Sprat (Sprattus sprattus)

[Thamnophis]

On the mailing list of my fish supplier I saw he offered Sprot (Dutch for Sprat), frozen, per kilo, for 8 euro.
These fish are 9 to 12/13 cm long (and sometimes a few centimeters larger). They seemed to me the perfect size for the larger Thamnophis species, like the females of T. eques scotti and T. s. tetrataenia. So I ordered one bag together with some bags of smelt and some blisters of Dillies. Just to give it a try.
On this site Thiaminase - The Free Freshwater and Saltwater Aquarium Encyclopedia Anyone Can Edit - The Aquarium Wiki and this one Thiaminase (Chemicals Summary) mention that Sprattus sprattus does not contain Thiaminase.
Well, on the pictures you can see if they liked this new food item...

[Stefan-A]

Journal of Fish Biology (2008) 72, 787–802
Thiaminase activity of Baltic salmon prey species: a comparision of net- and predator-caught samples
S. WISTBACKA* AND G. BYLUND
Laboratory of Aquatic Pathobiology, Department of Biology, Åbo Akademi,
20520 Åbo, Finland (Received 2 February 2007, Accepted 9 October 2007)

Thiaminase activity was determined for Gulf of Bothnia (GB) and Gulf of Finland (GF)
Baltic herring Clupea harengus membras, sprat Sprattus sprattus and three-spined stickleback
Gasterosteus aculeatus sampled from either trawl or gillnet catches or from Baltic salmon Salmo
salar stomachs. The thiaminase activity in Baltic herring was about 10-fold higher than that in
sprat, and there was almost no thiaminase activity in three-spined stickleback. Thiaminase
activity of undigested Baltic herring found in Baltic salmon stomachs was significantly higher
than that of trawl-caught Baltic herring from the same sea area, suggesting that there may be
a higher risk of predation for Baltic herring with high thiaminase activity, possibly linked to
their health. Thiaminase activity of the gastrointestinal contents of Baltic salmon, feeding
almost entirely on Baltic herring in the GB, was significantly higher than for Baltic salmon
feeding on both Baltic herring and sprat in the GF. Therefore, Baltic herring may be the major
source of thiaminase for Baltic salmon. A tank experiment demonstrated that thiaminase
activity in Baltic herring may vary, even within very short time periods. The results were
consistent with the hypothesis that the thiaminase content in Baltic salmon forage fish may be
an important link in the aetiology of the thiamine deficiency syndrome, M74, in Baltic salmon.

[Invisible Snake]

Looking good, thanks for sharing the pics. =]

[Thamnophis]

After some research it shows that Sprat contains a fair amount of salt (Natrium). So ... some restraint with the feeding is in place, I think.
So I'm going to restrict the feeding of spratto about 1 x per month.
Although ... every living creature at times needs salt.
Salt is important for nerve impulse conduction. Additionally, salt is important for the moisture balance in your body and plays a role in regulating blood pressure.
Salt is filtered in your body by your kidneys and then enters the bloodstream.
If you have too much salt in your body, your blood salinity gets higher. The ratio of fluid / salt balance is off.
This makes you thirsty, so you start to drink. This ensures that the ratio of water / salt gets back into balance. The kidneys ensure that the additional fluid is discharged, together with the salt.
Generally too much salt is no problem, if you drink enough water. Then the excess of salt which gets discharged. But when you eat toom uch salt all the time, the kidneys are taxed too much and that's not good for your heart. You can then get cardiovascular problems.

[Thamnophis]

Thanks Stefan. But since I often add some Thiamne too the fish I feed I do not worry. And I have never had a snake that had Thiaminase, so i think the amount I add is ok.
And more often than once a month I will not feed sprot.

[-MARWOLAETH-]

Are all salt water fish high in salt?

[Thamnophis]

No, not all salt water fish are high in salt, Sprat is an exception as far as I know.
All my garter snakes have eaten sprat once now and I have not see any problems. None of them was drinking more than normal as far as I could observe.
In a few weeks they get sprat again as a part of their menu.