**2. Telemetry technologies**

#### **2.1 Comparison of radio and acoustic tag technologies**

Radio and acoustic telemetry were the two methods used to study animal movements but there are differences in their applications and the type of data acquired. Acoustic signals must be received underwater while radio signals are received in the air. Data from radio tags can be received from boats, airplanes and through the ice and is best for large scale studies where animals move considerable distances but is usually less precise in terms of location and is also labour intensive, especially the way we applied it. Both types of tags provide repeat data. Acoustic receivers are more precise (especially the VRAP system of Vemco Ltd.) and tags can measure variables such as depth and temperature, and are good for fine scale studies. Initially acoustic tags were large and the equipment was expensive and cumbersome to handle due to bulk and weight. More recently tags and receivers have been constructed that are reduced in size and the life of the tags has increased. Both radio and acoustic tags can be detected with mobile receivers but precision in locating animals is lower, for both systems, and there are usually fewer observations.

Gill nets were used to capture all lake sturgeon. Three different nets were used: 30 cm stretched mesh, 22.5 cm stretched mesh and a standard gang with six panels (3.1, 5, 6.9, 8.8, 10.6, 12.5 cm stretched mesh). Fish were brought to shore and placed on a damp canvas sheet. Weight, length was recorded and on a few fish a pectoral fin ray was removed to establish a size to age relationship.

This following section deals with a comparison between the two technologies. Both radio and acoustic tags were attached externally to the dorsal fin. For short term studies over days or a few months, external tags are adequate but for longer term studies of several years internally implanted tags are necessary. Radio tags were obtained from Lotek, Missassauga, Ontario, Canada and the acoustic tags were obtained from Vemco Ltd. (Halifax, Nova Scotia). Two types of acoustic tags were used. Large fish were tagged with V16 pressure tags, the remaining fish were tagged with V8 position tags. Pressure tags transmitted information on swimming depth as well as positional information. The V8 tags transmitted positional data. The tag weight to body weight ratio for both radio and acoustic telemetry was less than 1% for all fish. A piece of neoprene was placed between the tag and the dorsal fin and a piece of neoprene was placed on the opposite side of the fin for support of the attachment wires. Two hypodermic needles, spaced apart the length of the tag, were pushed through the neoprene backing and then through the dorsal fin of the fish. The attachment wires were fed through the tag, through the second piece of neoprene, and then through the needles. The needles were then pulled out pulling the attachment wires through the fin and the neoprene on the opposite side of the fin. The attachment wires were pulled snug and several knots were tied to secure the tag. Excess wire was removed using wire cutters. Later, a 40 gauge neoprene was used between the tag and the fin instead of the foam and neoprene also replaced the foam and plastic backing on the opposite side. This method gave a tighter fit for the tag when tested by hand, however there was no tag loss using either method. The radio tags were manufactured by Lotek Engineering, Missassauga, Ontario, Canada. All tools were sterilized before use and salt was applied to the tagged area after the procedure to reduce infection. Lake sturgeons, after attaching external tags, were held in a holding net placed in the lake at a depth of 2.0 meters. Fish remained inactive for periods of 20 to 40 minutes but as soon as normal swimming behaviour was observed they were released.

(VRAP) system. Round Lake.

374 Modern Telemetry

Radio and acoustic telemetry were the two methods used to study animal movements but there are differences in their applications and the type of data acquired. Acoustic signals must be received underwater while radio signals are received in the air. Data from radio tags can be received from boats, airplanes and through the ice and is best for large scale studies where animals move considerable distances but is usually less precise in terms of location and is also labour intensive, especially the way we applied it. Both types of tags provide repeat data. Acoustic receivers are more precise (especially the VRAP system of Vemco Ltd.) and tags can measure variables such as depth and temperature, and are good for fine scale studies. Initially acoustic tags were large and the equipment was expensive and cumbersome to handle due to bulk and weight. More recently tags and receivers have been constructed that are reduced in size and the life of the tags has increased. Both radio and acoustic tags can be detected with mobile receivers but precision in locating animals is

