Backyard Aquaponics
A place to discuss aquaponics

Nah... half that time...

Do you Ausies have the same rainbow trout that we have here? I'm wondering because some of the info given here doesn't really jive with the common knowledge of rainbows around here.

I'm looking at the Nebraska state hatchery website which annually raises about 150,000 trout for stocking. They start with 4" fingerlings and raise them in ponds and raceways that are fed by springs and a cold water creek. They say optimum temp is 57F. It takes a year to raise them to a 9-10" size and then they are stocked in lakes, rivers, and creeks. They are harvestable at 10" but I'd rather eat them at 12-14".

Maybe under ideal aquaculture or AP conditions the temp and time constraints could be pushed a little but from the research I've done (including talking to 2 DNR biologists), I'd say it'd be a tough go for a beginning APer.

Don't know where you're getting your info... the Canadian aquaculture association lists them as ranging from 0-27C.... same as here...

http://www.aquaculture.ca/files/species-trout.php

Unless you're perhaps refering to the North Atlantic strains.... rather than Oncorhynchus mykiss... commonly known as the "steelhead"...

My info on the hatchery came from here: http://outdoornebraska.ne.gov/Fishing/programs/hatcheries/fish_hatcheries_Grove_Trout.asp I have talked to a fisheries biologist who has been with Nebraska Game & Parks for over 20 years about this. I can PM his name if you want. Also, one of his college classmates is the AP instructor at the local community college. I've taken AP and other classes under him and have spent a decent amount of time talking AP outside of class, as recently as yesterday. He has worked in fisheries biology for both the Iowa DNR and the Nebraska G&PC. I think these guys know a bit about trout.

I'm not disputing that they will survive 0-27C, if other conditions are appropriate. But, optimal weight gain will be reduced outside of a certain temp range. The OP was asking about raising them in a 50 gallon tank, at temps up to 40C, from May to September. I don't think he'll get them to eating size in that amount of time, let alone the other 2 criteria. Even the site you referenced says 9-22 months, and that's starting with 8-10cm fish.

Here's a decent document of trout culture as well: http://www.ustfa.org/Trout%20production/Trout%20Culture%20in%20the%20North%20Central%20Region%20%20%20ncrac%201993.pdf

JMHO

You also need to account for the fish being "acclimated" to a climate. For example catfish grown in TX will do terrible in NC due to the differences in climate that they have been breed in for generations, even though the exact same species thrives there. I know that from a guy moving some in his outdoor pond when he moved. Cattle are the same way they will build up immune systems for the local stuff and not build up for the stuff that is not in their area, that is why they tell people starting to raise cattle to buy local if at all possible it increases the survival and reduces the issues. I highly suspect it could be the same with trout where the temperature ranges will vary by areas and the fish have essentially gotten used to it through generations of only the ones most tolerant to it surviving. As mentioned there are some in west TX that grow and breed natively, and that river is barely in the normal bands for trout most of the year if at all, if my memory serves. I suspect if you took those to Canada they would rapidly die from the temperature drop, by the same token I suspect if you dropped some form a Canadian hatchery there they would die rapidly from it being too hot. The OP's best bet is going to be to contact the local hatcheries/universities and talk to people in the area about the ones that are breed and raised up there.

Yeah, I saw that bit.... seems a wide range of grow out data...

I suspect it is probably based on differences between the grow out systems... and how intensively they are fed... and it's based on period of time from "hatching"...

The other thing that might be confusing the time taken to grow out... when we reference it...

Is that when we stock into our aquaponics tanks... the "fingerlings" are already at least 9 months old...

Hence while we say "our" grow out period is 5-6 months.... the actual period... from hatching... is more like 14-15 months.... to around 0.5kg...

To get to 1kg... you could add another 3 months to that... depending how you feed them...

Some members get them to around 1kg within 6 months... but they're usually a bit obese, and distorted looking... in comparison to an "optimum" commercial fish...

Good points, Rupert. I'm sure the range of grow-out times has a lot to do with where the fish are raised. Times in a somewhat temperature controlled raceway would be different from those grown in a pond that fluctuates from freezing in winter to the hottest point in summer (I guess you guys are the opposite of that - correct?).

How long are the "fingerlings" you guys stock with? I suppose they would be harvestable size to some at that point, and the next guy wouldn't consider them harvestable until a year or so later so that's a variable as well. To really know what one can expect from a new species they really need to know the range of their water temps throughout the year and what the growth rates would be at those temps. Throw in all the other variables and it ends up just being a theory. And there's nothing like a little real world experience to muck up a theory.

In any case, I think the OP, being in Ontario Canada, has a few climate related challenges to overcome. As do I in the midwest USA. Forgive my ignorance of your part of the world, but am I understanding correctly in that your climate is much more temperate - kind of like California is here in the USA?

We get them here between 30-45g, not very big, and people have got them to over a 1kg in the one season.. And yes we are probably fairly similar to California in many areas..

Yeah... temperature will definitely affect the grow out times... and the 0-27 range quoted is essentially their "lethal" range...

Above 22.. and they'll go off the feed... 27 they'll die... and at 0... they'll turn into iceblocks...