Effects of Explosives on Incubating Eggs of Lake Trout. (Salvelinus namaycush) in Lac de Gras in the Canadian Arctic

Transcription

1 Effects of Explosives on Incubating Eggs of Lake Trout (Salvelinus namaycush) in Lac de Gras in the Canadian Arctic Update September 2003 to August 2004 Submitted by: S.G. Faulkner & W.M. Tonn Department of Biological Sciences University of Alberta 1

2 Methods Egg Take and Handling Angling surveys suggested that the spawning period in 2003 commenced around the first week of September, and continued for a few weeks. However, collection of ripe females was difficult, presumably because more spawning males than females were on the spawning grounds. Ripe females, freely releasing eggs, were only caught using gill nets after sunset (approximately 11 pm-1:30 am). This technique of capture was difficult however, because of low light, and cold conditions. Angling was another capture method that was tested. Angling produced ripening females, as well as numerous males, but after these females were held in recovery boxes for 4 days they were freely releasing eggs when handled. This technique was much less traumatic for the fish. Another benefit of this technique was that it did not rely heavily on weather conditions. Since the fetch of the lake is so long, even a moderate wind can produce unsafe conditions. These conditions can last for many days, therefore being able to take advantage of good weather and holding captured fish until they ripen would help ensure a supply of eggs would be available if conditions subsequently turned unfavourable. This year all eggs were collected from females caught using gill nets. In total three females were spawned with 4 males. The egg take and fertilization was done outside in subfreezing temperatures late at night (2 am) after returning from fish collection over the nights of September 15 th and 16 th when the water temperature was approximately 8.5 o C. These eggs were then fertilized, allowed to water-harden in lake 2

3 water, and then loaded into incubators the following morning in the lab. This procedure was time consuming, but the water temperature was kept below 10 o C. Incubators were then randomly assigned to sites (including a laboratory control) and put into the lake that afternoon. The unused eggs and control incubators were then sent to U of A to incubate in the lab to assess fertility, abnormality, and mortality within control incubators. Eggtake and associated activities was a long process but seemed to go well. The only potential problems of this were the cold temperatures during the egg take and the warm temperatures during the incubator loading. If females are caught by angling next year and held until ripe, the entire process can be accomplished in an outdoor lab. This would alleviate the problems of temperature change. Sites Four sites were chosen this year for incubator deployment. Of these sites, 3 were chosen within the predicted blast zone, and one outside as a reference. Two sites were chosen close to the dike wall: East Dike and South Dike (Fig. 1). The South Dike site was chosen because it was composed entirely of rock from the dike wall. East Dike contained natural spawning substrate, but was directly connected to the dike wall. The third site (Tern Island) chosen within the predicted blast zone was approximately 200 m from the dike wall (Fig. 1). The reference site (Reference Island) was located to the east of the dike wall outside of the predicted blast zone (Fig. 1). These sites all had appropriate spawning material at the appropriate depths (3-8 m) and were also close to land to enable deployment of the geophysical monitoring equipment. 3

4 Figure 1. Map showing sites chosen in the first year of the study (labelled and marked by red dots). At these sites two chains of 10 incubators were deployed, as well as geophysical monitoring equipment to record blast levels. For each of these sites, 2 separate chains were deployed, with 10 incubators attached to each chain. Each site also had a geophone attached to one chain to record the blasts. The two chains were placed relatively close to each other in similar conditions (depths of 3-5 m, boulder substrate with sufficient interstitial spaces, with similar exposure to wind and blasts). Deployment was all done on the same day starting with the Reference site, then Tern Island, South Dike and, finally East Dike. 4

