VARIATIONS IN TIME AND INTENSITY OF SETTING OF THE STARFISH, ASTERIAS FORBESI, IN LONG ISLAND SOUND DURING A TWENTY-FIVE-YEAR PERIOD

Abstract

1. Setting of starfish (A. forbesi) was recorded at all depths of Long Island Sound from several feet above mean low water mark to 100 feet. No systematic observations were made at greater depth. 2. Starfish commence spawning when water temperature reaches approximately 15° C., which usually occurs about the middle of June. In some individuals spawning may continue into early September. 3. With the exception of 1945, when setting began and ended within the same day, September 11, the date of beginning of setting during the 25-year period varied from the last week of June to the last week of July. 4. The end of setting in the different years occurred between July 23 and October 1. In only 5 years setting continued into the second part of September. 5. The length of the setting period varied from one day, in 1945, to 91 days in 1961. In four years setting continued for 80 days or longer, but the average annual length of the setting period was about 52 days. 6. Intervals extending from the beginning of setting to the peak of the first or second waves of setting, and the time relationship between the first and second waves of setting did not show any orderly pattern. 7. During the 25-year period of observations the year 1938 held the highest rank in numbers of starfish set, while the year 1945 was the lowest. In general the ranking indicated that there was no definite succession of good and poor years. 8. During the period of 17 years, 1940-1956, no appreciable relationship was found between numbers of adult starfish present during the pre-spawning period and intensity of starfish setting later in the season. 9. Our observations do not support the contention that peaks of the adult starfish population in Long Island Sound should have occurred in 1942 and in 1956. 10. No definite relationship was found between the intensity of starfish and oyster setting in Long Island Sound. 11. Larval diseases of specific nature, caused by various microorganisms, quality and quantity of food available, and the presence in the water of various ectocrines may be principally responsible for the survival or mortality of starfish larvae and therefore, for variations in intensity of setting of starfish in different years.