A Three Year Study of an Isolated Brook Trout Population in the Eastern Adirondacks: Sustainability, Propagation and Genetics

Over the past several years changing weather patterns have led to costly and destructive storms that are damaging both environmentally and economically. In 2011, Hurricane Irene was an unusual storm because it struck the eastern Adirondack Mountains in New York. The Adirondack region mainly relies on tourists to make money and fishing is a large part of what draws people to this region. Three years ago, a study was started to explore the impact of Hurricane Irene on the brook trout population.  During the first year, stream bed and water quality were analyzed to determine if a brook trout population could be supported a year after Hurricane Irene. After determining conditions could support a brook trout population, the fish were aged using their scales, invertebrate counts were determined using kick-net methods and dissolved oxygen levels were collected. It was collected to determine if the stream could support the propagation and continued survival of the brook trout population despite the post-storm exposure glacial till from 10,000 years ago was exposed from the storm. It was determined that the environment could support future generations of brook trout in certain areas of the study site where hurricane damage was minimal. Currently during the third year, brook trout age, length (n = 60, p=.000064) genetics are being analyzed to see how much deviation in relatedness had occurred since the last event of domestic strain stocking over 20 years ago.

Introduction

Over the course of recent decades there has been a general scientific consensus that weather patterns are changing. While the reasons behind these changes are widely debated, it cannot be argued that these weather patterns are responsible for costly and devastating storms that wreak havoc economically and environmentally. One such storm, Hurricane Irene, was particularly unusual in the fact that it wreaked massive devastation in the eastern Adirondacks. Examples of this devastation were homes and livestock being washed downstream, the collapse of the back half of the Keene Fire Department into the Ausable River, and the displacement of boulders as large as small sheds or cars. Brook trout fishing is one of the Adirondack region’s greatest attractions, and the region relies on the tourism for revenue. The Brook trout, Salvelinus fontinalis, also known as speckled trout, is the state fish of New York and is one of the only fish native to the Adirondack Mountain region. Brook trout can have up to a five year life span, with females releasing thousands of eggs every spawning season from September to November, with about fifteen percent surviving to adulthood. Brook trout are excellent indicators of the health of their aquatic ecosystem because they can only live in the cleanest water and generally do not live in water warmer than 72° F, with an optimum growing temperature between 52° to 60° F ((McCullough, Russell and Eileen Stegemann." The Trout of New York" New York State Conservationist, March-April 1991. 24-31.)). Higher temperatures can affect the production of redds, egg pits dug into gravel or sand by the tail of the female brook trout. Their ability to hunt revolves around the ambient light of their environment; low visibility due to either sediment in the water or dawn/dusk light conditions can inhibit their hunting ability. Populations of native brook trout have gone extinct in certain areas due to the introduction of competing and predatory fish species. One example is in the Saranac Lakes Wild Forest where brook trout historically inhabited 94 percent of the water. Today that number has dropped to only 3 percent, most likely due to the introduction of competitive non-native fish such as brown trout, rainbow trout, bass and perch ((NYSDEC, “Protecting Adirondack Fish”. Department of Environmental Conservation. 2007. Web. 20 June. 2012. http://www.dec.ny.gov/outdoor/31920.html)). In addition, brook trout do not defend their eggs after they have been fertilized and this makes the unborn offspring vulnerable to consumption. Other competitors such as crayfish, smallmouth bass, and a small minnow-like fish known as fallfish, Semotilus corporalis, will eat brook trout eggs if given the opportunity. Larger adults are also being outcompeted by the more aggressive and nonnative brown or rainbow trout ((Ficke, A.D., D.P. Peterson, and W.A. Janowsky (2009, June 26). Brook Trout (Salvelinus fontinalis): a technical conservation assessment [Online]. USDA Forest Service. Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/brooktrout.pdf {July 30, 2012])). New York brook trout are considered more acid tolerant than other fish because unlike other fish, they can survive water that has a pH as low as 5.0. However, brook trout populations in areas such as the Catskill Mountains and the southwestern Adirondack Mountain have been greatly reduced due to numerous years of acid rain. Their disappearance within a watershed indicates environmental decline in possibly both the aquatic and terrestrial ecosystems surrounding the watershed ((EBTJV (Eastern Brook Trout Joint Venture). 2007. Eastern Brook Trout: Roadmap to Restoration. 16 p)). As brook trout populations have declined over the past 50 years, the percentage of ponds and lakes that contain brook trout is now measured in single digits. One way fisheries management tries to remedy this problem is through stocking hatchery raised fish into rivers and streams that may have a threatened brook trout population. Evaluation of maintenance trout stocking programs have typically focused on survival and harvest of the stocked fish with little attention placed towards the potential impacts of combining two distinct stocks on native populations ((Krueger, Charles and Bruce W. Menzel (1979) Effects of Stocking on Genetics of Wild Brook Trout Populations, Transactions of the American Fisheries Society, 108:3,277-287, DOI: 10.1577/1548-8659(1979)108<277:EOSOGO>2.0.CO;2)). Stocked fish can negatively affect wild fish through genetic contamination, predation, competition, induction of premature migration, mixed-stock exploitation problems, predator attraction, and disease transmission ((Weber, Edward D., and Kurt D. Fausch. "Interactions between hatchery and wild salmonids in streams: differences in biology and evidence for competition." Canadian Journal of Fisheries and Aquatic Sciences 60.8 (2003): 1018-1036.)). In all salmonids, local populations adapt variably to different situations making each population, while close in proximity, very distinct genetically. The introduction of stocked fish can muddle the unique genetics of a highly adapted local population and it may take generations for natural selection to weed out the domestic genes that were introduced. Much of the morphological and ecological divergence among local populations reflects local adaptation ((Hindar, Kjetil, Nils Ryman, and Fred Utter. "Genetic effects of cultured fish on natural fish populations." Canadian Journal of Fisheries and Aquatic Sciences 48.5 (1991): 945-957.)). My family owns a camp near Styles Brook, a feeder stream to the East Branch of the Ausable River that sustained heavy damage during Hurricane Irene. I was concerned about the brook trout population after the storm, so three years ago I started exploring the impact of Hurricane Irene on brook trout population. First and foremost, I wanted to see if the changed stream could support brook trout. In the second year I wished to see if the stream could support the propagation and continued survival of brook trout. During the third year, I looked at the genetics of the brook trout to view their deviation from the domestic strain that they started from.

