ABSTRACT A series of intertidal field experiments was conducted from 1986-2003 in eastern Maine to examine biotic and abiotic factors influencing the growth and survival of wild and cultured individuals of the softshell clam, Mya arenaria L. Separate experiments examined: (1) the efficacy of transferring sublegal wild clams (
<50.8 mm SL) from areas near the high intertidal zone where shell growth was slow to areas where growth was predicted to be faster; (2) effects of tidal height on wild and cultured clam growth; (3) effects of spatial variation on cultured clam growth; (4) dispersion and growth of cultured juveniles in small experimental units; (5) effects of the naticid gastropod, Euspira heros Say, predation on survival of wild and cultured clams and (6) the species composition of large, crustacean predators that forage intertidally during periods of tidal inundation. Protective netting (4.2 mm aperture) increased recovery rate of transferred clams by 120% and resulted in a 3-fold enhancement of wild recruits. Effects of tidal height on wild clam growth revealed complex behaviors in>0 y-class individuals. Clams growing near the upper intertidal take >8 y to attain a legal size of 50.8 mm SL, whereas animals near the mid intertidal generally ...
<2 mm of new shell in a year, which was 8-10 mm SL less than animals at higher shore levels. It is hypothesized that biological disturbance by moon snails, that consumed>
<35 mm added, on average, 8.1 [+ or -] 1.14 mm (n = 13) of new shell between May and October 1998 compared with 3.4 [+ or -] 0.56 mm (n = 27) for animals>
<18 mm SL) per 0.02 [m.sup.2]
sample taken on October 27, 1998 at Carrying Place Cove, Eastport,
Maine. Two random samples were taken from each of five replicates of
each treatment (2 x 6 x 5 = 60 samples). A priori contrasts appear
under the Treatment source of variation and a decision rule equal
to [alpha]' = 0.0170 was used.
Source of Variation df SS MS F Pr>