North American Journal of Fisheries Management 25:130–137, 2005 q Copyright by the American Fisheries Society 2005 DOI: 10.1577/M03-196.1
[Management Brief]
Evaluating the Effectiveness of Instream Habitat Structures for Overwintering Stream Salmonids: A Test of Underwater Video LEAH D. CARLSON
AND
MICHAEL S. QUINN*
Faculty of Environmental Design, University of Calgary, 2500 University Drive Northwest, Calgary, Alberta T2N 1N4, Canada Abstract.—Instream habitat structures are often employed by fisheries managers to enhance habitat quality. The effectiveness of instream habitat structures, however, is hindered by a lack of critical and systematic assessment of their success, especially in winter conditions. This study tested the use of underwater video as a method to evaluate the use of instream habitat structures (V-weirs) by overwintering salmonids in the Crowsnest River of southwestern Alberta, Canada. The use of readily available and relatively inexpensive video equipment was shown to be effective in documenting salmonid use of winter habitat both under the ice and in open water. This technique may be particularly appropriate in areas where sampling mortality is a concern and where other methods are impractical or dangerous (e.g., small, ice-covered streams or rivers).
Winter alters the physical habitat features of many temperate, lotic environments and influences the behavior and survival of stream salmonids (Heggenes et al. 1993; Cunjak 1996; Jakober et al. 1998). Lower water temperatures result in decreased digestion rates, lower food requirements, reduced swimming ability, and elevated net energy costs (Maciolek and Needham 1952; Chapman 1966; Cunjak and Power 1986; Cunjak 1988). Subsurface ice development can significantly limit accessibility and effectiveness of habitat, especially in conjunction with low instream flow rates (Berg 1994; Prowse 1994; Brown and Mackay 1995; Jakober et al. 1998). Salmonid overwinter survival in adverse lotic environments requires habitat characterized by low water velocity, adequate depth, structural cover, and groundwater discharge. Such habitat is thought to be the primary factor regulating stream fish populations in winter (Cunjak 1996). Instream habitat structures are often employed by fisheries managers to enhance habitat quality. However, most are designed with summer conditions in mind and little consideration is given to their functionality in winter. Furthermore, our un* Corresponding author:
[email protected] Received October 6, 2003; accepted April 14, 2004 Published online February 28, 2005
derstanding of instream habitat structure utility is hindered by insufficient physical and biological assessments of their performance (Fitch et al. 1994; Kondolf and Micheli 1995; Minns et al. 1996). Evaluations of artificial structure effectiveness in winter are particularly scarce. One obstacle to evaluating fish use of reclaimed or enhanced habitat in winter is the limitation of existing field techniques under shallow, ice-covered lotic conditions. Conventional fish sampling techniques are biased toward open-water studies. Modifications of electrofishing techniques and equipment, which rely on divers to operate equipment and retrieve fish (James et al. 1987; Emmett et al. 1992), may be adaptable to ice-covered lotic conditions. Scuba and snorkel surveys have been conducted under ice-covered river conditions (Schmidt et al. 1989; Emmett and Convey 1990; Jakober 1995; Jakober et al. 1998). Schmidt et al. (1989) reported a technique to sample fish under the ice using divers with seine and fyke nets for fish collection. Underwater video sampling has been used under both open-water and ice-covered conditions (Schmidt et al. 1989; Groves and Garcia 1998). However, under shallow, ice-covered river conditions, these methods can be dangerous or impossible. The purpose of this study was to determine the effectiveness of underwater video as a method for comparing the relative use of enhanced and natural pools by stream salmonids in winter. The study was designed to test the null hypothesis that there was no difference in the relative number of salmonids between treatment (V-weir) and control sites (high-quality natural habitat) in the Crowsnest River, Alberta. Study Area The Crowsnest River, a headwater stream of the South Saskatchewan River basin, is located in southwestern Alberta on the eastern slopes of the Rocky Mountains. During the open-water and icecovered study periods, the average daily discharge rates of the Crowsnest River were 0.997 m3/s and 1.08 m3/s, respectively. The average river width
