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Darter Temperature Experiment and Pre-Treating

Started by Guest_UWYO_* , Oct 24 2013 02:21 PM

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29 replies to this topic

#21 Guest_centrarchid_*

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Posted 25 October 2013 - 01:52 PM

System as described seems sound although one concern I have dealing with two heated side streams used for the 20 and 16 C treatments. Rapid elevation of temperature without vigorous aeration will result in supersaturation of gasses such as oxygen and nitrogen (N₂) which is likely to cause issues for those exposed fishes. Otherwise concentrate on minimizing handling stress associated with capture and transport. Take more containers, stock them very lightly, and fill them as much as possible to minimize sloshing. The breathable bags might have some real advantages for preventing mechanical damage during transport.

Edited by centrarchid, 25 October 2013 - 01:59 PM.

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#22 Guest_EricaLyons_*

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Posted 25 October 2013 - 05:00 PM

I've seen fish die from cavitation. It's more rapid than the onset of disease like saprolegnia. They have little bubbles precipitated on their scales and they act like they're suffocating. You can lose whole masses of them at once, over the course of hours.

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#23 Guest_Irate Mormon_*

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Posted 26 October 2013 - 09:09 AM

Based on all the information above -

It sounds like a problem in collection methodology, as others have said.

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#24 Guest_Irate Mormon_*

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Posted 26 October 2013 - 09:11 AM

P.S.: Saprolegnia is typically a secondary infection.

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#25 Guest_centrarchid_*

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Posted 26 October 2013 - 05:14 PM

I've seen fish die from cavitation. It's more rapid than the onset of disease like saprolegnia. They have little bubbles precipitated on their scales and they act like they're suffocating. You can lose whole masses of them at once, over the course of hours.

Chronic low level exposures can be more gradual in there impacts and result in secondary health issues.

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#26 Guest_UWYO_*

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Posted 28 October 2013 - 09:40 PM

I agree that it is likely due to stress from the collection method and from simply being moved to a lab setting. Got my pathology results and coming straight from the river, these Johnny Darters had no external parasites, fungus, or bacteria. Internally they did have a very large bacterial load in the kidney and spleen, but the bacteria was sparse in the other organs. Based on this, these guys could probably cope with the internal bacteria in the field, but the stress from handling and moving to a lab setting exacerbated it. This is likely why they eventually got the secondary saprolegnia and external bacteria load issues. Lesson leaned! Thanks for the help. I will likely be back when it comes time to get these guys spawning... Hopefully I have no issues though. I can't thank you guys enough.

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#27 Guest_Irate Mormon_*

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Posted 28 October 2013 - 11:07 PM

Keep in touch! Better yet, Join NANFA before the dues go up.

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#28 Guest_centrarchid_*

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Posted 29 October 2013 - 06:28 AM

Something to do I normally consider evil is expose fish during transport to an antibiotic that will suppress bacteria through initial stages of stress. I see no reason such treatment would impact temperature impacts but you would want to point out use in methods and discussion sections.

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#29 Guest_daveneely_*

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Posted 29 October 2013 - 04:11 PM

Shocking darters is probably more damaging than seining. They dont necessarily die within minutes, so shocking "seems" non-lethal if you're just counting, measuring and tossing them back after a few minutes, but I think it's more damaging than the electrofishing proponents care to admit, especially on small fish like darters and shiners.

Ahem...

All the darters in my home aquarium were collected by electrofishing. Mortality depends on a lot of factors, particularly voltage settings and how long they are kept close to an anode. If done correctly, it's no more lethal than seining. Perhaps the best option is shocking downstream into a seine with just high enough settings to cause them to flee -- none of the habitat damage you get from aggressive kicking.