Hi Steve,

Here are a few references to scientific studies that back up my claims about fish density affecting growth patterns. If I were to choose only one to read, it would be the Rose article. They're basically saying that changing water more frequently cuts down on stress hormones, improves water quality (pH, ammonia, etc.) and ultimately enhances growth and survival. However, crowding reduces growth rates independent of food availability, water quality, and so on.

Rick


Bolasina S, Tagawa M, Yamashita Y, & Tanaka M. 2006. Effects of stocking density on growth, digestive enzyme activity and cortisol level in larvae and juveniles of Japanese flounder, Paralichthyes olivaceus. Aquaculture. 259:432-443.

Ellis T, North B, Scott AP, Bromage NR, Porter M & Gadd D. 2002. The relationships between density and welfare in farmed rainbow trout. Journal of Fish Biology 61:493-531.

Ewing RD & Ewing SK. 1995. Review of the effects of rearing density on the survival to adulthood for Pacific salmon. Progressive Fish-Culturist 57:1-25.

Rose KA, Cowan Jr. JH, Winemiller KO, Myers RA, & Hillborn R. 2001. Compensatory density dependence in fish populations: importance, controversy, understanding, and prognosis. Fish and Fisheries. 2:293-327.