Gill nets were used to capture all lake sturgeon. Three different nets were used: 30 cm stretched mesh, 22.5 cm stretched mesh and a standard gang with six panels (3.1, 5, 6.9, 8.8, 10.6, 12.5 cm stretched mesh). Fish were brought to shore and placed on a damp canvas sheet. Weight, length was recorded and on a few fish a pectoral fin ray was removed to

This following section deals with a comparison between the two technologies. Both radio and acoustic tags were attached externally to the dorsal fin. For short term studies over days or a few months, external tags are adequate but for longer term studies of several years internally implanted tags are necessary. Radio tags were obtained from Lotek, Missassauga, Ontario, Canada and the acoustic tags were obtained from Vemco Ltd. (Halifax, Nova Scotia). Two types of acoustic tags were used. Large fish were tagged with V16 pressure tags, the remaining fish were tagged with V8 position tags. Pressure tags transmitted information on swimming depth as well as positional information. The V8 tags transmitted positional data. The tag weight to body weight ratio for both radio and acoustic telemetry was less than 1% for all fish. A piece of neoprene was placed between the tag and the dorsal fin and a piece of neoprene was placed on the opposite side of the fin for support of the attachment wires. Two hypodermic needles, spaced apart the length of the tag, were pushed through the neoprene backing and then through the dorsal fin of the fish. The attachment wires were fed through the tag, through the second piece of neoprene, and then through the needles. The needles were then pulled out pulling the attachment wires through the fin and the neoprene on the opposite side of the fin. The attachment wires were pulled snug and several knots were tied to secure the tag. Excess wire was removed using wire cutters. Later, a 40 gauge neoprene was used between the tag and the fin instead of the foam and neoprene also replaced the foam and plastic backing on the opposite side. This method gave a tighter fit for the tag when tested by hand, however there was no tag loss using either method. The radio tags were manufactured by Lotek Engineering, Missassauga, Ontario, Canada. All tools were sterilized before use and salt was applied to the tagged area after the procedure to reduce infection. Lake sturgeons, after attaching external tags, were held in a holding net placed in the lake at a depth of 2.0 meters. Fish remained inactive for periods of 20 to 40 minutes

but as soon as normal swimming behaviour was observed they were released.

**2. Telemetry technologies** 

establish a size to age relationship.

**2.1 Comparison of radio and acoustic tag technologies** 

lower, for both systems, and there are usually fewer observations.

Precise positioning of lake sturgeon was done using two radio linked acoustic positioning arrays (VRAP, Vemco Ltd.). Each array consisted of a base station which communicated with each of three buoys anchored in the lake (Fig. 4). Each buoy contained an acoustic transmitter, an omnidirectional hydrophone, and a VHF modem.

Buoy location was determined using survey techniques and having an understanding of the lake morphometry so that there was a clean line of site between receivers so that a tag signal was picked up by atleast two receivers. Test tags determined if a signal could not be picked up by a receiver due to an under water obstruction, such as a boulder, and if the receiver was obstructed it was re-positioned. The chosen positions covered 80% of the surface area of the lake. Figure 5 shows the distribution of the two 3-receiver arrays.

#### **2.2 Telemetry data**

Telemetry data analysis and presentation was done using Idrisi for Windows (Clark University, MA). Some maps were created in Idrisi for Windows. Acoustic telemetry data was imported from the VEMCO system program.

Determination of depth selection and substrate selection was done by hand. Seven days were selected for analysis. Selection was based on movements to include the widest possible range of movement patterns. Days 206 and 221 were selected for sturgeon 4014. Days 210 and 222 were selected for sturgeon 4015. Days 206, 211 and 219 were selected for sturgeon 4017. For each location on each day bottom depth was determined.

Swimming depth minus bottom depth was calculated to determine all locations in which the fish was in contact with the substrate. All values of 1 or less were included. All figures and comments pertaining to substrate selection only include locations in which a fish was in contact with the bottom. Other location statements and figures used all the positional data available.

*Radio tags*: These tags were attached externally to the dorsal fin. Initially, a piece of foam was placed between the tag and the dorsal fin and a piece of foam and a plastic backing were placed on the opposite side of the fin for support of the attachment wires. Details on tag attachment are outlined above.

