616 
BULLETIN OF THE BUREAU OF FISHERIES 
rises and fails, does not sweep through. In the other productive areas the tide is 
very strong. 
In the adjoining intermediate section the tide is reduced but still periodic. 
Growth is less rapid so that year-old scallops are of moderate size (60 to 70 millimeters). 
The third section is that termed western Bogue Sound in this paper. Tidal 
flow generally is slow or, over the great expanses of scallop shoals, wanting or almost 
wanting and the water level greatly affected by winds. The main channel is a dredged 
one along the north shore. Scallop-producing areas constitute a large, perhaps the 
larger, portion of this section and yield great numbers of scallops. Growth is slow 
and the year-old scallops small but varying considerably in size over this large area 
(40 to 60 millimeters). Two-year-old scallops attain a much larger size. 
The sound salinities normally are high, generally over 30 parts per mille and 
rarely as low as 27 parts per mille. Summer salinities in western Bogue Sound run 
as high as 37 parts per mille. 
Although no quantitative data are available to show the relation between current 
and growth rate, it seems to me that the case is a fairly obvious one and that there 
is no reasonable ground for doubt that current is the chief physical factor governing 
growdh in Bogue Sound. In other sections the case is not quite so simple and obvious 
but higher growth rate still is attributable to stronger current. Presumably this is 
in part because the current brings food, but the fact that it brings an abundance of 
0 2 and carries away products of vegetable decay besides C0 2 , and so prevents injuri- 
ous results from stagnation, may be more important. It should be considered that 
in the sluggish, slow-growing areas, the severity of warm-weather conditions may be 
a principal retarding factor. 
SALINITY 
Although salinity is an essential condition of the environment of the bay scallop, 
the limits are not easily determined. Only the lower limit is of presumable practi- 
cal importance, because bay scallops are to be found in the most saline waters of 
their range (total salinity about 38 parts per mille). The minimum salinity may 
well be considered under two heads, which I term the “freshet” or temporary mini- 
mum and the distributional or continued minimum. 
The distributional minimum is taken to be the lowest salinity to be found within 
scallop areas except during extreme freshets. This minimum has been sought par- 
ticularly in Core Sound, which ordinarily contains scallops only in its southerly 
saltier portion but which in the winters of 1926-27 and 1927-28 contained them also 
in its northern portion near where it joins the less saline Pamlico Sound. The lowest 
salinity found in scallop areas in Core Sound or elsewhere, except during severe 
freshets, was 20 parts per mille, with 21.3 parts per mille or higher almost universal. 
(See Giral, 1926, as to the accuracy of salinity determinations.) This figure of 20 
parts per mille therefore is taken as the distributional minimum. 
Even in the saltier portions of the scallop-producing areas severe freshets occur 
which are extremely destructive. In September, 1924, a freshet occurred which 
almost completely destroyed the scallops (unless perhaps the very young) in all areas 
except those off Morehead City in lower Bogue Sound. The salinities prevailing off 
Morehead City during this freshet are not known, but those at Pivers Island became 
as low as 6 parts per mille (Table 8 and fig. 29). Because of the tidal conditions 
appreciably higher salinities might well have prevailed, and doubtless did prevail 
off Morehead City. In 1921 freshets reduced the salinities in the Plarkers Island 
