Electro-olfactory and behavioral responses of grass carp, bighead carp, silver carp, and black carp to chemical stimuli in laboratory exposures

Using juvenile individuals of four species of carp (Family: Cyprinidae), we tested the potential for two amino acids and one commercial bait stimulus to elicit an extracellular electro-olfactory response within the naris using gelatin-based electrodes. The amino acids alanine and lysine were tested on grass carp (Ctenopharyngodon idella), bighead carp (Hypophthalmichthys nobilis), silver carp (H. molitrix) and black carp (Mylopharyngodon piceus) to provide a comparison among compounds both within and among species. Each row in the electro-olfactogram (EOG) data set represents exposure to a single stimulant in a single fish. Each individual fish was exposed to all three stimulus solutions sequentially in a random order, representing a trial; each individual was a subject for exactly one trial. The response metric was the measured response peak, in millivolts, corrected by subtracting the mean baseline during exposure to well water 60 seconds prior to the stimulant response. The baseline-corrected, absolute value of the response to ultrapure, deionized (UDI or Nanopure) water immediately preceding and following a trial is also included. Other relevant factors that could influence measured individual response, such as nominal concentration of stimulants, fish mass, holding tank temperature, and flow rate of water and solutions over the naris are included. Identifying data, namely date of trial and an individual subject ID (equivalent to a trial ID), are also included. Expanding on the EOG study, we conducted behavior trials on the same four species of invasive carp in a laboratory setting between the dates of 07 July 2024 to 06 November 2024. The feeding stimulant and amino acids alanine and lysine were again used, as well as a fish food solution, to analyze how exposure may impact fish behavior, with a specific focus on avoidance and attraction. Each trial involved two individuals of the same species being exposed to one of the stimulant solutions and well water in a long exposure chamber which drained in the center to maintain a delineation between amino acid and the control water. For each combination of species (4 total) and compound solution (4 total), we performed 10 replicates, totaling 160 trials with each trial utilizing two fish (320 individuals). The tank and fish were recorded from overhead video cameras and fish movement and position within the tank determined using tracking software. After the software provided the initial tracking analysis, additional manual tracking was done to address any errors that occurred due to fish overlap. Data reported includes cumulative duration in percent of time spent on either side of the tank that would help indicate either attractant or avoidance behavior. Other relevant factors such as water temperatures of holding tanks, temperatures of the behavior tank before and after trials and individual fish length and mass were also included.