DOI: 10.5061/dryad.p8cz8w9zh
title: When is it safe to go home? Post-predation assessment of risk and safety when personal information conflicts with social cues

description: Navigating the risk of predation is a major driver of behavioral
 decision-making in small fishes. Fish use personal information from
 olfactory and visual indicators of risk, and also rely upon social cues to
 inform behavioral trade-offs between risk avoidance and fitness-positive
 activities such as foraging. Here, fathead minnows (Pimephales promelas),
 were captured, clipped, and released at 48 field sites chemically labeled
 with either fathead minnow alarm cue (high risk) or water (low risk). We
 removed the chemical label after 2 h, then monitored area use by clipped
 and non-clipped fish. In addition, a shoal was placed in traps in half of
 the risky and half of the safe locations as a visual social cue of safety.
 We caught 2919 fish in the first sample, of which 594 were fathead
 minnows. These were clipped and released. The second sample caught 1500
 fish, of which 164 were fathead minnows including 11 bearing marks from
 the first sample. Fathead minnows and northern redbelly dace in the
 general community, which lacked personal information about risk status
 associated with trap sites, avoided areas previously labeled with alarm
 cues for at least 2 h after the source of alarm cue was removed, unless an
 experimental shoal was present at the risky site, in which case they
 joined the shoal in the trap. Clipped fathead minnows with direct personal
 knowledge of risk showed a significant shift away from areas labeled with
 conspecific alarm cues and a significant attraction toward sites seeded
 with a shoal. Moreover, unlike fish in the general community, clipped
 fathead minnows were not influenced by experimental shoals at sites
 previously labeled as risky. These data indicate that the influence of
 social cues on safety depends on whether individual minnows have access to
 recent personal information about risk assessment.
description: <em>Preparation of chemical stimuli</em>
 Chemical alarm cues were collected from 10 adult fathead minnows
 (mean ± 1 SE total length = 65.5 ± 1.3 mm) collected by seine net from
 Deming Lake a few days before the field experiment. Fish were euthanized
 by an overdose of methane tricaine sulfate (500 mg/L MS222) and cervical
 dislocation (University of Minnesota IACUC protocol #2103-38900A). We
 measured the total length and then removed the skin from each side of the
 fish. The length and height of each skin fillet were measured before
 placing the fillets into a beaker of reverse-osmosis deionized (RODI)
 water resting on a bed of crushed ice. Keeping the solution cold during
 skin collection minimized the biochemical degradation of alarm cues. A
 total of 61 cm<sup>2</sup> was collected. We used an immersive
 blender to homogenize skin fillets in two bouts of 30 s to simulate
 predation by rupturing epidermal cells. The resulting homogenate was
 filtered through cheesecloth to remove connective tissue and then diluted
 to a final volume of 480 mL with RODI water. Skin extract solution was
 infused into 24 blocks of cellulose sponge (38 x 36 x 50 mm). Each sponge
 block received 20 mL of skin extract solution, representing the equivalent
 of about 2.5 cm<sup>2</sup> of fathead minnow skin per sponge.
 An additional 24 sponges were prepared and infused with 20 mL of blank
 RODI water to serve as a control. All sponges were placed in labeled bags
 and frozen at -20 °C until needed. <em>Shoal
 treatment</em> Shoals comprised five fish, three
 fathead minnows, and two blacknose shiners. The initial plan to use a
 shoal of five fathead minnows was modified on the day of the experiment
 because we could not collect a sufficient number of fathead minnows to
 apportion five fathead minnows per shoal. Earlier work has demonstrated
 that fathead minnows respond to shoals of conspecifics (Wisenden et al.