Movements and Habitat Use by Lake Sturgeon (*Acipenser fulvescens*)

**A B**

sturgeon movements are not being recorded.

Table 2. Lake sturgeon data for the acoustic tagged fish.

in an Unperturbed Environment: A Small Boreal Lake in the Canadian Shield 377

Fig. 6. A) Total movements of lake sturgeon in Round Lake using radio telemetry,

B) Total movements of lake sturgeon in Round Lake Round Lake using acoustic telemetry A series of transects were run at the same time each day on the acoustic tagged sturgeon to test the hypothesis that boat activity affected lake sturgeon movements. The results showed that movements of lake sturgeon during periods when boat transects were run do not differ from the sturgeon movements when no boat was on the water (Fig. 5**)**. Lake sturgeon 4014 was located at the inlet and in the middle of the lake with and without boat activity. Lake sturgeon 4015 was located at the inlet with and without boat activity. Lake sturgeon 4017 was located generally in the area of the outlet with and without boat activity.The swimming depth of lake sturgeon during periods when the boat was on the water did not change from depths of lake sturgeon directly prior to when the boat was on the water **(**Figs.7 and 8). Lake sturgeon swimming depth changed often but was not correlated with presence or absence of boat activity. Mean depths were similar for times when boat transects were being run and times immediately prior to boat activity. We conclude that boat activity had no impact on lake sturgeon movements in our study and the lack of correlation between boat activity and lake sturgeon movements may relate to lake depth. By contrast, the application of radio tags and a mobile receiver in a shallow (2-3m) prairie river did affect lake sturgeon movements (Dick, unpubl. data). Clearly the type of aquatic system one is working in needs to be assessed, for impacts of boats and other anthropogenic activities, to be certain that abnormal

**Number Total length(cm) Fork Length(cm) Weight(g) Age**  4010 54 48 632 - 4013 49 44 572 - 4011 49 45 562 - 4012 48 43 506 4 4014 143 128 16900 - 4015 125 117 13250 - 4016 138 126 14750 31 4017 119 113 11620 - 4009 101 95 6790 22

A total of 20 radio tags were used and lake sturgeons were tracked periodically by boat (Table 1). When a signal was received the exact location of the fish was determined by circling the area until the signal was strong enough to trigger the code on the receiver. The locations were plotted on a map of the lake by visual triangulation with known points on land. A GPS location was recorded. Fig. 6A shows the total movements of all lake sturgeon in Round Lake fitted with radio tags. Twenty lake sturgeons were monitored over a three year period. The main patterns of movements over the deeper areas of the lake related to the flow of the river through the lake.



*Acoustic telemetry*: Figure 6B illustrates the overall movements of nine tagged lake sturgeon in Round Lake in July and August 1997 using acoustic telemetry and provides details on each tagged fish (Table 2). Figs. 4 and 5 illustrate an array configuration and the base station (VRAP system) and the relative positions of two arrays. The main patterns trends are related to the deeper areas of the lake and related to the flow of the river into, through and out of the lake. Since stationary receivers were used we had the opportunity to run transects to determine if boat activity influenced lakes sturgeon movements as there have been concerns that boat activity may affect lake sturgeon movements.

A total of 20 radio tags were used and lake sturgeons were tracked periodically by boat (Table 1). When a signal was received the exact location of the fish was determined by circling the area until the signal was strong enough to trigger the code on the receiver. The locations were plotted on a map of the lake by visual triangulation with known points on land. A GPS location was recorded. Fig. 6A shows the total movements of all lake sturgeon in Round Lake fitted with radio tags. Twenty lake sturgeons were monitored over a three year period. The main patterns of movements over the deeper areas of the lake related to the

