No evident effect of domestication on the anti-predator behaviour of European abalone (Haliotis tuberculata): Implications for stock enhancement programs

Abstract

Stock-enhancement programs for the European abalone (Haliotis tuberculata) might be an efficient way to restore collapsed natural populations or preserve fishing activities. Specifically, this practice consists of releasing hatchery-reared juveniles from wild or farmed broodstock into natural environments. However, the process of selection and adaptation to farming conditions may result in domestication, thus leading to genetic and behavioural changes in farmed animals. Therefore, evaluating the effects of the domestication process on juveniles is a critical first step toward the development of successful abalone stock-enhancement programs. To this end, the behaviour and survival of sixteen-month-old H. tuberculata juveniles from wild and from farmed broodstock (the product of three generations of shell-length based selection) were compared. We used three assays at different spatial and temporal scales: (1) short-term responses to simulated contact with predators, (2) the activity pattern in the presence of a natural predator (the velvet crab Necora puber) in aquariums during a 2-week trial, and (3) survival in large mesocosms in the presence of predators during a 3-week trial. No significant effects of the broodstock origin of the juveniles were detected on any of the studied parameters (P > 0.05). In addition, the estimated size effects were small compared to the overall mean for most of the variables, suggesting that the domestication process was too recent to induce important behavioural changes in juveniles from farmed broodstock.Introducing crabs into the mesocosms significantly decreased abalone survival rates (P < 0.05). In the activity pattern trial, most of the abalone mortality in aquariums with crabs (55%) occurred within the first three days, which was largely attributed to initial exploration of areas outside of shelters by the abalone. In the second week, abalone spent much less time moving when crabs were present (P < 0.05).These results suggest that juveniles from both origins would likely have the same survival rates if released in the wild. The commonly reported high abalone mortality immediately after seeding is likely due to a lack of hiding behaviour or exploration of the new environment during the first few days of exposure to predators in the wild. Therefore, current release systems may need to be adjusted to the ethological characteristics of abalone juveniles to avoid high mortalities due to an initial lack of predator avoidance.