Since the mid-1970s, wild abalone populations in California (USA) and Baja California (MX) have significantly declined owing to overfishing, illegal catches, diseases, and warming seawater. This decline led to the development of abalone farming. In Mexico, the commercial aquaculture of red abalone (Haliotis rufescens) is performed in land-based facilities. However, abalone farming has faced several challenges recently, including slow growth rates and pathogens exacerbated by climate change. To address these issues, pilot projects for abalone mariculture have been developed to conserve the fishery and restock natural stocks. Offshore suspended sea cages have allowed abalone to reach commercial size faster and at lower costs than land-based farms. However, more information is needed on managing abalone sea farming in the context of climate change. Given the effectiveness of sea farming, we evaluated the biological performance of juvenile red abalone cultured in a bottom-sea cage system.
Red abalone farming was conducted over seven months at the small bay of Puerto Arbolitos, Ensenada, Baja California, MX. A bottom sea cage system containing 6 Australian baskets, each with 100 juvenile abalone (3 mm shell length), was placed at seven meters of depth. At sea, abalones were monitored every 15 days when fed, and water samples were taken to assess environmental parameters. A parallel land-based system was set up at the CICESE Marine Biotechnology Laboratory, consisting of a recirculating system with six 250-L semicircular tanks. Water temperature was maintained at 16°C, and ammonia, dissolved oxygen, and pH levels were measured daily. Biometric measurements were performed in both systems every two months to determine growth and mortality rates. In both systems, abalone were fed a fresh Eisenia arborea and Pterygophora californica diet, collected in the field. After 7 months, land-based abalone farming showed a higher growth increase in shell length (Figure 1) and wet weight than sea-based farming. Furthermore, the mortality rate was only 1% on land compared to 5% at sea. Environmental factors, including severe storm surges in December, predation risk, and system location, played a significant role in the sea-based system, adversely impacting marine culture and highlighting the challenges of sea farming.