Feeding smelt

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Chub_by said:
Could you kindly explain this?


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F1 VET said:
+1

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http://www.monsterfishkeepers.com/forums/showthread.php?504763-Cheap-plants-less-nitrate!-POTHOS

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Ok. Sorry it took me so long to get back to you guys. I did see this this morning, however I work night shift and by the time I saw the requests for clarification, I was ready for bed (lol).

Ok. The reason that I feel that smelt is bad for fish is because introduced smelt populations in the Lake Ontario have been shown to have detrimental health effects on the native salmonine pedators. I often see quotes of "well there's not one single study showing that thiaminase hurts fish!" Well, actually there are, I suspect people just weren't looking in the right place. The government has studied the introduced populations of smelt in detail and has found that their becoming forage primarily for intermediate sized salmonines has resulted in dangerously low thiamine levels in those fish. The adaptive measure in those wild fish is that once they grow from intermediate size to full adult size they move on to forage other species of prey items which are thiaminase free. Our aquarium fish, if fed only smelt, obviously don't have the ability to adapt by changing their diet.

Incidentally, the same studies found that salmonine predators in lakes were the introduced smelt were scarce or absent, such as Spray Lake or Lake Superior, the thiamine deficiency was dramatically reduced or absent.

It strikes me as fairly obvious that feeding your aquarium fish a staple or exclusive diet of smelt would then have a negative effect on the health of your fish. Granted, the wild populations do consume thiaminase containing forage, however, the wild fish can and do adapt their diet in order to adapt to this situation and continue to thrive. If we give our fish a staple diet of smelt, it will have negative effects and will harm the fish. I see no problems in using it as an occasional treat, however I also feel that using a non-thiaminase containing species would be better in every way. This is why I favor trout, and if I can't get trout I'll feed tilapia or salmon, all three of which do not contain thiaminase.

Hope this helps guys, and I hope my point is a little more clear. :)

Reference:
Fitzsimons, J., Honeyfield, D. (2008). Thiamine status and diet of sub-adult salmonines in Lake Ontario. US Geological Survey.

There's plenty of studies on the effects of thiaminase in the Great Lakes for you guys to research. :)
 
You are of course right that thiaminase should be avoided when possible and cyprinid fish such as smelt should not make up the main part of our fishes diets.
However, there are a few factors that should be worth a thought.
1. Thiaminase is supposed to be very harmful for omnivore and herbivore fish, less so for mainly or solely piscivore species.
2. It also varies from species to species. Many northern pike have a diet consisting of 90% thiaminase-containing fish. These do not show any ill-effects at all.
I think we can agree that smelt can be fed but not as a main diet part, rather as a treat :)

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Chub_by said:
You are of course right that thiaminase should be avoided when possible and cyprinid fish such as smelt should not make up the main part of our fishes diets.
However, there are a few factors that should be worth a thought.
1. Thiaminase is supposed to be very harmful for omnivore and herbivore fish, less so for mainly or solely piscivore species.
2. It also varies from species to species. Many northern pike have a diet consisting of 90% thiaminase-containing fish. These do not show any ill-effects at all.
I think we can agree that smelt can be fed but not as a main diet part, rather as a treat :)

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Exactly. :cheers:

We can't deny the fact that the fish seem to really enjoy it!
 
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