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 (10°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 probabilities (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 comspicuous, but nonetheless important limiting effect that 
real-world sublethal stress can have on organisms. In the case of laboratory 
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