NOTE Witting and Able Probability of predation for juvenile Paralichthys dentatus and Pleuronectes amencanus 



579 



M 



to 



1 



£ 



25 



35 



45 



55 



65 



Total Length of Predator (mm) 



Figure 1 



Relationship between size of sevenspine bay shrimp preda- 

 tors and predation on summer flounder prey. Graph presents 

 original data with sample sizes above each bar (A), raw prob- 

 abilities as predicted by logistic regression (B), and probabili- 

 ties after being standardized for the effect of prey size (C). 

 These probabilities and those for Figure 2 are based on the 

 equation: Logit = 1.66+10.15 * predator sizeM0.59 * prey 

 size). See text for discussion of logits. 



9 11 13 15 17 



Standard Length of Prey (mm) 



Figure 2 



Relationship between prey size and probability of predation 

 on summer flounder by sevenspine bay shrimp. Graph pre- 

 sents original data with sample sizes above each bar I A), raw 

 probabilities as predicted by logistic regression (B), and prob- 

 abilities after being standardized for the effect of predator 

 size(C). 



Discussion 



Summer and winter flounder that survive the egg and 

 larval stage and settle to estuarine substrates inhab- 

 ited by adult sevenspine bay shrimp may be subject to 

 significant predation. Summer flounder of 11-16 mm 

 SL, the size at which they enter the estuary 

 (Szedlmayer et al. 1992, Keefe and Able, 1993), are 

 vulnerable to predation by a large size range of 

 sevenspine bay shrimp. This interaction is likely be- 



cause these species co-occur under natural conditions. 

 Previous studies indicate that abundance of adult 

 sevenspine bay shrimp, in estuaries to the south and 

 north of the study area (Modlin 1980, Price 1962), be- 

 gin to increase in the fall and continue to do so until 

 they reach a peak in the spring. This temporal pattern 

 overlaps completely with the period (October-May) that 

 summer flounder enter the estuaries of New Jersey 

 (Able et al. 1990, Szedlmayer et al. 1992). These shrimp 

 range from 10-50 mm TL (Price, 1962). Our data sug- 



