Upstream Passage Assessment of American Shad Using 3D Acoustic Telemetry

Transcription

1 Upstream Passage Assessment of American Shad Using 3D Acoustic Telemetry Timothy Hogan, Alden Research Laboratory Corey Wright, Blue Leaf Environmental Skip Medford, Enel Green Power North America Abstract The upstream passage of anadromous fish at hydroelectric facilities can be a contentious issue for hydro operators. Regulators and resource agencies advocate for hydro owners to provide upstream passage routes for migrating fish that not only provide the opportunity to move upstream, but do so without creating unnecessary delays in migration. Efforts to improve the upstream passage of American shad (Alosa sapidissima) at hydro dams along the Atlantic Coast of the U.S. have been ongoing for decades. At one project on the Atlantic Coast, research has been ongoing in an effort improve the success of a fish lift for moving migrating adult shad upstream to historic spawning areas. This paper will summarize the results of a study conducted using three-dimensional acoustic telemetry to track upstream migrating American shad. The objective of the study was to collect detailed information on the behavior of adult shad as they move through the project tailrace and approach the entrance to the fish lift. Detection data from the 25-day acoustic tracking study provided detailed behavioral information on fish movement within the project tailrace. These high-resolution tracking data are valuable to the hydro operator for making operational and/or structural changes to the upstream passage system in their efforts to increase passage success. In addition, this study indicates that three-dimensional acoustic telemetry, used heavily in downstream passage evaluations of salmonids on the West Coast, is also a viable technology for conducting upstream passage evaluations in relatively turbulent tailrace environments. 1.0 Introduction The Merrimack River Anadromous Fish Committee (Committee) is charged with managing important anadromous species present in the Merrimack Basin (American shad, Atlantic salmon, and river herring, among others). The Committee is comprised of federal and state (MA and NH) resource agencies (Brady et al. 2005). The Committee is committed to the restoration of Atlantic salmon, American shad, and river herring in the Merrimack River. Moreover, in 2011, the Technical Committee for Anadromous Fishery Management of the Merrimack River Basin (TCAFM) issued a plan focused solely on restoring a shad run to the Merrimack in which unrestricted access to spawning and rearing habitat is available. A principle tenet of this restoration effort is the successful passage of shad at the two downstream-most barriers in Massachusetts. Although passage at the first barrier (Essex Dam at the Lawrence Hydroelectric Project [Lawrence]) has been good historically, passage at the second barrier (Pawtucket Dam at the Lowell Hydroelectric Project [Lowell]) has been lower than expected. For the years between 1989 and 2011, between zero and 38% of the shad passed at Lawrence were successfully lifted at Lowell. Considering the total number of fish passed at Lawrence during these 23 years, 16% also passed Lowell. Since the construction and operation of fish passage facilities further upstream on the Merrimack is dependent on meeting target passage numbers at Lowell, there is a strong focus on improving the efficacy of the Lowell fish lift. 1

2 A previous field evaluation was completed in 2002 (Sprankle 2005) to determine how many of the shad passed at Lawrence reached the Lowell tailrace and to monitor the movement of shad as they migrated through the river reach between Lawrence and Lowell. Of the 65 fish released at Lawrence, 55% (36 fish) reached the Lowell tailrace. Of the 36 fish reaching the tailrace, 11% (4 fish) were successfully lifted at Lowell. These passage rates were considered poor and Sprankle (2005) made recommendations for improvements. The objective of the present study was to collect high resolution data about fish behavior in the tailrace to determine what impediments to upstream passage may exist. Three-dimensional acoustic telemetry was selected as the technology of choice due to its ability to provide greater resolution than radio telemetry. In addition, the successful application of acoustic telemetry in a tailrace of relatively high acoustic noise demonstrates a novel application of a technology which is often used only in project forebays. A common impediment to the application of acoustic telemetry is the presence of entrained air which can distort the acoustic signal. 2.0 Site Description Lowell Project The Lowell Hydroelectric Project dam (Pawtucket Dam) was constructed in 1830 and was enlarged in 1876 (TCAFM 2011). The Lowell Project is located in Lowell, MA 13.7 miles (22 km) upstream of Lawrence, MA at river mile 43.5 (river km 70) (Figure 1). It constitutes the second barrier to upstream migration for shad. Figure 1. Map of the Merrimack River (MA) depicting the location of the Essex and Pawtucket Dams. In 1986, upstream fish passage facilities were constructed at Lowell following issuance of the project s Federal Energy Regulatory Commission (FERC) license. The upstream passage system is comprised of two separate structures: a dual vertical slot fish ladder at the base of the Pawtucket Dam and a fish lift system at the Eldred L. Field Powerhouse (hereafter referred to as the Lowell powerhouse). The fish lift system is roughly 0.5 miles downstream of the dam. The fish lift is the primary fish passage system used at this project. In general, the fish ladder at the base of the dam is operated only during high flow or dam spill periods during the fish passage season when there is substantial flow in the bypassed reach. Higher flow conditions are more typical during the early spring. During the shad passage season, the 2

