4 TJ. S. BUREAU OF FISHEEIES. 



Although, as before stated, no exact rule as to the effect of tem- 

 perature on the spawning of oysters can be formulated, something 

 of the relationship between the two can be given. At temperatures 

 below 70° such spawning as occurs is almost invariabl}^ of the slow, 

 little at a time, or dribbling sort, but under certain circumstances 

 ripe oysters, previously deterred from spawning by low water tem- 

 peratures, will spawn vigorously when a rise comes, even if this rise 

 stops somewhat short of attaining 70°. In general, however, spawn- 

 ing at temperatures appreciably below 70° is of the dribbling sort, 

 which does not produce hea\^' sets. If temperatures approaching 

 70° have been maintained sufficiently long to insure seasonal sexual 

 maturity, but not long enough to allow the dribbling of most of the 

 spawn, an increase tO' 70°, if maintained for a day or two, will 

 produce active concerted spawning. Under similar circumstances an 

 increase in temperature markedly above 70° will cause extremely 

 vigorous and almost universal spawning. In northern waters 

 abundant larvse and " heaw '' sets are produced only by these vigor- 

 ous concerted spawnings. 



The accompanying maps (figs. 1 and 2) make clear the historic 

 fact that the great natural oyster areas of Connecticut were harbors, 

 lower reaches of rivers emptying into the Sound, and sections in 

 the Sound just oft' the mouths of these estuaries and so situated as 

 to be affected by the flow from them. These were the great self- 

 maintaining areas and the natural producers of seed oysters. As 

 they became depleted and were turned over in greater or less measure 

 to private enterprise they, with some extensions in the Sound, became 

 the great private seed-producing grounds. 



The principal reason for this condition is to be found in the early 

 and high warming of the water in the estuaries. This warming 

 produced concerted and vigorous spawning, which in turn produced 

 vast numbers of embryos and then larvae. Coming at an early date 

 it gave excellent opportunity for the larvae to develop and set and 

 for the set to make a good growth and pass through the more delicate 

 early stages before the September storms set in. These sets were 

 not confined to the estuaries themselves but extended naturally some 

 distance into the Sound. By planting shells for the larvae to set on, 

 oyster-culturists increased these Sound setting areas. 



Under private culture, as long as conditions in the harbors and 

 rivers made oyster growing or conditioning profitable, fairly large 

 beds were maintained. As conditions became worse, fewer and 

 fewer oysters were planted on the private harbor or river grounds, 

 and those grounds that were still public became depleted. With 

 the general passing of harbor and river production came the gen- 

 eral failure of "sets."' With the failure of "sets" came such an 

 extended depletion of Sound areas that the chance of good "sets" 

 from the spawning of Sound oysters was reduced. Obviously, if 

 the Connecticut oyster industry is to be kept going, either effective 

 estuarial spawning beds must be maintained or oyster planting in 

 the Sound must be of such a type that reasonably good sets' may 

 occur at reasonably frequent intervals.^ 



» This consideration of the question takes no notice of the possible success of " arti- 

 ficial " set production, but even if this were developed, it is quesjtionable how much it 

 would benefit Connecticut with its be&l oyster areas so' largely destroyed. 