Study Sites for Three Year Project

The primary research site is Styles Brook (ends 44.298°N, 73.78°W), a five and a half mile long, third order tributary to the east branch of the Ausable River. It is located within dominant brook trout territory, and its thermal regime is at the upper margin of the species’ thermal tolerance. The brook flows through public and private lands in the northern Adirondack Mountain region of New York. The brook is suitably shaded, with the exception of the area surrounding six small bridges that were built over the brook where the surrounding brush was cleared, as well as some areas where the soil on the banks cannot yield plant growth. Brook trout are the only fish species of salmonid that inhabit Styles Brook and the surrounding water bodies in the area. However, a member of the cyprinid family, black-nosed dace Rhinichthys atratulus, is also present predominantly in Styles Brook and has some coverage elsewhere in its tributaries. Rarely observed slimy sculpin, Cottus cognatus, have been known to inhabit Styles Brook as well. Two other feeder brooks to Styles Brooks were included in this study. One was a two mile long, second order brook that fed into Styles Brook known as Madden Brook (ends 44.301°N, 73.72°W). The other brook that was studied was a half mile long first order brook that flowed into Madden Brook called Kiln Brook (ends 44.29°N, 73.70°W). Styles Brook was first stocked back in 1956 and 1957 with 4800 brook trout, though it is possible that undocumented stocking occurred before this. There has been no annual stocking in either of the feeder streams in approximately four decades. Styles Brook was stocked by both New York State and Essex County with the state fish coming from hatcheries in Randolph and Chateauguay, NY. State stocking was canceled after a 1992 survey showed the stream had adequate natural spawning for brook trout (Richard Preall, NYSDEC Region 5, personal communication). My concentrated area of study is roughly a one mile section of Styles Brook that changes in elevation and has many areas of suitable spawning habitat and tree cover. The secondary research stream was Spruce Mill Brook (ends 44.31?N, -73.48?W), a ten mile long, second order tributary of the north branch of the Boquet River. This stream was employed during the third year of study to act as a genetics comparison to Styles Brook. This stream is generally cold and has a neutral pH for most of the year. Research was concentrated in a half mile section that was closer to Styles Brook so fish taken from both streams could be used to determine local genetic characteristics. Spruce Mill Brook is annually stocked with brown trout and brook trout but does have its own sustained brook trout population. These fish are stocked downstream towards the northern branch of the Boquet River, and only fish from the upper reaches of Spruce Mill Brook were collected.