3 majority of river flow is diverted by the Pawtucket Dam into the canal system which supplies water to the Lowell powerhouse and fish lift. The Lowell powerhouse has a total rated capacity of 17.3 MW at a typical head of 37 ft. It operates two 8.6-MW horizontal Kaplan turbines, each with a hydraulic capacity of approximately 3,300 cfs. The tailrace is approximately 90 ft wide and 410 ft long. The tailrace is located on the right side of the river (southern side) and is bounded by shoreline bedrock on the right and bedrock topped by a concrete training wall on the left (Figure 2). The tailrace is approximately 30 ft deep from the powerhouse to a point 75 ft downstream where the depth changes to approximately 15 ft for the remainder of its length. The bathymetry creates turbulent upwelling between 50 and 100 feet downstream of the powerhouse (Figure 2). Figure 2. View of Lowell tailrace looking downstream: a) showing the shoreline bedrock on the right and bedrock topped by a concrete training wall on the left, and b) showing turbulent upwelling in tailrace. Lowell Fish Lift The Lowell fish lift system has two entrances, one on the river side and one on the shore side (Figure 3). During this study, only the river side entrance was in operation. The river side entrance is 6 ft wide and about 4.5 ft deep at the normal tailwater elevation, and is fitted with an adjustable weir gate. After fish pass through the entrance, a brail floor pushes fish to a crowder V-trap, which travels upstream moving the captured fish to the hopper. The concrete channel leading from the entrance to the hopper is 10 ft wide and 81 ft long to the back of the hopper elevator shaft. The water depth in the channel can range between 10.7 ft and 4.5 ft depending on tailrace water surface elevation. Once in the hopper, fish are lifted approximately 30 ft and released into the fish lift exit channel. Lifted fish pass a counting window and then enter the project s Northern Canal and finally the headpond. 3

4 Figure 3. Lowell powerhouse and fish lift entrances looking upstream (modified from image courtesy J. Warner, USFWS). The river side entrance was used during this study. 3.0 Materials and Methods Fish Tagging Adult American shad were collected from the fish lift hopper at Lawrence with dipnets. Acoustic tags were implanted gastrically, fish were measured for total length, and fish were allowed to recover in a holding channel overnight (Figure 4). Fish were released from the holding area on the following morning. Two separate groups of shad were collected and tagged on two separate days during the upstream run. The two tagging events were conducted on May 26 and on June 8, Figure 4. Photos of the tagging process: a) lift hopper from which adult shad were dipnetted, b) gastric implantation of tag, and c) length measurement 4

5 Telemetry Equipment Two separate HTI acoustic detection systems were set up: one at Lawrence and one at Lowell. Each system was comprised of multiple HTI Model 590 hydrophones, an HTI Model 290 acoustic tag receiver, and a laptop computer for logging/storing detection data. The acoustic tags used were HTI Model 795LD. The Lawrence system was designed only to detect the presence/absence of tagged fish and was comprised of 3 hydrophones. The Lowell system was designed to collected detailed 3D behavioral data of tagged fish in the tailrace and the fish lift channel and was comprised of 16 hydrophones (Figure 5). The HTI acoustic telemetry system was capable of providing 3D positioning accurate to approximately 1 meter (3.3 ft). Figure 5. Locations of the sixteen hydrophones in the Lowell tailrace. Yellow circles indicate bottommounted hydrophones and red circles surface-mounted hydrophones. 5

