Angling pressure and trout catchability: Behavioral observations of brown trout in two New Zealand backcountry rivers

Angling pressure is increasing in many recreational trout fisheries throughout the world. There is a strong perception among anglers that trout become harder to catch after being disturbed by other anglers, thus affecting the quality of their angling experience. However. there is little scientific evidence to support or refute this perception. We measured the response to angling pressure in two rivers in New Zealand: the remote Ugly River and the more heavily fished Owen River. Both of these rivers have fisheries for brown trout Salmo trutta. The numbers of trout seen and caught over the length of four 3-d angling trips were compared between rivers. The behavioral responses to angling of naive trout in the Ugly River were compared with those of Owen River trout and trout that had been angled previously from the Ugly River. The proportion of the trout population in the study reaches caught by two anglers after four 3-d trips was estimated as between 11% and 23% in the Owen River and tip to 47% in the Ugly River. The most marked behavioral response to angling pressure was in the Ugly River. where trout that had been caught and released or merely disturbed by anglers were rarely seen over the following days. No such hiding response was observed in the Owen River. A learning response was also evident, as trout that had been fished previously were more likely to be scared by anglers or required smaller, low-profile flies before being caught than naive trout. Faced with increasing angling pressure, anglers can perhaps cope with the observed learning response by improving their techniques to outsmart trout. However, the hiding response observed in the remote river indicates that controls on angling, such as access restrictions, may be required to maintain quality angling experiences in these wilderness fisheries.