The bullfrog (Rana catesbeiana) was introduced into California in the early part of the present century. The extensive marshland habitat of the Central Valley was ideally suited to this species and it quickly spread. However, bullfrogs have become scarce in recent years. Sport and commercial users tend to blame each other's activities for this decline. It is also apparent that agricultural practices, such as ?clean-farming? and the use of pesticides in adjacent croplands, have reduced the range and density of the bullfrog populations. In late 1971 the California Department of Fish and Game initiated a study of the bullfrog problem. Background and life history data were collected in 1972. The basic life history of the bullfrog in California is similar to that in its native range in the East. A large scale field survey was conducted in 1973. Seventeen "primary" canals were surveyed four times and 23 ?secondary? canals were surveyed once. In general, bullfrog densities were lower in canals that were open to frogging than in canals that were closed to frogging. Because of low bullfrog population densities in the Central Valley, the California Fish and Game Commission adopted regulations in 1974 which closed much of the Sacramento Valley to commercial frogging and placed restrictions on the commercial season in the San Joaquin Valley. The Commission also reduced both the bag limit and the open season for sport frogging in the Central Valley.
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