. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. TIIK FRESIl-WATKK Ml'SSKI, IN' TU('<'KI'.K KIVKK !tl This corrosive action is counteracted by "oil spots" or "Tullberg's layers" of periostracum on the inner side of the shell layers (Altnoder, 1926). Muskrats probably eat some adults, and a few glochidia may be eaten by fish and other water animals. Breeding Season In this discussion the "breeding season" of the mussels will be defined as the time be
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. TIIK FRESIl-WATKK Ml'SSKI, IN' TU('<'KI'.K KIVKK !tl This corrosive action is counteracted by "oil spots" or "Tullberg's layers" of periostracum on the inner side of the shell layers (Altnoder, 1926). Muskrats probably eat some adults, and a few glochidia may be eaten by fish and other water animals. Breeding Season In this discussion the "breeding season" of the mussels will be defined as the time between the first appearance of "undeveloped eggs" in the gill chamber or "marsupium" and the date of their last appear- ance. By "undeveloped eggs" is meant eggs either before division or in the early stages of embryonic development. In 1941 new eggs started to form in the ovaries of the Truckee River mussels in July, a week or two after discharge of their glochidia. Maturation of eggs apparently continues slowly in the ovaries over the winter, with movement into the marsupia taking place in the spring. In 1941, May 15 was the earliest date on which mussels were taken with "undeveloped eggs" in the marsupia. From then until June 25, in from 3 to 20 per cent of the individuals collected,3 the marsupia con- tained undeveloped eggs. From March 25 to August 5, 1941, a recording thermometer was kept in the Truckee River at the Fly Casting Club. From March 25 to May 15, the average daily temperature was ° F., ranging from 42° on March 25 to ° on May From May 15 to June 25 (the "breeding season" in 1941) the average daily temperature of the river was ° F., ranging from ° on Mav"l5 to ° on June 25. (See Fig. 27.). PIG. 27. Average daily temperatures of Truckee River at the San â â ⢠l'l- Casting Club, 1941. A. "Breeding Season" of mussels. B. Period of embryonic de
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