6 5/2/2011 5/6/2011 5/10/2011 5/14/2011 5/18/2011 5/22/2011 5/26/2011 5/30/2011 6/3/2011 6/7/2011 6/11/2011 6/15/2011 6/19/2011 6/23/2011 6/27/2011 7/1/2011 7/5/2011 7/9/2011 7/13/2011 Number of Shad Passed River Flow (cfs) Release 1 Release 2 Results General Results The assessment of shad passage at Lowell began on May 26, 2011 and was completed on June 21, 2011 for a total tracking period of 25 days. Sixty adult shad were tagged in two groups. The first group of 30 was released on May 27; the second group was released on June 9. Both releases of tagged fish occurred during the peak of the run, though release group 2 may be more characteristic of later-run shad (Figure 6). A total of 13,835 shad were passed at Lawrence in 2011; whereas a total of 1,202 shad (9% of those passed at Lawrence) were lifted at Lowell. This represents an improvement in passage over 2010 in which 10,343 shad passed Lawrence and 479 passed Lowell (5% of those passed at Lawrence). During the study period, river flow was initially high and slowly decreased (Figure 6). Flow through the Lowell turbines approximated river flow trends during the project period, constrained only by project capacity. Flow in the bypassed reach decreased steadily over the course of the study as total river flow decreased. Mean daily river flow and water temperature were 13,986 cfs and 18 C (64 F), respectively for release 1; 4,063 cfs and 21 C (70 F), respectively for release 2. During the project period, the mean flow through Lowell was 4,493 cfs. An estimated attraction flow of 65 cfs was provided at the river side entrance to the fish lift for the first 19 days of the study, after which attraction flow increased to 115 cfs for the remaining 6 days Shad Passed at Lawrence Shad Passed at Lowell 30,000 25, River Flow 20, , , , Date Figure 6. Daily totals of shad passed at Lawrence and Lowell and corresponding river flow data for the majority of the upstream passage period (May 2 June 30, 2011). The two releases of tagged fish are indicated by red arrows. 6

7 The mean total length of tagged shad was 493 mm. The mean total lengths of male and female shad were 454 mm and 527 mm, respectively. A total of 28 males and 32 females were tagged during this study. A total of 10 tags (17%) were assumed to have been regurgitated and one tag failed (2%). These 11 tags were subsequently grouped as nonviable for the purposes of this passage evaluation. Of the remaining 49 tagged fish released during this study, 100% were detected passing the Lawrence forebay hydrophone indicating that they had moved out into the river and 28 fish (57%) were detected in the Lowell tailrace. Of the 28 shad reaching Lowell, 13 were male and 15 were female. One tagged fish was classified as a fallback. A summary of detection data is presented in Table 1. For those fish that reached the Lowell tailrace, mean travel time between the release location (Lawrence fishway exit channel) and the Lawrence forebay was 1 hr 2 min. Mean travel time between Lawrence and the Lowell tailrace was 74.4 hrs (3.1 days). Mean residence time in the Lowell tailrace was 9.3 hrs. The mean number of unique entrances into the Lowell tailrace was 5.5. The mean time absent from the Lowell tailrace in between periods of presence was hrs. A summary of the detection data for 28 tagged shad that reached Lowell is presented in Table 2. When detection data were parsed by release group, there was no difference in the number of tagged shad reaching the Lowell tailrace (59% for group 1 released May 27 and 55% for group 2 released June 9). Group 1, however, took more than twice the time (mean of 4.2 days) to travel from Lawrence to Lowell than release group 2 (mean of 1.7 days). This longer travel time is likely the result of the higher flow in the river during the first release of tagged fish (daily mean of 13,986 cfs for May 27 and 3,412 cfs for June 9). Three shad entered the Lowell fishway s entrance channel during this study. The mean residence time in the tailrace for these 3 fish was 21.3 hrs, suggesting that some shad may spend a relatively long period of time in the tailrace before attempting entrance into the fishway channel. Two of the 3 shad (67%) that entered the fishway channel were successfully lifted upstream. 7

