An Automated System for Monitoring Fish Activity Patterns

Abstract

Passive integrated transponder (PIT) tags potentially allow the automated recording of the movements of individual animals. Here we describe a system designed to log the activity patterns of fish that use a discrete refuge when they are not feeding. The system was demonstrated with juvenile salmonids, which in winter seek shelter during the day in crevices under stones in the streambed but emerge to feed at night. The PIT tag antennae monitored a tube connecting a refuge to a standard hatchery tank and recorded each movement of a fish in or out of the refuge. This method allowed the quantification of individual time budgets for a group of fish sharing the same tank. The efficiency of the system was high, but occasionally the direction of movement could only be ascertained by referring to the previous position of the fish. The technique revealed very synchronized movement by Atlantic salmon Salmo salar out of the refuge at dusk and into it at dawn and intermittent brief excursions from the refuge during daylight hours. The system could be adapted for any species that is large enough to be given a PIT tag and that uses a refuge or burrow (e.g., for breeding or predator avoidance).

Rearing conditions influence refuge use among over‐wintering Atlantic salmon juveniles

“…Similarly, in a near-natural manipulation, wild Atlantic salmon tested at a range of densities did not exceed on average 1·5 fish per refuge (Armstrong & Griffiths, 2001). These results differ markedly from those of other studies, in which up to 20 fish occupied each 1·3 l shelter (Burns et al, 1997;Metcalfe et al, 1999). There were many differences among these studies in the habitats and populations of fish.…”

“…There were many differences among these studies in the habitats and populations of fish. An important variable, which may explain between-study variation in the results, was that unlike the other studies, Burns et al (1997) and Metcalfe et al (1999) used hatchery-reared fish.…”

Effects of food availability on temporal activity patterns and growth of Atlantic salmon

“…Fraser, Metcalfe & Thorpe 1993; Fraser et al . 1995; Burns, Fraser & Metcalfe 1997; Gries et al . 1997; Valdimarsson et al .…”

“…However, despite lower foraging efficiency at night than during the day (Fraser & Metcalfe 1997), salmon are almost exclusively nocturnal during winter (Cunjak 1988; Fraser et al . 1993; Burns et al . 1997; Valdimarsson et al .…”

Density‐dependent refuge use among over‐wintering wild Atlantic salmon juveniles

“…However, tank-reared Atlantic salmon may exist in sub-gravel refuges at high densities, for example 20 fish per refuge (1·3 l) (Burns et al, 1997; ‡Author to whom correspondence should be addressed. Tel.…”