Browsing by Author "Walker SP"

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    Prevalence of spinal abnormalities in Chinook salmon smolt and influence of early rearing temperature and growth rates
    (John Wiley and Sons, Ltd, 11/06/2018) Munday JS; Perrott MR; Symonds JE; Walker SP; Preece MA; Davie PS
    Spinal abnormalities can be detected at harvest in around 40% of farmed Chinook salmon in New Zealand. However, whether these abnormalities are present in smolt is unknown. Radiographs of 3,736 smolt were taken immediately prior to transfer to sea water and evaluated for fusions, compressions, vertical shifts, and lordosis, kyphosis and/or scoliosis (LKS). The survey included smolt from two different chilling strategies that had been graded into slow- or fast-growing fish. Overall, 4.34% of Chinook salmon smolt had at least one spinal abnormality, similar to the rates of reported in Atlantic salmon smolt. The rate of abnormality was significantly higher in faster-growing fish. Fusions were most common with 2.68% of smolt affected. Smolt subjected to longer chilling times had lower rates of fusions. Compressions and vertical shifts were both observed in 1.31% of smolt. Although LKS is the most common abnormality of harvested fish, LKS was detected in just five smolt. The results suggest that some fusions in harvest fish have developed at the time of seawater transfer while LKS develops late in the production cycle. Overall, spinal abnormalities are uncommon in Chinook salmon smolt and may be influenced by chilling times and growth rates.
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    The problems with pin bones: Intermuscular bone development and function in salmonids and their implications for aquaculture
    (John Wiley and Sons, Inc., 2024-06-22) Lyall BA; Witten PE; Carter CG; Perrott MR; Symonds JE; Walker SP; Waddington Z; Amoroso G
    A healthy skeletal system is fundamental to fish welfare and performance and a key physiological feature of a robust fish. The presence of skeletal deformities in farmed salmonids is a persistent welfare problem in aquaculture, and one which threatens to impede industry growth. Deformities of the fine bones of fish, such as ribs and intermuscular bones (IBs), have received less attention than vertebral body deformities, despite their potential to compromise fish welfare and product quality. IBs, commercially known as pin bones, are small spicule-like bones embedded in the muscle fillets of salmonids, cyprinids and other basal teleost species. In farmed basal teleosts, they impact fish processing, have negative effects on the economic value of fish and present a potential consumer health concern if ingested. Current understanding of IB development and function in teleosts has mostly relied on morphological research. More recently, advances in our understanding of molecular mechanisms of IB development in cyprinids have been made, largely due to the exploration of breeding IB-free fish for use in aquaculture. In this review, we explore the existing literature on IBs in teleosts, highlight the points of contention within this field of research and identify the significant knowledge gaps about the development and function of salmonid IBs. To our knowledge, there is no available research on the function of IBs and scarce research concerning IB development in salmonids. Future research on teleost IBs would benefit from the use of consistent terminology to facilitate interdisciplinary collaboration and identify research outputs in this field.
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    Unilateral perivertebral fibrosis associated with lordosis, kyphosis and scoliosis (LKS) in farmed Chinook salmon in New Zealand.
    (27/10/2016) Munday JS; Perrott MR; Symonds JE; Walker SP; Lovett B; Preece MA; Davie PS
    Vertebral column lordosis, kyphosis and scoliosis (LKS) can result in downgrading of farmed Chinook salmon Oncorhynchus tshawytscha in New Zealand. No cause of LKS has been identified. Radiography and histology were used to quantify LKS and perivertebral fibrosis in 27 fish with LKS visible at harvest and 30 visually normal fish from 3 New Zealand farms. Radiographic LKS was present in all 27 fish with LKS and in 18 of 30 fish without visible LKS. Quantification of the radiographic severity revealed significantly higher radiographic severity scores in fish with visible LKS (mean ± SD = 5.89 ± 2.41) than in fish with no visible, but radiographic LKS (1.44 ± 0.86, p < 0.001). The most frequent histological finding was unilateral perivertebral fibrosis that often extended into the horizontal septum and adjacent myomeres resulting in separation or loss of myocytes. Fibrosis was visible in all fish with LKS and in 12 of 30 fish without visible LKS. Fibrosis scores were higher in fish with visible LKS (3.32 ± 1.71) than in fish without visible LKS (0.35 ± 0.57, p < 0.001). The radiographic LKS severity scores were significantly correlated to the fibrosis scores (R2 = 0.59 p < 0.001) in the fish. Histology of other tissues revealed multifocal inflammation within muscle, peripheral connective tissues and myocardium which were considered most likely incidental in these fish. In this study, LKS was consistently and significantly associated with perivertebral fibrosis, suggesting that perivertebral fibrosis is an important process in the development of LKS. Further research to determine the cause of the fibrosis is required.