8 Table 1. Summary of detections of tagged shad at Lawrence and Lowell for the two release groups and combined. Failed and regurgitated tags were omitted; detections at Lawrence and Lowell were based on viable tags (i.e., those detected outside of the Lawrence fish lift exit channel). Tag failure Regurgitation Detected in Lawrence forebay Detected in Lawrence tailrace (fallback) Detected in Lowell tailrace Release date Number tagged N % of released N % of released N % of viable tags a N % of viable tags a N % of viable tags a 5/27/ % 3 10% % 0 0% 16 59% 6/9/ % 7 23% % 1 5% 12 55% Combined % 10 17% % 1 2% 28 57% a Viable tags = total number released - (number of tag failures + number of regurgitations) Table 2. Summary of detections of tagged shad that were detected in the Lowell tailrace. All reported values are means (N=28). Travel time from release point to Lawrence forebay a Travel time from Lawrence to Lowell (days) a Residence time in Lowell tailrace (hr) a Unique entries into Lowell tailrace a Time absent from the Lowell tailrace (hr) Travel time from Lowell to Lawrence (days) b 1 hr 2 min a numbers based on the 28 shad that reached Lowell b numbers based on the 12 fish that were later detected at Lawrence after having been in the Lowell tailrace 8

9 3D Acoustic Telemetry Results Bin density plots display the percent of tagged fish in the tailrace that were detected in each of the bins of space in the tailrace. Bins were created by dividing the tailrace into a grid of 10-ft by 10-ft squares; the percent of tagged fish that was detected in each bin was recorded over the duration of the study and this percent is shown by color in the plot. Using bins reduces the potential for a single fish to skew the results since it only counts a fish s presence in a bin once; it displays the use of space by the population of fish, rather than the amount of time spent in each bin. Figure 7 presents the bin density for all tagged fish that were detected in the Lowell tailrace. Density plots display the density of 3D positions of all tagged fish in the tailrace and therefore incorporate a temporal component of the detection data. However, as such, there is potential for density plots to be skewed by individual fish that spend long periods of time in particular areas. Figure 8 presents the density of the 3-dimensional tracks for all tagged fish that were detected in the Lowell tailrace. In general, tagged shad in the Lowell tailrace followed a horseshoe swimming pattern. Fish approached along one side of the tailrace, rounded the corner near the powerhouse, swam along the downstream face of the powerhouse, rounded the other corner, and swam back down the opposite side of the tailrace. As seen in Figure 7, at a location in the tailrace on the river side near the bend in the training wall, 100% of the tagged fish were detected. This location corresponds to a point in the tailrace that is downstream of the turbulent upwelling flow created by the turbine discharge (see Figure 2). Other areas that logged high bin densities (80-100%) were on the shore side along the tailrace bank in a narrow strip extending downstream approximately 170 ft from a point approximately 50 ft downstream of the powerhouse. Bin densities in the middle areas of the tailrace were lower (Figure 7). These results are consistent with visual observations of the swimming behavior of surface-oriented shad (not necessarily tagged study fish) in the Lowell tailrace. Some shad displayed active movement to and from the Lowell tailrace, with tagged fish making up to 30 unique entrances into the tailrace. The majority (75%) of the tagged shad, however, were detected making 6 or fewer unique entrances. For the 6 fish (21% of those detected at Lowell) that entered the tailrace only once, the mean residence time was 2.5 hrs (range hrs). The density plot of the 3D tracks of tagged fish (Figure 8) indicates that while in the Lowell tailrace, tagged shad spent the greatest amount of time on the shore side of the tailrace near the bend in the tailrace wall. As with the data in Figure 7, tagged shad preferred the edges of the tailrace and were detected at the greatest frequency within the horseshoe pattern shown in reddish/orange. Although Figure 7 indicates that 100% of the tagged shad were detected in a greater portion of the area (i.e., more bins) near the tailrace bend on the river side than the shore side, Figure 8 indicates that that more time was spent swimming near the tailrace bend on the shore side. 9

