The key to this is "sufficient cover".
They were extirpated in my personal pond. Water level dropped, no cover in shallow water, they all got eaten over the winter one year.
esshup,
Most GAMs surviving winter will be mid-summer or later born fry. This is normal even for a population of without predator fish. Their numbers get relatively weak by spring. Kingfisher, Green Heron, Crayfish, Frogs, large carnivorous insects etc take a toll on them too. The good news for anyone who can maintain a population is that winter survival of only a percent or two is probably enough to keep them going. Their footprint, even when they peak in numbers will always be a minor portion of the biomass. But they can produce more than one generation in the summer that able reproduce grandchildren in the same year. This is what tips the balance for them making them able to grow a population while being cropped.
GAMs show promise as annual introductions because of the same. In other words, one can stock a relatively small number of them at the start of the reproductive season and they can produce a lot of forage before they are fully consumed over winter in a pond like yours even with insufficient cover. So when you build those little production ponds, you might consider dedicating one of them to GAMs. Anyone following a annual introduction regimen could get a big boost of cover for GAMs if they have a syphon with a standpipe where they could adjust the maintained pool at two different levels. In the north of the GAMs range, lower the level after ice-out and grow a winter annual along the ponds edge (something like Italian Ryegrass) or even winter wheat. Time flooding with the start of the first releases of fry and stock the adults at that time. This cover will only last a few weeks but it would be sufficient to get off a couple of generations all the while providing cover for them and habitat and food for the organisms they would feed on. In the south, one could lower the levels in the fall if they wanted more growing season.
A similar flooding regimen could be used with buried crayfish introductions also. For a slope of 3 to 1, a 16" drawdown provides a perimeter of 4 foot of crayfish habitat. These crops should be grown in late summer and fall and flooded early spring with berried crayfish introduction at or after flooding. 20 to 30 berried females/acre (around two to three pounds) would probably be ideal.
