Control and conservation are two extremes of a spectrum.  If you have too many muskrats, you may need to control them.  If you don't have enough, you need to conserve what you have and encourage growth in the population.  In the middle is the happy medium where you just enough muskrats and can just enjoy them.

Control

Muskrat Control - Geese repellant, Critter Control - Geese and Steps to prevent muskrat destruction of shore lines from Aquatic Systems, Inc.

Control of Muskrat Damage in Ponds Ideas to prevent muskrat damage to ponds and description of muskrat habits and Muskrat and Beaver Management in Wetlands: Planning Ahead for Wildlife Survival from The MDC Landowner Tips Page, Missouri Department of Conservation.

Controlling Nuisance: Muskrats gives information about controlling muskrats via trapping and mechanical methods.  From XPLOR - Extension Publications Library on Request, University of Missouri-Columbia Extension.

Control of Beavers and Muskrats describes methods for controlling muskrat at Canadian airports; from Integrated Control Methods (Mammals), Wildlife Control Procedures Manual, Aerodrome Wildlife Control, Transport Canada.

"Muskrat", a Wildlife Endangered Species Fact Sheet, gives suggestions for managing property damage by muskrats.  From Bureau of Natural Resources, Wildlife Division, Connecticut Department of Environmental Protection.

Sabine National Wildlife Refuge is on land that was previously used for trapping and hunting.  The web page contains a brief discussion of using trapping to control the muskrat population.  From GORP.com Great Outdoor Recreation Pages.

"Muskrat Control" on Rodent Control, from Dam Safety, Water Management, Michigan Department of Environmental Quality.

Muskrats are discussed under "Other Pond Problems" on Pond Management Guide Chapter 4 from Fisheries and Pond Management, Wildlife, Fisheries, and Aquaculture Extension, North Carolina State University/A&T State University Cooperative Extension.

Muskrat Products lists a number of items for nuisance muskrat control.  From U-Spray, Inc.

Controlling Muskrats from Natural Resources Program, Michigan State University Extension - Genesee County.

FOR-51 Managing Muskrat Problems in Kentucky is an on-line publication available from Agricultural Communications Services, College of Agriculture, University of Kentucky.  It describes lethal and non-lethal methods of controlling muskrats.

The web page Difetiolona from Spain describes a anticoagulating raticide targeted at the muskrat (rata almizclera in Spanish) and other rodents.  From Número 4 de Terralia, Terralia.

"Muskrat Tips for Landowners Signs to Look For" by Ron Scheller appears in the Fall 2000 issue of Outdoor Guide Magazine.  It discusses what to look for to determine if you have muskrats on your property.

Conservation

"Muskrat Environmental Impact Potential and Management" is discussed on the Wildlife page at WaterSHEDSS (Water, Soil, and Hydro-Environmental Decision Support System) from NCSU Water Quality Group, North Carolina State University, North Carolina Cooperative Extension, Department of Biological and Agricultural Engineering.  What appears to be the same information is also at http://h2osparc.wq.ncsu.edu/descprob/wildlife.html.

"Eyes Front No. 26", a 1945 film, includes "Rehabilitation of Muskrats: Manitoba's muskrat conservation program" involving the creation of marshlands and a controlled method of trapping.  It is in the collection of The National Film Board of Canada.

State Wildlife Laws Handbook allows you to view each state's wildlife policy, protected species of wildlife, and habitat protection, although the information is getting old.  It was produced in 1993.  From Center for Wildlife Law, Institute of Public Law, University of New Mexico.