1 NOVEMBER 1999
R.D. Roberts, T. Kawamura, C.M. Nicholson-1999
Journal of Shellfish Research, 18(1): 243-250
Abstract:
Postlarval abalone (Haliotis iris) were reared on five unialgal diatom diets from 3 to 68 days postsettlement. Diatom strain affected both survival and growth, which were positively correlated (r = 0.88, p = 0.05, n = 5). The digestibility and ingestibility of diatoms were both important. Survival ranged from low (<l0% on day 37 postsettlement) on Pleurosigma sp. diet, to high (>70% on day 68) on Cocconeis scutellum, Cylindrotheca closterium, and Navicula ramosissima diets. Diet had little effect on growth and survival in the first 16 days after settlement, provided postlarvae were ingesting adequate food. Growth rates during the week to day 10 were relatively high (means of 20-29 micro m shell length per day). Growth rates from days 10 to 16 were lower than in the first week (t = 7.33, p < 0.001) and again similar among all diets (means 15-20 micro m/day) except Pleurosigma sp. (2 micro m/day), which was not ingested by larvae <1 mm shell length. After day 17, postlarvae grew fastest on the strains that were most efficiently digested (C. scutellum and C. closterium). The digestion efficiency of two diatom strains increased markedly during the experiment, because of changes in diatom condition. Postlarvae were feeding on small diatoms (12 x 4 x 3 micro m) by day 2 postsettlement, and digestive gland development became visible on day 3. Fecal volume increased approximately cubically in relation to shell length, indicating rapidly increasing food consumption.
(Cawthron Institute, Nelson, New Zealand)