Year One: Determination of Sustainability

Temperature and pH Monitoring Methods—Air temperature, pH, and water temperature were monitored daily (summer) and biweekly (autumn) at nine different locations, using a HM PH-200 pH/temperature meter. Seven locations were in Styles Brook, and the last in the outlet of a naturally-formed pond created by the Madden and Kiln Brooks.

Thermal and pH Conditions ResultsThermal conditions had shifted sporadically throughout the summer. In one area of Styles Brook on August 27th, the water temperature was just four degrees Fahrenheit below the upper initial lethal temperature for brook trout (78.08°F). In the fall, water temperatures were considered normal as the both the air and water temperatures slowly dropped near freezing (32°F) by the beginning of November. From October 20th to November 3rd, the water temperature dropped an average of 10.21°F throughout the entire stream system. Throughout the research area, thermal conditions were most favorable for brook trout from the beginning of August to end of October. Alkalinity levels were consistently above neutral levels through the summer and fall; sudden drops or spikes in the pH levels were attributed to increased rainfall or an increase in water temperature.  

Fish Monitoring Methods—Brook trout were visually monitored from the shoreline. Their behavior was recorded with an underwater video camera attached to the end of a ten foot long pole. Videos would be reviewed by my mentors and I, and any notable behavior would be documented for later analysis.

Fish Population ResultsDuring the summer and fall, between 60-80 brook trout individuals of different age categories were seen throughout Styles Brook and the surrounding areas. 70 percent of these individuals were categorized as young-of-the-year (first year of life) based on the prevalence of the dark par marks that run down the sides of their bodies, while the remaining 30 percent were categorized as either juveniles or adults. In Styles Brook it was noted that most of the brook trout that were sighted inhabited areas where the stream bottom substrate was comprised of almost entirely gravel and/or cobble. In Madden Brook and in Kiln Brook, there was only young-of-the-year present, most likely due to the shallow depth of both the streams. It was also discovered that a whole school of up to thirty brook trout individuals of different age categories had centered themselves near an area of upwelling groundwater. However, this area had a bottom substrate entirely composed of sand and silt, meaning that this area was insufficient for brook trout spawning because there would most likely be a high mortality rate of embryos and trout fry. During the fall, it was observed that fewer adult fish were seen compared to the summer, most likely due to the fact that they had retreated to more remote areas of Styles Brook in order to spawn. In areas where adults and young-of-the-year had been seen during the summer, only young-of-the-year remained in the fall since they were not sexually mature and therefore do not necessarily have to migrate downstream in autumn. The school of brook trout that inhabited the area that had a sandy substrate composition and upwelling groundwater was the subject of the underwater videos. Feeding behavior was documented by introducing night-crawler worms into the environment and observing the fish’s reaction. The feeding behavior observed brook trout lunging up to catch the worm once it had floated down within sight. This is evidence that of the brook trout is an opportunistic sight predator. The feeding behavior also reveals that this particular school of brook trout had adapted to feeding on the bottom, rather than feeding at the top as some brook trout are known to do. The adult and juvenile brook trout in this school also displayed a social agonistic behavior towards the young-of-the-year individuals, which is a typical behavior among salmonids.

Year Two: Supporting Propagation

Temperature/Ambient Light MethodsWater temperature and ambient light were recorded using data loggers (1-hr intervals) during July through mid-October (Figure 1). Ambient light is important because it affects their behavior not only in a diurnal/nocturnal cycle but also in a yearly cycle. Brook trout prefer areas where there is overlying cover and the light intensity is low. This causes most of their activity to go unseen during the night as they forage and travel from place to place.  As the year progresses and the days get shorter, the amount of time increases for brook trout to perform these various activities.water pic

 

Figure 1: Locations of data loggers in Styles Brook (red dots)

