Publication Abstract

Regulation in fish populations: myth or mirage?

J.G. Shepherd and D.H. Cushing

There is abundant evidence of long-term changes in the abundance of fish populations, but the causes are not known. It is almost certain that climatic changes are responsible in part, but the role of population regulatory mechanisms is unclear. The evidence is conflicting. The ability of fish populations to sustain levels of fishing mortality several times the level of natural mortality suggests strong regulatory mechanisms. The persistence of stocks for centuries, with few extinctions or explosions, also implies some regulation, but not necessarily strong regulation. The high levels of fluctuation in recruitment suggest weak regulation except in the earliest stages of the life history. Under weak regulation the time taken for effective explosions or extinctions is long, maybe a century for 1000-fold changes in abundance.

Reference:

J.G. Shepherd and D.H. Cushing (1990) Regulation in fish populations: myth or mirage? Proceedings of the Royal Society. London, 830B: 151-164.