kurt-
your descriptions fit exactly what sudden fright syndrome is, essentially a short circuiting of the nervous system during simulation. In your case, the ingestion of food was the stimuli-
sometimes they do recover after their fainting spells, sometimes, not, and as mentioned swirling of the water is frequently all that is needed.
Heres a section on SFS from an article i published last yr (banggers are my term for baby banggai cardinalfish)
Frequently I’ll read or hear about breeders experiencing a “fainting or heart attack like syndromeâ€Â, in which the banggers receive a stimuli, such as turning lights on suddenly, or quickly adding large volumes of food to the grow out tank. The fry will freeze and start drifting, motionless to the bottom of the tank. This general phenomenon is considered sudden fright syndrome (SFS). What actually happens is the stimuli essentially short-circuits (shocks) the nervous system and the fish becomes paralyzed. Depending on the severity and frequency of the event(s), it is often lethal. However, what SFS really means is a nutritional insufficiency during development, primarily a lack of highly unsaturated fatty acids during the development of the fry.
Briefly, all animals require certain polyunsaturated fatty acids in their diet, two essential fatty acids were noted as critical during development, Omega-3 and
Omega-6 fatty acids, which are an key components of cellular membranes, and are critical in the development of nervous tissue, such as brains, eyes, as well as heart and the innervations to the heart. Omega-6 fatty acids principally originate from animal sources (such as animal fats), while Omega-3 fatty acids are derived from plants. Importantly, Omega-3 fatty acids tend to be lacking in the diet of captive animals, since plant based foods are rarely fed, therefore since fatty acids are not converted from one type to the other, a proper balance of both classes of fatty acids is important to the health and proper development. Important, to a fish breeder are the two Omega-3 HUFAs; are DHA (docosahaxaenoic acid: 22:6 n-3) and EPA (eicosapentaenoic acid: 20:5n-3), which are synthesized almost exclusively by marine algae, such as phytoplanktons.
While newly hatched baby brine shrimp (Artemia) are the main stay of first foods for banggers, they lack sufficient quantities of EPA & DHA, and most marine fish fed exclusively on baby brine can begin to die, due to lack of HUFAs. The good news is this situation and resulting SFS is readily corrected, through enrichment of BBS using phytoplanktons (alive or pastes) or if your using dead or prepared foods, then the use of a liquid HUFA suppliment such as Selco, Selcon, Zoecon, etc. Feeding the BBS with phytoplanktons overnight or hours before using them for food is sufficient, and after a week feeding of enriched BBS the fry shouldn’t experience SFS.
Common features of HUFA deficiency are
1) Sudden fright syndrome: shock, convulsion or death when the animals are frightened
2) High mortality and disease rates, particularly when stressed
3) Worn or eroding fins.
4) Poor growth rates
5) Poor vision, and reduced ability to locate prey;
6) Sudden massive die offs during early development
7) Low egg viability or infertility in adults
8) Inability to heal after wounding.
