Project number: 2008-217
Project Status:
Completed
Budget expenditure: $95,327.66
Principal Investigator: Ned Pankhurst
Organisation: Griffith University Nathan Campus
Project start/end date: 31 Jul 2008 - 30 Dec 2009
Contact:
FRDC

Need

Strategic R & D plan
This application fits within the Salmon Aquaculture Subprogram.

Reason for need
Currently, variable and unpredictable egg production has a potential opportunity cost for the Tasmanian salmon industry of $15-20 million per annum. Solving this problem is essential for the industry to maintain its continued strong commercial performance; however, the capacity to reach that solution is currently hindered by our limited understanding of the processes that regulate egg shell assembly and how these contribute to chorion and egg abnormalities, and also how these processes change with stock age and rearing temperature. This application addresses the need to overcome that knowledge gap. Industry results to date show that egg survival can be increased through thermal management; however, the relationship between stock age (maidens or repeats) and thermal conditions have not been systematically investigated, and the industry management protocols are essentially informed guess work.

Benefits
The economic viability of sea cage farming of Atlantic salmon is strongly influenced by the cost of production of smolts. Understanding the mechanisms that contribute to, or cause reproductive failure in spawning fish is an essential component of reducing those industry production costs, and at a broader level, ensuring that there are sufficient smolts produced each year to maintain industry production. The issue has been identified as an industry priority with the stated SALTAS aim of reducing the reliance on repeat spawning fish for egg production. The potential cost of failing to solve the problem is high. The survival of eggs to the eyed embryo stage can be as low as 30-50%, compared with 80% for eggs from best performing fish (SALTAS data). Modelling of this cost gives direct increases in smolt production costs of $225,000 per annum, but a potential industry shortfall in production terms of $15-20 million per annum.

Objectives

1. Determine the effect of age class (maidens or repeats) and thermal regime on reproductive performance (ovarian growth and size, follicle size, time of ovulation, fertility and hatching success) and endocrine parameters (plasma levels of the steroids T and E2, and vitellogenin).
2. Isolate the cDNAs encoding for the G-coupled protein receptor GPR54 and its peptin ligand KiSS-I and develop quantitative expression assays for GPR54 ,KiSS-I, FSH beta subunit (FSHß) and egg shell protein (ZP) mRNAs in Atlantic salmon.
3. Measure plasma levels of ZP in maturing fish.
4. Utilise DNA microarray technology to screen ~650 known salmon genes for differential expression during puberty and sexual development and in response to change in thermal environment, to identify gene networks associated with the above processes.
5. Define histological characteristics and chorionic structure of eggs in relation to stock and rearing conditions
6. Assess endocrine intervention and thermal manipulation as a strategy for increasing fertility, and develop outcomes into a management tool for industry use.

Final report

ISBN: 978-0-646-52772-7
Author: Ned Pankhurst

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