130
MANAGEMENT BRIEFS
at the study sites was 10.25 m. A substantial waterfall, Lundbreck Falls, is a barrier to upstream fish passage and functionally divides the river into upper and lower sections. Ice cover on the Crowsnest River is highly variable between years, with many reaches remaining ice free. Historically, the Crowsnest River flowed for 55.2 km to a confluence with the Castle and Oldman rivers. In 1992, the construction of the Oldman River Dam (OMRD) near this confluence shortened the length of the Crowsnest River by approximately 9.1 km. The construction of the dam resulted in an objective by the managing authority to achieve no net loss of recreational fishing opportunities (Dominion Ecological Consulting, Ltd. 1988). To compensate for an estimated 225,000 m2 of critical salmonid habitat lost to inundation, habitat structures were constructed upstream of the reservoir in the Castle, Crowsnest, and Oldman rivers (R. L. & L. Environmental Services, Ltd. 1993). Assessing the achievement of a no-net-loss management goal requires a substantial commitment to effectiveness monitoring. Six sport fish species are present in the Crowsnest River: mountain whitefish Prosopium williamsoni, rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, cutthroat trout O. clarkii, brook trout Salvelinus fontinalis, and bull trout Salvelinus confluentus (Ash et al. 1987). Mountain whitefish and rainbow trout are the most numerous sportfish, accounting for 60% and 30% of individuals, respectively (Ash et al. 1987; R.L. & L. Environmental Services, Ltd. 1994). Brown trout and bull trout are found only in the lower Crowsnest River (e.g., below Lundbreck Falls; Fitch 1997). Methods The locations of 45 potential sample sites (treatment and controls) were located and marked with flagging tape in the fall of 1998. Marking the sites ensured that they could be relocated after ice formation. We anticipated that an adequate sample size of ice-covered pools could be obtained from the potential sites. However, an unusually warm winter resulted in few areas with substantial surface ice formation. Conditions dictated that we were only able to utilize four ice-covered sites and 10 open-water sites to provide an adequate representation of treatment and control pools within a practically feasible sample area. The four icecovered sites were selected in the lower Crowsnest River, below Lundbreck Falls. Ten open-water sites were chosen in two separate portions of the upper Crowsnest River: four directly downstream
131
FIGURE 1.—Photograph of Sony High-8 video camera used for recording observations.
of the town of Blairmore, and six approximately 5 km upstream, west of the town of Coleman. In each open-water and ice-covered area, half of the sites were V-weirs (the instream habitat structure chosen as the treatment) and half were high-quality habitat control pools. Definition of control sites as high quality was based on professional judgment and the presence of deep, low-velocity habitat, considered important instream qualities in winter (Cunjak and Power 1986; Brown 1994; Brown and Mackay 1995; Jakober 1995). Observations were recorded with a Sony High8 video camera (Model CCD-TRV72) in a waterproof housing (Sony Underwater Video Marine Pack [MP], Model MPK-TRV2; Figure 1). The video camera was equipped with a standard wideangle (37-mm) lens. One SONY MP light was mounted on top of the housing exterior. Camera and light battery power was supplied by 12-h and 8-h lithium batteries. This design was selected because of its proven performance in dive situations, availability, and relatively low cost. A 4.2-cm-wide steel bracket was molded around the housing to provide a frame for pole attachment. A rubber strip (5 cm wide) installed between the housing and bracket prevented bracket slippage. The bracket base (under the housing) was widened into a steel foot (24.2 3 8.9 cm) to provide a protective and stable resting platform. Modified aluminum pipes functioned as extension devices to maneuver the housing in ice-covered and open-water conditions. The poles (2.5 cm
132
CARLSON AND QUINN