 2003) and to shoals of blacknose shiners (Wisenden et al. 2023). Fathead
 minnows and blacknose shiners used for test shoals were collected by seine
 net from Deming Lake the day before testing. These fish were held
 overnight at the University of Minnesota Itasca Biological Station and
 Laboratories. <em>Experimental
 protocol</em> On May 25, 2023, we placed 48
 unbaited Gee’s minnow traps around the perimeter of Deming Lake, placed
 approximately 10 m apart. Previous work demonstrated that traps placed
 more than 8 m apart do not influence each other (Wisenden 2008). Traps
 were set in groups of eight to provide for two replicates of the four
 treatment combinations (Alarm cue – shoal, Water – shoal, Alarm cue – no
 shoal, Water – no shoal) to control for spatial and temporal variation in
 littoral habitat (Fig. 1A, Table 1). All eight traps within each grouping
 were set simultaneously, approximately 1 – 2 m from shore in a depth
 ranging from 0.3 – 1.5 m, and secured to riparian vegetation with rope.
 After setting each group, we waited 15 min before setting the next group
 of eight traps. In this way, six groups comprising a total of 48 traps
 were set over 75 min. We pulled the first block of traps at the 120-minute
 mark giving ourselves 15 min to process the catch before the traps in the
 next block had been fishing for 120 min. In this way, fishing time for all
 traps was held constant at 120 min. If excessive processing time required
 delaying the pulling of the next group of traps (which was never more than
 a few minutes), the fishing time of all treatments was affected
 equally. At the 120-min mark, we pulled each trap,
 disconnected the clip from the minnow trap, attached the clip to a
 weighted sponge (Fig. 1B) containing either a frozen alarm cue or blank
 water control, and placed the sponge in the lake in the same location the
 trap had been. For each trap, we counted the number of fish caught by
 species. These data represent the “pre-sponge” use of each area. Fathead
 minnows received one of four fin clips, each representing one treatment
 combination (Fig. 1A, Table 1). All fish were returned to the lake
 directly over the sponge to ensure that they detected the chemical cue
 being released by the sponge. At the 240-minute mark,
 we returned to the first group of traps, removed the sponges reattached,
 and reset the trap in the same location. Traps now contained a 973-mL
 glass jar (Fig. 1B) with either a mixed-species shoal of three fathead
 minnows and two blacknose shiners (shoal treatment) or nothing (control).
 Five fish fit into a 973-mL jar at natural shoaling density and a shoal of
 five has successfully attracted fathead minnows into traps in earlier
 experiments (Wisenden et al. 1995b, 2003, 2023). Fathead minnows and
 blacknose shiners form mixed-species shoals and earlier work has shown
 that fathead minnows are drawn into traps by the presence of a five-fish
 shoal if the shoal is of fathead minnows (Wisenden et al. 2003) or
 blacknose shiners (Wisenden et al. 2023). The jar lids were replaced with
 window screen mesh to allow the free exchange of lake water into and out
 of the jar. We reset the remainder of the traps in groups of eight with
 jars at 15-minute intervals. At the 360-minute mark, we
 began pulling traps in groups of eight at 15-minute intervals, as before.
 We counted the number of fish caught by species and inspected fathead
 minnows for the presence of fin clips applied to fish caught in the first
 sample. These data represent the first post-sponge use of areas previously
 labeled by sponges as either risky or safe. All captured fish were
 immediately returned to the lake and the traps and jars were reset for a
 second post-sponge measure of area use. At the 480-min mark, we pulled the
 traps, counted fish by species, and noted the presence of clipped fathead
 minnows. The mean fishing time for traps was 126 ±
 2.3 min (n = six groups of eight traps) for the pre-sponge sample, sponges
 were in the water for 121 ± 0.8 min before being removed, traps for the
 first post-sponge sample were in the lake for 122 ± 1.6 min, and traps for
 the second post-sponge sample were left in the water for a mean of 106 ±
 3.0 min. <em>Statistical
 analysis</em> Catch data were not normally
 distributed (Kolmogorov-Smirnoff tests, <em>p</em> &lt;
 0.05). We rank-transformed catch data for each species across the 48 traps
 within each sample. Separate rankings were performed for each sample. We
 then tested for independent and interactive effects of the chemical label
 by sponge (alarm cue or water) and presence of a shoal (shoal or no shoal)
 using separate factorial ANOVAs for fathead minnows, redbelly dace,
 blacknosed shiners pumpkinseed sunfish, and brook stickleback. The effect
 of chemical information (sponge treatment) and the effect of visual
 information (jar shoal treatment) on recapture rates of clipped fathead
 minnows were tested using a binomial test. Data were analyzed using SPSS®
 v 28.0.