Temperature/Ambient Light ResultsTemperatures were adequate during the summer for a trout population. During the second week of July the water temperature rose stream-wide, peaking differently with location, 70 degrees Fahrenheit at one end of the stream and 76 degrees Fahrenheit at the other end. The water temperature displayed a downward trend through the summer and into the fall. While the temperature was on the rise towards the potentially lethal July temperature peak, brook trout were seen only in isolated pockets throughout the stream. The majority of the brook trout sightings occurred as the water temperature was decreasing. As the stream-wide temperature leveled out, the brook trout were free to move where they wanted in order to meet their needs for food and reproduction. Data loggers that were placed in more open areas showed spikes in ambient light and less impermanence. The spikes in ambient light were attributed to the direct exposure to sunlight on the data logger. At these same data loggers, light readings showed a more cyclic pattern into the fall, as the sun was lower in the sky for a shorter amount of time; the spikes did not appear as random as the other data loggers that were previously mentioned (Figure 2). Brook trout can be easily spooked during the daytime so the amount of ambient light in a given pool can affect sighting frequency. Even with this in mind, this observation was not made frequently.

graphreal

Figure 2: Styles Brook temperature data collected by data logger

pH Monitoring MethodsMonthly pH measurements were taken at six different areas along Styles Brook using a pH-200 pH/temperature probe (Figure 1).

pH Monitoring ResultsThe pH in Styles Brook was consistently above neutral throughout the summer and fall. Any sudden drops in the pH of the water were attributed to rainfall or an increase in water temperature. It has been documented that an increase in temperature may affect ion mobility and/or probe accuracy ((Ashton, John J. Barron Colin, and Leo Geary. 2006. "The Effects of Temperature on pH Measurement." TSP 1.)). A shift of pH towards the neutral/low acid range was noted during the temperature peak in July. Water acidity at this level was not enough to harm the brook trout; however this could cause them to change location to seek out a more favorable area. Safe pH levels are between 7 and 8, so neutral or slightly basic. Brook trout have been known to tolerate pH levels as low as 4.1((Karas, Nick, et al. Brook Trout. Guilford, Connecticut, The Lyons Press, 2002. Print)).

Dissolved Oxygen Monitoring MethodsDissolved oxygen was recorded using a probe connected to a LabPro interface. Readings taken to represent the summer were performed in August; readings taken to represent autumn were performed in November. These readings were taken at three sites throughout the brook, determined to be key testing points due to prevalent brook trout presence and optimal stream flow.

Dissolved Oxygen Monitoring ResultsThe dissolved oxygen readings taken in Styles Brook were well above optimal. Two of the three areas measured approximately 9 mg/L, while the third measured around 7 mg/L; this was most likely due to the higher temperature in that particular area. In the fall, all three areas measured dissolved oxygen readings around 10 mg/L due to the lower temperatures throughout (Figures 3 and 4).

summer dissolved

Figure 3: Styles Brook summer dissolved oxygen data

autumn dissolved

Figure 4: Styles Brook autumn dissolved oxygen data  

Kick-net Surveying MethodsIn several areas in Styles Brook, kick-netting was performed in order to determine stream bottom invertebrate presence. The kick-net was placed in a level area facing immediately downstream from an area of more preferable cobble substrate. The substrate was then stirred up which released the invertebrates into the flow which led directly into the kick-net. The invertebrates were collected out of the kick-net and stored into a flat sterile container for later analysis.

Kick-net Surveying Results—The kick-net survey was performed after many of the major fly hatches, so a lower invertebrate count was both expected and observed. However invertebrates collected were typical for an inland Adirondack stream. Overall stonefly (Plecoptera) and caddisfly (Trichoptera) larvae were the most common families of invertebrates collected. Both of these invertebrate types are viable food sources for brook trout, especially the smaller or younger individuals (Table 1).

Table 1: Invertebrate collected in Styles Brook in a kick-net survey

Species Number of Individuals
Crayfish 1
Stonefly 2
Caddis Fly Larvae 4
Odonates 2

 

Scale Analysis MethodsAs fish age, their scales gain growth rings. It is only during the winter when these growth rings become more clustered; this is due to the fact that the ectothermic fish grow slower in the winter. Fish were aged to determine if new trout had been born since Hurricane Irene. Scales were safely removed from nine live fish to determine their ages. The scales were sent to the NYSDEC for age analysis and then once returned, photographed under a microscope at 500 times magnification using a microscope camera.

