The level of predation used as an indicator of tagging/handling effects

Abstract

In most telemetry studies, there can be adverse effects of capture, handling and tagging. Possible tagging effects include impaired competitive performance and predator avoidance. These effects are not easily studied in the laboratory, and field studies include too much variability to test such indirect effects. Predation experiments were conducted in four outdoor ponds to test for the possible effects of transport/handling and tagging by surgical implanting. Pikeperch, Sander lucioperca (L.), were used as predators and trout, Salmo trutta (L.), as prey. The level of predation was highly dependant on water temperature, but no significant difference was seen in the level of predation between any of the treatment and control groups. This can be interpreted as a lack of effect or as a failure to detect such effect under less than field conditions.

Effects of tagging on migration behaviour, survival and growth of hatchery‐reared Atlantic salmon smolts

“…However, differences were not observed in predation between smolts tagged with dummy radio transmitters and untagged ones in experimental conditions (Jepsen et al . ), lending support to similar, earlier results for radio‐tagged and untagged smolts in a study conducted in a Danish reservoir (Jepsen et al . ).…”

Stocking location and predation by marine fishes affect survival of hatchery‐reared Atlantic salmon smolts

“…Other mortality factors could include tagging effects, but these transmitters were not expected to cause high mortality as studies have shown no or little negative effects of similar surgical implants (Jepsen et al. 2006, 2008a,b).…”

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

“…Thus, this proportion takes into account the number of PIT tags regurgitated outside the colony as well as undetected tags in the colony (see also Frechette et al., ). The overall question of whether capture, handling and tagging of smolts increase the probability of being eaten by a cormorant is relevant, but hard to resolve (see Jepsen, Christoffersen & Munksgaard, ). However, since a range of different methods provided similar predation estimates suggests that this was not a major problem in these studies.…”