A new design for a submersible chronographic tethering device to record predation in different habitats

We describe a design for a submersible chronographic tethering device which can be used to measure the survival time of small tethered prey. This technique can be used to compare survival in different habitat types. We tested the tethering device using juvenile tiger prawns Penaeus semisulcatus both in the laboratory and field using 3 levels of shoot density of artificial seagrass (0, 15 and 60 shoots m(-2)). Tethering did not prevent burying behaviour in the laboratory. In the field, more prawns were taken from the 0 and 15 shoots m(-2) than the 60 shoots m(-2) treatment and prawns that were tethered in the 60 shoots m(-2) treatment also survived longer than those in the other treatments. This device should prove useful for estimating predation potential for a variety of small key prey among different habitats and seasons.