1 Robert C. MacWaters Interns in Aquatic Sciences BFS/Fisheries & Wildlife Dept., SUNY Cobleskill, NY. 2 BFS Visiting Researcher/Fisheries & Wildlife Dept., SUNY Cobleskill, NY.

Diel movements and habitat utilization of walleye (Sander vitreus)

in Otsego Lake, New York

John M. Byrne1, Daniel S Stich1, and John R. Foster2

Abstract: While habitat utilization and movements of walleye (Sander vitreus) have been studied extensively, previous data have been recorded primarily during daylight hours with sampling intervals of days or weeks. In this study, hourly movements and habitat utilization over 24-hour periods were observed in Otsego Lake, New York using sonic tags implanted in fourteen, 4-7 year old walleye. Hourly position data indicate that walleye move frequently, with occasional bursts of activity, resulting in an average movement of 220 m per hour with a cumulative movement of 5277 m per day. Hourly movements resulted in substantial differences in habitat utilization over what was observed from daily/weekly position data. While significant heterogeneity was recorded among habitat utilization of individuals, most walleye occurred in a variety of lake habitats over a 24-hour period, including shallow weedy areas, rocky drop offs and deep open waters. The utilization of both inshore and offshore habitats differed from most observations made in shallow, warm-water lakes and reservoirs. Hourly position data over entire 24-hour periods provide a much more accurate measure of walleye movement and habitat utilization than daily/weekly position data.

INTRODUCTION

The use of sonic and radio-biotelemetry techniques has great potential in revealing and contributing to the understanding of fish movements and habitat utilization. Walleye (Sander vitreus) movements have been studied extensively but these earlier studies have primarily been focused on shallow, weedy, warm-water reservoirs (Ager 1976; Ross and Winter 1975; Schlagenhaft and Murphy 1985; Johnson et al. 1988; Munger 2002), lakes (Holt et al. 1977; Nate et al. 2003; Foust and Haynes 2007), and rivers (Yu et al. 2003; DePhilip et al. 2005). Except for the recent work of Golding et al. (2007), Stich et al. (2008) and Decker et al. (2008) in Otsego Lake, walleye habitat utilization and movements have not been studied in deep, steep-sided, cold-water lakes.

Another drawback of previous walleye habitat utilization and movement studies was that

position data were collected primarily during daylight hours in sampling intervals of days or weeks. When position data were collected at hourly intervals throughout the entire diel cycle, substantial differences in movement patterns and habitat utilization were revealed (Stich et al. 2008). Diel abundance studies such as that of Yu et al. (2003) also demonstrate changes in habitat utilization by walleye living in riverine ecosystems.

New York State Department of Environmental Conservation stocks Oneida Lake strain walleye extensively in New York State lakes, reservoirs and rivers (Festa et al. 1987) and has been stocking walleye fingerlings into Otsego Lake since 2000 (Cornwell 2005). The purpose of this study is to characterize the diel movements and habitat utilization of these walleye in a deep, steep-sided, oligotrophic lake. In order to meet this goal, this study will build on the earlier work of Stich et al. (2008) and utilize hourly position data recorded over entire 24 hour periods.

MATERIALS AND METHODS

Otsego Lake (42.40ºN latitude, 74.55º W longitude) is a relatively young glaciated lake with a maximum depth of 51 m (Figure 1). While Otsego Lake has the physical characteristics of an oligotrophic lake, high nutrient input (Harman et al. 1997) has resulted in a water chemistry more typical of a mesotrophic lakes (Albright 2004, Harman et al. 1997). This has resulted in low light penetration, providing optimum walleye habitat (Chu et al. 2004).

This research utilizes walleye sonically tagged in 2008 as well as fish tagged in earlier studies by Stich et al. (2008), Decker et al. (2008) and Golding et al. (2007). These include five walleye tagged in 2006, which were captured 9-11 April in Cripple Creek and walleye tagged on 12 April 2007 at Cripple Creek, and on18 April 2007 at Leatherstocking Creek. In 2008 five walleye were tagged: one fish from Cripple Creek on 9 April 2008, two fish from Hayden Creek on 11 April 2008 and two fish in Shadow Brook on 13 April 2008. Figure 1 provides a map of Otsego Lake and identifies the collection sites. All fish captured in 2008 were implanted with 36 month Sonotronics Model CTT-83-I acoustic tags sensitive to temperature. Tag frequencies (hereafter to designate each fish), the pinger pattern, pulse interval and sex of each tagged fish is summarized in Table 1. Implantation methods followed Paragamian (1989).

