INVESTIGATION OF OYSTER SPAWNING, ETC., MILFORD, CONN. 497 



Milford Harbor is a natural oyster region, and virtually every year there is 

 a set of oysters that varies in intensity in accordance with the conditions shown in 

 the table. In Long Island Sound, oyster setting is less regular, and here there was 

 a similar fluctuation from a good set in 1925 to virtually none in 1926 and 1927. 



Though the method is new and far from being a statistical computation as to 

 the probability of the time of spawning and intensity of setting, it has proved to be 

 reliable after a trial of three years, and the results obtained strongly indicate that it 

 is based on the predominating factors that control oyster propagation. By accumu- 

 lating a greater number of data of this sort the method can be placed on a statistical 

 basis, definite values can be given to each variable, and more accurate predictions 

 can be made as to the yield of seed oysters per year. 



PRACTICAL APPLICATION OF THE METHOD 



Advance knowledge of the time and intensity of setting of oysters is of value 

 from a practical standpoint, because it can be utilized in controlling shell-planting 

 operations so as to obtain the maximum yield of seed oysters per year. On the 

 results obtained on July 1, deductions can be made as to (1) the quantity of shells or 

 cultch to be planted so as to take full advantage of the years of good set; (2) how 

 rapidly shell-planting operations must be carried on in order that they may be com- 

 pleted before setting occurs; and (3) the areas or beds that are most favorable for 

 obtaining a set under the existing conditions. 



There is no better way to increase the yield of seed oysters during favorable years 

 than by increasing the amount of cultch, especially on the best setting areas. An 

 acre of bottom that produces 500 to 1,000 bushels of set, averaging 25, 50, or more 

 spat per shell, has been poorly utilized, because its production could easily have been 

 increased many times by additional shell plantings. By obtaining the maximum 

 yield during the best setting years the industry is benefited not only by having seed 

 to grow for the market but by having, in the coming summers, a good supply of 

 oysters for the production of spawn and future sets. 



This method of predicting the intensity of oyster setting can be used in the future 

 in conjunction with the improved methods of seed collection that have been developed 

 by the bureau and will be described in a later report. 



SUMMARY 



1. The physical conditions in MUford Harbor and vicinity during the summers 

 of 1925 and 1926 have been discussed with special reference to the more important 

 factors — temperature, salinity, hydrogen-ion concentration, tides, and currents. 



2. The most important factor, water temperature, varies according to climato- 

 logical conditions and is affected most by them when the daily range of tide is greatest. 



3. The water temperatures from April to July were found to have a pronounced 

 efifect upon the quantity and ripeness of spawn in the oysters, while the temperatures 

 in July and August were found to be important in affecting the time of spawning. 



4. Annual fluctuations in the intensity of setting and the production of seed 

 oysters in Milford Harbor and Long Island Sound can be correlated ^vith water 

 temperatures during the spring and early summer months. 