5 Early Retrieval Incubators deployed in the lake were then exposed to blasting activity for 20 days (Sept 17 to Oct 7). At this stage half of the incubators were removed (5 from each chain) to test for early mortality when the eggs are at their most sensitive stage. The rest of the incubators were left in place to be removed after the entire incubation period. Of the 5 incubators removed after 3 weeks, 2 were fixed in Davidson s solution to assess mortality and 3 were shipped to the U of A to complete incubation and to assess developmental abnormalities. Control egg samples from the lab at U of A were also fixed at this time for comparison. These preserved eggs were analyzed at the Department of Fisheries and Oceans Freshwater Institute in Winnipeg. Analysis involved observing if epiboly was reached and quantifying the rate of deformity. This was done using a dissecting microscope at 40x magnification and Northern Eclipse Software. The embryos that were alive upon retrieval had all completed epiboly and formed a caudal bud, suggesting mortality had only occurred at a very young stage. At this young stage, deformity was very difficult to assess therefore, only massive deformities were recorded (eg. Twoheads) and only two were observed out of a sample of approximately 800. At the U of A the eggs were incubated in 4 o C water in a recirculation system. Egg samples included left over eggs from the bulk sample used in filling incubators, the left over eggs from each of the three females (kept separately), eggs in the control incubators, and eggs in the incubators that underwent the 3-week exposure. All egg samples were examined for mortality, hatch, and deformity throughout the incubation period. 5

6 Hatching started on Dec 8 th and was complete on Feb 9 th. This is much earlier than is expected in the lake, but this is certainly the result of the warmer temperature of the lab water (ca. 4 o C) then in the lake (less than 1 o C for much of the incubation period). In addition, due to human error, the chiller unit was turned off for a 10 hour period on Oct 9 th, during which the water warmed to approximately 13 o C. The temperature was then slowly lowered (1 o C/day) back to 4 o C over the following week. Hatching success varied greatly between the three females. The sample of eggs from Female 1 had the lowest hatching success and lowest deformity rate, Female 2 had highest hatch, and Female 3 had intermediate hatch and the highest deformity (Table 1). The bulk sample (a random mixture of eggs from the 3 females) had a 54% hatch and a 2.3% deformity consistent with a mixture of the 3 source females. Table 1. Hatch success and deformity of lab raised lake trout eggs from the three different females. % Dead % Deformed % Hatch Female Female Female Bulk Sample The differences observed between females could have resulted from a number of reasons. Female 1 was spawned and fertilized 24 hrs prior to Females 2 and 3 and the fertilized eggs were held in lake water at approximately 6 o C before they were mixed in the bulk sample. This suggests that this renders them more sensitive to handling or that mortality occurred during this holding time. Females 2 and 3 also had substantial differences between both % hatch (22%) and % deformity (3%). Since these fish and gametes were subjected to the same conditions and handling, these differences are most likely due to individual variability in quality of the gametes used. 6

7 Egg samples fixed after 3 weeks incubation were generally consistent (+/- 4%) with the overall % hatch results (Table 2). Most differences were likely due to sampling error. However, the greater discrepancy (11%) between % alive after 3 weeks and final % hatch for females may have been the result of both sampling error and death due to deformity. Deformity at hatch was 3.7% for Female 3 s eggs, but no deformity was observed at 3 weeks. This high degree of deformity at hatch suggests that other deformed embryos may have died before hatching, contributing to the lower % hatch. Table 2. Percentage of eggs that were alive and had reached epiboly for the samples from the female lake trout that were raised at the U of A laboratory. Sample Mean alive when fixed at 3 weeks (%) Female 1 fixed 22.5 Female 2 fixed 84.5 Female 3 fixed 71 Bulk fixed 50.5 The Incubators Of the 5 incubators/chain retrieved after 3 weeks incubation in Lac de Gras, 2 were fixed at retrieval and 3 were shipped to U of A for further incubation. The analysis of the fixed eggs revealed that all the eggs that had died did so very early on in development (up to the time they were placed in the substrate). There were few qualitative differences in mortality observed between the egg samples fixed at early retrieval and the lab-raised incubators after the 3-week lake exposure (pairwise t-test, p>>0.05). This result shows that there was no additional mortality associated with the incubation method used in the lab. Because of this, both lab-raised and fixed incubators were combined to form site and chain means. 7

