To Harvest or Not to Harvest (Fish that is)

[Dan Ponton]

Being in North Central Florida my water temperature is staying 45-50 degrees a lot of the time. My catfish have not eaten well since late November . Even when the air temperature gets into the 60's for a short time the water temperature remains around 50 degrees. Two weeks ago the water temp rose to about 55 degrees, I fed them but most of the food went uneaten.

Questions to think about are:How long can catfish go without eating? ( they look thin already)

Should I harvest now, and get new catfish in the spring?

 

[Frank Cates]

Hi Dan,

I am in Ocala and have a mix of Channel Catfish and Tilapia.  I can't tell how well the Tilapia are feeding, but the catfish do come to the surface so can see how they are doing.  I just came back in, water temp was 54 degrees and the catfish did come up to feed.  Since mid November there have only been a few days we did not feed them at least once, and they have come up and eaten everything I tossed in.  They have been rather active, lots of splashing.  We did have a stretch of about 10 days back in early November where they went to the bottom and stayed there out of sight and not eating much, but they seem OK now.  I am thinking as long as the fish are not floating, they are down there somewhere, and they will eat when they get hungry enough.

[Ned Berndt]

Don,

Put in a tank heater??

[Dan Ponton]

I had considered that but it would be expensive since I would have to run additional power and I have a long way to go.

Ned Berndt said:

Don,

Put in a tank heater??

[Dan Ponton]

where did you get the Tilapia?
Frank Cates said:

Hi Dan,

I am in Ocala and have a mix of Channel Catfish and Tilapia.  I can't tell how well the Tilapia are feeding, but the catfish do come to the surface so can see how they are doing.  I just came back in, water temp was 54 degrees and the catfish did come up to feed.  Since mid November there have only been a few days we did not feed them at least once, and they have come up and eaten everything I tossed in.  They have been rather active, lots of splashing.  We did have a stretch of about 10 days back in early November where they went to the bottom and stayed there out of sight and not eating much, but they seem OK now.  I am thinking as long as the fish are not floating, they are down there somewhere, and they will eat when they get hungry enough.

[Frank Cates]

We got the Tilapia from another aquaponics guy in our area.  They seem to be doing well, but we do have quite a variety of sizes in the Tilapia, and in the Catfish, even though they all started out at roughly the same size.

[Dan Ponton]

Do they grow fast? I would have to start in spring and harvest in the fall, so they would only have 8-9 months.

Frank Cates said:

We got the Tilapia from another aquaponics guy in our area.  They seem to be doing well, but we do have quite a variety of sizes in the Tilapia, and in the Catfish, even though they all started out at roughly the same size.

[Frank Cates]

Ours seem to be growing quickly enough, there is a Tilapia group here that would have a lot of information about growth.

[TCLynx]

I'm Down in Inland Central FL (near where the turnpike runs into I75) so probably a tad warmer here than North FL.

I keep catfish year round and they grow well for me, I can get small fingerlings when ever they are available and in 12 months I can generally have fish that are between 3-5 lb.  I don't heat my water because my systems are outdoors but I have rather large systems so the temperature swings generally lag a couple days behind the air temperature.

In winter I'm normally only feeding the fish once per day, before sunset.

If the water temperature is below 55 F or expected to fall below that overnight, I won't feed the catfish.

If the water temperature is above and expected to stay above overnight, I feed the fish some.  I track how much I feed them and I increase the feed as they eat more and that generally trends up with the water temperature.

So far this winter I've had a few weeks worth of time where they were not eating or being fed.  If the temperatures are remaining boarder line for them, you might go to a feeding pattern where you only feed them once every few days just to help them maintain weight but it isn't good for catfish to have food in their belly when the water temperature is much below 55 F since they will have trouble digesting.

If the fish are not tiny fingerlings, they can go weeks even months without eating and survive though they will get quite skinny if it goes on too long.

If you are having trouble keeping catfish, then I would definitely say DON'T bother with Tilapia unless you are very happy to heat your water ALOT.

If you want your catfish to grow more though the whole year, then a small bit of heating from Nov through Feb to keep the water above about 58-60 F would likely keep your fish eating while also allowing you to grow more veggies without causing as huge an electric bill as if you were trying to keep the water above 70 F to keep the tilapia eating.

There is probably not much point in harvesting all your catfish now unless they are big enough to eat and you don't have much veggies going at this point and you are certain you will be able to get new fingerlings ASAP when you think things are warm enough for them.

Keep in mind also that system size contributes greatly to system stability.  If your system is too small or has too much temperature swing between day and night, that can put the fish off their feed even worse than just simply being a bit chilly.

I actually experienced this last spring, I had too many towers on the system and because we were having such hot sunny days but still having very chilly clear dry nights, one of my systems was having water temperature swings of more than 10 degrees F between the low and high for the day.  Even though both the low and high temperature were well above the minimum feeding temperature, those extreme temperature swings were putting my fish off their tucker.  Taking steps to minimize those extreme swings got the fish eating well again.  (Beware that towers or NFT can work as very effective heat exchangers warming the water when the air and sun are HOT and chilling the water while it is COLD and dark and it can have a startling temperature effect on even a relatively large system.)