depict current levels of success in achieving each stage: green = achieved reliably at large scale, yellow = achieved somewhat reliably at reduced scale, red = not yet tested. The transition from green to yellow depicts a shift from reliable, successful production of hundreds of thousands of late-stage larvae to relatively fewer metamorphically competent larvae at 28-35 days post fertilization. Figure by Joseph A. Henry. Reprinted from Pilnick et al. (2021), https://www.nature.com/articles/ s41598-021-90564-1.
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