8 For all of the sites the mean 3-week survival of the two chains within each site was not significantly different (pairwise t-test, p>>0.05) (Table 3). There was a fair amount of variation in survival among incubators on a chain however, variation between chains within the sites was small therefore they were combined to form site means. This suggests that this within-site replication of the chains is not needed in future field seasons. Table 3. Egg survival means of counts (out of 50) after 3 weeks of exposure at the different sites and for the different chains within the sites (including both fixed and lab raised samples). P-value is for pairwise t-test between chains within sites. Site Chain Alive St.dev P South Dike East Dike Tern Island Reference When the data from all incubators at a site are combined, the lowest 3-week survival occurred at Tern Island site (mean 22.2, SD 3.34), with highest at South Dike (mean 26.8, SD 3.65)(Table 4). Analysis of variance reveals no clear difference between survival between the sites (p=0.059). When the 3-week survival rate within the lab control incubators (mean 22.4, SD 4.4) was compared with the sites, analysis of variance showed a difference (p=0.048). Pairwise t-tests revealed that the Lab control is only significantly different (less) from South Dike (p<0.05), and Tern Island is significantly different (less) from South Dike (p<0.05) and East Dike (p<0.05). This shows that effects of early shipping (before epiboly) appear to have had at most a limited effect on survival of eggs compared to the effects of deploying them into the lake. 8

9 Table 4. Egg survival mean counts (out of 50) after 3 weeks of exposure at the different sites including incubators from both chains (n=10 for all sites). Site Alive St.dev South Dike East Dike Tern Island Reference Lab Control Overall there did not appear to be any effects from blasting up until the 3-week stage, when the eggs are at their most sensitive stage. However, the PPV guideline of 13 mm/s (Wright and Hopky 1998) was never exceeded at any site for all of the blasts measured in the first 3 weeks, so this is not an unexpected result. Summer Retrieval Summer retrieval occurred July 16-18, Fog, ice and high wind delayed retrieval so it was done over the three days. The five incubators left per chain were retrieved. Each incubator was examined and each cell was classified as dead egg, dead hatch (dead after hatch), empty, or alive. The empty cells were unexpected and may have resulted from experimental design error. The screen used was large enough to allow some young fish to escape and this was observed, but not measured in the lab. The chains within sites agreed for most of the counts (Table 5). Pairwise t-tests revealed that the only counts that differed between chains within sites were Tern Island empty (p=0.009) and alive (p=0.004). The most dead eggs were observed at South Dike. The empty cells were highest at Tern Island, then Reference, South Dike and lowest at East Dike. However, Tern Island and Reference Island agreed well with each other (highest), as did South Dike and East Dike (lowest). The opposite was true for the alive counts at these sites. 9

10 Table 5. Summer retrieval showing means of counts and standard deviations for incubators retrieved from each chain. Site Chain Dead Eggs StDev Dead Hatch StDev Empty StDev Alive StDev South Dike East Dike Tern Island Reference o 1.73 The number of cells that were alive verses empty were highly negatively correlated (r= 0.75, n=40) (Fig. 2). This suggests that the empty cells could have been fish that escaped, therefore to allow comparisons to be made between early and summer retrieval these two categories were combined. Figure 2. Scatter Plot of alive to empty cells recorded from all incubators at summer retrieval (n=40, correlation coefficient 0.75). 25 Number of alive fish Number of empty cells There were no differences between chains within each site, except for south dike (pairwise t-test, p<0.05)(table 6). Indeed among all 8 chains only south dike chain 2 differed from the rest (pairwise t-test, p<0.05). Since effects from blasting are very similar between chains within a site and there is general agreement between the replicate 10

