Distribution, Density and Production of the Crayfish Pacifastacus leniusculus Dana in Lake Tahoe, California - Nevada

The standing crop of the California crayfish Pacifastacus leniusculus (Dana) is concentrated in the narrow littoral zone of Lake Tahoe and is estimated by trapping returns at 55.5 million adults weighing 1,100,000 kg. The population density differs in relation to substrata and local eutrophication with an average of about 0.9 adults per M2. A more eutrophic area of the lake yielded over twice as many crayfish per trap as less productive areas. Maximum density is found between 10 and 20 m withover 900, of the population found between 0 and 40 m of depth. Because the average depth of Tahoe is 313 m this represents only 12 %? of the lake surface area. Wave action and light appears to limit crayfish density above 10 m depth and water temperature below 40 m. The temperature distribution factor is supported by an experiment where females held at an average of 6.8 C failed to hatch eggs. Substrata which provide good protection from predators produce larger numbers of smaller individuals while more open areas of the lake bottom have a smaller number and larger individuals. Between 80 and 100 % of the population over 95 mm in length are sexually mature. Females carry an average of 1 10 eggs.