Are your fish swimming up yet?
Some teachers have reported that their fish have swum up and are eating. These are at classrooms that used the "warm and fast" temperature protocol. Most, schools, however, have kept their tanks cooler--perhaps 43 degrees or so--in order to have the swim-up occur after the winter break.
As we've discussed both at the fall workshop and in previous blogs, the key to knowing when your fish are likely to swim up is tracking DI (Development Index). You do this by entering daily temperatures, including estimated temperatures over weekends and school breaks, in the spreadsheet titled "NEW 2019 Temp and DI record and swim-up calculator" (using the Temp entry and DI record worksheet after you've opened the spreadsheet in Numbers). Even if you haven't been keeping up this spreadsheet, as long as you've been recording temperature, you can reconstruct the Temp and DI record and find out what your DI is.
So what DI are we looking for? The experiences of TIC teachers in the past suggest that a DI of 82 is the time to be hyper vigilant. We believe that most fry will start swimming up between DIs of 82 and 87.
When your fry swim up, you should try feeding them a tiny bit of food. If the alevin don't eat it fairly quickly, scoop it out and discard.
Over the next couple of weeks, it will be critical that teachers and students whose fish haven't yet swum up are watching their alevin/fry very carefully, looking for signs that the alevin are getting ready to swim up. Here's a short video that tries to explain what that swim-up readiness looks like.
National TIC/SIC network discussions
I'm sure you recall that I participate in the TU national TIC/SIC network. Here Areva few extracts from recent exchanges on that network's e-mail list serve.
Teacher Douglas Bell, of Lyons, Colorado, raised two issues in a recent e-mail to the group (BTW, Colorado's TIC program starts much earlier in the fall): he reported inter-fish aggression resulting in casualties and wanted to know how many of his fish he should expect to carry through to their release day (they now have 70 in their 55-gallon tank).
Scott Hood from Oklahoma answered:
A good question ... but one you will only answer when you are one your way to the release point.
Be delighted when you have 20. I got a text this morning from one of my schools ... all trout dead. Seems the school janitorial staff had orders to spray the school with disinfectant for flu virus. In spite of signs to Please Do Not Spray in the area of the tank, they did it anyway! Very sad day for these students.
Doug replied in turn:
Oof, I'm sorry to hear that. We had a substitute cleaning staff turn off our power strip over the weekend when the fish were pretty small. They weathered it, but now we're always on guard.
Scott, came back with:
Douglas, power failures due to weather or construction, accidental and not so accidental unplugs by helpful janitorial staff, and anti-bacterial soap on little hands that find there way into the water ... number one killers.
However, we've had huge celebratory releases for as few as 3 surviving trout before with class of over 75 kids. Some have gone to the release area with zero. We always go.
Chuck Dinkel, my favorite TIC support person, contributed this:
A school in Maryland had the exact same result when their school was sprayed 4 times with a mist to control the flu virus. This was a first for us. If the teacher had had advanced warning of this would there have been some way of covering the tank to protect the fish?
Lessons to be learned
So what's the take-away from these conversations?
As far as Doug's question about how many fish to expect to still be alive at the end of the process, there really is not great answer.
Paradoxically, having all your fish survive may give kids the wrong message. They might graduate from the program thinking that brook trout are hardy, can tolerate all sorts of suboptimal conditions, and have high survival rates in nature. No, no, and no!
Joe Mark is Lead Facilitator of Vermont's Trout in the Classroom program.
In June 2012, I retired after 40 years in higher education, having spent the last 32 years of my career as dean at Castleton. One of the first things I volunteered to do in retirement was to work with a parent-friend to help the Dorset School, where his kids and my Vermont grandkids attend, start a TIC program. Gradually that commitment grew into my current role, which is both demanding and highly rewarding.