Here Fishy Fishy

We've lost some fish, yes, it's true. But before anyone panics and thinks the lake is in trouble, let me tell the story as I know it.

About half of the Threadfin Shad minnows in Lake Elsinore died over the last two days from low oxygen levels. These fish are bait fish. When I was a kid, we chopped them in half and used them as bait on Lake Erie to catch the "fresh water sharks". (Fresh water sharks are what the grumpy old guy on the lake said would "eat us alive" if we didn't stop doing cannonballs off of his dock).

These minnows reproduce pretty darn fast, and are famous for overpopulating warmwater lakes. The rough estimate of Shad minnows in Lake Elsinore was over 10,000 per surface acre, before mother nature killed them off of course.

To put this into perspective, a good sport fishery only requires 200 - 300 baitfish per surface acre. I'd say we had a few too many.

Threadfin Shad minnows are a very sensitive little species and are prone to massive die-offs from sudden temperature changes and low oxygen levels. In other words, their shelf-life isn't very long.

Our sport fish have remained unaffected, thriving. This is where survival of the fittest comes into play I suppose.

So where did all of the oxygen go you ask? Well, let me see if I can explain this so that it makes sense.

Algae need oxygen to live. Some of the lake's algae died, which had an effect on the oxygen levels in the lake. Keep in mind that SOME algae is good, but too much of anything is bad, even algae.

Due to the warmer weather, the scads of minnows in the lake that consume oxygen, a low lake level of water, and some other nature driven events, much of the oxygen needed for the minnows to survive literally evaporated.

This isn't exactly a bad thing, since the minnows tend to take more than their fair share of oxygen from the lake to begin with. They're greedy little buggers.

Too many minnows are a detriment to water quality, because they feed on large bodied zooplankton, which are the "algae eaters".

We need zooplankton in the lake, because they eat algae, which increases oxygen levels, which keep all the fish happy.

Dead algae decreases oxygen levels. So we have the minnows sucking up all of the algae eaters, which we need, and a little too much dead algae sucking up the oxygen, which we also need. And that, my friends, is where the oxygen has gone.

The whole lake aeration (artificial circulation) system is working to mix the Lake; however without sufficient oxygen production from algae, the oxygen levels will remain low.

So we need the algae to come back to life just a bit and the minnows to stop going back for seconds and thirds on the algae. And now it seems we have less minnows to cause us problems.
Get it?

In summary

More sport fish = less minnows = more algae eaters = less algae = sufficient oxygen