We conducted all experimental trials in 50 gallon (ca. 190 l) acrylic aquarium tanks (91.5 \u00d7 38 \u00d7 51 cm) with continuous flow-through seawater systems. Food was withheld from predators for 24 h prior to observation to ensure predator response to the presence of prey. Tanks were divided in half with a removable central barrier of solid aluminum (Fig. 1). We released a single predator into one side of the tank and placed 2 basslets in the other side. Basslets were held in identical small glass containers (~500 ml) with mesh covers (1 basslet per container) positioned in each corner of the tank. These prey containers ensured that predators were able to receive both visual and chemical cues from basslets, but could neither make physical contact nor consume any basslets.
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To determine whether the preference of predators for basslets was driven by basslet species (fairy and blackcap) or basslet size (small and large: 1.7\u20132.5 and 3.5\u20135.2 cm TL, respectively) we presented pairs of basslets in cross-factored combinations of the 2 variables, resulting in the following treatments: (1) small fairy and large fairy, (2) small blackcap and large blackcap, (3) small fairy and small blackcap, (4) large fairy and large blackcap, (5) small fairy and large blackcap, and (6) large fairy and small blackcap. In addition to randomizing the order of basslet treatments presented to each predator, we also randomized the corner of the tank basslets were placed in every time a treatment was presented.
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Once the predator and basslets were in their respective sides of the tank, we allowed them to acclimate for 20 min, after which we removed the central barrier and observed the predator\u2019s behavior for 10 min. Observations were performed either in person (74 lionfish trials; 73 graysby trials) or filmed with a digital video camera (16 lionfish trials; 17 graysby trials) positioned outside of the tank. During each 10 min trial, we recorded (1) which basslet the predator hunted first (initial hunting preference); (2) the number of times the predator\u2019s mouth made physical contact with each glass container (number of strikes); and (3) the amount of time the predator hunted each basslet (hunting time). We defined the hunting behavior of lionfish as occurring when an individual directly faced a basslet with flared pectoral fins and/or blew pulsed jets of water towards a basslet (Cure et al. 2012). We characterized graysby hunting behavior as occurring when an individual positioned itself near a basslet (<10 cm in this experiment) while directly facing the basslet (Webster 2004).
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At the conclusion of the 10 min trial, we separated the predator from the basslets and placed the central barrier back in the tank. A new combination of basslets were placed in the glass containers, and all fish were allowed to acclimate for 20 min before removing the barrier and observing predator response for another 10 min. This procedure was repeated until all 6 basslet treatments had been presented to each predator in random order.
Behavioral response of invasive lionfish versus native grouper when presented with two congeneric prey fishes (fairy and blackcap basslets) in aquaria.
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For related datasets, please visit the project link: https://www.bco-dmo.org/project/561017
When testing for significant differences in predator response between fairy versus blackcap basslets, we analyzed only the 4 treatments where predators were presented with 2 different basslet species (lionfish: n = 11; graysby: n = 11). Similarly, we analyzed the 4\u00a0treatments where we presented predators with 2 bass lets differing in size (small versus large) when comparing predator response between basslet sizes (lionfish: n = 13, graysby: n = 12). If a predator did not display any predatory behavior during any of the 4 treatments described in the treatment groupings above, then the individual was dropped from that respective group prior to analysis (resulting in the final sample sizes reported above).
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BCO-DMO Processing Notes:
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- reformatted column names to comply with BCO-DMO standards
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