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Anderson K.,University of The Sunshine Coast | Anderson K.,Australian Seafood Cooperative Research Center | Swanson P.,National Oceanic and Atmospheric Administration | Pankhurst N.,Griffith University | And 3 more authors.
Aquaculture | Year: 2012

Exposure of female Atlantic salmon to elevated temperature can result in a dramatic reduction in egg fertility and embryo survival. Reductions in plasma 17β-estradiol (E 2) levels are associated with much of the observed reduction in reproductive performance; however, the molecular basis for reduced E 2 levels remains unknown. This study examined gene expression of ovarian steroidogenic enzymes and plasma levels of gonadotropins in maiden and repeat spawning Atlantic salmon exposed to higher than normal temperatures. Circulating levels of follicle stimulating hormone (Fsh) were significantly elevated in both maiden and repeat spawning fish maintained at 22°C compared to 14°C during vitellogenesis, but plasma luteinising hormone levels were mostly unaffected. In contrast, gene expression of the ovarian p450 aromatase a and cholesterol side chain cleavage protein were depressed at 22°C compared to 14°C. Hepatic gene expression of estrogen receptor alpha did not change with thermal challenge. The results show that the ovarian response to Fsh is inhibited at 22°C, at least partly as a result of reduced expression of genes coding for steroidogenic enzymes. © 2011 Elsevier B.V.

Dominik S.,CSIRO | Henshall J.M.,CSIRO | Kube P.D.,CSIRO | King H.,Salmon Enterprises of Tasmania | And 3 more authors.
Aquaculture | Year: 2010

Ninety-five genomic DNA samples were extracted from fin clips of Tasmanian Atlantic salmon and genotyped using a 15,225 single nucleotide polymorphism (SNP) chip for Atlantic salmon, which was developed by the Center for Integrative Genetics (CIGENE) in Norway. Infinium assay intensity data suggested that 2991 polymorphic SNPs were single copy and another 952 polymorphic SNPs were present in two copies. A further 467 SNPs would fail quality control thresholds. However, the majority of SNPs that failed quality control departed from Hardy-Weinberg equilibrium. It is discussed that with a larger sample the threshold might need to be re-evaluated to ensure that quality control only removes SNPs for technical not biological reasons. Moderate linkage disequilibrium (LD) indicates the usefulness of loci pairs for whole genome selection. Pairwise LD was calculated between all of the 2991 loci from unique regions, with 9004 pairs of SNP loci found to be in moderate LD, which is significantly more than the 2078 expected by chance (established by permutation testing). The low numbers of SNPs that were evaluated to be useful make an LD-based genome-wide selection approach unfeasible with the resources available. However, the population structure of large numbers of offspring with phenotypic records within large numbers of families is ideally suited for a reference population design that capitalises on linkage information from the SNPs for within-family selection. © 2010 Elsevier B.V.

Pankhurst N.W.,Griffith University | King H.R.,Salmon Enterprises of Tasmania | Anderson K.,University of The Sunshine Coast | Elizur A.,University of The Sunshine Coast | And 2 more authors.
Aquaculture | Year: 2011

Groups of maiden or repeat spawning Atlantic salmon were maintained during vitellogenesis in austral autumn at either 14°C or 22°C through until April when all fish were transferred to a spawning temperature of 8°C. There was no difference in body weight within groups for maidens and repeats, with repeats being consistently larger than maidens, no difference in condition factor amongst groups, but consistently higher gonad weight in repeats than maidens. Gonadosomatic index (GSI) and follicle diameter were suppressed in both maidens and repeats at 22°C, with the effect being most marked in repeat spawners. Relative fecundity (eggkg-1) determined from ovarian tissue samples also showed depression in repeats at 22°C. Fish from both age classes held at 22°C had a higher proportion of atretic follicles. Plasma levels of estradiol-17- (E2) were strongly depressed in both maidens and repeats exposed to 22°C throughout autumn but there was some evidence of recovery amongst maiden fish by late April. A similar effect was seen on plasma testosterone (T) levels. Plasma cortisol levels were generally low and typical of levels in unstressed fish indicating that stress did not account for the inhibitory effects observed. Hepatic zona pellucida protein gene expression was significantly inhibited in both maiden and repeat spawning fish reared at 22°C, but with some evidence of recovery after temperature reduction to 8°C. Hepatic vitellogenin (Vtg) gene expression was also lower in both maiden and repeat spawning fish exposed to 22°C and this was accompanied by reduced plasma Vtg levels in maidens, but not repeats at 22°C. Maidens at 14°C began ovulating first followed by repeats at 14°C, then repeats at 22°C followed by maidens at 22°C. There was reduced fertility in maidens at 22°C relative to both maidens and repeats at 14°C, whereas repeats at 22°C showed intermediate fertility between 14°C fish and 22°C maidens. Survival to the eyed egg stage was highest in maidens at 14°C, significantly suppressed at 22°C in maidens, and at intermediate levels in repeats at both temperatures. This suggests that repeat spawning Atlantic salmon may be more robust in the face of thermal insult which combined with their larger size and egg production, could make their use desirable under production situations where there was any threat of exposure to higher than normal temperature. © 2011 Elsevier B.V.

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