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Spinal curvatures and onset of vertebral deformities in farmed Chinook salmon, Oncorhynchus tshawytscha (Walbaum, 1792) in New Zealand
Author(s) -
Perrott M. R.,
Symonds J. E.,
Walker S. P.,
Hely F. S.,
Wybourne B.,
Preece M. A.,
Davie P. S.
Publication year - 2018
Publication title -
journal of applied ichthyology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.392
H-Index - 62
eISSN - 1439-0426
pISSN - 0175-8659
DOI - 10.1111/jai.13663
Subject(s) - oncorhynchus , lordosis , biology , deformity , chinook wind , kyphosis , fishery , scoliosis , radiography , anatomy , zoology , surgery , fish <actinopterygii> , medicine , genetics
Summary The prevalence and onset of radiological skeletal deformities in tagged Chinook salmon ( Oncorhynchus tshawytscha ) were investigated after 129 days in seawater at grading for removal of fish that failed to thrive (mean weight ± SEM , 432 ± 6.5 g) and again at harvest after 395 days (mean weight ± SEM , 3,721 ± 43 g). A scoring system identifying four categories of the radiographic deformity phenotype was established based on literature and evaluation of X‐rays of harvest‐size Chinook salmon. Deformity categories were: spinal curvature or Lordosis, Kyphosis, Scoliosis ( LKS ); Fusion; Compression and/or reduced inter‐vertebral ( IV ) space; Vertical shift. Of the 432 fish surviving to harvest and for which there were weights and diagnostic radiographs, 38.4% were affected by at least one deformity. Late onset LKS , detected at harvest, was the most prevalent deformity in 29.4% of all harvested fish. LKS was present alone with no other potentially confounding deformities in 10% of harvested fish. Cranial lordosis, a common LKS variant, in the postcranial region comprised half of LKS ‐deformed fish. LKS commonly co‐existed with compression, a combination prevalent in harvest fish at 13.4%. Compression and/or reduced IV space detected in 22.0% of harvested fish was commonly associated with other deformity phenotypes (84/95 of fish with compression). Fusion and vertical shift were present in 7.6% and 4.6% of harvested fish, respectively. More than 77% of fish with any type of deformity developed the deformity within 9 months of harvest. Fusions that were visible in radiographs at grading persisted in fish that survived until harvest. In contrast, LKS , the most visible harvest deformity, was difficult to detect in radiographs from the earlier time point, suggesting that this economically important deformity develops at a relatively late stage of seawater growth. Deformed fish at harvest were smaller (mean ± SEM 3,479 ± 76 g) than normal (mean ± SEM 3,875 ± 51 g). Fish with no deformity grew at a significantly ( p < .05) faster rate than fish that developed a deformity during this period or were already deformed at grading. The scoring system performed with a sensitivity of 92.4% and a specificity of 97.6% for Chinook salmon >500 g, and thus has a potential utility for other farmed salmonids.