USE OF A LABORATORY PREDATOR-PREY TEST 



AS AN INDICATOR OF SUBLETHAL 



POLLUTANT STRESS 



Christopher Deacutis 



U.S. Environmental Protection Agency 



Environmental Research Laboratory 



Narragansett, Rhode Island 02882 



ABSTRACT 



A method is presented to quantify the effects of sublethal stress on newly 

 hatched and older ichthyoplankton using predation vulnerability as a 

 measurable parameter. A laboratory predator-prey system was developed and 

 tested using sublethal thermal shock (lO^C above ambient water temperature) 

 as the stressing factor. Fundulus majalis was chosen as the predator and larvae 

 of Menidia menidia and Paralichthys dentatus as prey organisms. Predation 

 interactions were quantified by recording all attacks, escapes, and captures, 

 allowing comparison of escape probabiUties (no. escapes/ attack) for control 

 and shocked prey groups. 



Predator escape ability of four and six week old larvae M. menidia was 

 significantly impaired following a 15 minute, +10°C thermal shock in summer 

 (thermal test exposure = 30.0^C). Newly hatched and two week old shocked 

 M. menidia were not significantly different from controls. Tests with P. 

 dentatus showed an increase in total number of escapes following 10 C 

 thermal shock in late fall tests (thermal test exposure = 25.2°C). 



The potential for laboratory predator-prey tests as behavioral bioassays to 

 assess sublethal pollutant stress is evaluated, with consideration given to the 

 several techniques developed to date. 



INTRODUCTION 



The present study was undertaken to develop a laboratory predator-prey 

 test system to evaluate relative ecological fitness of larval fish following a 

 sublethal pollutant stress. Thermal shock was employed in this case. Behavioral 

 bioassays are considered to be more sensitive indicators of low-level stress in 

 comparison with mortality bioassays (22). Hence, behavioral tests should serve 

 to identify the less conspicuous, but nonetheless important limiting effect that 

 real-world sublethal stress can have on organisms. In the case of laboratory 



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