predator-prey tests, changes in prey escape success serve to indicate changes in 
ecological fitness, which can affect natural mortality rates in localized 
populations. 
MATERIALS AND METHODS 
For this study, larval prey species were restricted to those available from 
laboratory culture. Wild ichthyoplankton were not considered because of the 
potential for damage due to capture methods, and the difficulty in acquiring 
adequate numbers of a single species of the same age. The cultured larval prey 
species used were Menidia menidia and Paralichthys dentatus. Six hatched lots 
500/lot) of M. menidia were reared to six weeks of age and tested during 
this period. Studies with P. dentatus were limited to newly hatched larve only, 
as this species experiences high mortality at time of first feeding. All larvae 
were reared at the prevailing Narragansett Bay water temperature (M. menidia , 
summer—20.5 ±0.7°C;/ > . dentatus, late fall—15.1 ± 0.8°C). 
An attempt was made to correlate prey and predator species. Fundulus 
majalis , a carnivorous near-shore predator, was chosen as a spatially coexisting 
predator of estuarine larval fish (6). Larvae of P. dentatus are not highly 
correlated with near-shore predators since they are usually found offshore at 
hatching. However, this species was utilized to provide a larval fish with 
different swimming abilities. Paralichthys dentatus relies on high fecundity for 
successful development and eventual recruitment. Larvae of this reproductive 
strategy are usually weak-swimming relative to larvae of a species such as M. 
menidia , which has a lower fecundity, but relies on advanced morphological 
development and strong swimming capabilities at hatching. 
Biological variables controlled for this study include: reproductive condition 
of predator (a L:D 10:14 photoperiod was used to minimize reproductive 
development interference); nutritive condition (all predators were fed a mixed 
daily diet of Tetramarin flake food and adult frozen Artemia salina until 48 
hours prior to a test); predator size in relation to prey size (preliminary tests 
indicated selection of a predator size of 6-8 cm total length (TL)); feeding 
periodicity (all tests were performed at the same time of day); and hunger state 
(all predators were starved 48 hours prior to a test). 
Forty-eight hours prior to a test, each predator was placed into an 
experimental predation tank, which consisted of a polypropylene tube 30 cm 
diameter x 12.5 cm deep, with a clear Plexiglas bottom (Figure 19-1). Test 
tanks received a continuous flow of filtered seawater (y 400 ml/min.) pumped 
directly from Narragansett Bay. All predation tests occurred between 1300 and 
1500 hours at ambient bay water temperatures. 
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