Physiological Responses of Rainbow Trout (Salmo gairdneri) to Electroshock

Abstract

Electroshocking elicited an immediate increase in plasma corticoid and lactate concentrations and thrombocyte:leucocyte ratio in rainbow trout (Salmo gairdneri). Plasma glucose concentrations increased significantly after 3 h. Plasma protein, calcium, magnesium, and androgen levels were not measurably affected. Plasma lactate returned to preshock levels within 3 h, but corticoid and glucose concentrations remained elevated for at least 6 h. The fish coughed violently or did not resume normal breathing rates for 60 s post shocking. Although breathing frequency did not increase, buccal pressure increased substantially and required at least 1 h to return to preshock levels. Cardiac activity was irregular immediately after shocking, but no predictable alterations in rate were evident thereafter. The height of the T wave in ECGs increased markedly 1–3 min after shocking. The electrophoretic patterns of 13 isoenzymes from liver, white muscle, and plasma did not differ between fish captured by dipnet and those captured by electrofishing.Responses exhibited by fish to shocking are most likely attributable to combined effects of trauma, factors associated with paying off of an oxygen debt, and attributes associated with the general adaptation syndrome of stress. A substantial period of time of more than 6 h is required for fish to return to "normal" preshock conditions.

Comparative assessment of sodium edta and heparin as anticoagulants for the evaluation of haematological parameters in cultured and feral african catfish (Clarias gariepinus)

“…However, the feral catfish, demonstrated significantly higher PCV, Hb, MCV, MCH, lymphocytes, monocytes and eosinophils values (p=0.001 for all except monocytes with p=0.01). Higher hematological parameters might have resulted from the difference in water temperature and oxygen concentration of the culture environment (Kocabatmaz & Ekingen, 1978); while an increase in leucocytes has been attributed to stress conditions; which is more common under feral condition relative to the more conducive pond environment (Schreck et al 1976). High MCV suggests that a hemo-dilution mechanism is operational; the mean corpuscular volume gives an indication of the status or size of the red blood cells and reflects an abnormal/ normal cell division during erythropoiesis.…”

The influence of anaerobic muscle activity, maturation and season on the flesh quality of farmed turbot

“…This corresponds with a previous study by Roth et al (2007b) where use of computer imaging on post rigor filleted and unbled turbot revealed that percussive killed fish had higher reddishness and less whiteness than and electrically stimulated carcasses. Forcing blood out using electrical stimulation might only be feasible in newly killed animals, as electrical exposure on a live specimen would cause an autonomic release of catecholamines (Schreck et al 1976), potentially known to redirect the blood from the gut and into muscles (Farrell et al 2001).…”

The physiological stress response of salmonids: considerations for field procedures and environmental monitoring

“…Schreck et al (1976) reported similar findings for electroshocked rainbow trout. In contrast, Barton and Grosh (1996) found that granulocytes (neutrophils and thrombocytes) declined within the first 15 min after shocking.…”

“…There is also evidence that a brief electroshock influences specific immune function of fish by altering the abundance of circulating leucocytes. Schreck et al (1976) found that rainbow trout exposed to a brief electroshock (230 volts; 2.3 amperes) exhibited an immediate but transient increase in the number of circulating thrombocytes, while granulocytes (e.g. neutrophils) may decline in response to an electroshock (Barton and Grosh 1996).…”

“…neutrophils) may decline in response to an electroshock (Barton and Grosh 1996). It is thought that the effects of electroshocking are similar to those of recovery from hypoxia (Schreck et al 1976), possibly due to oxygen debt resulting from severe muscular activity or tetanus. To my knowledge, electroshocking impacts on non-specific immune function in fish have not yet been explored.…”