Tethering induces increased stress artifacts in social fish species

Abstract

Behaviour of juvenile mulloway Argyrosomus japonicus were investigated under laboratory conditions to determine the efficacy of estimating predation mortality using tethering. The occurrence and duration of stressed behaviour was evaluated for individual A. japonicus that were hooked but untethered, hooked and tethered and unhooked and untethered (free swimming), both in schools and in isolation. Tethered and hooked treatments showed a significantly higher incidence and duration of stressed behaviour over controls, but stressed behaviour was lower for hooked but untethered fish in the presence of a school. Artifacts associated with elevated stress may reduce the reliability of estimates of relative predation derived from tethering data for schooling fishes.

Post‐release monitoring of site and group fidelity in acoustically tagged stocked fish

“…Although the size of the acoustic tag in this study necessitated use of fish larger than those that are usually stocked (280 mm as opposed to 80 mm, Taylor & Piola 2008), these results are still relevant to informing stocking strategies as the biology and ecology of mulloway do not change substantially between these sizes (Gray & McDonall 1993;Taylor et al 2006a). In conjunction with previous research on diet (Taylor et al 2006a), key habitat preference (Taylor et al 2006b), prey dynamics (Taylor 2008), predatory impact (Taylor & Suthers 2008), release strategies ) and social dynamics (Pursche et al 2009), this study further improves our understanding of life histories and optimises stocking strategies for mulloway. By releasing at three spatially distinct sites within the river it has been shown that juvenile mulloway reside within the region about which they are released, although they demonstrate a preference for mid-river sites and intermediate salinities, similarly to wild con-specifics (Gray & McDonall 1993).…”

“…) and social dynamics (Pursche et al . ), this study further improves our understanding of life histories and optimises stocking strategies for mulloway. By releasing at three spatially distinct sites within the river it has been shown that juvenile mulloway reside within the region about which they are released, although they demonstrate a preference for mid‐river sites and intermediate salinities, similarly to wild con‐specifics (Gray & McDonall ).…”

“…1, Table 1). At each site, seven tagged fish were released within a school of 50 con-specifics (also sourced from the same sea cages), as mulloway are a schooling species and are most comfortable in a moderate sized school (Pursche et al 2009). Movements were tracked passively by the array for 6 months post-release.…”

Effect of closed v. intermittent‐flow respirometry on hypoxia tolerance in the shiner perch Cymatogaster aggregata

“…As C . aggregata is a gregarious species (Eschmeyer et al , ), four individuals collected on the same day as the focal individual were placed in the experimental aquarium around each of the respirometry chambers to avoid isolation stress (Pursche et al , ). This was done for all trials.…”

Tethering mobile aquatic organisms to measure predation: A renewed call for caution

“…That tethered prey are likely more vulnerable to predation than untethered free-swimming prey is widely recognised, and most authors acknowledge this by interpreting their results as estimates of relative predation pressure rather than absolute predation rates (Aronson, 1989). Restraining mobile prey on a tether may alter its behaviour and thereby alter the probability of detection or consumption by predators relative to naturally behaving un-tethered prey (Aronson, 1989;Zimmer-Faust et al, 1994;Halpin, 2000;Pursche et al, 2009). The usual assumption in field tethering studies, as articulated by Peterson and Black (1994), is that if experimental methods are applied identically across all treatments, then any artefacts of this intervention will also be equal among treatments, and thus not bias the observed patterns.…”