Warner Lake Ecological Observatory: Insights into Fish Behaviour Using a Whole-Lake Three-Dimensional Acoustic Telemetry Array K.C. Hanson 1, S.J. Cooke 2, C.D. Suski 3, G. Niezgoda 4, F.J.S. Phelan 5, R. Tinline 6, C.T. Hasler 6 and D.P. Philipp 1 1 University of Illinois at Urbana-Champaign; 2 University of British Columbia; 3 Ontario Ministry of Natural Resources; 4 Lotek Wireless Inc.; 5 Queen’s University Biological Station; 6 Queen’s University Observatory Consortium ABSTRACT A whole-lake acoustic telemetry array was utilized to monitor the three- dimensional position of 20 largemouth bass (Micropterus salmoides) as part of an ecological observatory. Code discrimination multiple access (CDMA) technology enabled the simultaneous monitoring of the 20 transmitters (equipped with pressure and temperature sensors) at 15 sec intervals with sub-meter accuracy. We used three representative days between November 2003 and April 2004 to evaluate the behaviour of fish across different temporal and spatial scales. The distance moved by largemouth bass, assessed both on a daily and hourly basis, varied by season and was positively correlated with water temperature. Daily movement rates were 2.69 ± 1.45 km/day in late November (average daily water temperature 5.9ºC), 2.24 ± 0.73 km/day in early January (5.1ºC), and 7.28 ± 2.62 km/day in April (7.7ºC). Interestingly, daily movement rates varied by as much as 25 fold among individuals. Visualization of fish swimming paths revealed that some fish occupied discrete areas and made only localized movements, whereas other individuals made lengthier journeys covering much of the lake in periods of as little as one day. Analysis of fish behaviour at a finer temporal scale revealed that during the winter, fish spend more than 95% of their time swimming at speeds less than 0.1 m/sec (0.07 ± 0.24 m/sec). During late fall, and especially in spring, swimming speeds were higher with mean swimming speeds of 0.11 ± 0.27 m/sec and 0.19 ± 0.29 m/sec, respectively. An analysis of associations (average hourly X,Y,Z position of two fish with in 2 m of each other) among the 20 fish was also carried out using the array. It was found that fish do in fact associate in groups and there is a spatial component to the associations. This study identifies the importance of evaluating fish activity at multiple spatial (whole lake to sub-meter position) and temporal (seasonal to seconds) scales and illustrates the potential of CDMA telemetry to yield such data. Warner Lake Ecological Observatory The Warner Lake Ecological Observatory represents a unique approach to the address questions concerning the ecology of freshwater fish on both an individual and population level on a whole-lake scale. Continuous, remote monitoring of tagged individuals’ movements allow for the creation of a massive, detailed, and extremely accurate database of largemouth bass movements across multiple seasons with comparatively minimal effort expended on the part of researchers CDMA protocols allow multiple individuals to be implanted with transmitters that all function on the same frequency and then tracked simultaneously The current database of transmissions represents one of the most comprehensive and detailed assessments of largemouth bass movements and behaviours across multiple seasons METHODS In 2003, the Warner Lake Ecological Observatory, an acoustic telemetry array consisting of 13 moored hydrophones and two fixed receiving stations, was donated and installed at Queen’s University Biological Station The system utilizes CDMA protocols to simultaneously monitor the movements of multiple individuals implanted with transmitters on the same frequency In November 2003, as a pilot study, twenty two adult largemouth bass were implanted with acoustic transmitters that provide information on three dimensional position and temperature with a transmission rate of every 15 seconds FIG 2. FINDINGS Spatial and Temporal Relations Daily distance traveled by individual for all seasons Surgical implantation of an acoustic transmitter into the intraperitoneal cavity Instantaneous swimming speeds by position estimates for two individuals across seasons Kernel Density Estimation of the location of the associations. FIG 3. FIG 1 Transmitter Implantation and Release Live release of a telemetered largemouth bass McQuitty Linkage analysis of the groups of associating fish and their members Inter-individual Associations Tracks of six individual largemouth bass on April 13, 2004 Average depth, temperature, and daily distance traveled across the Winter season,