A context analysis of bobbing and fin‐flicking in a small marine benthic fish

Abstract

Most antipredator strategies increase survival of individuals by signaling to predators, by reducing the chances of being recognized as prey, or by bewildering a predator's perception. In fish, bobbing and fin‐flicking are commonly considered as pursuit‐deterrent behaviors that signal a predator that it has been detected and thus lost its surprise‐attack advantage. Yet, very few studies assessed whether such behavioral traits are restricted to the visual presence of a predator. In this study, we used the yellow black‐headed triplefin Tripterygion delaisi to investigate the association between these behaviors and the visual exposure to (a) a black scorpionfish predator (Scorpaena porcus), (b) a stone of a size similar to that of S. porcus, (c) a conspecific, and (d) a harmless heterospecific combtooth blenny (Parablennius sanguinolentus). We used a laboratory‐controlled experiment with freshly caught fish designed to test for differences in visual cues only. Distance kept by the focal fish to each stimulus and frequency of bobbing and fin‐flicking were recorded. Triplefins kept greater distance from the stimulus compartment when a scorpionfish predator was visible. Bobbing was more frequent in the visual presence of a scorpionfish, but also shown toward the other stimuli. However, fin flicks were equally abundant across all stimuli. Both behaviors decreased in frequency over time suggesting that triplefin become gradually comfortable in a nonchanging new environment. We discuss why bobbing and fin‐flicking are not exclusive pursuit‐deterrent behaviors in this species, and propose additional nonexclusive functions such as enhancing depth perception by parallax motion (bobbing) or signaling vigilance (fin‐flicking).

Scorpionfish adjust skin pattern contrast on different backgrounds

“…We used D65 as illuminant because fish adjusted to backgrounds under this spectrum. We modelled the vision of the yellow black‐faced blenny Tripterygion delaisi , a common prey species of scorpionfish in the Mediterranean Sea (Santon et al., 2021 ), following previous studies (Bitton et al., 2017 ; John et al., 2023 ; Santon et al., 2020 ). T. delaisi has single cones with average peak sensitivity at 468 nm, and double cones with average sensitivity peaking at 517 and 530 nm (Bitton et al., 2017 ).…”

“…We defined the luminance channel as the average cone catches of the two longer wavelength‐sensitive cones, as fish likely perceive achromatic (luminance) contrasts through this channel (Lythgoe, 1979 ). The routine further processed the images to adjust for T. delaisi foveal spatial acuity of 7 cycles per degree (Fritsch et al., 2017 ; Santon et al., 2019 ), for a viewing distance of 20 cm (a relevant viewing distance in nature (Santon et al., 2021 )), by using the Gaussian Acuity Control and the Receptor Noise Limited (RNL) Ranked Filter functions of the MICA toolbox (van den Berg et al., 2020 ). We then ran a granularity (pattern energy) analysis on the fish body using the ‘Pattern Colour & Luminance Measurements’ function of the toolbox (Troscianko & Stevens, 2015 ).…”

A versatile workflow for linear modelling in R

“…N values are the number of observation pairs in the dataset within each distance step indicated on the x-axis. Dataset reworked fromSanton et al (2021).…”