Babies!
Most of the time on the farm, animal parenthood is planned. The rams are turned in with the ewes at a certain time of year in order for the ewes to give birth in the spring. The sows are turned in with the boar according to schedule for appropriate farrowing times. Eggs are collected regularly from the chicken coop and select ones incubated for hatching in the spring to avoid parades of unexpected babies in the yard that the other older birds might attack.
Knowing when animal babies are coming means that you can be prepared for their arrival, with adequate housing and supplies. But this last week brought a baby oopsie that we weren’t expecting! Here’s how that development happened.
It really started much earlier than last week. When Mom and Steve were on their honeymoon in December, I went to harvest lettuce in the aquaponics greenhouse for a delivery to Northland College. In the greenhouse, part of the growing system is two large raft tanks (about 8 by 24 feet in size), where plants float on top of the moving water via 2 by 4 foot chunks of rigid Styrofoam. Holes drilled in the foam offer a place to wedge the baby plant so that the roots grow down into the water to draw up nutrients.
But the funny thing about that day is that when I pulled out the heads of lettuce, their roots were nipped off about a half inch below the plant. This was very strange—never seen that before. It didn’t appear to be root rot, which causes brownish decay and dehydration of the plant (the lettuce on top looked completely unperturbed). The issue started just in one raft bed, then over the course of two weeks moved to the second one.
The other odd bit was that only the lettuce and endive was affected—not the kale, kohlrabi, bok choy, or fennel. These other plants had nice, long roots. Very odd!
We dove into researching causes of root loss. Was it a spike in ammonia or nitrites? Was it a depletion of oxygen in the water? Was it a root parasite? And then we began to wonder if the roots were being eaten…by fish.
In traditional aquaponics environments, you want to try to raise all male tilapia. There are several reason for this: one is that the males grow quickly, and the other is that it discourages competitive and aggressive behaviors that occur when females are present. Another reason for wanting to raise all males is that the fish won’t spawn, spewing baby tilapia into the system that can make their way downstream and populate in places where fish shouldn’t be (e.g. where they’ll eat the plants)!
We had been purchasing all male tilapia since starting the system in 2012. The fish breeders are able to adjust the environment where the eggs are to induce the fish to be male. But, apparently, this is not a completely fool-proof system. Somehow, at least one lady fish snuck into our system.
As we began learning more about the triggers for spawning, we realized that we also had a perfect storm for suddenly finding fingerlings where none had been before. For the past couple of winters, there have been stretches of time when it’s much too cold to ship new baby fish to the farm. We can’t lose the nutrients in the system that the fish population provides, so if new fish can’t come in, that means that older fish can’t be harvested. Each of the four 300-gallon tanks holds a group of fish of a different age. As the waiting game for new fingerlings stacked up, some of the fish in the tanks grew quite mature—big, tasty fish, some as much as 5 to 7 lbs. live weight.
Our process of harvesting a mature batch of fish is also in stages. We have a special “purge” system that holds the fish being readied for harvest in waters that gradually cool. We don’t feed the fish in the purge, which cleans out their digestive track, and the cooling water firms up the meat—creating a superior product in comparison with netting a fully-fed fish right out of warm water. But there’s one catch: the purge can only take 12 to 15 5-lb. fish at a time, and one of those big tanks can hold up to 100 fish.
That means it takes a while to clean out a full tank, leaving fewer and fewer fish behind in the same amount of water as they wait their turn in the process. Tilapia won’t spawn if they feel their environment is too crowded to effectively protect their brood from the other fish. As mouth brooders, they keep the eggs and young fry safe in their mouth for incubation, but the parents still have to eat, so there are times when the young are exposed as well.
So as the tank of mature tilapia gradually thinned in its ranks, those renegade females got busy with the guys. We were harvesting the last round, pumping the tank level down so we could more readily catch the fish, when one gave a burp and there were tiny babies everywhere! All over the fish, all over the tank, on the floor, all over us, everywhere! One tilapia spawn can create as many as 20,000 baby fish! It was insane! We stopped the pump and looked into the tank. There were little ¼ inch silvery fish everywhere, swimming about in a school, and a few bigger ones darting about as well.
Who knows how many batches these girls had been up to, since the root eating had appeared much earlier and these were so tiny. It dawned on us that we had a real mess on our hands at this point.
Messes happen on a farm. The pigs get out. The beehive swarms. A new pest appears overnight in the garden. Expect the unexpected. And so the process begins of unraveling the situation to find a way to get back to equilibrium. First, we didn’t have the heart to kill all those baby fish. Maybe it’s not the right choice for us in the long-run, but when you take care of animals, throwing away young just isn’t part of your nature. The nursery was already full of 4-inch fish which would have immediately devoured these little ones, so we kept a little water in the big tank, turned on the air stones, and worked on plan B.
Years ago, when we lived in a condominium in Madison before moving up to the farm, we had a small aquarium. Neon tetras, an otocinclus, and the likes. So Mom ran off to the storage to grab that system, while Kara headed to town for a heater, new aeration and filtration systems, media for the base, etc., while I watched over the little school down at the bottom of the tank, looking like fishy ants in a football stadium.
Upon assembly, it was quite a task to get those little fishes out of there! By then it was dark, and we worked with nets and headlamps, knowing that time was not on our side before stress worked its ills on these delicate creatures. The next morning, Mom and Kara and Steve also flushed out the pipe that runs from the tank to its clarifier, finding more fish hiding in there! The clutch of over 100 shiny miniatures now resides in the aquarium, swimming and growing, until they are eventually big enough to move into the nursery once the present batch is big enough to move out and into a tank.
But the issue still remains in the raft beds. The other day, a frond of fennel dipped into the water, and I saw it getting a good tug by something beneath the surface. Catching those renegades in such a huge volume of watery space that can’t be drained is going to be the next challenge. I’m sure that will be an adventure story of its own! But for now, as I’m hauling water to Dutch buckets filled with tomato plants and fresh herbs, it’s fun to take a moment to watch the antics of the newest babies on the farm—baby tilapia fish. Who would have thought that would be part of the journey! See you down on the farm sometime.