10 Figure 7. Bin density of 3D positions of all tagged shad present during the study period in the Lowell tailrace. Figure 8. Density of 3D tracks of all tagged shad present during the study period in the Lowell tailrace. 10

11 The vast majority (over 80%) of tagged shad were detected between 5 and 15 ft deep in the water column. There were no obvious differences in the distribution of shad among the designated depth zones. When detection data were parsed by sex, females appeared to favor the sides of the tailrace more than males, with fewer females detected in the bins in the middle of the tailrace where flows are the most turbulent (Figure 9). Females may prefer the sides of the tailrace due to their need to seek out lower velocity zones to conserve energy for spawning, as maintaining position in turbulent flow requires the expenditure of energy. Females were also slower to travel the distance between the release point and the Lawrence forebay and the distance from Lawrence to Lowell. Figure 9. Bin density of 3D positions of all tagged male (left) and female (right) shad present during the study period in the Lowell tailrace. Greater numbers of shad were detected in the Lowell tailrace during periods of lower tailrace flow (Figure 10). With lower flows in the bypassed reach and the tailrace, fish were much more likely to enter the tailrace. However, only one fish was detected in the fishway (was not lifted) during this period indicating that, despite the presence of more shad in the tailrace, there was no corresponding increase in passage success. Figure 11 (top) illustrates the record of detections in each 10 ft by 10 ft bin of the tailrace during periods of high and low flow essentially indicating which areas of the tailrace the tagged fish prefer. More intense color indicates that a greater number of shad were detected in these zones. During high flow conditions in the tailrace, tagged shad were more concentrated along the sides and were not often detected in the middle (Figure 11, top right). However, under low flow conditions, tagged shad were less concentrated along the sides and used more of the area towards the middle of the tailrace (Figure 11, top left). In addition, under high flow conditions, tagged fish were detected in more downstream bins and more bins located at the edges of the tailrace than under low flow conditions. These data may suggest that higher tailrace flows concentrate shad in certain areas. Figure 11 (bottom) illustrates the density of the 3D swimming paths of the tagged shad during periods of high and low flow. Areas of more intense color indicate that fish were more frequently detected in these zones as they swam in the tailrace. During the high flow period, tagged shad displayed a preference for the area on the shore side near the tailrace bend (Figure 11, bottom right), presumably where there were lower velocities behind the bend in the tailrace bank. During the low flow period, tagged shad spent more time traveling on the upstream portion of the general horseshoe pattern the 11

12 5/2/2011 5/5/2011 5/8/2011 5/11/2011 5/14/2011 5/17/2011 5/20/2011 5/23/2011 5/26/2011 5/29/2011 6/1/2011 6/4/2011 6/7/2011 6/10/2011 6/13/2011 6/16/2011 6/19/2011 6/22/2011 6/25/2011 6/28/2011 Flow (cfs) Number of tagged shad in the Lowell tailrace group had followed (Figure 11, bottom left). The greatest amount of time (most intense color) during the low flow period was spent in a typical U-shaped pattern extending from just upstream of the tailrace bend on the river side and wrapping around downstream of the powerhouse. During such low flow periods, the attraction flow would constitute a greater proportion of the tailrace flow. The behavior seen in Figure 11 likely results from the increased influence of the attraction flow under the reduced turbine flow conditions Tagged shad in Lowell Tailrace Merrimack River Flow at Lowell Lowell Project Flow Date Figure 10. Daily counts of individual shad detected in the Lowell tailrace during the study period. 12

13 Figure 11. Bin density of 3D positions (top images) and density of 3D tracks (bottom images) of all tagged shad in the Lowell tailrace during periods when tailrace flow was above and below the mean (4493 cfs). 13

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