Incidental damage of blacklip abalone (Haliotis rubra) by commercial divers in New South Wales, Australia

Rates of incidental damage to blacklip abalone (Haliotis rubra) were investigated in a retained, commercial catch in New South Wales, Australia. On average, 10.2% (8.9-11.6%, 95% CI) of retained abalone were damaged, but there was no relationship between the level of experience of divers and the degree or frequency of damage. Most damage was relatively minor, such as small abrasions to the foot or cuts to the mantle, and wounds healed rapidly in aquaria. Major damage, such as large cuts and abrasions to the foot, occurred in 4.2% (3.6-4.9%) of retained abalone. For individuals with major damage, any mortality was rapid and significantly greater than for undamaged abalone in aquaria. Rates of growth were also lower for individuals with major damage. An average of 19.1% (17.2-21.1%) of abalone removed from the reef were found to be under the minimum legal size and replaced. Experienced divers removed and replaced significantly fewer abalone under the minimum legal size (11% vs. 23.8% of those handled) than inexperienced divers. Using the estimated rates described here, approximately 40 tons of abalone are estimated to be damaged by the fishery each year. Most damaged abalone are retained, heal rapidly in aquaria, and can be exported live, but approximately 3 tons of damaged abalone (both retained and discarded) may die.