11 chains, they were combined for comparison between sites and for within-site comparison between the early and summer retrieval. Using these combined data, analysis of variance reveals that there is a difference between the sites (p<<0.05)(fig.3). Pairwise t-tests reveal that only South Dike is significantly lower than the other sites (p<0.05). Table 6. Summer retrieval showing means of counts (out of 50) and standard deviations for the empty+alive cell counts. P is the p-value obtained from pairwise t-tests between empty+alive for the chains within a site. Site Chain Empty+Alive Stdev P South Dike East Dike Tern Island Reference Figure 3. Summer retrieval means of counts (out of 50) with chains within sites combined for empty plus alive cell counts. Error bars shown are standard error. Sites significantly different marked with * (pairwise t-tests, p<0.05). 40 Number of alive fish and empty cells * South Dike East Dike Site Tern Island Reference 11

12 Comparisons using pairwise t-tests between early and summer retrieval showed no significant difference between sites or chains for all sites and chains except for south dike (p<0.05)(fig. 4). This suggests that there was no increased mortality from the time of early retrieval through to the end of the incubation period, at all sites except South Dike. Preliminary blasting data has shown that blasting effects were not higher at South Dike then East Dike or Tern Island and therefore it is unlikely that this increase in mortality was due to blasting. A more likely cause is that South Dike is located in a sheltered area of the dike, and the bottom substrate was composed of boulder used in construction of the dike, rather than natural spawning substrate. Overall, it appears that there was no effect of blasting on survival of developing lake trout eggs over the entire incubation period and unless blast size is likely to be larger over this next year, a second field season is not likely to show any effects. Figure 4. Early retrieval (red bars) and summer retrieval (blue bars) survival rates (means of counts out of 50) for each site. Error bars are standard error. Significant differences between retrievals at the sites marked with * (pairwise t-test, p<0.05). 40 Mean of alive fish * 0 South Dike East Dike Site Tern Island Reference 12

13 Update on Objectives Results indicate that because guidelines were rarely exceeded, the spatial extent of the acute blast zone is much less than what was proposed (Objective 1). It appears that neither the occasional guideline-exceeding blast, nor the repeated exposure to blasts increased mortality of post-epiboly eggs. No dead or injured fish were observed in the dike area throughout the spawning season (Objective 2). In fact, many lake trout were seen and captured (gillnets and angling) in close proximity to the dike, even shortly after blasts. Initial results from the 3-week exposure suggest that there are no differences in egg survival after early development between the reference site and the other three sites within the predicted blast zone (Objective 3). This is most likely the result of the low blast levels that occurred during this time period. After this time occasional blasts did exceed guidelines, but this did not appear to increase mortality; the increase in mortality at South Dike is most likely due to site characteristics. To date, increased egg mortality has not been observed, therefore a realized blast zone cannot be determined (Objective 4). Based on the data from the early-retrieval incubators, there is no evidence to indicate that the early development period is an exceptionally sensitive phase for lake trout eggs (Objective 5). This preliminary result must be tempered by the absence of guideline-exceeding blasts. Thus early retrieval would only be warranted next year if PPV levels from blasts were exceeding guideline values during the early development period. Clearly, close monitoring of the blasts must be undertaken during the first few weeks of incubation. 13

14 Measuring the blasts (and possibly the effects) over the next year will allow determination if the effects are attenuating (Objective 6). Additional Objective As a result of the minimal number of guideline-exceeding blasts (and none occurring prior to early retrieval of incubating eggs), we propose another objective for the study: 7) Determine the peak particle velocity (and possibly the overpressure) that will cause increased mortality of incubating lake trout eggs at different stages of development using blast simulation procedures in the laboratory. Lab Study If blasts do not exceed PPV guidelines within the predicted blast zone it can be expected there will be no increase in mortality of eggs. Although such a result would address the question about effects of this specific development, it would not address more general questions concerning blasting effects on developing fish embryos. A recent laboratory study (Jensen 2003) however suggests that it would take a PPV of 14.6 cm/s to cause mortality in the most sensitive stage of chinook salmon (Oncorhynchus tshawytscha), the most sensitive Pacific salmon. This level is an order of magnitude higher than the guideline (13 mm/s) of Wright and Hopky (1998), which is not based directly on biological study (Wright personal communication). Jensen (2003), however, relied on a mechanical disturbance (dropping eggs from various heights) to simulate 14

