Discovery rate is assumed to be approximately equal in all methods cited 
here since exposure of all prey groups to the predators is complete and equal. 
This parameter is best measured by recording the reactive distance to the prey 
item (Beukema, 5), a difficult task which is not addressed in any of the above 
techniques. 
Attack rate can influence differential predation rate in that certain 
characteristics of the prey may be perceived by the predator and produce 
active selection. This behavior could occur in predation tests where 
simultaneous introduction of treated and control prey groups occur, as in the 
methods employed by Bams (2), Coutant (8), and Kania and O’Hara (16). 
However, as Bams noted, this parameter cannot be quantified by these 
methods because group identity of individual prey is not discernible during 
attacks. 
Differences in capture rate between prey groups are a result of differences in 
prey ability to evade an attacking predator. The techniques used by Bams (2), 
Coutant (8), and Kania and O’Hara (16) cannot discern between differences in 
capture rate and differences in attack rate since the overall result of predation 
is measured, and not individual attacks and captures. It is in this regard that the 
method devised by Yocum and Edsall (27) is superior, because it specifically 
measures the actual instantaneous predation rate as affected by changes in the 
rate of capture. Although Sylvester (25) also measured rate of capture (in 
terms of mean survival time), Yocum and Edsall found excessive variance 
between predator groups in time-to-capture when using his method. Of the 
various techniques, those of Yocum and Edsall (27), Bams (2) and Coutant (8) 
are considered best suited for laboratory predator-prey studies. The technique 
used by Kania and O’Hara (16), is similar to that of Coutant and Bams, but 
with the addition of an escape area. This modification limits its application to 
those prey species with a specialized behavioral characteristic of shallow water 
refuge. Also, there is a probable complication of learning, as prey become 
familiar with the predator’s area, and the “safe”, shallow, screened area used in 
the tests. Finally, the 60 hour test duration is fairly lengthy. 
In this particular study with larval fish prey, Bams’ (and Coutant’s) method 
of simultaneous presentation of prey from different treatment groups could 
not be utilized, as a tag to distinguish prey treatment groups is necessary. 
Common methods for identification, such as fin clipping and cauterization 
branding, were not feasible with larval prey. A visual dye is unacceptable 
because of potential alteration to predator-prey relationships due to 
conspicuousness of prey and color preferences in the predator. A number of 
fluorescent dyes were tested, but successful dyes were found to alter normal 
behavior in fish larvae (Pseudopleuronectes americanus). Efforts to label fish 
larvae with a radioisotope were also unsuccessful. Due to these difficulties 
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