Vertebral deformities in farmed Atlantic salmon (Salmo salar L.) - etiology and pathology

Abstract

Summary The present review sums up and discusses the current literature on occurrence, causation and pathology of vertebral deformities in farmed Atlantic salmon, and also gives a brief introduction into the normal ontogeny and anatomy of the vertebral column of Atlantic salmon. Skeletal development and growth are sensitive processes that can be affected by many factors. Many of these factors can be manipulated under farming conditions, and are thus regarded as risk factors. Several risk factors that relate to environmental conditions and to feed composition have been identified. Elevated temperatures and photoperiod manipulation to speed up growth are likely the most important environmental factors that cause skeletal deformities. Among the nutritional factors, optimal phosphorus nutrition during specific periods, for example after transfer to sea water, appears to be critical for development of deformity at later stages. More research is needed to understand the interdependency of genetics, development, aging, phosphorus nutrition, temperature and photoperiod, in order to establish the best practice procedures for salmon farming that improve fish welfare.

Ossification of Atlantic cod ( Gadus morhua ) – Developmental stages revisited

“…In Atlantic salmon (Salmo salar) it has been demonstrated that suboptimal nutrition can cause a softer skeleton during development which can ultimately lead to pronounced skeletal abnormalities, such as compressed vertebrae and craniofacial abnormalities (Fjelldal et al, 2012). Vertebral compressions like those reported here in cod larvae might be a result of heterochronic bone growth/remodelling as a reaction to high workload (Fjelldal et al, 2012).…”

Unilateral perivertebral fibrosis associated with lordosis, kyphosis and scoliosis (LKS) in farmed Chinook salmon in New Zealand

“…In the present study, the severity of the fibrosis was correlated to the radio graphic severity of the LKS, suggesting that a greater degree of fibrosis results in more contraction, and therefore higher severity of LKS. While defects in vertebral bone development are hypothesized to cause most spinal deformities in Atlantic salmon (Fjelldal et al 2012b, Boglione et al 2013b, the possibility that perivertebral inflammation and fibrosis could cause spinal curvature in Atlantic salmon has been previously suggested (Kvellestad et al 2000). Additionally, the possibility that LKS in Atlantic salmon has a neuromuscular rather than a bone aetio logy has also previously been hypothesized (Witten et al 2009).…”

“…Other potential factors that have been associated with spinal curvature in Atlantic salmon include environmental factors such as water temperature and currents, growth rates and the age at smoltification (Silverstone & Hammell 2002, Fjelldal et al 2012b, Boglione et al 2013b, Berillis 2015. While studies have not revealed an influence of growth rate or age at smoltification on the development of LKS in Chinook salmon (J. E. Symonds unpubl.…”

“…In farmed Atlantic salmon, deformities have been detected by visible examination and palpation in around a quarter of fish at harvest and in up to 70% of fish by radiography (Fjelldal et al 2012b). Spinal deformities have been reported to result in slower growth and reduced harvest weights (Hansen et al 2010).…”

Effects of temperature on body chemical composition and incidence of deformities in juvenile tench, Tinca tinca (Actinopterygii: Cypriniformes: Cyprinidae), fed a commercial dry diet and/or natural food

“…Body deformities and chemical body composition. Elevated temperatures and photoperiod manipulation to speed up growth are considered the major environmental factors that cause skeletal deformities in fish, while among the nutritional factors phosphorus nutrition appears the most important (Fjelldal et al 2012). Fish diet and water temperature both significantly influenced the incidence of body deformities in juvenile tench (Table 6).…”