in diameter) were composed of several detachable, articulating sections to allow for length or angle adjustments. Pole lengths of 2.0 m (ice covered) and 3.0 m (open water) proved to be sufficient for pool filming in the Crowsnest River. Poles were fitted with foam tubing or bicycle handles to provide grip and protection from the cold. A lightweight polypropylene rope was attached to the top of the housing and taped along the exterior length of the pole; this functioned as a safety line to retrieve the camera–housing in the event of pole– joint failure. At each ice-covered site, four holes were drilled in the ice using a large, gas-powered auger. The size of the hole was made just large enough to lower the camera housing through the ice (approximately 40 3 60 cm). Holes were located across the pool in a manner intended to cover the entire pool area. The influence of noise was minimized by maintaining at least 20 min of quiet between ice chipping or drilling and filming. To decrease the likelihood of detection by fish, filming commenced at the downstream hole and moved sequentially upstream (assuming that the fish face the current). At each hole, the camera was lowered to approximately 15 cm from the riverbed. Filming parallel to the river bottom in automatic focus, the camera was slowly rotated 3608 twice in each hole (approximately 2 min per rotation). Each filming rotation commenced facing upstream and included a brief pause every 908. Pauses were intended to document underwater structures (e.g., boulders, woody debris) and to aid in the definition of new or duplicate individuals. Open-water filming commenced with the camera operator standing on the streambank at the downstream extent of the pool. The preferred bank was determined by access and the angle of incident solar radiation (avoiding casting shadows over the pool). As with ice-covered filming, the video camera was set on automatic focus, parallel to the riverbed. The operator held the distal end of the pole and swept the camera–housing unit in an upstream direction. The first sweep was shallow, advancing upstream from the furthest downstream portion of the pool, followed by a return sweep downstream. The second sweep reached as deep into the pool as possible and was directed upstream and downstream similar to the first sweep. Filming from the streambank continued upstream to cover the length of the pool. Larger pools required that the operator film from both banks and wade into stream margins. Pool sweeps continued until the pool area was covered.
Each of the selected pools was sampled six times. Pools in close proximity to each other were sampled on the same day to maintain independence of samples. The number of fish observed at each of the seven treatment (five open-water and two ice-covered) and seven control (five open-water and two ice-covered) pools was recorded for each of the six replicates. To judge whether the relative abundance of salmonids was significantly different between V-weirs and controls and to test for the effects of ice cover, we employed a two-factor analysis of variance (ANOVA; Zar 1996). In addition, we used Mann–Whitney U-tests to test for differences between the number of fish at treatment (V-weir) and control (high-quality natural habitat) pools for all sample sites combined as well as for ice-covered and open-water sites separately. Results Ice-Covered Sites Filming under river ice occurred in the periods of 15–25 January and 19–25 February, 1999. During these dates, water and air temperatures ranged from 08C to 18C and from 2158C to 188C, respectively. Collection of data comprised six replications separated by at least 24 h at each of the two V-weirs and two control sites (24 samples). A period of unseasonably warm weather during sampling lead to ice and snowmelt and interruptions in filming due to flowing water over the ice surface. Approximately 10% of ice-covered video data were severely compromised by increased suspended solids during this warm period. These results were not included in the analysis. Twenty-nine salmonids were observed in the four ice-covered sites. Of this total, 21 fish were present in V-weirs and 8 in control pools (Table 1). Similar numbers were documented within the V-weir (10 and 11) and control (4 and 4) sites. No fish were observed in groups. Salmonids under the ice were relatively inactive, usually resting and swimming slowly. Feeding was not recorded. All identifiable fish observed were adults (no parr marks visible). It was not possible to differentiate between trout and mountain whitefish for 31% of fish observed. Open-Water Sites Data were collected at open-water sites on 7– 13 March 1999. Six replications, at least 24 h apart, were conducted at each of the five V-weirs and five control sites (60 samples total). Water temperatures ranged between 0.58C and 3.58C. Air temperatures varied between 268C and 168C.