15 PPVs from blasts; whether this approach is an adequate substitute for blasts remains untested. Because of the large difference between the existing guidelines and the dropheight study of Jensen (2003), an additional lab study is required to determine the PPV that would affect lake trout egg incubation. The most effective study and one that would provide results that are applicable to a field situation, would use a blast simulation procedure that would expose eggs held in incubators to actual or simulated blasts of different intensities, while simultaneously measuring PPV with a geophone and Blast- Mate (as is used in Lac de Gras). Furthermore, if this simulated blast procedure was used in conjunction with the drop height apparatus (Jensen 2003), the latter could possibly be calibrated to actual blast effects, which would facilitate testing of additional species and developmental stages over a broader range of PPVs (or their drop-height equivalents). This, in turn, would promote more detailed and reliable guidelines. Methods To properly assess egg sensitivity to blast levels, a range of blast sizes will be needed over a range of developmental stages. Minimally, blast sizes should include a control, the existing 13 mm/s guideline, the 14.6 cm/s proposed by Jensen (2003), and a blast that produces a PPV well above 14.6 cm/s. Actual levels will have to be determined when the set up is complete but they should range from 0 mm/s to over 200 mm/s. To assess changes in sensitivity, eggs will be exposed during at different stages of development. These stages would include; as soon as possible after fertilization, before 15

16 epiboly is complete, after epiboly is complete, at the eyed stage, and after hatch. Cumulative exposures could also be done to assess if it increases mortality. If 3 (3-5) developmental stages and 8 (6-8) exposure levels (including control) per stage are tested this would mean there would be 24 different treatments per method. If a cumulative treatment was added this would increase the treatment number to 32 per method. Replication of these treatments would be needed. We propose 3 replicates per treatment, using samples of 50 eggs. Therefore 96 samples would be needed per method for a total of 4,800 eggs per method. Comparison of the 2 methods (drop height and simulated blasts) would therefore require 9,600 eggs. Because fecundity is high in individual fish, a random sample of eggs from 3-4 females would ensure individual female effects are minimized. This combination of techniques would allow determination of the most sensitive stage for the lake trout eggs, as well as, the determination of the PPV that causes mortality and/or deformity. If a second field season was not undertaken, then more effort would be made on this lab study, increasing the number of developmental stages and exposure levels. References Jensen, J.O.T New mechanical shock sensitivity units in support of criteria for protection of salmonid eggs from blasting or seismic disturbance. Canadian Technical Report of Fisheries and Aquatic Sciences. 2452: 18 p. Wright, D.G. and G.E. Hopky Guidelines for the use of explosives in or near Canadian Fisheries waters. Canadian Technical Report of Fisheries and Aquatic Sciences

17 Effects of Explosives on Incubating Eggs of Lake Trout in the Canadian Arctic (Blasting Effects Study) Geophysical Component One Year Summary September 3, 2003, to August 9, 2004 Marek Welz and Douglas R. Schmitt Institute of Geophysics, Dept. of Physics, University of Alberta, Edmonton, Alberta, Canada August 16,

