The effect of stocking density on growth and seven physiological parameters with assessment of their potential as stress response indicators for the Atlantic salmon (Salmo salar)

Abstract

Inappropriately high stocking density can lead to chronic stress that causes many problems in fish culture. We examined the influence of stocking density on growth performance and a number of key serum parameters of Atlantic salmon (Salmo salar) to investigate stress-induced changes. Salmon were reared at low-density (~7.57-15.71 kg/m 3 , initial to final density), mediumdensity (~15.12-31.11 kg/m 3 ), and high-density (~30.18-61.34 kg/m 3 ) stocking levels for 10 weeks. The results showed that stocking density had significant influence on the growth rate, specific growth rate, and feed conversion ratio (p < 0.05) but not on condition factor and mortality. All examined seven serum parameters showed significant change in the first few weeks. Five parameters increased in all three stocking densities, while the serum superoxide dismutase (SOD) and alkaline phosphatase (ALP) activities decreased. At the end of the experiment, the immunoglobulin M level and SOD activity were lowest in the high-density group (p < 0.05), while the cortisol level, ALP activity, and maleic dialdehyde content were significantly higher than in the other two groups (p < 0.05). The acid phosphatase (ACP) and lysozyme activities were not affected by stocking density. These results indicate that high stocking density could affect the growth of Atlantic salmon and the selected serum parameters, except for lysozyme and ACP, could be used as good indicators for chronic stress caused by stocking densities that are too high.

Effects of stocking density on growth performance and welfare‐related physiological parameters of Atlantic salmon S almo salar L. in recirculating aquaculture system

“…In this study, the salmon in the HSD group showed significantly higher cortisol level than those in the LSD and MSD groups. These findings are consistent with earlier studies on Atlantic salmon (Mazur & Iwama ; Liu, Liu & Wang ) and those in other fish species such as Asian seabass Lates calcarifer and Senegalese sole Solea senegalensis (Salas‐Leiton et al . ; Sadhu, Sharma, Joseph, Dube & Philipose ).…”

Effect of handling and crowding on the susceptibility of Atlantic salmon (Salmo salar L.) to Lepeophtheirus salmonis (Krøyer) copepodids

“…(2004) observed similar effects on plasma cortisol and lymphopenia in male jundià ( Polycentrus jundia , Coutinho et Wosiacki, Perciformes, Polycentridae) after acute and chronic stress, respectively, induced by classical aquaculture management procedures (handling and high density of fish in the tank, respectively). In salmon aquaculture, several classical procedures have also been shown to be detrimental to fish health status and welfare (Liu et al., 2015; Turnbull et al., 2005). For instance, handling during a vaccine injection can be a cause of stress, inducing immune suppression and thus being a limiting factor for vaccine efficacy (Sommerset et al., 2005).…”

“…Handling and overcrowding have already been demonstrated to be stressful situations resulting in activation of the hypothalamus–pituitary–interrenal axis (i.e. cortisol or other related stress indicators variations; Erikson & Misimi, 2008; Liu et al., 2015; Merkin et al., 2010). However, the consequences of these procedures on salmon‐sea lice interactions have never been studied.…”

Effects of&nbsp;Stocking&nbsp;Density and FeedingfFrequency on the Growth Performance,&nbsp;Digestive Enzyme Activity, and Tissues Histology of&nbsp;Hybrid Grouper (Epinephelus Fuscoguttatus♀×E. Lanceolatus♂)

“…Previous studies have demonstrated that high stocking densities were associated with decreases in SOD activity in some sh [39,40] and shrimps [41,42].…”