Dat Diet

[Midwater]

I have long been feeding my dats primarily with ghost shrimp and secondarily with tilapia fry. I am aware that shrimp do have thiaminase, but my dats have always done well on them, and it is the only thing I can grow out really small dats with.

So I have often wondered whether dats - and many other predators - are not overly affected my thiaminase.

I have previously ordered NTT and other fish from the far east of Thailand, from the Mekong and some of it many tributaries. I often receive pictures of what is available.

But below is an unsorted picture of what was just caught. Bear in mind that this is the hot season, there has been virtually no rain for a few months, and rivers, streams and tributaries are low, slow flowing and hot.

Amongst other fish are NTT and lots of ghost shrimp.

I think shrimp are the natural prey of dats, and unlike many other fish, thiaminase is not really an issue.

 

[krichardson]

I wonder if all shrimp species contain Thiaminase?

 

[kno4te]

I wonder if all shrimp species contain Thiaminase?

Never could find any specific info on this.

 

[jjohnwm]

I always wonder about this. There must be at least some predatory species which subsist on a diet consisting largely of thiaminase-inclusive prey items. Are those predators adapted to require only minute amounts of thiamine that can be provided by perhaps the stomach contents of their prey?

When Pacific Salmon were introduced into the Great Lakes, one of the driving forces behind this was to combat the invasive Alewives which were overrunning the lakes. The salmon did well, and all the studies seemed to indicate that their food once they were past the smallest stages consisted largely of Shad, Alewives and Smelt (all of which are invasive in the lakes and all of which are apparently high-thiaminase). The fourth species listed was a species of whitefish that constituted only a small percentage of the diet, and which was free of thiaminase.

How do the salmon survive this diet? They're open-water pelagic predators, feeding on the relatively small number of pelagic forage fish in the lakes, most of which are thiaminase-rich. So one assumes that their diets would be lacking in thiamine...or that they are adapted to need very little...or that somehow they are getting it in a manner which isn't immediately obvious, like perhaps in the stomach contents of prey.

Another question: I have read over and over that the thiaminase enzyme breaks down thiamine, resulting in there being none in the food item being consumed. This implies that a varied diet, containing some items that may be rich in thiaminase and others that are thiaminase-free, would be safe. But I recently stumbled upon this report:

Lack of Vitamin B1 Killing Great Lakes Fish | U.S. Geological Survey

Great Lakes fish in the salmon family that rely on the fish “alewife” as part of their diet face a major obstacle in restoring naturally reproducing populations, according to new U.S. Geological Survey research published in the journal Fish and Shellfish Immunology.

www.usgs.gov

...in which it is stated that thiaminase in forage fish "destroys the thiamine in fish that consume them". It mentions a link between thiaminase and, among other things, reduced spawning success in affected fish. The wording of the report seems to imply that eating some thiaminase items will affect even the thiamine available from other items in the predator's body?

This is turning into a "the more I learn, the less I know" kind of thing.