**ID Total (cm) Fork(cm) Weight(g) Age**  code 33 140 129 21000 code 31 129 121 13200 code 64 144 138 25970 code 63 132 122 14900 code 75 123 110 10185 code 65 122 112 9870 code 60 47 41 499 code 66 47 42 485 code 68 55 49 734 5 code 70 62 55 1202 7 code 72 50 45 551 code 32 114 106 8700 code 56 107 98.5 7120 34 code 51 66 60.5 2272 code 41 99 91 5350 code 42 114 109 9945 code 43 119 112 11596 code 40 135 122 14470 -

code 55 124 116 12840 code 45 104 99 7920

*Acoustic telemetry*: Figure 6B illustrates the overall movements of nine tagged lake sturgeon in Round Lake in July and August 1997 using acoustic telemetry and provides details on each tagged fish (Table 2). Figs. 4 and 5 illustrate an array configuration and the base station (VRAP system) and the relative positions of two arrays. The main patterns trends are related to the deeper areas of the lake and related to the flow of the river into, through and out of the lake. Since stationary receivers were used we had the opportunity to run transects to determine if boat activity influenced lakes sturgeon movements as there have been concerns

Table 1. Biological data for the radio tagged lake sturgeon.

that boat activity may affect lake sturgeon movements.

flow of the river through the lake.

A series of transects were run at the same time each day on the acoustic tagged sturgeon to test the hypothesis that boat activity affected lake sturgeon movements. The results showed that movements of lake sturgeon during periods when boat transects were run do not differ from the sturgeon movements when no boat was on the water (Fig. 5**)**. Lake sturgeon 4014 was located at the inlet and in the middle of the lake with and without boat activity. Lake sturgeon 4015 was located at the inlet with and without boat activity. Lake sturgeon 4017 was located generally in the area of the outlet with and without boat activity.The swimming depth of lake sturgeon during periods when the boat was on the water did not change from depths of lake sturgeon directly prior to when the boat was on the water **(**Figs.7 and 8). Lake sturgeon swimming depth changed often but was not correlated with presence or absence of boat activity. Mean depths were similar for times when boat transects were being run and times immediately prior to boat activity. We conclude that boat activity had no impact on lake sturgeon movements in our study and the lack of correlation between boat activity and lake sturgeon movements may relate to lake depth. By contrast, the application of radio tags and a mobile receiver in a shallow (2-3m) prairie river did affect lake sturgeon movements (Dick, unpubl. data). Clearly the type of aquatic system one is working in needs to be assessed, for impacts of boats and other anthropogenic activities, to be certain that abnormal sturgeon movements are not being recorded.


Table 2. Lake sturgeon data for the acoustic tagged fish.

Movements and Habitat Use by Lake Sturgeon (*Acipenser fulvescens*)

Fig. 8. Depth selection of lake sturgeon with and without boat activity

Acoustic tags can also provide depth data.

**Percent of Frequency of Occurrence**

30

0

The major difference between radio and acoustic telemetry in freshwater is the receiving systems for the radio system can be above the surface of the water while acoustic telemetry receivers requires the more dense water to transmit the signal. This allows the former to be detected by aircraft as well as on the water surface but is labour intensive. A weakness of the acoustic system is bubbles in the water column interfere with transmission of the signal while a major advantage is that repeated collection of signals by well placed receivers can save considerable time and provide a much better indication of frequency of use of an area.

Swimming Depth (m)

123 4 5 6 7 8 9 10 11

We conclude that while there is a place for both types of tags, radio tags work best below rapids and waterfalls where there are usually plenty of air bubbles and in small stretches of rivers where there are dramatic current shifts, some air bubbles and up welling currents. Acoustic technology allows repeated measures but is scale limited due to the distance that the signal can be received. However, the Vemco VRAP system it is highly useful for relatively small aquatic systems with well defined boundaries, little or no emigration from the system and where accuracy to a few metres is important to describe habitat use,

especially when pressure sensors are used to collect depth data on individual fish.

in an Unperturbed Environment: A Small Boreal Lake in the Canadian Shield 379

with boat no boat

Fig. 7. Movement of lake sturgeon during movements of the boat and during times when no boat was on the lake

With boat No boat

4014

4015

4017

Fig. 7. Movement of lake sturgeon during movements of the boat and during times when no

boat was on the lake

The major difference between radio and acoustic telemetry in freshwater is the receiving systems for the radio system can be above the surface of the water while acoustic telemetry receivers requires the more dense water to transmit the signal. This allows the former to be detected by aircraft as well as on the water surface but is labour intensive. A weakness of the acoustic system is bubbles in the water column interfere with transmission of the signal while a major advantage is that repeated collection of signals by well placed receivers can save considerable time and provide a much better indication of frequency of use of an area. Acoustic tags can also provide depth data.

