Stuart Smith

Research Assistant

BSc Masters (Macquarie University)

Department of Biological Sciences
Macquarie University
Sydney NSW 2109
Australia

Ph : +61 2 9850 8234
Fax: +61 2 9850 8245
Email: ssmitth@bio.mq.edu.au

Summary of Research Interests

Fiji trip 2004

Barramundi (Lates calcarifer)

GH/IGF Axis

My masters (Hons) project focus is on the role of hormones (IGF-I) in growth of a cultured juvenile finfish that represents a significant contribution to finfish aquaculture production in Australia, barramundi (Lates calcarifer) .  All experiments were carried out using Macquarie University's brand new freshwater recirculating system, located at Tailor Made Fish Farm, located at Port Stephens which produces plate sized barramundi on a commercial scale.

IGF-I is released from the liver under the mediation of circulating growth hormone levels and is known to produce growth effects on skeletal tissue as well as have a role in regulation of fish development.  Any correlations between IGF-I and growth rate will therefore give some insight to mechanisms behind non-uniform batch growth in aquaculture and ultimately reduce costs to farms.

Three experiments were conducted thoughout the course of one year.

Experiment 1

Experiment 1 investigates the degree of growth variation (depensation) within a batch of 60 juvenile barramundi. Relatively little is known about non-uniform growth of similar aged fish in aquaculture and this variance in fish sizes in the juvenile stage increases cannibalism and stress of the stock and must be overcome by repeated grading of the batch which is both laboursome and time consuming. The experiment aims at finding correlations between different rates of growth and circulating Isulin-like Growth Factor I (IGF-I) in the blood.  

Experiment 2
Experiment 2 will investigate effects of different Australian commercial barramundi feeds on circulating IGF-I concentrations.  Feed cost still proves to be a significant cost factor on many farms, with up to 70% of costs feed related in some cases.  Many commercial feeds on the market today contain varying concentrations of macronutrients and energy compositions, and although most commercial feeds used in finfish growout full fill dietary and energy requirements, feeds tend to be chosen by farmers on an ad-hoc basis, with little research on the relative effects of the nutritional and energy complement of these different feeds on barramundi growth and physiology. 

This experiment will therefore further benefit the industry from a better understanding the nutrient and energy compositions in feeds that affect physical functions in animals that in turn influence growth.

Following growth effects of certain commercial feeds, a third experiment will be done to see if concentrations of mammalian growth hormone (GH), incorporated in commercial feed, produces greater growth in fingerling barramundi. This is of importance for industry in the future in which will possibly reveal information of most cost-effective GH concentrations to produce increased growth in barramundi and possibly further growth effects of commercial feeds. Also, clearance rates of elevated GH in circulation in barramundi will be determined by analysing IGF-I concentrations in the blood. This component of the experiment is of great importance for industry with respect to ethics and safety issues.

The experiment will further increase knowledge on growth effects of GH on tropical finfish species administered in feed. Also, by tracking clearance rates of increased hormone levels in the circulatory system of barramundi, it will aid establishment of re-administration procedures and times of GH in feeds to increase administration efficiency and increase growth effects of feeds in the industry.