Geology topics
Walter R. Courtenay
Publications and source records attributed to Walter R. Courtenay.
Bigheaded carps : a biological synopsis and environmental risk assessment
The book is a detailed risk assessment and biological synopsis of the bigheaded carps of the genus Hypophthalmichthys, which includes the bighead, silver, and largescale silver carps. It summarizes the scientific literature describing their biology, ecology, uses, ecological effects, and risks to the environment. Includes information on taxonomy and distinguishing characteristics, hybrids, native and introduced ranges, temperature and salinity tolerances, fecundity, sexual maturity and mating behavior, spawning, early development, feeding habits, growth rate and longevity, response to physical stimuli, associated diseases and parasites, human uses, environmental effects, potential range, population control measures. Summarizes United States federal and state regulations, and assesses the risk posed by these species in the United States.
Snakeheads ( Pisces, Channidae ): A biological synopsis and risk assessment
Snakeheads (family Channidae) are airbreathing freshwater fishes containing two genera, Channa with 26 species native to Asia, Malaysia, and Indonesia; and Parachanna with 3 species native to tropical Africa. Some snakeheads are small, reaching about 17 centimeters, but most are much larger, the largest reported to be 1.8 meters in length. All are considered thrust predators with most being piscivorous as adults. A few of the smaller snakeheads and colorful juveniles of some larger ones have been available to hobbyists through the aquarium fish trade. Several species are highly valued as food fishes within parts of their native ranges, especially in Asia where they are an important part of capture fisheries and aquaculture. Because of these uses by humans, introductions far beyond native ranges have occurred. One Asian snakehead has been established in Oahu, Hawaii, since before 1900. Another species was discovered established in southeastern Florida in 2000, and a third in a pond in Maryland in 2002. Others have been captured from natural waters of the United States without evidence of reproduction and likely represent released aquarium fishes. That snakeheads at or near sexual maturity were being sold alive in ethnic food markets raised fears that they could be introduced into novel waters. These concerns led to this study on the biology of snakeheads. A risk assessment is included that examines environmental and related aspects of snakehead introductions.