133
MANAGEMENT BRIEFS
TABLE 1.—Number of salmonids observed in the Crowsnest River sample sites. Site labels are as follows: B 5 Blairmore, C 5 Coleman, L 5 Lundbreck; v 5 V-weir, c 5 control; the number indicates the site number.
Replicate 1 2 3 4 5 6 Total
Bv-1 Bv-2 Cv-1 Cv-2 Cv-3 Total 26 21 12 20 17 18 114
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
1 1 4 0 0 0 6
Ice-covered V-weirs
Open-water control sites
Open-water V-weir sites
27 22 16 20 17 18 120
Bc-1 Bc-2 Cc-1 Cc-2 Cc-3 Total 3 0 5 2 6 8 24
4 3 10 1 0 0 18
None of the open-water video results were severely compromised by visibility problems. A total of 201 salmonids were identified: 120 in V-weirs and 81 in control pools (Table 1). Approximately 9% of individuals were not identifiable to species. Identifiable fish observed in video sampling were likely adults (no parr marks visible), with the exception of five large juveniles. One V-weir was highly preferred, with 114 of 201 (56.7%) of the total fish enumerated. Fish were observed at least once in all five control sites, and no fish were recorded in three of five V-weirs. Groups of sport fish, containing 3–22 individuals, were documented at three of five control sites and one V-weir site. Aggregations consisted of whitefish alone, trout alone, or trout and mountain whitefish. Behavior of congregations varied from actively feeding and schooling to resting in sheltered areas of the pool. Observations of aggregations at control sites were inconsistent over the six filming sessions. The largest aggregations of fish were consistently recorded at the preferred V-weir site. Statistical Tests The results of the two-factor ANOVA indicated no significant interaction effects between habitat and ice cover (F1,80 5 0.007; P 5 0.931). There were no significant differences in the number of fish observed between the ice-covered and openwater pools (F1,80 5 2.919; P 5 .091) or between treatment (V-weir) and control pools (F1,80 5 0.904; P 5 0.345). A Mann–Whitney U-test comparing the number of fish observed at treatment and control pools for all sample sites resulted in no statistically significant difference (U 5 799; P 5 0.428). When analyzed separately, there were no statistically significant differences in the number of fish observed at control and V-weir pools in the open water sites (U 5 353.5; P 5 0.118), but there were significantly more fish observed at
2 5 2 3 12 8 32
4 0 2 0 0 0 6
0 0 0 1 0 0 1
13 8 19 7 18 16 81
Lv-1 Lv-2 Total 3 1 1 1 2 2 10
4 2 4 0 1 0 11
7 3 5 1 3 2 21
Ice-covered controls Lc-1 Lc-2 2 1 0 0 0 1 4
2 1 0 1 0 0 4
Total 4 2 0 1 0 1 8
V-weirs than control sites in the ice-covered pool (U 5 37, P 5 0.045, one-tailed). Discussion Appropriateness of Methodology for Ice-Covered Effectiveness Monitoring Underwater video observation, as a technique to assess salmonid use of artificial and natural pool habitat, has numerous practical applications in icecovered river sampling. Species composition, relative abundance, behavior, and habitat use information were successfully recorded by filming through several ice holes over each pool. The level of enumeration and positive identification of fish observed was dependent on the distance between the camera and fish, turbidity, and fish activity. Experimentation with different camera–pole angles and focus improved the quality of underwater video observations. Due to the relatively shallow pool depths (,2.0 m) under the ice, horizontal filming (approximately 15 cm above the riverbed) allowed viewing of fish resting on the bottom as well as of individuals near the ice undersurface. Automatic focus was found to be more effective than the manual setting. However, filming in automatic focus resulted in focus on close objects, limiting the clarity of background objects. The focal capability of the camera is influenced by several factors. On warm days (air temperature . 08C), elevated runoff conditions increase the turbidity. The winter of 1999 was warmer than average and resulted in a considerable number of days with reduced underwater visibility. Instream debris and turbulence also decreased the depth of field. Since cloud cover increased the visibility by reducing light penetration through the ice, instream particle reflection was reduced. Thus, optimal video quality resulted on cold, cloudy days in calm portions of stream pools with minimal instream debris. Considering the range of factors