Scale Analysis ResultsOf the nine fish that were aged, five of the fish were aged to be between one and two years of age, the other four were aged at two years or older. While the sample size wasn’t significant it is evidence of older year class individuals survived the destruction of Hurricane Irene. After age analysis, it was noted that some of the scales were regenerated. Fish lose thousands of scales over the course of their lifetime for many different reasons; regenerated scales grow back to take their place. A regenerated scale is not an accurate way to determine the age of the fish, as an undamaged scale shows record of the fish’s age since it was born, whereas a regenerated scale only shows record of the fish’s age after that scale grows in. The way to determine the difference between the two scale types is the size of the core of the scale; a regenerated scale has a much larger core compared to an undamaged scale (Figures 5 and 6). Aging showed new brook trout had been born since Hurricane Irene.

      scales                                             

Figure 5: Regenerated Scale                                                   Figure 6: Undamaged Scale

Video Monitoring of Behavior and Preferential Location MethodsThroughout the summer and the fall, 20 underwater videos documenting brook trout behavior were recorded using a Panasonic™ underwater camera. Feeding behavior was encouraged in certain videos using worms attached to a snap-swivel rigging, causing no harm to the fish. When footage of more natural social behaviors was desired, this rigging was temporarily removed. Videos ran from several minutes up to thirty minutes in length.  

Video Monitoring of Behavior and Preferential Location Results—Underwater videos captured feeding and social agonistic/territorial behaviors by brook trout, the latter behavior only captured in videos without the added stimulus. However, both of these behaviors go hand-in-hand. In the area where the videos were taken, the largest trout was always chasing other competing trout away, trying to secure the best area in the stream. Like all predators, brook trout are energy conscious; they want to obtain food while expending the least amount of energy possible. It is for this reason that brook trout look for areas of slowest flow adjacent to the fastest flow (Figure 7). Brook trout will sit in the slow flow, expending little energy, and when they see something go past them in the faster flow, they attack it. Brook trout will compete with each other over these areas through this social agonistic/territorial behavior by jabbing, knocking or nipping at each other.

graphic

Figure 7: Stream flow and preferential brook trout location

Pool Mapping MethodsThe purpose of the pool mapping was to establish the amount of substrate movement in Styles Brook after major flood events and to see how well the brook trout adapted to the substrate movement. Mapping of quality pools or characteristic trout pools was performed in August. Pools were divided into quadrants, each quadrant’s length, width, and depth were then recorded. Pool sizes varied from 12 quadrants to 30 quadrants. The coordinates of the pools were recorded on GPS, and the pH and temperature of the water were taken at every site.

Pool Mapping Results—Many large pools were mapped during normal summer flows. After the measurements were taken, no major flood events occurred, no major difference in the pool size, depth or position was seen. Due to this, secondary measurements of the pool sizes were not taken. However, follow-up mappings will occur after the next significant flood event for comparison. After the initial change in stream bottom due to Hurricane Irene, no significant changes were observed.

Sediment Collection MethodsThere was a roughly three mile section of Styles Brook that was heavily damaged by Hurricane Irene. Upon examination of this section of the brook, it was noted the stream bottom was quite unusual—it wasn’t composed of the traditional sand or cobble substrate. Two pounds of this stream bottom were collected and given to two geologists for analysis.

Sediment Collection ResultsThe collected sediment in the heavily damaged portion of Styles Brook was revealed to be part of a glacial till layer (approx. 10,000 yrs. old). The sediment is considered to be glacial because it was semi-consolidated, unstratified, and comprised of different sized substrate. With more heat and pressure; it would be likely that this layer would become sedimentary rock. This is not consistent with the naturally occurring metamorphic rock of the Adirondack region. Despite this exposure, brook trout were able to find suitable streambed to spawn away from the lower reaches of Styles Brook where this exposure had occurred.

Year Three: Genetics

Water Temperature MethodsWater temperature was recorded using Onset® HOBO Data Loggers (1-hr intervals) during August through mid-October. Five data loggers were placed throughout Styles Brook in different areas than the year before to accurately determine overall stream temperature status at any point during the summer or fall.

Water Temperature Results—The summer was unusually wet and rainy; due to this, water temperatures were observed to be much lower than past years. Brook trout were much harder to find this year, as they didn’t retreat to their typical areas of thermal refuge because the water temperatures never approached their tolerance level of 70? Fahrenheit.

pH Monitoring MethodsMonthly pH measurements were taken at six areas different than year 2 along Styles Brook using a pH-200 pH/temperature probe. These readings were added to a larger set of records containing pH values over the past three years.

pH Monitoring ResultspH was consistently neutral or slightly basic for most of the summer, suitable for brook trout.

