Stress Shock Syndrome

Also known as: Shock Syndrome

Introduction

Stress shock syndrome can occur in any marine fish with essential fatty acid deficiencies in their diet.

Fatty acids are essential components of biomembranes and precursors of some physiological modulators such as the eicosanoids. They play an important role in allowing fish to mount an effective immune response. Marine fish in general, unlike their freshwater counterparts, cannot effectively elongate and desaturate saturated fats to unsaturated ones and so require the presence of unsaturated fatty acids in their diets. Essential n-3 fatty acids such as docosahexaenoic acid and eicosapentaenoic acid are commonly found in live food such as microalgae (e.g., Nannochloropsis), copepods, rotifers and Artemia.

It commonly occurs in marine fish kept in captivity and fed non-marine foods instead of more expensive marine fish oils.

This leads the fish to develop an unusual sensitivity to stress and any handling or disturbance can result in clinical signs and often mortality.

Clinical Signs

Signs occur during any handling or activity such as sorting or transfer of fish.

These include a general body weakness followed by a total body immobilisation caused by a muscular tetany.

Diagnosis

The clinical signs and their acute onset are suggestive.

A thorough investigation of the history, husbandry and nutrition of the fish is required. This usually involves marine fish which have recently been captive raised and fed on a non-marine source of oils.

Pathological findings of stress shocked fish include: tissues with amber-coloured oil globules showing deposition due to inadequate assimilation of non-marine lipids.

Treatment and Control

Short-term treatment is non-specific, but some fish may recover, despite there being a high rate of mortality (up to 80%).

Control relies on the correct nutrition of fish, especially fish larvae, with supplementation of fish oils in their diet. A diversity of marine foods will provide the best nutrition for captive-bred marine fish.

It is also good practice to minimise any unnecessary stressful situations.

Most commercial hatcheries now use marine oils in the diets and so this problem is usually avoided.

Stress Shock Syndrome Learning Resources
Flashcards Test your knowledge using flashcard type questions	Ornamental Fish Q&A 01

References

Chong, Y.C. and Chao, T. (1986) Common Diseases of Marine Foodfish Fisheries Handbook No. 2. Primary Production Department, Singapore

van Anholt, R. (2004) Dietary Fatty Acids and the Stress Response of Fish PhD thesis, Radboud University of Nijmegen, The Netherlands

Lewbart, G. (1998) Ornamental Fish: Self-assessment colour review Manson Publishing