Stehlik et al.: Distribution and abundance of brachyuran crabs on northwest Atlantic shelf 



491 



and their abundances are seasonally consistent within 

 each stratum. Depth or temperature, or their inter- 

 action, were significantly correlated with abundances 

 of all four crab species. 



Substantial gaps in the knowledge of these crabs re- 

 main. Temperature appears to affect distributions and 

 migrations, but data to identify critical threshold 

 temperatures are generally lacking. Besides depth and 

 temperature, other factors such as food availability 

 probably affect distribution, but are poorly known. The 

 mean size at maturity for each species, the time of egg 

 release, and locations of settlement and foods of 

 juvenile crabs are scarcely known. Mortality rates of 

 these crabs from fish predation are not known, and a 

 comparison of the relative importance of the crabs with 

 fishes as predators of benthic infaunal invertebrates 

 has not been made. 



Acknowledgments 



We thank Willard Van Engel, Dr. Linda Jones, and 

 anonymous reviewers for their valuable contributions 

 to this manuscript. 



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