TEMPERATURE °C. 



FiGUKE 2. — Averayo weight change of starfisli held at constant tcmiieratui-es for 2S days, with and without food. 

 (Points are based on combined data of replicates at each temperature.) Point (1) represents starfisli held 

 in a cage in Milford Ilarlior. April 1-30, when temperatures averaged 5.8° C. (range 2.7-9.5° C). 



feeding was low from uiid-Jaimary until the end 

 of March. For example, in 1965 the 20 starfish con- 

 smned about 0.6 oyster per 7 days (0.12 oyster p&r 

 starfisli per 28 day.s) during this i^eriod of 2.5 

 months. From mid-AiJril to late Jmie and early 

 July the rate rose sharply, apparently as a result 

 of the rise in water temperature. At the time of 

 most intense feeding, in late June 1965, the 20 star- 

 fish ate about 20 oysters per 7 days (four oysters 

 per starfish per 28 days). In late July, August, 

 and September the rate of feeding decreased to 

 about a third of its level in late June and early 

 July. In late October, November, and early Decem- 

 Ijer the rate increased again to about two-thirds of 

 the rate in late June and early July. Beginning 

 in late December, feeding rates began to decline 

 but did not really become low in 1965 and 1966 un- 

 til mid-Januaiy. In 1967, however, l)ecau.se of un- 

 usually warm water, feeding had not declined to its 

 previous winter low by late January when observa- 

 tions were terminated. 



As the experiment continued from 1961 tluoiigh 

 1966, the starfish grew larger. The new group of 

 oysters collected each spring was, however, of 

 about the same average size — 50 to 65 mm. (range 

 34-82 mm.) — as the original group fed to tlie star- 

 fish in 1964. Because the larger starfish consumed 

 more oysters (of a particular size) than the smaller 

 ones, feeding rates were higher in each successive 

 year. 



The feeding in the .second tray, observed from 

 May 17. 1966 to January 26, 1967 (to e\aluato tlie 

 effect of possible consumption of fouling orga- 

 nisms on feeding rate), was essentially similar to 

 that in the first tra_v. Because the supply of oysters 

 was low, ]iowe\er, it was necessary to use smaller 

 oysters in tiiis tray after late August. Tiie starfish 

 in this second tray, consequently, showed a mudi 

 higlier consumption of oysters than did those in 

 the first trav which were feeding on larger oysters 

 (fig. 3). 



70 



U.S. FISH AND AVILDLIFM SIOKVICE 



