The effects of depth and diet on red abalone growth and survival in cage mariculture at San Jeronimo Island, Baja California, Mexico

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 change-linked 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.