134
CARLSON AND QUINN
which influence visibility, the under-ice focal range varied from approximately 2 to 4.5 m. A fright response to the presence of camera and light was rare. An aversion was observed only when the camera was moved into close proximity with resting individuals. In a few cases, fish exhibited a phototactic response. This reaction was problematic in that it complicated observation results. For example, in rotation A, a salmonid swims by the camera, and then a similar fish is filmed in rotation B. Positive determination as to whether two observations of similar fish were for the same or different individuals is difficult. There are several factors that may compromise the utility of this technique under river ice. Problems associated with the extreme environmental conditions of winter were encountered. Difficulties were directly related to water freezing immediately upon bringing the camera out of the river. For example, a wind chill of approximately 208C resulted in housing control seizure and the development of a layer of ice over the housing lens. These conditions caused operation difficulties and blurred video results. The situation was remedied with a modest amount of alcohol applied with a mist bottle. Appropriateness of Methodology for Open-Water Effectiveness Monitoring Underwater video observation is an effective technique to assess the relative abundance of adult salmonids between V-weirs and natural high-quality pools in open-water river pools. Fish exhibited little or no response to the presence of the camera. This field method was also useful for recording behavior, species, and habitat use information under these conditions. Maximum depth of field capability of the camera was approximately 5.5 m in open-water conditions. The quality of information collected was dependent on the distance between the camera and fish, turbidity, and fish activity. A variety of pole and camera angles was tested in the field. As with ice-covered filming, optimal visibility was achieved with the camera filming in automatic focus, parallel with the river bottom. The appropriate pole angle (relative to the housing) for horizontal filming depended on the steepness of the riverbank and pool depth. Regular pole housing angle adjustments were necessary to adjust for differences in bank character between sites. The combination of the equipment weight and river current resulted in maneuverability difficulties. This situation was alleviated through the use
of a 40-m lightweight rope attached to the top of the housing and held taut by an assistant positioned on the upstream bank. Extra leverage aided in camera movement upstream and eased downstream movement. Consequently, pressure on the pole was decreased, filming was smoother and more controlled, and video quality was improved. The angle of the sun influenced the best time of day to film at each site. Video quality was degraded when sun rays penetrated the water column, resulting in high light refraction and reflection off instream particles. Optimal filming times were generally early morning, later afternoon, or cloudy days. The exterior mounted housing light was ineffective in open water. Certain difficulties were encountered in openwater testing. First, effective pool filming was limited by the stream character. Pools with extensive (.2 m) sand–silt bars along the stream margin were difficult to film by extending the pole from shore. Wading to access the pool resulted in reduced visibility because of disturbed sediment. Presence of the operator within the pool may also decrease the utility of this method to assess fish behavior and distribution in large pools. However, a fright response to wading was rarely observed. Experimentation with pole length extension may alleviate this problem. Testing Underwater Video Techniques for Evaluating Habitat Improvement in the Crowsnest River Small numbers of salmonids were consistently observed in ice-covered V-weir pools. All fish documented under ice were recorded individually and were relatively inactive compared with observations in open water. In contrast, most fish using open-water V-weirs were recorded in aggregations of three or more individuals and were observed feeding, resting, and swimming. One of the openwater V-weirs was highly preferred over all other sites. Further research is required to determine the reasons for salmonid selection of this site over other visibly similar sites. Underwater video observation results from both the open-water and ice-covered samplings showed no statistically significant differences in the number of fish observed between V-weirs and control habitats. The only exception was that more fish were observed in V-weirs than in control pools for the ice-covered sites. Therefore, the null hypothesis that there is no difference in the relative number of salmonids between V-weir and control sites in the Crowsnest River cannot be rejected for