Video Monitoring Methods—Throughout the summer and the fall, 10 underwater videos documenting brook trout behavior were recorded using a GoPro Hero3+™ underwater camera. Feeding behavior was encouraged in certain videos using worms attached to a snap-swivel rigging, causing no harm to the fish. When footage of more natural social behaviors was desired, this rigging was temporarily removed. Videos ran from several minutes up to thirty minutes in length.  

Video Monitoring Results—Underwater videos captured feeding and social agonistic/territorial behaviors by brook trout, the latter behavior only captured in videos without the added stimulus.

DNA and Length Collection Methods—Thirty adipose fin clips were collected as sources of DNA for genetic testing from brook trout in eight different areas of Styles Brook, thirty more fin clips were collected from brook trout in four different areas of Spruce Mill Brook, and thirty fin clips were collected from domestic strain brook trout from the Randolph Hatchery. The adipose fin is a small, fleshy vestigial fin that lies between the dorsal and the caudal fins and contains very few nerves. All collections were performed between July and September; lengths of all fish caught in the field were taken. Brook trout were caught via angling and were hooked in the lip with small hooks to reduce any injury. As an extra precaution, brook trout were placed in buckets of cold stream water with added ice to numb the fish and lower their metabolism in order to aid in a painless procedure. Brook trout were then released back into their natural habitat. The thirty adipose fin clips from the Randolph Hatchery were collected by DEC biologists and subsampled for this research. Fin clips were stored in vials of 95% denatured ethanol until analysis was performed.

DNA and Length Collection ResultsA great degree of care was taken to ensure that brook trout were released with the least amount of harm caused; this also made collecting 60 adipose fin clips from fish in the field very time consuming, however fish mortality was very low. The average fish in Styles Brook was determined to be around 16 cm and the average fish from Spruce Mill Brook was around 13 cm, with p=.000064 (Figure 8). Regardless of the length difference, the average age for brook trout between the two streams was the same at around a year and a half old. This was determined by observing and comparing the dark par marks that run down the sides of juvenile brook trout. All fish collected from the Randolph Hatchery were from the same year class of one and a half years old and an average length of 16 cm.  

graph2

Figure 8: Length-Frequencies of sixty brook trout caught in Styles Brook and Spruce Mill Brook (n=60, p=.000064)

DNA Analysis Methods:

Laboratory analysis was conducted by a geneticist at the U.S. Geological Survey, Biological Resources Division, Leetown Science Center, Aquatic Ecology Laboratory in Kearneysville, West Virginia. Genomic DNA was isolated from adipose fin tissue with the Puregene DNA extraction kit (Gentra Systems, Inc., Minneapolis, Minnesota) according to the manufacturer’s guidelines (Annett, 2012). Samples were screened at thirteen different microsatellite loci designed for brook trout: SfoB52, SfoC24, SfoC28, SfoC38, SfoC79, SfoC86, SfoC88, Sf0C113, SfoC115, SfoC129, SfoD75, SfoD91, and SfoD100. Details of master mix composition, thermal cycling parameters, and multiplexing are provided in a paper by (King et al. 2012).

DNA Analysis Results:

It was found that the Styles Brook population had the most private alleles (traits unique to a given population when compared to other populations) and highest overall heterozygosity out of the three populations, evidence that Styles Brook has been untampered with over the past twenty-three years since the last recorded domestic stocking (Figure 9). The Styles Brook population contained the highest average number of alleles found, which were almost twice as high as the number of alleles that were expected (ibid). Principle coordinate analysis of proportion of shared alleles distance shows Styles Brook to be genetically separate from the Randolph population (Figure 10). It was also found that Styles Brook had 100% polymorphic loci where Spruce Mill and Randolph both had 92.31%, more evidence that Styles Brook contains a diverse population of brook trout, polymorphic loci are locations on the chromosome that contain more than two alleles.

graph3

 

Figure 9: Allelic patterns across three studied populations, Na = Number of Alleles, Ne = Number of Expected Alleles, I = Information Index, No. Private Alleles = Number of Private Alleles, He = Heterozygosity

graph4

Figure 10: Principle coordinate analysis depicting the relationship of the proportion of the shared alleles distance from a survey of 13 microsatellite DNA markers between the Styles, Randolph and Spruce Mill populations.

