An investigation of optimal feeding ration and effects of probiotic bacteria on the growth of New Zealand Abalone (Haliotis iris)

Haliotis iris are long-rearing Pāua that take 4-5 years to reach market size (75mm). A clear gap exists within the aquaculture literature regarding the optimal nutrition in the cultivation of New Zealand Haliotis iris. Further, there has been much research across aquatic species to suggest that the use of probiotics can successfully stimulate growth and decrease the time it takes to grow farmed Pāua. The overall aim of this thesis is to first investigate and identify an optimum feeding ration of the currently used formulated feed, which can improve growth and eliminate wastage of nutrients in Haliotis iris. Second, this thesis aims to evaluate the effects of the formulated feed with added probiotic bacteria on the ingestion, digestion, assimilation of Pāua, with the goal to increase growth rates. There are two growth trials in this study, conducted over 10 weeks, both of which used 160 juvenile abalone (20mm). First, the feeding ration trial compared the growth of Pāua samples from three treatment groups, fed on 3 different rations based on bodyweight of formulated feed (1%, 2%, 5%). Formulated feed rations were calculated by taking a percentage of the mean wet weight of all the Pāua in each feeding treatment. The second growth trial compares groups of Pāua fed with a probiotic (2%) and non-probiotic (2%) diet at an optimum feeding ration determined from the first trial. Three multi-strain probiotics were used in this study: Exiguobacterium sp. strain (JHEb1) and Vibrio sp. strain (JH1), and Enterococscus sp. strain (JHLDc). Growth (i.e., shell size, animal wet and dry weights) and survival of abalone were recorded throughout the experiment, with initial measurements at the start of the experiment and every two weeks for a total of 10 weeks. Shell length measurements were obtained by recording the greatest length. Wet weights were measured by lightly drying individual animals using tissues or hand towels for approximately 30 minutes and weighing them to the nearest 0.001g. In addition to these morphological and survival parameters, physiological responses that the abalone exhibited under the probiotic treatment were recorded, with a particular interest in the enzyme functionality and the assimilation of nutrients into the body tissues. For this, biochemical analyses were conducted to identify protein, lipid and carbohydrate contents within the tissue of the experimental animals. The results indicated growth across all treatment groups in both trials as well as a 100% survival rates. For the feeding ration trial the weight gain of the Pāua were higher in the 2% and 5% rations. With regard to shell length, the 1% and 5% groups had greater increase over the 10 week trial. Based on the results of this study, the ideal optimum feeding ration for Haliotis iris is a 2% body weight feed ration. A 2% body weight food ration is enough to sustain the nutritional requirements of Pāua without storing an excess of lipids. The probiotic trial resulted in growth, both weight and shell length, for the probiotic (an average of 8.72g/9.13mm) and non-probiotic treatment (8.91g/11.39mm). However there was no significant difference between the two groups. This suggests abalone that are reared in ideal conditions do not require supplementary probionts to aid their digestive functions. Overall, the conclusions of this research are that probiotics are unlikely to add benefit if used coupled with ideal culturing conditions for the species. It is hoped that the findings of this work will contribute to efforts to minimize the cultivation period of Haliotis iris and will help reduce cultivation costs by making feeding, digestion and assimilation more efficient