MANAGEMENT BRIEFS
open-water sites, but can be rejected for icecovered sites. The management significance is that the installation of V-weirs provided winter habitat at least as good as high-quality natural habitat. Conclusions Underwater video is useful for recording winter species composition, relative abundance, behavior, and habitat use information in open-water and icecovered river pools. The methods employed in this study were particularly effective for highly variable conditions that precluded other, more conventional sampling techniques. However, the likelihood of the successful collection of winter habitat use data may be increased under consistently cold winter conditions. In the near freezing environment, salmonid metabolism is slowed, activity levels are reduced, and salmonids often congregate in deep, low-velocity pools (Cunjak and Power 1986; Heggenes et al. 1993; Jakober 1995; Jakober et al. 1998). These physiological and behavioral changes in winter increase the likelihood of recording relatively stationary fish with a filming device. In addition, under frozen conditions, visibility would be improved with reduced turbidity. Diurnal underwater video is not effective for sampling juvenile salmonids. Diurnal concealment behavior of juvenile salmonids in winter is well documented (Campbell and Neuner 1985; Heggenes et al. 1993; Riehle and Griffith 1993; Contor and Griffith 1995). The low number of juveniles observed in both portions of this study support the likelihood of this winter behavior in the Crowsnest River. Degraded video results and phototactic fish response hindered the effectiveness of open-water and ice-covered nocturnal testing. Snorkel observations have successfully recorded juveniles at night (Riehle and Griffith 1993). Further experimentation with the type and power level of the light source may improve the quality of night filming. The inability to observe video while filming decreased the potential quality of results. This problem was evident in both the open-water and icecovered portions of this research. Connection of a monitor to a similar underwater video–housing unit has been used successfully to survey salmonid redds and spawning habitat in a large, ice-free river (Groves and Garcia 1998). This capability would have improved the validity of salmonid quantification and identification in the current research project. Pole lengths tested in this study were sufficient-
135
ly long and functioned well in the Crowsnest River. To accommodate deeper or wider river studies, the maximum functional extension length would likely be 1.5 m. This extension would require greater reliance on the upstream rope for leverage and a strong, agile camera operator. Field testing revealed that a 1.3-cm-diameter pole was too weak to withstand the camera–housing weight and river current. The 2.5-cm-diameter pole (utilized in this study) was durable, but heavy and difficult to control. A 1.9-cm-diameter pole would likely be the optimal size, possessing both strength and a relative light weight. To increase pole maneuverability and balance the weight of the camera, design and operation modifications of open-water filming could also be explored. For example, use of a waist harness with a pole pocket (similar to a flag carrier) may be adaptable. The strength of this technique may be improved if it is used in conjunction with other methods. For instance, the addition of radiotelemetry techniques could determine movement patterns to ascertain whether these structures increase the overwintering survival of salmonids. The combination of underwater observation (snorkel–scuba) and telemetry has been successfully used in previous icecovered winter studies to collect information on micro- and macrohabitat use and movement (Emmett and Convey 1990; Jakober 1995; Jakober et al. 1998). The use