Factors Affecting Fin Damage of Farmed Rainbow Trout

Abstract

The aims of this study were to determine the influence of the factors affecting fin damage under different rainbow trout production systems and to compare the findings with the known experimental reports. The study was based on a questionnaire that included information about the main factors i.e. oxygen level in exit water, water temperature, stocking density, daily feed ration, number of meals and grading frequency on seven rainbow trout farms. Standard multiple regression analysis, based on a previously published fin damage dataset, was used to assess the relationship between the level of fin damage per fin and the factors. Daily feed ration received the strongest weight in the model for the caudal, anal and both pectoral fins, whereas number of meals received the strongest weight in the model for both pelvic fins. Grading frequency received the strongest weight only in the dorsal fin model. Lower levels of daily feed ration and number of meals combined with higher water temperature increased the level of fin damage, whereas stocking density had no effect. The results conform to the experimental research on fin damage in rainbow trout. The research model contributes to the overall assessment of fish welfare and the regression analysis used in this study could be used on rainbow trout farms to evaluate the effect of the main factors on the level of fin damage.

Scale cortisol is positively correlated to fin injuries in rainbow trout (Oncorhynchus mykiss) reared in commercial flow through systems

“…Fin injuries and its appearance in severity and acuteness are a result of recent and historical damage, as well as of healing and regrowth (Turnbull et al, 1996). The cause of fin injuries is in most cases considered to be multifactorial though mainly induced by abrasion, nipping, and biting due to aggressive behaviour and/or poor water quality (Latremouille, 2003;Ellis et al, 2008;Klíma et al, 2013;Cvetkovikj et al, 2015). Fin injuries caused by for instance prolonged biting or abrasion on a tank wall can be considered as a stressor and as such will result in (re)activation of the HPI axis, releasing cortisol into the blood enabling behavioural changes.…”

“…Other examples of factors decreasing the healing process are a poor water quality or secondary bacterial infections (Turnbull et al, 1996;Wedemeyer, 1996;Ellis et al, 2008). In this context, fin injuries in rainbow trout have been addressed in various studies (Latremouille, 2003;Ellis et al, 2008;Klíma et al, 2013;Cvetkovikj et al, 2015;Klíma et al, 2018).…”

Chronic stress negatively impacts wound healing, welfare, and stress regulation in internally tagged Atlantic salmon (Salmo salar)

“…Understanding the effects and relationships that cause fin erosion on each specific fin with biological factors, such as cortisol, or farming factors, such as feeding practices, can significantly increase our capacity to respond to harmful effects on welfare. The ease with which one can assess fin erosion should be appealing, as it can be a complementary observation to mandatory handling processes as well as possibly measured non-invasively with emerging imaging technology used for salmon lice counting ( Cvetkovikj et al, 2015 ; He et al, 2016 ; Guragain et al, 2021 ).…”