Effect of Shell Lesions on Survival, Growth, Condition, Reproductive Capacity and Hematology of the New Zealand Blackfoot Abalone, Haliotis iris
Golden-brown lesions of unknown etiology have recently been reported on the interior shell surface of New Zealand abalone Haliotis spp. These lesions occur in the apical region of the shell and may extend down to the attachment site of the adductor muscle. The aim of our study was to quantify the effects of these lesions on individually housed H. iris (n = 179) over a 12-month period. All abalone were collected from the wild, transferred to the laboratory, and anesthetized using sodium pentobarbitone. After full muscle relaxation was achieved, a rigid arthroscope was introduced via the gill chamber, inserted dorsally to the pericardium and advanced into the apex of the shell. Presence and position of lesions were noted. For analysis the animals were allocated to one of three groups: "unaffected" (n = 73), "mildly affected" (< 10 percent of shell area affected, n = 73) and "severely affected" (> 10 percent of shell affected, n = 33). Estimates of survival, growth, condition, reproductive capacity and hematological indices were made for each group at 4, 8 or 12 mo. Over the entire experiment seven affected animals (6.6 percent, n = 106) and two unaffected animals (2.7 percent, n = 73) died (P > 0.05). Growth was impaired (P < 0.05) in both mildly and severely affected animals. The condition of the severely affected abalone was lowered (P < 0.05) and reproductive capacity was diminished. These trends were consistent over the course of the experiment. Overall, mean number of circulating hemocytes (13.1 x 106 cells ml-1) and proportion of circulating hyalinocytes (53 percent) increased significantly (P < 0. 05) in severely affected abalone. Hemolymph glucose titers of severely affected animals (> 20 µg l-1) were elevated, whereas their attachment muscle contained the least glycogen (0.95 mg g-1). Our results indicate advanced lesions have a clear detrimental effect on their host. We suggest that the underlying mechanism of these effects is the animals exhibit an overall physiological stress response.