of underwater video in conjunction with under-ice gill netting may allow for population estimates to be made without incurring as high a mortality rate as with gill netting alone. Hill et al. (1996) developed a method to set and retrieve gill nets, without divers, under river ice. The use of video instead of snorkel–scuba methods may reduce the risk associated with diving in shallow, ice-covered conditions. To improve underwater video methodology, additional ice-covered studies should be conducted. Research that includes increased illumination or positions of lights (e.g., placement through another ice hole at different depths, alteration of light angle, or two lights at different locations) and the use of polarized lenses and light filters are two areas worth pursuing to improve video resolution. Experimentation with different filters and lenses may increase video clarity by reducing instream particle reflection or by increasing the sensitivity of the receiving body (fish). As a method for sampling salmonids under shallow river ice, underwater video possesses several advantages over the sampling alternatives. Other winter sampling methods, such as electrofishing
136
CARLSON AND QUINN
and netting, can unavoidably lead to fish mortality and generally involve scuba or snorkel. The unobtrusive nature of video is particularly favorable when dealing with an important recreational fishery and threatened species such as the bull trout. For fisheries planning, management, and decision making to be effective, fish use of mitigation structures must be evaluated throughout the year. We found underwater video to be a useful method for assessing relative abundance estimates between enhanced and natural pools during winter. With proper management of turbidity issues, this technology is appropriate to sample shallow, icecovered river systems in cold winter conditions. The use of underwater video equipment should be considered an affordable option which takes little time and personnel to operate. The findings of this methodological exploration are preliminary and should be expanded by a long-term assessment of the capabilities of underwater video observation. Acknowledgments The funding for the study was supplied by Alberta Sport, Recreation, Parks, and Wildlife, Alberta Environment, and Graduate Studies faculty, University of Calgary. Bob Fisher was instrumental in the pole and housing design. We appreciate the valuable project development comments provided by Lorne Fitch and Kerry Brewin. Two anonymous reviewers provided valuable comments on the original manuscript. We thank staff members of Alberta Fish and Wildlife for their expertise in fish identification. Rick Pattenden, Jim O’Neil, and John Englert were very helpful in many aspects of the project. We thank Stephen Lebeuf, Trent Carlson, Vernon Andres, and Shawn Tratch for their innovative ideas and valuable field support. References Ash, G. R., L. Hildebrand, and J. O’Neil. 1987. Oldman River dam project, fisheries mitigation pre-engineering studies: Crowsnest River fish population studies2data summary. R. L. & L. Environmental Services, Ltd., Report prepared for Alberta Public Works Supply and Services, Edmonton. Berg, N. H. 1994. Ice in stream pools in California’s central Sierra Nevada: spatial and temporal variability and reduction in trout habitat availability. North American Journal of Fisheries Management 14:372–384. Brown, R. S. 1994. Spawning and overwintering movements and habitat use by cutthroat trout (Oncorhynchus clarki) in the Ram River, Alberta. Master’s thesis. University of Alberta, Edmonton. Brown, R. S., and W. C. Mackay. 1995. Fall and winter
movements of and habitat use by cutthroat trout in the Ram River, Alberta. Transactions of the American Fisheries Society 124:873–885. Campbell, R. F., and J. H. Neuner. 1985. Development of seasonal habitat preference criteria for rainbow trout (Salmo gairdneri) in western Washington Cascade Mountain streams, volume II. Puget Sound Power and Light Company, Bellevue, Washington. Chapman, D. W. 1966. Food and space as regulators of salmonid populations in streams. American Naturalist 100:345–357. Contor, C. R., and J. S. Griffith. 