We conclude that while there is a place for both types of tags, radio tags work best below rapids and waterfalls where there are usually plenty of air bubbles and in small stretches of rivers where there are dramatic current shifts, some air bubbles and up welling currents. Acoustic technology allows repeated measures but is scale limited due to the distance that the signal can be received. However, the Vemco VRAP system it is highly useful for relatively small aquatic systems with well defined boundaries, little or no emigration from the system and where accuracy to a few metres is important to describe habitat use, especially when pressure sensors are used to collect depth data on individual fish.

Movements and Habitat Use by Lake Sturgeon (*Acipenser fulvescens*)

particles and larger particles were then treated separately.

siphoned water was also dried and weighed as the clay category.

was imported from the Vemco system program.

and recorded.

sonar.

available.

categories, and settling velocity was used for silt and clay particle sizes.

in an Unperturbed Environment: A Small Boreal Lake in the Canadian Shield 381

*Laboratory analyses*: Gravel and larger particle sizes were separated individually by hand, sieve analysis was used to separate the portion of the sample in the very fine sand to gravel

The sample was placed in a tray and mixed thoroughly. The sample was added to water and dispersent (Calgon-sodium hexametaphosphate), mixed, and let sit overnight. The sample was then mixed, frozen, thawed and mixed again. The process was repeated a second time to ensure that the particles were completely separated. After the sample was separated thoroughly by the above mentioned process the silt and clay particles were removed from the sand and gravel particles. The sample was wet sieved through a 4 phi sieve to remove the silt and clay from the sample. The sediment left in the 4 phi sieve was placed in a beaker and the sediment falling through the sieve was stored in a separate container. The fine

Sand samples were placed into a pyrite beaker and allowed to dry in the oven until the sample was completely dry. A pestle and mortar were used to break up any chunks formed by the drying process. The total sample was weighed and placed in the top of a series of sieves ranging from -1.5 phi to 4 phi (0.5 phi intervals). The sieves were then placed into a Ro-tap shaker and then shaken for ten minutes. The material left in each sieve was weighed

Silt/clay samples were placed in a 4000 ml graduated cylinder. Water was added to the cylinder to make the total solution 4000 ml. The solution was then shaken thoroughly and allowed to settle for the appropriate amount of time necessary to separate silt from clay. Five phi (1/32 mm) particles are the largest size category and were removed first. Five phi particles fall at a rate of 4 mm/second. The 4000 ml suspension is 500 mm high therefore the suspension was allowed to settle for 6 minutes and 15 seconds to allow all 1/32 mm particles to fall the full length of the cylinder. The supernatant (water and particles smaller than 1/32 mm) was siphoned off and saved. The process was repeated twice more to remove any smaller particles that would settle from the bottom portion of the cylinder. The remaining precipitant after the third siphon was dried and weighed as the silt category. The

The particle size classification used was Cummins (1962) modification of the Wentworth Scale. Thirty-seven sediment grabs were taken and analysed from Round Lake. GPS locations for the sediment grabs were compared to hardness values from the Round Lake map at the same GPS location to obtain a system of classifying hardness values obtained by

*Telemetry data analysis*: Data was presented in maps using Idrisi for Windows (Clark University, MA). Some maps were created in Idrisi for Windows. Acoustic telemetry data

Determination of depth selection and substrate selection was done by hand. Seven days were selected for analysis. Selection was based on movements to include the widest possible

Days 210 and 222 were selected for sturgeon 4015. Days 206, 211 and 219 were selected for sturgeon 4017 (Table 2). For each location on each day bottom depth was determined. Swimming depth minus bottom depth was calculated to determine all locations in which the fish was in contact with the substrate. All values of 1 or less were included. All figures and comments pertaining to substrate selection only include locations in which the fish was in contact with the bottom. Other location statements and figures use all positional data

range of movement patterns. Days 206 and 221 were selected for sturgeon 4014.
