This is usually the time of year when I send out information about raising the temperature of the water in your tanks to simulate the rise in temperature of our local streams and facilitate egg development, but this year is a bit different due to Covid-19 and the school cancellations across Maine.
Below is a series of options for winter/spring 2020 Fish Friends participants who are caring for ~20,000 endangered Atlantic salmon during these challenging and constantly changing times. I have developed these in consultation with the hatcheries and the Department of Marine Resources. I have listed them in order of best to worst options and invite you to choose what option works best for you given your particular reality.
- Keep tanks where they are, but make sure someone can check on them regularly to ensure the chiller is working and remove any dead eggs/fish. If you choose this option, see the end of this post about how to handle the temperature adjustment piece. Please consider that many of our Mentors are in the highest risk category for Covid-19, so please minimize asking for their in-person support during this time.
- Move tanks to a place where they can be checked on regularly. There is a higher risk of mortality due to moving them, especially once they’ve developed into alevin due to the possibility of damaging the yolk sac. In the likely case that you can’t move your whole tank at once, you’ll have to: 1) carefully move the salmon into a cooler with water at the same temperature as your tank’s water (put a bunch of ice cubes in the cooler’s water and add ice cubes as necessary), 2) drain the tank, 3) move your whole setup, 4) refill the tank and get the water back to the right temperature (this can be expedited by adding sanitized jugs of ice to the water), and 5) move the eggs back into the tank. The key thing here is to maintain consistency of temperature that the fish are in–any changes in temperature can cause problems. As above, please consider that many of our Mentors are in the highest risk category for Covid-19, so please minimize asking for their in-person support during this time. Also review the temperature adjustment considerations below.
- Put your eggs into someone else’s tank that can be checked on regularly, assuming they have the same stocking location on their permit as you. If you need help figuring out who near you does Fish Friends, let me know.
- Leave tanks where they are without being able to check on them or adjust temperature. Not being able to remove dead eggs or ensure that the chiller is running could cause complete mortality. If you’re not able to start raising the temperature by mid-May, you won’t be able to stock them and they’ll die.
- Stock salmon into river now. Please only use this option if you feel confident you won’t be able to check on your tank before the summer. Stocking them into the river now may kill them, but it may be a better option than letting the chiller run and having them die in their tanks in the event that you can’t get into the school before the summer. If you do choose this option, please stock them where your permit says to stock them and email me with the date, water temperature, and how many of what life cycle you stocked (e.g. x# alevin, x# eyed eggs, etc.). If they’re alevin, simply let them go in the water. If they’re eggs, find some gravel out of the main current, dig down a few inches (adult salmon usually dig down 6-12,” but do your best!), and “plant” the eggs there–gently covering them back up with gravel afterwards. Using a section of pipe or a cup with the bottom cut off may help you place them in the hole without them floating away.
Option A: Leave temp low: You can keep the temperature of your tank low as it currently is for awhile longer. This will delay egg development. It’ll take about a month to raise the tank temp from 35 to 50F, so if you’re not back to school until mid-May, you should still be able to start raising the temps then and stock them by the end of the school year in mid-June.
Option B: Raise tank temperatures as usual. Some general guidelines for raising the temperatures:
- Have your tank’s water at 50F by the time the fish need to be stocked (usual goal: late May/early June)
- Keep the temperature as cold as possible as long as possible
- Don’t increase the temperature abruptly—a change of 1F twice per week (e.g. Monday and Thursday or Tuesday and Friday—resulting in a total change of 2F per week) should be tolerable.
For example, if your goal is to stock your fish on May 31st, working backwards from there would look like this:
- 49F on May 28th
- 48F on May 24th
- 47F on May 21st
- 46F on May 17th
- 45F on May 14th
- 44F on May 10th
- 43F on May 7th (and so on).
It takes about a month to raise the temperature from 35F-50F. Once your tank’s water is at 50F, your fish have developed into fry (no yolk sacs attached), and the stream where you’ll release them is right around 50F too, they should be ready to go into the wild.