The Response of Lake Trout to Manual Tracking

Abstract

The use of telemetry is widespread in fisheries research, and manual tracking of fish is considered acceptable for data collection. However, it has never been shown whether the use of boats with powered engines, which is common in manual tracking, influences the distribution and behavior of fish. We examined whether general boat traffic or focused manual tracking activity altered movement patterns of adult lake trout Salvelinus namaycush in a small boreal lake at the Experimental Lakes Area of northwestern Ontario, Canada. In the summer and fall of 2002, we used automated fish positioning systems to compare the behavior of lake trout during 1-h disturbance periods (boat traffic or manual tracking) with behavior in the preceding 1-h baseline periods (no disturbance). In addition, we compared behavioral differences of lake trout during disturbance and baseline periods (experimental trials) with a similar period of time when no boats were on the lake (control trials). This comparison allowed us to determine whether the observed changes in behavior during normal boat traffic or manual tracking were within the natural range of variation. Overall, we observed no effect of boat traffic or manual tracking on the depth, speed, and path predictability of lake trout. Similarly, the changes in lake trout behavior between the disturbance and baseline periods of the experimental trials were all within the natural range determined by control trials. The response of lake trout to manual tracking was not related to their proximity to the motorboat, both when lake trout were in deep water (6 m; summer) and when they were in shallow water (2 m; fall spawning season). The lack of significance of the relationship between patterns of fish behavior and manual tracking activity provides support for the continued use of this method in fisheries research.

A method of spatial correction for acoustic positioning biotelemetry

“…Unfortunately, this can result in areas that are often biologically important, such as nearshore regions, with positional data of low precision and accuracy. As a result, these data are often excluded from analyses, even after filtering to ensure the highest quality data [7,8].…”

“…The triads were linked to an onshore computer via radio link, which allowed for real-time monitoring of acoustic tag signals. A more complete description of the RAPT systems is provided by Blanchfield et al [7,13]. In Lake 375, two separate RAPT systems were in operation, one each in the north and south basins (Fig.…”

Seasonal habitat selection by lake trout (Salvelinus namaycush) in a small Canadian shield lake: constraints imposed by winter conditions

“…In the spring of 2002, ten adult lake trout were captured by angling and surgically implanted with coded, acoustic, pressure-sensing transmitters (Model V16P-4 L, Vemco Ltd, Halifax, Nova Scotia) (see Blanchfield et al 2005 andPlumb and for a more complete description of the transmitters and surgical procedures). Tagged lake trout were, on average, 445 mm in fork length (1 SD: ±16 mm; range: 427-480 mm), weighed 990 g (±152 g; range: 825-1,331 g) and were 6-30 years of age (Plumb and Blanchfield 2009).…”

“…1). Details on the operation of these systems can be found in Blanchfield et al (2005). We chose only those fish positions that met the highest detection criteria for our spatial analyses, as defined by the RAPT software.…”

“…summer), with fish mainly distributed at depths between 6 m and 15 m (Plumb and Blanchfield 2009). Here, we combine pelagic and spatial distribution data, collected using an automated positioning system (see Blanchfield et al 2005Blanchfield et al , 2009, to quantify seasonal changes in Fig. 1 Map showing the location of the Experimental Lakes Area (ELA; star) in northwestern Ontario, Canada.…”