Killer tags: estimating the effect of eavesdropping predators in acoustic tagging projects on fish

Deecke, Volker B., Stansbury, Amanda L., Götz, Thomas, Smout, Sophie and Janik, Vincent M. (2015) Killer tags: estimating the effect of eavesdropping predators in acoustic tagging projects on fish. In: The Society for Marine Mammalology 21st Biennial Conference on the Biology of Marine Mammals, 13-18 December 2015, San Francisco, California, USA. (Unpublished) Full text not available from this repository.

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Abstract

Ultrasonic coded transmitters (UCTs) operating at frequencies inaudible to humans are widely used to study behavior and life history of fishes including some highly endangered stocks. Recent research has demonstrated that most marine mammals can detect the transmission signal and that some species will spontaneously learn to associate such signals with a food reward. Sensory data from pinnipeds suggest they are able to detect fish tagged with UCTs at functional distances of several tens of meters. Detection by odontocetes may well occur over several hundred meters. In addition to detection range, mortality inflicted by eavesdropping predators depends on the encounter-rate of individual predators with tagged fish, as well as the predator’s learning rate. We present the results of a meta-analysis to determine the number of studies using UCTs in situations where predator eavesdropping may be an issue and to determine the number of tagged fish. We also use agent-based models to estimate mortality under different predation and learning scenarios in two Canadian study systems: Gray seals predating on gadid fish on the Scotian Shelf, and killer whales feeding on salmonids in the coastal waters of British Columbia. These models use predator and prey movement data from the published literature to estimate encounter rates and compare these to exposure rates known to cause associative learning in empirical studies. The meta-analysis showed that, while globally at low densities, the use of UTCs in some areas has reached levels where predator eavesdropping could be a serious concern. The agent-based models suggest that some predators in both systems experience tagged fish at sufficiently high frequencies to facilitate a dinner-bell effect. While the results of these models must be seen as preliminary, they clearly indicate that further research is required to investigate tag-effects of UTCs caused by eavesdropping predators.

Item Type: Conference or Workshop Item (Paper)
Departments: Centre for Wildlife Conservation
Depositing User: Anna Lupton
Date Deposited: 10 May 2016 10:27
Last Modified: 31 Jul 2017 10:29
URI: http://insight.cumbria.ac.uk/id/eprint/2129

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