Originally Posted by FishinRod
In a Swingle type experiment, if there were fewer gams but a great abundance of some small zooplankton would the BG have shown as much weight gain? (Correcting for the relative nutrition between fish protein and zooplankton protein.)

In Swingle's experiment he credited the sequestration of nutrients into the GAMs as the reason for the outperformance. So the BG were stocked at 2" and could not use all the nutrition that the fertilization was providing (they had a low standing weight). But the GAMs reproduced extensively and utilized the foods in the early going when there was insufficient weight of BG to fully consume them. The GAMs could not achieve sizes to evade predation so by the end of the season most of them were consumed by BG (the stocking rate was 1 lb GAMs and 1500 BG/acre). The difference was remarkable with an 87 percent increase in production. FHM performed similarly in combination with BG and LMB.

As to the differences between zooplankton and fish, there are notable differences. Seems like I have read that some of the protein (chitin) in invertebrates is not digestible by fish. Also the water content of most aquatic invertebrates tends to be higher than fish (less energy in a given volume). Fish are high in minerals relative to invertebrates and these are building blocks for skeletons, fins, and scales. Swingle could not get a similar performance from PK shrimp as he did minnow. In part, it may be the quality and/or density of the nutrition playing a role. I am not certain but this seems plausible. IMHO forage isn't just forage. I think some forage is better than others.

It sounds like a clear water pond is definitely your recommendation for big and/or "trophy" BG. In that circumstance, would you recommend periodic fertilization? The resulting algal bloom would hurt water clarity for a little while, but you would jumpstart all of the food chain items that directly feed BG as well as the indirect food chain that results in fat minnows to also feed the BG. After the bloom cleared, the BG should be able to slaughter the once again easily visible forage.

I like a compromise. Maybe oligotrophic water clarity is best for long life and maximum size. Given the many examples of record fish coming from such waters this may be the path to the largest fish. But I think I would personally sacrifice a world record fish to have more fish and better fishing. Seems a risky proposition to focus on very few very large fish. For example, what if you grew the world record fish but never caught it? Seems like a lot is lost in being too focused on individual weight.

One of the things I have learned is that doubling the phytoplankton standing weight does not lead to doubling of invertebrates and fish. When we push, we get less than 1 to 1 reward for the pushing. Here I am speaking solely about natural food chain even if artificially enhanced by fertilization. I am not sure why this is so but I suspect that it is water quality. So I think more oxygen, less pathogens, and better visibility help the consumers and so less bloom and double the secchi doesn't halve the carrying capacity. It takes it down by around 30% instead. Consequently, having 1.3 acres with half the bloom is equivalent to 1 acre.

I think a good compromise is to attempt to maintain meso-tropic water. This would include fertilizing or feeding in water leaner than that or sequestering nutrients through with species like TP that are harvested and removed from the water. Water >3' secchi is not risky water and rarely experience fish kills. A person doesn't have to give up much and the potential for longer lived fish is improved.

Supplemental floating food would be easy to find during the bloom and then you might be able to cut back during the post-bloom natural forage boom. It seems that would make it easier for management rookies (like me) to push the total weight of BG a little without significantly risking a crash from pushing the pond to carrying capacity ALL of the year.

I like a strategy that pushes when temps are forgiving and then eases when temps are not.