Beginning in late June 2008, all walleye were tracked with Sonotronics DH-4 directional hydrophone and USR-96 receiver. Position was obtained with a Garmin Global Positioning System (GPS) unit. Water depth was recorded using a Vexilar FL-18 flasher. Position, temperature, and time of day were recorded for each walleye, and analyzed using Microsoft Excel and GIS. Fish 77D was tracked four times. Fish 73D, 74D, 69J were tracked twice, and Fish 76E, 70D, 71D, 71J were tracked once over 24 hours. Positions were recorded hourly over the entire diel cycle.

Depth of the fish in the water column was determined by comparing temperature of the

fish indicated from the tags to water column temperature records measured by the Biological Field Station. Sonotronics ACT (aural coded transmission) displays temperature as a function of a time interval (ms) on the receiver. Temperature data were analyzed using the following ACT coding: Temperature (˚C) = 45-((full scale pressure-550)/6).

Figure 1. Contour map of Otsego Lake, NY showing tagging sites at Cripple Creek, Hayden Creek, Leatherstocking Creek and Shadow Brook.

Table 1. Sonic tag frequencies of walleye used in this study.

Carrier Frequency

Sex Pinger Pattern

I.D. Pulse Interval (ms)

69E Male 3334 970

69J Male 5577 1210

70J** Male 5578 1200

70D* Female 334 860

71J** Female 5767 1230

71D Male 3436 1010

73J** Female 6678 1250

73D** Male 447 910

73E* Female 4858 1190

74D Female 3344 960

75D** Male 344 870

75E Female 3667 1090

76E Female 3557 1040

77D** Female 5787 1230 * Indicates CT-05-36-I depth tag (tagged in 2007) (Not used in this study) ** Indicates CTT-83-I temperature tag (tagged in 2007/2008). Unmarked frequencies indicate CT-82-2-I acoustic tags (tagged in 2006).

RESULTS

Walleye habitat distribution was highly variable over the course of the study. Fish were located in shallow and deep waters often within the same 24-hour period. For example, Fish 73D started in the shallows of Hyde Bay, traveled across some of the deepest portions of the lake, then moved along the rocky shoals of the west shore before ending up in the shallows below Five-mile Point (Figure 2). Home Range

Some fish had a relatively limited home range. Movements could be restricted to shallow weedy areas or deep water. For example, Fish 77D stayed in the deepest portion of the lake off of Five Mile point for the entire 24 hour period (Figure 2), while Fish 76E remained in the littoral zone of Clark Point (Figure 3). However, most of the walleye tracked (e.g. Fish 73D, 74D, 69J, all 76E) utilized a variety of lake habitats and showed the least home range affinity.

Figure 2. Movement of fish 73D from 21-22 August 2007.

Figure 3. Movement of Fish76E from 23-24 September 2008.

Figure 4. Movement of Fish77D from 25-26 June 2008.

Figure 5. Movement of Fish 74D from 23-24 October 2008.

Figure 6. Movement of Fish 69J from 6-7 October 2008.

Distance Travelled per Day Distance travelled per day has often been measured using position data collected every day to every few days. When position data were collected hourly, walleye were found to travel five times farther than was indicated by daily position data (Mann-Whitney U Test P < .01). When walleye were located only once per day the average distance travelled over a 24-hour period was only 1050 meters/day. However, when walleye were located hourly, then the cumulative average distance travelled over 24-hour periods increased to 5325 meters/day (Figure 7).

Distance traveled over 24 hours varied greatly between fish (Figure 7). Diel horizontal movement ranged from 2,787 meters (Fish 77D) to 9,607 meters (Fish 73D). The data suggest that males move more than females and that there are differences in average distance travelled per month. However, samples sizes were not large enough for statistical analysis.

Figure 7. Differences in distance travelled per day when measured using hourly position data versus daily position data.

Diel Patterns of Activity

The distance travelled per hour was quite variable among individual observations and fish. In order to reduce this variation, diel patterns of activity were examined by first calculating the distance travelled per hour, and then dividing that by the total distance travelled over a 24-hour period. From this figure the per cent of the daily distance travelled could be calculated (Figures 8-10).

Diel activity patterns amongst walleye observed were not correlated. There was only one

significant correlation among individual walleye, when the hourly distance travelled or the percent of daily distance travelled were compared (Figure 8). The activity pattern of walleye 71J and 74D was highly correlated (r = .837, P < .001) when they were observed on 23-24 October 2008.

