Posted 08 June 2011 - 09:36 PM
Pylodictis- Mortality rates of a darter project I've been working on have been low (0-5%) during cool weather, but higher in hot weather (probably about 15%). Don't quote me on those numbers, it's a colleague's project and I don't have the data in front of me. These fish were not only shocked, but also anesthetized and injected with elastomer dye before being released, so the extra stress and handling time undoubtedly increases mortality. Certain fish (silversides, for example) are especially delicate and often succumb when shocked or even netted. Breeding male stonerollers and striped shiners seem to have high mortality too, perhaps due to already deteriorated condition from putting all their energy into sex-related issues.
Precautions you can take to minimize mortality:
Keep handling time short
If you're hanging onto fish for a while, as for photography, keep them as cool and well-aerated as possible (set bucket or cooler in the shade or partly submerged in stream, and use battery-powered air pumps)
Do not overcrowd bucket or cooler
Use the lowest voltage setting on the shocker that effectively stuns fish (this will depend on the conductivity of the water; a higher setting is needed in soft than in hard water)
Some people add salt or commercial electrolyte solutions to the water in the cooler/bucket to help reduce stress; I haven't tried this but it seems reasonable.
Posted 09 June 2011 - 05:01 PM
Of course, species does matter. Each species has a unique body shape and size, and some get shocked "harder" than others, and are more sensitive to handling. Think about the difference body shapes (surface area) of sunfish vs. gar vs. shad etc.
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