Effect of nutritional status and sampling intensity on recovery after dorsal aorta cannulation in free-swimming Atlantic salmon (Salmo salar L.)

Abstract

Recovery from implantation of a cannula in the dorsal aorta (DA) of Atlantic salmon (Salmo salar) was studied in relation to nutritional status and sampling intensity. The incentive for the study was the inconsistency between published reports and our own experience of recovery and longevity of fish exposed to this protocol. In two studies using starved fish, blood (0.3 ml) was sampled 0, 1 and 24 h after DA-cannulation, and thereafter at 48 and 72 h and thereafter once weekly for four weeks. In a third study using fed fish, four consecutive samples (0, 3, 6 and 12 h after a meal) were obtained twice a week over a four-week period. All fish displayed a sharp increase in pCO(2) and haematocrit (Hct) during surgery, followed by a marked raise in cortisol, glucose, sodium and potassium (1 h). pCO(2), pH and Hct approached baseline levels as early as the 1 h post-surgery sample, while this was not the case for cortisol and electrolytes before the 24 h post-surgery sample. Glucose did not display any significant changes post surgery. From then on, all variables displayed minor but non-significant (P > 0.05) changes indicating a steady state close to baseline values for unstressed fish. This pattern was independent of sampling procedure, i.e. repeated single or multiple samples and thus volume of blood removed. Nutritional status (fed vs. starved) did not affect post-surgical recovery pattern. Only K(+) and Hct displayed consistent and significant post-prandial patterns. We found marked differences between baseline level of cannulated fish and uncannulated control fish, in pH, K(+) and Hct indicating that cannulation may be the preferred method to obtain representative resting values in fish.

Lack of arterial PO2 downregulation in Atlantic salmon (Salmo salar L.) during long-term normoxia and hyperoxia

“…However, the experimental conditions and sampling was optimized to avoid stressful conditions and sampling disturbance, and extensive evaluation of the suitability of the experimental setup has been conducted (Djordjevic et al 2009). Similar experimental setups have demonstrated the presence of low P a O 2 regulation in other fish species (Forgue et al 1989).…”

“…Most reported studies using DA-cannulated salmonids are relatively short-term studies focussing on various aspects of physiological regulation (e.g., Wood and Jackson 1980;Gilmour and Perry 1994;McKenzie et al 2004) or uptake and metabolism of various foodstuffs (e.g., Hamre et al 2001;Sunde et al 2003). Recently, improvements in surgical procedures Olsen et al 2005) combined with novel experimental tank design (Djordjevic et al 2009) have been documented to give stable haematological values and background cortisol levels in Atlantic salmon during long-term experiments.…”

“…In the aquatic environment, hyperoxia may occur periodically as a result of algal photosyntehsis, being most pronounced in enclosed areas with little circulation (e.g., Dejours 1981). In commercial land-based salmonid aquaculture, pure oxygen is added to the water to increase the production potential of limited water supplies.…”

Fast water currents reduce production performance of post-smolt Atlantic salmon Salmo salar

“…The lack of detectable treatment effects on haematocrit and haemoglobin levels may be affected by sampling time, as Djordjevic et al (2012) discerned that values over 30 in haematocrit likely reflect sampling stress. However, they used cannulated fish, a method that reduces sampling stress, but unfortunately that was not possible in our setup.…”

Changes in arterial PO2, physiological blood parameters and intracellular antioxidants in free-swimming Atlantic cod (Gadus morhua) exposed to varying levels of hyperoxia

“…Because of this replacement, six cod had a recovery period of 96 h, while two cod recovered for 72 h prior to the experiment. The experimental tank setup was identical to the one described by Djordjevic et al (2010). In brief, the cod were free-swimming in individual 1-m 2 tanks with cannulas trailing freely behind them and were provided with water current to swim against and shelter to hide under.…”