While walleye moved frequently throughout the day, virtually all of the fifteen 24-hour

observations had periods of extraordinary activity (Figure 9). In over half of the 24 hour observations, walleye moved more than 30% of the daily distance they travelled in just two hours. Peak periods of activity occurred throughout the day, although there was a lull in peak activity from 1500-2000 hours. This afternoon-early evening lull in activity occurred over most observational periods June – October (Figure 10).

Figure 8. Diel activity pattern of walleye 69J and 74D were highly correlated on 23-24 October 2008.

Figure 9. Walleye diel activity patterns for fifteen 24-hour periods showing peak periods of activity.

There was no clear pattern of activity among the different observational periods. For

example, the hourly movements in September indicated no clear pattern. The three walleye observed 23-24 October had the strongest pattern, showing activity at night and relatively little activity during the day. However, the walleye observed two weeks earlier on 6-7 October had almost an opposite pattern of activity, being less active at night than during the day. In August walleye had yet another pattern being more active in the early morning hours and continuing to move right through the morning and early afternoon (Figure 10).

Figure 10. Diel activity patterns for walleye tracked for 24-hour periods on various dates.

Water Depth Utilization The water depth in which walleye were located (not the depth at which they were suspended; see Depth Preference below) ranged from the shallowest waters of Otsego Lake to the deepest waters. Some fish tended to remain in the same water depth throughout the diel cycle (Figure 11). In four observations walleye remained suspended over the deeper portions of the lake throughout the diel cycle (77D June, 77D September, 77 October and 70D October). While some walleye moved into shallow littoral zone waters (10 m or less), no fish stayed in the littoral zone consistently throughout the diel period. However, there were walleye that consistently stayed in the deeper portions of the lake (Figure 11).

Figure11a,b. Water depths where walleye were observed over a diel cycle.

Figure 11c,d. Water depths where walleye were observed over a diel cycle.

The pattern of habitat utilization by individual walleye was not consistent. For example, in August 2007 Fish 77D was observed in the shallow littoral moving into the edge of the littoral zone in the afternoon and evening, but in June, September and October, Fish 77D remained in the deepest waters of the lake throughout the diel cycle (Figure 5, 11a & b).

Some walleye (77D and 69J) spent at least some time in very shallow near-shore waters and some time in deeper water at the edge of the littoral zone. However, there was no consistent diel pattern. For example, in September Fish 76 was in shallow water in the early morning hours but moved into deeper water around dawn were it remained until dusk, when it moved back into the shallows (Figure 11a). In October, Fish 69J did the opposite, occurring in waters averaging 12-13 meters, moving into very shallow water at dawn, and the moving into deeper water at dusk. In August 2007 two walleye were in shallow water from midnight to noon, before moving off into deeper water for the next twelve hours (Figure 11B).

The habitat utilization of some walleye seemed to be correlated, showing similar patterns

over the same 24-hour cycle (Figure 11). In August 2007, walleye 70D, 71D and 73D were in deeper water from midnight to 500 hours, then moved into shallower water until mid-afternoon, before moving back out into deeper water (Figure 11a). On 23-24 October, the diel habitat utilization of walleye 71J and 74D were correlated (r = .623, P < .01). They were in deeper water until 200-300 hours, moved into shallower water until 700-800 hours, moved back into deeper water, and then back into the shallower water at 2100-2300 hours.

Depth Preference

Temperature and depth tags were utilized to determine the actual depth of suspension of walleye in the water column (Figure 12). Although Otsego Lake has a maximum depth of 51.2 meters, walleye were only found in depths down to 15 meters. In October, three fish (69J, 70J & 74D) had a strong depth preference of 2 meters and remained at that depth through the entire diel period. In June walleye 74D had a preference for a depth of 4 meters, diving out of that depth briefly at 2000 hours before returning. Three other walleye changed depth more frequently during the 24-hour observation period. Fish 69J had the most consistent pattern, occurring at 2 m of depth at night and at around 14 m during daylight hours.

While walleye were often suspended in the water column, some walleye (e.g. 69J) spent

some time in close proximity to the bottom (compare Figure 12 with Figure 7).

Temperature Preference Because of the limited number of temperature and depth tags, only seven diel

observations were made of temperature utilization. Sample sizes were thus too small to characterize walleye diel temperature preference. Overall, the average temperature preferred by walleye was 16˚ C, but fish occurred at temperatures ranging from 8.7˚ to 21.2˚C. Walleye preferred temperatures around 20˚C in June (one diel observation), 15˚C in October (four diel observations), and 16˚C in August (two diel observations). Day and night temperature selection did not differ. The average diurnal and nocturnal temperature preferred was 16°C

Figure 12. Location of walleye in the water column throughout the diel cycle.