 

Discussion

The last survey done on Styles Brook was over 20 years ago, so there is no reliable population estimate immediately before Hurricane Irene. Since Hurricane Irene there has not been a survey to resample population numbers so during the duration of this research population parameters were subject to estimation. Brook trout presence was less predictable this year compared to years prior. Due to higher than average rainfall in the Adirondacks over the summer, water temperatures never came close to their thermal tolerance level of 70?F, thus discouraging brook trout from finding areas of thermal refuge such as upwelling groundwater sites. Instead of congregating in small pockets throughout Styles Brook, brook trout were spread thin across the middle and upper reaches, making them harder to find. Water acidity has been fairly predictable over the past three years, almost always at neutral or slightly basic during normal conditions and only becoming slightly acidic during high temperature periods. It has been documented that an increase in temperature may affect ion mobility and/or probe accuracy ((Ashton, John J. Barron Colin, and Leo Geary. 2006. "The Effects of Temperature on pH Measurement." TSP 1.)). Underwater videos recorded feeding and territorial behaviors typical of salmonids. Brook trout are opportunistic sight feeders that hunt primarily during the day ((Ficke, A.D., D.P. Peterson, and W.A. Janowsky (2009, June 26). Brook Trout (Salvelinus fontinalis): a technical conservation assessment [Online]. USDA Forest Service. Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/brooktrout.pdf {July 30, 2012])). Due to this, brook trout can be very competitive over food as well as territory where they can conserve energy. The average age for brook trout in Styles Brook and Spruce Mill Brook was the same, around one and half years old, however their respective average lengths had a three cm (1.18 inches) difference with n=60 and p=.000064. Factors that determine the size of a brook trout, or any other fish, are: genetic coding, available foods, duration of annual growing periods, rate of growth, sex and individual age ((Karas, Nick, et al. Brook Trout. Guilford, Connecticut, The Lyons Press, 2002. Print)). A possible reason for large size deviation in this study could be the location of the two streams; while they are both located on the same mountain, Styles Brook is located near the base of the mountain while Spruce Mill Brook starts on the western side of the mountain’s peak and continues over and down the eastern side of the peak. Styles Brook is more prone to increased fishing due to ease of accessibility; the dirt road leading up to Spruce Mill Brook is only maintained seasonally and is heavily scoured with ruts and dips from spring runoff or heavy summer rain. The increased fishing in Styles Brook leads to fewer individual fish per given area, leading to certain fish taking advantage of less competition and growing larger than average (as shown by the single 24 cm individual). Between having the highest heterozygosity, highest number of alleles, highest number of private alleles, and having 100% polymorphic loci, Styles Brook is by far the most diverse population out of the three studied. It was also noted that there were two individuals from Styles Brook that were so genetically similar that it is likely that they are siblings.

 

Future Studies

Water quality conditions are expected to remain consistent with previous years. In the event of a random temperature spike between the two streams, Styles Brook would be more affected than Spruce Mill Brook. Besides the factor of elevation, the smaller average size of brook trout in Spruce Mill Brook makes them less vulnerable to increases in water temperature during the summer. For a given species, larger fish are generally more sensitive to temperature increases than smaller fish due to greater metabolic demand and lower thermal preferences ((Robinson, J.M., D.C. Josephson, B.C. Weidel and C.E. Kraft. 2010. Influence of variable summer water temperatures on brook trout growth, consumption, reproduction and mortality in an unstratified Adirondack lake. Transactions of the American Fisheries Society 139:685-699.)). DNA analysis will be performed in October in order to determine the genetic deviation of the current Styles Brook population from the domestic strain that they started from. It is expected that the genetics of the Styles Brook population differs somewhat compared to the domestic strain from the Randolph Fish Hatchery. If this is the case, then that means that after twenty generations or so the introduced domestic genes had been erased from the gene pool, thus supporting the previous notion that these brook trout ‘looked’ native. This could be helpful to fisheries management because Styles Brook could be used as a model stream, taking a stream without brook trout and stocking it with domestic brook trout acting as a ‘genetic blank slate’, allowing natural selection to determine what genes are best suited for the particular environment.

Acknowledgements

First and foremost I would like to thank Professor Clifford Kraft and Daniel Josephson from Cornell University for their help and guidance with this project. I’d like to thank Dr. Timothy King with the USGS Leetown Science Center for his help with the genetics analysis. I would also like to thank Richard Preall and Rob Fiorentino from Region 5 Fisheries NYSDEC for retrieving stocking records and for their advisement. Sabine Erickson from Burnt Hills-Ballston Lake High School for her help with my statistics. My science research instructor Regina Reals for her continuous guidance. My friends and family for their constant support.

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