18 Summary of underwater ground motions observed at DDMI September 3, 2003, to August 9, 2004 Marek Welz and Douglas R. Schmitt Summary: Seismic blast monitoring is being carried out to assist fish habitat studies at Diavik Diamond Mines Inc. (DDMI) in the N.W.T. This report summarizes the 317 events recorded over 4 sites at a variety of distances from the A154 pit where blasting is used for excavation and ore recovery. Unique underwater sensors were used in this monitoring in order to record the ground motions in direct proximity to fish habitat within Lac de Gras. Relative to existing Department of Fisheries and Oceans (DFO) guidelines, pressures induced in the water column did not exceed 0.1% of the DFO limit of 100 KPa. Peak Particle Velocity (PPV) limits (13 mm/s) were exceeded in 13 separate records. Introduction The University of Alberta was asked to assist in a study of the effects of mine blasts on the fish hatchery within Lac de Gras, N.W.T. in the vicinity of the DDMI mine Site. This initial design of the study consists of both biological monitoring of fish hatching carried out by Sean Faulkner under the supervision of Dr. W. Tonn of the Department of Biology and correlative ground shaking measurements conducted by Marek Welz with Dr. Douglas Schmitt of the Institute for Geophysical Research in the Department of Physics. The Biological measurements have been reported under separate cover, this brief provides a description of the geophysical measurements and a preliminary summary of 2

19 typical blast parameters observed over the period from September 3, 2003 to August 9, The report first describes the measurement techniques employed then summarizes the results. To date, a total of 317 separate blasting events were monitored. Of these 317 measured events 13 exceed the current 13 mm/s DFO guideline for shaking of the solid substrate. (Fig. 1). Over pressures within the water column (Fig 2.) measured are mostly small with the highest recorded at11 Pa., well below the current DFO guideline of 100 KPa. Figure 1: Measured Peak Particle Velocities for all 4 sites and all measured blasts versus calendar date. Of the 317 measured events only 13 exceed 13 mm/s. Red horizontal line represents current published DFO guidelines. Values are the Peak Vector Sum of the 3 components. 3

20 Figure 2: Measured over-pressures for all 4 sites and all measured blasts versus calendar date. The highest recorded value is 11 Pa. well below DFO guidelines of 100 KPa. Recording Equipment: Each of the four study sites has a four-component sensor (Fig 3.) deployed to measure the Peak Particle Velocities and Over Pressures created by blasting. The sensors, originally designed for deep-ocean reservoir monitoring, have been adapted by Instantel to work with the Minimate Plus (blast mate) monitors. Three self-orienting 30CT 10Hz OYO geophones and an MP25 10 Hz hydrophone are contained in a waterproof container with a 100 metre cable connected to the Instantel Minimate Plus vibration and overpressure monitor. The recording unit monitors all activity, but only records events that exceed a predetermined threshold. It is important to briefly describe these sensors as the authors are not familiar with the use of such underwater four-component detectors previously. As noted, each unit contains 4

21 three geophones specially mounted in a gimballed arrangement such that two of the geophones will lie horizontally and a third vertically regardless of the orientation at which the sensor package is placed on the lakebed. A geophone is a type of seismic detector that consists primarily of a magnetic mass that oscillates through a coil to produce a voltage that depends on the velocity of the ground (i.e. particle) motion induced by the blasts. All three geophones detect the arriving seismic energy; the values shown represent a vector summation of all three values to provide the actual peak particle velocity (PPV). A fourth sensor, the hydrophone, is also included in the sensor package, and is sensitive to the variation in pressure within the water due to the passing of the seismic waves. Figure 3: Display model of the OYO 4C sensor showing the internal workings. Methodology: Prior to each blast, whenever possible, DDMI personnel connect the blast mates to the sensors which record any shaking that exceeds the thresholds. After blasting the units are collected and the data is downloaded to a PC and sent to U of A personnel for analysis. Three of the sensors are set to trigger on either of the geophone channels at 1.5 mm/s 5

22 while the Reference Island site sensor is set at the minimum threshold of.51 mm/s. Travel to two of the four study sites is hampered by extreme weather conditions, freeze up or spring thaw, resulting in less than ideal data collection for these sites. The data is routinely scrutinized by University of Alberta personnel to determine if recorded events can be attributed to, either blasting, real events or electrical noise. A simple correlation between blast times and event times is observed. Blasts were noted to display a distinct waveform within the data set. Plots of PPV vs. event number are plotted for each site. Data is plotted in its 3 components, Transverse, Longitudinal and Vertical, which are used to determine the Peak Vector Sum (PVS) Peak Particle Velocity. The peak vector sum is used to determine if guidelines are exceeded. The results from each of the different sites are discussed separately below. 6