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DISCUSSION

Habitat utilization and movements of Oneida Lake strain walleye have been studied in

Otsego Lake by Golding et al (2007) and Decker et al. (2008). Walleye habitat utilization and movement studies have also been carried out in Oneida Lake, a moderately shallow, cool-water, mesotrophic lake (Tarby 1977; Forney 1979), and Honoeye Lake, a shallow, warm-water, eutrophic lake (Foust and Haynes 2007). In these previous studies, walleye activity and distance travelled were grossly underestimated by using position data taken at sampling intervals of days or weeks. In this study, the distance traveled by Otsego Lake walleye over a 24 hour period was much greater than previously reported by Golding et al. (2007). The difference in distance traveled was primarily due to the data collection method. In this study, when the cumulative distance traveled from hourly samples was compared to the distance traveled between two sample locations 24 hours apart, walleye were found to travel on average 5 times further.

However, observed differences in distance traveled could not just be attributed to

differences in sampling methods. Lake ecology also appeared to be a major factor. The same strain of walleye in nearby Honoeye Lake restricted their movement to shallow weedy areas and showed discrete home ranges, traveling 37 meters daily (Foust and Haynes 2007). In Otsego Lake, some walleye used a variety of lake habitats, within one diel period, while others roamed the open water of the deepest parts of the lake. Very little home range fidelity was observed.

The diel activity pattern (distance travelled per hour) of walleye has not been studied

before. Walleye were found to move frequently during the diel cycle. Most walleye had periods of extraordinary activity having more than 30% of their daily activity concentrated in 2-hour

period. Unfortunately there was no consistent pattern when this burst of activity occurred, although it seldom occurred in the afternoon

The diel pattern of activity and habitat utilization of two tagged walleye were highly

correlated. This may indicate coordinated behavior such as schooling. Walleye have been reported to confine themselves to shallow, weedy littoral waters

(Foust and Haynes 2007) in some lakes, while utilizing deeper open waters in other lakes and reservoirs (Ager 1976; Festa 1987; Palmer 1999). In Otsego Lake, walleye made use of virtually all habitat types available, and were shown to move freely between them over a 24-hour period.

In some observations, walleye spent the entire 24-hour period in deep open water.

However, depth and temperature tags indicated that walleye only utilized the top 2-15m of the water column, and so there were significant deep water habitats in this 51.2 m lake that walleye did not utilize. For the most part, walleye appeared to be suspended in the water column. In the vast majority of observations (Figure 12), walleye occurred in the upper 10 meters of water, at the same depths (Brooking & Cornwell, 2008) as their principle prey, the alewife (Cornwell & McBride 2008).

Thus the depth/temperature preference of alewives may be influencing the

depth/temperature selection of walleye. While temperature preference varied among walleye and observation periods, the average temperature utilized was 16°C. This temperature selection was much lower than walleye observed in Oneida Lake, where fish congregated at or near 20°C (Tarby 1977, Nate et al 2003). Since optimum temperature for gonadal maturation in walleye is 20°C (Munger 2002), the occurrence of walleye at lower temperatures in Otsego Lake may indicate that other factors, such as food availability, may be influencing temperature selection.

In conclusion, hourly position data over an entire 24-hour period provide a much more

accurate measure of walleye movement and habitat utilization than daily/weekly position data collected during daylight hours. However, much more research is needed to characterize the diel and seasonal habitat utilization and movement patterns of walleye in Otsego Lake. There were few apparent patterns consistent with different fish or from month to month. Causes of bursts of movement (activity) need to be determined. The question of coordinated movements and habitat utilization among walleye should also be examined. Perhaps a joint approach utilizing bio-telemetry for walleye location and hydro-acoustics to determine details of habitat, prey density and aggregation behavior will provide more insight into habitat utilization and movement patterns of walleye.

ACKNOWLEDGEMENTS

Mark D. Cornwell, Dr. Willard Harman, Mathew F. Albright and the SUNY Cobleskill Fisheries and Wildlife staff provided help and guidance for this study. Henry J. Whitbeck provided guidance, and hours of personal time constructing the digital elevation models, and contour maps (modified from Harman), for this project. Biological Field Stations interns; Lisa Zack and Carter Bailey, Fisheries and Wildlife Students; Joseph Lydon, Robert Botha, and Kristen Wokanick helped track fish.

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