Association behavior between sand tiger sharks and round scad is driven by mesopredators

Abstract

In marine systems, behaviorally-mediated indirect interactions between prey, mesopredators, and higher trophic-level, large predators are less commonly investigated than other ecologic interactions, likely because of inherent difficulties associated with making observations. Underwater videos (n = 216) from SharkCam, a camera installation sited beneath Frying Pan Tower, a decommissioned light house and platform, on a natural, hard bottom site approximately 50 km off Cape Fear, North Carolina, were used to investigate association behavior of round scad Decapterus punctatus around sand tiger sharks Carcharias taurus. Videos containing sand tiger sharks were analyzed for the simultaneous presence of round scad, and six species of scad mesopredators, with scad-shark interactions assigned to one of three categories of association: no visible interaction, loosely associated, or tightly associated. The likelihood of scad being loosely or tightly associated with sharks was significantly higher in the presence of scad mesopredators, suggesting that sharks provide a predation refuge for scad. This behaviorally-mediated indirect interaction has important implications for trophic energy transfer and mesopredator control on hard bottoms, as scad are one of the most abundant planktivorous fish on hard bottoms in the western Atlantic Ocean. Although we were not able to provide statistical evidence that sand tiger sharks also benefit from this association behavior, we have clear video evidence that round scad association conceals and attracts mesopredators, enhancing predation opportunities for sand tiger sharks. These interactions potentially yield additional trophic consequences to this unique association and highlight the value of exploring behaviorally-mediated interactions in marine communities.

New Insights About the Behavioral Ecology of the Coelacanth Latimeria chalumnae Video Recorded in the Absence of Humans Off South Africa

“…Our first attempt to place cameras to observe a daytime habitat of coelacanths provided an example of an alternative method to observe these habitats. Underwater video camera systems have been increasingly used in studies of marine fishes or marine biodiversity using baited, stationary, or moving camera systems (Mallet and Pelletier, 2014;Zarco-Perello and Enríquez, 2019;Piggott et al, 2020;Coleman and Burge, 2021). Our study suggests that fixed cameras may be a highly useful method for studying the communities of fishes that interact with coelacanths.…”

“…Sand tiger sharks are present in several specific regions worldwide, and their behaviors have been studied in some locations (e.g., Haulsee et al, 2016;Coleman and Burge, 2021). They are present along the southern and eastern parts of Africa up to about 15 • S, so they overlap with L. chalumnae; and they have a stable population where coelacanths are present off Sodwana Bay (Dicken et al, 2007;Klein et al, 2020).…”

Community science informs movement and reproductive ecology of sand tigers Carcharias taurus off North Carolina, United States of America

“…We also collected information about associations with parasites, commensals and other fish species. Data about sand tigers and intraspecific fish associations are currently being assessed (A. McClanahan, unpublished) and will add to work on sand tiger, round scad, and mesopredator associations reported by Coleman & Burge (2021).…”

“…Our findings are consistent with telemetry data from Marens (2021) showing Atlas, Caribsea, Aeolus, and Papoose in the central region had the longest residency of male as well as immature and pregnant female sand tiger sharks (ranging from hours to 75+ days) compared to the other two regions. Coleman and Burge (2021) quantified frequency of sand tiger shark occurrence at Frying Pan Tower in more than 1000 video clips from Nov 2014-Jan 2019, reliably finding them every year fall through winter.…”

“…Frying Pan Tower is situated above natural hard bottom habitat (Figure 1; NC Division of Marine Fisheries, 2022) in approximately 17 m of water at the seaward edge of Frying Pan Shoals. Additional details about the camera and setting are found in Burge and Harris (2021) and Coleman and Burge (2021). Still images from SharkCam were collected from a gallery of snapshots submitted by viewers, by extracting them from recorded video files, and as screenshots taken in real-time while technicians watched the live feed.…”