Static water sink rate trials to improve understanding of sink rates estimated at sea

Sink rate trials conducted in still water under controlled conditions are a useful adjunct to sink rates collected in at-sea experiments. Static water trials eliminate the variances associated with data collected at sea and can be useful in informing the decision making process regarding the design of at-sea experiments and the interpretation of findings. In this report we describe the results of trials designed to examine the effect on the sink rates of baited hooks of 1) bait thaw status; and 2) bait species, bait size (length and mass) and hooking position in baits. We also completed trials on the effect of attaching star oddi DC Centi time-depth recorders (TDRs) on sink rates, and the effect of Wildlife Computers Mk9 TDRs on sink rates. The results of the last two trials are presented in the appendices of Robertson et al., (in press) and Robertson, et al., (submitted), respectively.

This report presents information on items 1 and 2, which are addressed separately below. The trials were conducted in a 3 m high, 2 m diameter, tank of stationary seawater at the Australian Antarctic Division in August 2009.