The Effect of Environmental Variables on Capture Success of The Platypus Using Gill and Fyke Nets.

Abstract

Capture success of platypuses using gill and fyke nets over the period 1986-1993 has been assessed against a range of environmental variables using the Spearman's Rank Correlation Coefficient and in some cases simple linear regression models. Approximately 90% of all animals captured during this study have been netted between 1730 hours and 0I00 hours regardless of age or sex. The peak capture period during which approximately 60% of animals were captured is between 1730 and 2230 hours. Variables examined included; number of platypuses captured, giII and fyke net hours, number of nets used, time nets set up and taken down, maximum and minimum day temperatures, time of sunrise and sunset, moon phase, time of moon rise and set, cloud cover, wind and rain conditions during trapping, 24 hour rainfall history prior to netting and some flow data. The number of nets, netting time, rainfall within 24 hours and temperature conditions all effect the chance of platypus capture in fyke nets (p<0.05). The number of gill nets and the time they are utilised are both positively correlated with platypus captures (p<0.05). However, there are differences between sexes and age groups. Using gill nets, platypuses are more likely to be captured during clear nights and less likely to be captured during summer months. The probability of trapping males, females, adults and juveniles varies with the seasons.