23 Reference Island East Dike Tern Island South Dike Figure 5: Locations of the 4 sensors in relation to the dike and proposed pit. Four sites were selected for sensor placement. The furthest site (approximately 3 km from the blast zone) is called Reference Island ; it was selected to provide some baseline measures for comparison. Two sites were selected at strategic locations along the dike to allow for ease of access. A fourth site at Tern Island, about 1 km offset, was selected to provide additional distances from the blasts. An important criterion during selection of the sites was the quality of the lake beds for fish hatching based on maps provided by Diavik. 7

24 South Dike Sensor 8902 The South Dike site is easily accessible from the dike, where the blast mate is directly connected to the sensor. Data Collection for this site took place during the period September 3 rd 2003 through August 4 th, A total of 133 events were recorded during this period. Six of the recorded events exceeded current DFO guidelines. Figure 6: PPV histogram for the South Dike location. 8

25 Reference Island Sensor 8903 The Reference Island site is located some 3km north east of dike. Access to site was hampered by extreme weather conditions, and thus limited the amount of data generated. It should be noted that many of the small blasting events were out of range and thus not measurable from this site (i.e. the recording devices did not trigger). Data Collection for this site took place during the period September 3 rd 2003 through August 4 th, (no events between July 28 th and August 4 th, 2004 triggered the sensor). A total of 15 events were recorded during this period. None of the recorded events exceeded current DFO guidelines. Figure 7: PPV histogram for the Reference Island location 9

26 Tern Island Sensor 8904 The Tern Island site is located some 300m west of the dike offshore. Access to the site was again hampered by extreme weather conditions and again limited the quantity of data collected. Data Collection for this site took place during the period September 3 rd 2003 through August 9 th, A total of 48 events were recorded during this period. Two of the recorded events exceeded current DFO guidelines. Figure 6: PPV histogram for the Tern Island location 10

27 East Dike Sensor 8905 The East Dike site is easily accessible from the dike, where the blast mate is directly connected to the sensor. Data Collection for this site took place during the period September 3 rd 2003 through August 9 th, A total of 118 events were recorded during this period. Five of the recorded events exceeded current DFO guidelines. Figure 9: PPV histogram for the East Dike location Summary of Observations: Briefly, it would appear that there is a direct correlation between measured responses and the proximity to the blast, as evidenced by the data, which shows some blasts to exceed guidelines at one site near the dike while other sites near the dike do not exceed the stated guidelines. The largest PPV of 28.5 mm/s was recorded at East Dike; the same blast was 11

28 measured at both Tern Island and South Dike where it showed values less than the stated DFO guidelines. Overall no significant differences between the blast sizes at the three sites are seen. Average recorded PPVs were about 6mm/s for all three sites within the blast zone; 5.9 at East Dike, 6.2 at Tern Island and 6.4 at South Dike. While South Dike is slightly closer to the centre of the pit than East Dike, Tern Island is the furthest. Comparison between sites is difficult due to the lack of records, particularly from Tern Island and Reference Island. Future Work: A scaled distance plot will be created once the appropriate blast data parameters are provided. This plot is used to predict PPVs at distances from blasts based on the size of the blast size per delay. Continued monitoring of blasts using the current field equipment will enable us to increase our data set for scaled distance plots and comparison to scaled distance functions created DDMI and Ekati. The study of effects on fish eggs by blasting at the mine site will continue under laboratory conditions where shaking of the substrate can be reproduced in a controlled manner. PPVs from 10 to 150 mm/s will be achieved. The controlled study designed by Sean Faulkner will allow for different levels of exposure on different sets of eggs in a manner not achievable in field conditions. 12