NATURAL HISTORY OF THE BAY SCALLOP 
621 
and culminating in mid or late summer. However, it is to be noted that January 
temperatures fluctuate from a minimum of 3° to 5° C. to a maximum of 12° to 15° C. 
so that there is opportunity for growth at this season even if feeding does not occur 
at or below 5° C. or some temperature close to this. A further complicating factor is 
the early maturing, with short life. Thus growth rate for one year is complicated 
by all the physiological changes involved in the transformation from minute larva or 
early postlarva to large mature adult. The “annual” (about 1 year old) growth 
line generally is formed in the fall when it could be explained as directly due to tem- 
perature only on the assumption that the sudden autumnal temperature drop, or 
the loss of summer warmth, temporarily inhibits growth. 
Table 10. — Monthly maximum and minimum water temperatures (° C.) at Pivers Island, 1924-1928, 
based on one reading daily 
Month 
Year 
Janu- 
ary 
Febru- 
ary 
March 
April 
May 
June 
July 
August 
Septem- 
ber 
Octo- 
ber 
Novem- 
ber 
Decem- 
ber 
MAXIMUM 
1924 
15 
14 
16 
20 
25 
30 
31 
28 
29 
23 
20 
18 
1925 - 
12 
15 
17 
23 
27 
29 
29 
28 
30 
25 
19 
15 
l‘J26 
15 
15 
19 
22 
26 
30 
32 
33 
32 
30 
20 
16 
1927 
14 
20 
22 
23 
26 
30 
31 
31 
29 
27 
26 
23 
1928. 
15 
14 
17 
23 
27 
30 
30 
32 
30 
36 
25 
18 
MINIMUM 
1f )24 
5 
7 
8 
14 
20 
24 
23 
24 
21 
14 
9 
6 
1925 
5 
8 
7 
12 
18 
23 
24 
23 
25 
12 
10 
4 
1926 
8 
9 
9 
15 
20 
22 
28 
28 
26 
16 
13 
6 
1927 
3 
11 
6 
13 
20 
21 
26 
23 
22 
17 
13 
8 
1928 - - 
4 
8 
10 
14 
16 
23 
26 
28 
22 
16 
8 
5 
A noticeable direct effect of temperature comes with extreme cold. Thus late 
in December, 1928, unusually cold weather was accompanied by extreme ebb tides 
that left the scallop flats exposed (but not quite free of water which, as usual, was 
impounded by vegetation, etc.) for considerable intervals. As previously stated, it 
is believed th^t the considerable scallop mortality which followed was due to unusual 
chilling. Extreme water temperatures on the flats under such conditions doubtless 
exceed those recorded, as do also those under similar tidal but reverse temperature 
conditions in summer. Thus in the instance cited, with an air temperature (at night) 
of about —10° C., it is not impossible that the little water left on the flats at low 
water became colder than 0° C. Some few scallops may have been directly exposed to 
the air temperature. The recorded minimum water temperature (4° C.) is extreme 
for December. 
ENEMIES AND PARASITES 
Of the animals which prey upon post-larval scallops, the best known are the 
starfish, the oyster drill, and the herring gull. Of these the herring gull is much the 
most conspicuous. From fall to spring at Pivers Island the gulls are daily to be seen, 
as the tide drops, floating over the scallop flats and — when the flats become suffici- 
ently exposed — catching the scallops, dropping them on the beach to crack the shells, 
and eating them. This happens also at other beds about Beaufort and Morehead 
City where the scallops are especially valuable. Obviously many marketable scallops 
are thus destroyed. However, it is to be considered that the greater portion of the 
scallop-producing areas are not sufficiently exposed by the tide to enable herring 
