25|— 



I'lcaiiE ;j. — Xumber of oysters consumed by 20 adult starfisli lield with 140 oysters in a tray from January 1964 to 

 January 1907 and (in a second tray) from May 1900 to January 1907. Both trays were suspendwl in Alilfnrd Harbor. 

 Temperatures are given in the upjier panel. 



In 1964, 1965, and 1966, during the period of 

 little feeding from mid-January to the end of 

 March, water temperatures averaged 1° C. (range 

 -2.2° to 3.2° v.). Olxservations of starfish in trays 

 in Milford Harbor and of those dredged from the 

 bottom showed that they feed on oysters and other 

 food at temperatures at least as low as 0.2° C. 

 Temperatures increased to 7° to 9° C. by the end 

 of April, to 13.5° to 15° C. by the end of May, 

 and to 18.5° to 19.5° C. by the end of June (wlien 

 the rates of feeding were highest). By mid-to-late 

 July temperatures reached 22.5° C. and stayed 

 at or above that level until early or mid-Septem- 

 ber (during the jDcriod when rates of feeding were 

 about a third as intense as they were in the spring) . 

 In the 3 years temperatures averaged 13.5° to 15.3° 

 C. during October, 7.9° to 11.6° C. during Novem- 

 ber, and 3.6° to 5.8° C. during December, and dur- 

 ing this period of 3 months feeding rates were 

 about two-tliirds as intense as they were in late 

 June. 



SUMMARY OF EFFECTS OF WATER 

 TEMPERATURES AND SEASONS ON 

 FEEDING RATE 



A comparison of feeding rates of starfish at 

 constant temperatures with those in different sea- 

 sons shows that the rates in different seasons are 

 controlled primarily by seasonal temperatures. 

 Though laboratory studies were not conducted to 

 determine feeding rates at temjaeratures below 5° 

 C, low rates from mid-January to the end of 

 March are undoubtedly a result of temperatures 

 which average only 1° C. As temperatures rise in 

 tiie spring to nearly 20° C, the optimum tempera- 

 ture for feeding, by the end of June feeding in- 

 creases rapidly. 



In summer the decline in feeding coincided with 

 high temperatures. For example, in 1964 tempera- 

 tures exceeded 22.5° C, the temperature at which 

 feeding probably begins to decline, on July 15, 

 about 2 weeks after a sharp declme in feeding had 

 already begun. In 1965 temperatures rose to above 

 22.5° C. for only a few days during July, coincid- 



FEEDIXO R.VIES OF STARFISH 



71 



