. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. ECOLOGY OF GAPER CLAM 55 40 r 35 CO q: UJ 30 H UJ S 25 _j _i s 20 z I (- 15 C3 Z UJ -J 10 5 0. m'j'j'ais'o'n'dIj'fim'a'm'j'j'a' MONTH FIGURE 7. Hand-fitted growth curves of mean growth of gaper clam recruits in Primary Study Area. The growth rate of the 1971 year class in Qi and Q4 approximated the growth rate of 1970 year class (Figure 7). However, the growth of this year class seemed to exhibit a lag phase prior to rapid growth. Bet
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. ECOLOGY OF GAPER CLAM 55 40 r 35 CO q: UJ 30 H UJ S 25 _j _i s 20 z I (- 15 C3 Z UJ -J 10 5 0. m'j'j'ais'o'n'dIj'fim'a'm'j'j'a' MONTH FIGURE 7. Hand-fitted growth curves of mean growth of gaper clam recruits in Primary Study Area. The growth rate of the 1971 year class in Qi and Q4 approximated the growth rate of 1970 year class (Figure 7). However, the growth of this year class seemed to exhibit a lag phase prior to rapid growth. Between April 25 and May 26, 1971 very little growth of the 1971 year class took place. Rapid gro\\i^h occurred in June and July. Samples taken on August 9, 1971 indicated that the growth rate had started to decrease. Growth of the 1971 year class was monitored in four other areas of Humboldt Bay: Clam Island (Qe), Elk River, Gunther Island (Qd), and Woodley Island (Figure 1). The form of the growth curve for each area was similar to the form of the growth curves for the plots mon- itored in the Primary Study Area. The growth rate was slow in each area until late May or early June, was rapid through June and July, and decreased in August (Figure 8). Growth of adults occurred primarily in the spring and summer. Growth is evidenced by a peripheral annulus which is covered by a fresh and clean periostracum and thin shell margin. Growth rates of adults were determined using annuli of clams from Elk River (1966 year class), Clam Island (Qa) (1966 year class), and the Primary Study Area (Q2 and Q15) (1964 and 1966 year classes). Log Trans- formations of the length-time data were plotted and the slopes com- pared utilizing analysis of covariance (Li 1966). The slopes or growth rates showed no significant difference between clams of the 1966 year class from Q2, Q15, and Qie (F = , p > ). Growth rates were also similar when the 1964 year class was tested by Q2 and Q15 (F = 2.
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