Effect of nutrients on cavefish.

[gillip]

I was wondering if anyone had any information on the effect of nutrients on cavefish. I am doing some research on the Ozark cavefish (Amblyopsis rosae). I have found that nutrients are enriched in the cave. Nitrate-N values of 8mg/L. This is below the EPA threshhold and I have found reports of much higher N, but it is well above background for our area (<2mg/L). I read that cavefish are dependent on nutrients, so depletion can be a problem. One scenario for depletion would be bats abandoning a roost in a cave. Enrichment is much more likely. The main source of N in our area is the spreading of chicken litter as fertilizer. In general it is free of pesticides. It often does contain antibiotics, but that is out of the scope of my project. Does anyone have any information about the thresholds of contaminants, especially N, of cave fish?
Any input would be appreciated.

[Azurerana]

On the other hand, species which are used to nutritional deprivation can be adversely affected by too much enrichment. See Dave Culver's book Cave Life for discussion of this, including reproductive rates and longevity as related to a greater food source. The one case I know of for T. sub in which a sinkhole is literally teeming with cavefish is where that open karst window has an abundant supply of leaf litter, bugs, and other nutrients, but further back in the cave, away from the sunlight, the fish are few and far between. Nutrient levels in a cavefish cave are related to the DO levels as well--cavefish require fairly high DO and water clarity, both of which can be negatively impacted by nutrient load. Check your PMs, also, Mr. Gillip.

Azurerana