description: # When is it safe to go home? Post-predation assessment of risk and safety
 when personal information conflicts with social cues This Excel file has
 two tabs. The first tab contains the catch data for the first (pre-sponge,
 no shoals) and second (post-sponge, with jars). Data shown are the number
 of fish caught by species, and the rank of that catch total within
 species, within the sample. The second tab shows the recapture rates of
 clipped fish in the second sample. Key to variables in the dataset: ###
 Sheet 1 Catch data * Set = replicate grouping of traps * SpongeA1W2 =
 chemical cue in sponge blocks used to label each site, code 1 is = fathead
 minnow alarm cue, code 3 is W = blank water control * ShoalY1N2 = whether
 an experimental shoal was added in post-sponge samples, code 1 = yes, code
 2 = no * Clip = the fin clip applied to fathead minnows captured in the
 pre-sponge sample, LP = left pectoral fin, RP = right pectoral fin, LV =
 left pelvic fin, RV = right pelvic fin * FHM1 = the number of fathead
 minnows captured in the first 2-h sample * fhm1rank = rank of the number
 of fathead minnows caught relative to the other sites within the presponge
 sample * RBD1 = the number of redbelly dace captured in the first 2-h
 sample * rbd1rank = rank of the number of fathead minnows caught relative
 to the other sites within the presponge sample * BNS1 = the number of
 blacknose shiners captured in the first 2-h sample * bns1rank = rank of
 the number of blacknose shiners caught relative to the other sites within
 the presponge sample * PKS1 = the number of pumpkinseed sunfish captured
 in the first 2-h sample * pks1rank = rank of the number of pumpkinseed
 sunfish caught relative to the other sites within the presponge sample *
 SB1 = the number of brook stickleback captured in the first 2-h sample *
 sb1rank = rank of the number of brook stickleback caught relative to the
 other sites within the presponge sample * FHM2 = the number of fathead
 minnows captured in the first post-sponge sample * fhm2rank = rank of the
 number of fathead minnows caught relative to the other sites within the
 first post-sponge sample * RBD2 = the number of redbelly dace captured in
 the first post-sponge sample * rbd2rank = rank of the number of redbelly
 dace caught relative to the other sites within the first post-sponge
 sample * BNS2 = the number of blacknose shiners captured in the first
 post-sponge sample * bns2rank = rank of the number of blacknose shiners
 caught relative to the other sites within the first post-sponge sample *
 PKS2 = the number of pumpkinseed sunfish captured in the first post-sponge
 sample * pks2rank = rank of the number of pumpkinseed sunfish caught
 relative to the other sites within the first post-sponge sample * SB2 =
 the number of brook stickleback captured in the first post-sponge sample *
 sb2rank = rank of the number of brook stickleback caught relative to the
 other sites within the first post-sponge sample ### Sheet 2 Recaptured
 fathead minnows: * Set = replicate grouping of traps * SpongeA1W2 =
 chemical cue in sponge blocks used to label each site, code 1 is = fathead
 minnow alarm cue, code 3 is W = blank water control * ShoalY1N2 = whether
 an experimental shoal was added in post-sponge samples, code 1 = yes, code
 2 = no * Clip = the fin clip applied to fathead minnows captured in the
 presponge sample, LP = left pectoral fin, RP = right pectoral fin, LV =
 left pelvic fin, RV = right pelvic fin * FHM1 = total number of clipped
 and unclipped fathead minnows captured in the first post-sponge sample *
 LP = number of fathead minnows bearing an LP clip from the first sample *
 RP = number of fathead minnows bearing an RP clip from the first sample *
 LV = number of fathead minnows bearing an LV clip from the first sample *
 RV = number of fathead minnows bearing an RV clip from the first sample