Vol. 16—1962 - NorthEastern Weed Science Society

TABLE1. Responseof oysters t~ different concentrations of 2,4-D.
Total animals
in 4 plots
Days
ExPosed Control
14 Live 100
Dead
24 Live
Dead
o
98
2
3.5 Live
Dead 2
Total animals
in 3 plots of
.30 lb. MIA
Cen- "
ter edge ~200f
75 75
o 0
7.5 7.5
o 9
74 73
1 2
7.5
o
Total an1ma.ls Total animals
in 2 plot. of in 1 plot of
60 lb," AI/} ~o lb, AELA
Cen- .... enter
ed9'200' teredge 200'
so SO 50 25 2.5 25
o o o o 0 o
75 48 .50 50 2.5 23
o 2 0"" 0 o 2
7.5 47 49 50 2.5 23
o 3 1 o o 2
2.5
o
2.5
o
453
~. Noclams in the containers died durtng the first weekex- I
cept in one of the controls where nine were dead·on-the sixth day. Crabs
were feeding upon these and attacking the remaining live clams. During
the second weekdead clams with crabs feeding upon themwere found in all
of the remaining plots. At the end of the second weeknone of the experimental
clams were left •
. Crabs have been'observed elsewhere to attaclt::and consumelive sort
clams that are exposed above the bottom. It is theorized that in our
plots crabs were attracted as scavengers soon after the first death occurred
in each container of clams. Since the liv4ng clams were thinly
covered by soil they were easily uncovered and at~cked by the scavengers.
Crabs continued to be attracted until all clams ~re destroyed.
CRABS.The normal morta:H.tyrate amongcaptive crabs is hIgh, es';
pecial!y after the first few days of conrtnenent, Furthermore, dead crabs,
together with any that becomeinjured or that molt, are rapidly consumed
by other crabs. and predators s~h as eels that canenter the cages.
The large numbermissing from our cages exceededexpectations and rendered
the numberof dead recorded, two from the controls and two from the outer
cages, of no significance. If it can be assumedthat most of the missing
had died, a doubtful possibility, then the numbei~of survivors gives some
indication of the extent of mortality. For this reason, the survivors
are summarizedin Table 2. Initial numbersare fisted since a fewcra~s
were lost before herbicide application.