Abstract
In recent decades, global abalone aquaculture has significantly increased, while wild abalone fishery landings have decreased drastically, shifting production from fishing to farming. In California (USA) and Baja California (Mexico), overfishing and climate changelinked diseases are thought to be responsible for mass mortalities and significant declines in abalone fisheries landings. Conservation aquaculture is an option for enhancing abalone populations through captive propagation and cage mariculture with subsequent restockings into the wild. To test, inform, and promote innovative sustainable seafood production strategies in the Northeastern Pacific, we designed an experimental mariculture system at San Jeronimo Island, Baja California. We explored the feasibility of rearing juvenile red abalone, Haliotis rufescens, in a near-shore mariculture cage-based production system to supply individuals for local restoration programs. We tested the effects of 2 different depths, surface and bottom (5 m), and 3 macroalgal diets (Macrocystis pyrifera, Eisenia arborea, and a mixed diet of Pelagophycus porra with M. pyrifera) on the survival and growth of juvenile red abalone (32 ± 3.33 mm in shell length) inside cages attached to a long-line system. Over the 90-d experiment, survival was 99% for the surface treatment and 95% for the bottom treatment. Mean daily increment in shell length was 93 ± 12 µm·d–1 in surface cages and 82 ± 13 µm·d–1 in bottom cages. Depth did not affect growth or survival. Growth was highest using the E. arborea diet (99 ± 7 µm·d–1) but not significantly different from the M. pyrifera and mixed diets (88 ± 10 and 74 ± 13 µm·d–1, respectively). High survivorship and growth indicate that San Jeronimo Island can support cage-based mariculture of red abalone and that this strategy may be a useful tool in developing climate-resilient abalone restoration solutions aimed at bolstering seafood production.
Highlights
Given the multiple environmental and anthropogenic stressors, the current worldwide abalone production has dramatically changed from fishing to farming
In northern California, wild abalone populations have been affected by extreme warming events combined with other stressors, which caused mass mortalities of red abalone leading to the closure of the fishery in 2018 (Rogers-Bennett and Catton 2019)
On average, during the experimental period, the abalone from the surface cages grew more than the abalone from the bottom cages, 8.33 ± 1.06 vs. 7.38 ± 1.13 mm total growth (TG), respectively, and 2.8 ± 0.4 vs. 2.5 ± 0.4 mm·month–1 monthly growth rate (MGR), respectively
Summary
Given the multiple environmental and anthropogenic stressors, the current worldwide abalone production has dramatically changed from fishing to farming. Wild abalone populations have declined in Mexico and recovery is uncertain owing to climate change impacts. Fishing in the northeastern Pacific, including Baja California, has deteriorated because of a combination of multiple stressors, such as overfishing, diseases, extreme warming events, and hypoxia (Lafferty and Kuris 1993, Karpov et al 2000, Micheli et al 2012, Ben-Horin et al 2016, Boch et al 2018, Lonhart et al 2019). In northern California, wild abalone populations have been affected by extreme warming events combined with other stressors, which caused mass mortalities of red abalone leading to the closure of the fishery in 2018 (Rogers-Bennett and Catton 2019). It is crucial to increase aquaculture production, as it has been shown around the world to support the local fishery both ecologically and economically
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