1995. Nocturnal emergence of juvenile rainbow trout from winter concealment relative to light intensity. Hydrobiologia 299:179–183. Cunjak, R. A. 1988. Physiological consequences of overwintering: the cost of acclimatization? Canadian Journal of Fisheries and Aquatic Sciences 45: 443–452. Cunjak, R. A. 1996. Winter habitat of selected stream fishes and potential impacts from land-use activity. Canadian Journal of Fisheries and Aquatic Sciences 53(Supplement 1):267–282. Cunjak, R. A., and G. Power. 1986. Winter habitat utilization by stream-resident brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences 43:1970– 1981. Dominion Ecological Consulting, Ltd. 1988. A strategy for fisheries mitigation in the Oldman River basin, volume I. Upstream component. Report prepared for Alberta Environment, Planning Division and Alberta Forestry, Lands, and Wildlife, Fish and Wildlife Division, Edmonton. Emmett, B., and L. Convey. 1990. Overwintering of juvenile Chinook salmon in the Nechako River: 1989–90 studies. Report prepared for the Department of Fisheries and Oceans, Canada, Victoria, British Columbia. Emmett, B., C. D. Levings, P. Kerfoot, and R. B. Lauzier. 1992. A prototype submersible electrofisher: design and user manual. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2143. Fitch, L. A. 1997. Bull trout in southwestern Alberta: notes on historical and current distribution. Pages 147–160 in W. C. Mackay, M. K. Brewin, and M. Monita, editors. Friends of the Bull Trout Conference Proceedings. Friends of the Bull Trout, Calgary, Alberta. Fitch, L. A., M. Miles, J. O’Neil, R. Pattenden, and G. Van Der Vinne. 1994. Defining the variables that influence success of habitat structures in southwestern Alberta: a work in progress. In The 9th International Trout Stream Improvement Workshop. Trout Unlimited Canada, Calgary, Alberta. Groves, P. A., and A. P. Garcia. 1998. Two carriers used to suspend an underwater video camera from a boat. North American Journal of Fisheries Management 18:1004–1007. Heggenes, J., O. M. Krog, O. R. Lindas, J. G. Dokk, and T. Bremnes. 1993. Homeostatic behavioral responses in a changing environment: brown trout
MANAGEMENT BRIEFS
(Salmo trutta) become nocturnal during winter. Journal of Animal Ecology 62:295–308. Hill, T. D., S. T. Lynott, S. D. Bryan, and W. G. Duffy. 1996. An efficient method for setting gill nets under ice. North American Journal of Fisheries Management 16:960–962. Jakober, M. J. 1995. Autumn and winter movements and habitat use of resident bull trout and westslope cutthroat trout in Montana. Master’s thesis. Montana State University, Bozeman. Jakober, M. J., T. E. McMahon, T. F. Thurow, and C. G. Clancy. 1998. Role of stream ice on fall and winter movements and habitat use by bull trout and cutthroat trout in Montana headwater streams. Transactions of the American Fisheries Society 127:223– 235. James, P. W., S. C. Leon, A. V. Zale, and O. E. Maughan. 1987. Diver operated electrofishing device. North American Journal of Fisheries Management 7:597– 598. Kondolf, G. M., and E. R. Micheli. 1995. Evaluating stream restoration projects. Environmental Management 19(1):115. Maciolek, J. A., and P. R. Needham. 1952. Ecological effects of winter conditions on trout and trout foods in Convict Creek, California. Transactions of the American Fisheries Society 81:202–217.
137
Minns, C. K., J. R. M. Kelso, and R. G. Randall. 1996. Detecting the response of fish to habitat alterations in freshwater ecosystems. Canadian Journal of Fisheries and Aquatic Sciences 53(Supplement 1):403– 414. Prowse, T. D. 1994. Environmental significance of ice to streamflow in cold regions. Freshwater Biology 32:241–260. Riehle, M. D., and J. S. Griffith. 1993. Changes in habitat utilization and feeding chronology of juvenile rainbow trout at the onset of winter in Silver Creek, Idaho. Canadian Journal of Fisheries and Aquatic Sciences 50:2119–2128. R. L. & L. Environmental Services, Ltd. 1993. Fish population responses in Crowsnest River to OMRD mitigation program, 1987–1991. Draft report prepared for Alberta Public Works Supply and Services, Edmonton. R. L. & L. Environmental Services, Ltd. 1994. Fisheries evaluation program: 1992 annual report—Crowsnest River. Final report prepared for Alberta Public Works Supply and Services, Edmonton. Schmidt, D. R., W. B. Griffiths, and L. R. Martin. 1989. Overwintering biology of anadromous fish in the Sagavanirktok River delta, Alaska. Biological Papers of the University of Alaska 24:55–74. Zar, J. H. 1996. Biostatistical analysis, 3rd edition. Prentice-Hall, Upper Saddle River, New Jersey.
