Monitoring the Moe Pond ecosystem and population estimates of largemouth bass (Micropterus salmoides) post unauthorized introduction Stephen G. Stowell 1 ABSTRACT A study of Moe Pond, located in Otsego County, NY, at N42 43.00 W74 56.75 (Albright et. al 2004) was conducted to evaluate the water quality, estimate a population for largemouth bass (Micropterus salmoides) through mark and recapture, and analyze the stomach contents of the largemouth bass within the pond. Bass abundance was also estimated using seining techniques, as has historically been conducted at Moe Pond. Water temperature average was 20.7 C, average conductivity was 0.068 (ms/cm), ph averaged 7.6, average oxidation-reduction potential (ORP) was 64.67, average DO (%) was 67.43, DO (mg/l) average was 6.35, and the average Secchi disk reading was 2.33m. The estimated population of largemouth bass within Moe Pond was 4,205, down from 2012 s estimate of 6,480 bass (VanDerKrake 2013). The stomach contents of 40 largemouth bass showed mostly Daphnia spp., damselfly larvae, and amphipods. INTRODUCTION As part of ongoing research through the SUNY Oneonta Biological Field Station (BFS), Moe pond in Cooperstown, NY (Figure 1), was monitored for several weeks. Water quality, turbidity, chlorophyll a, and fish abundance, diet and growth were studied. At the start of the study, data collected from 1972, 1994, 2000-2008, and 2012 had been previously compiled. Continuing the study in 2013 enables the BFS to add to the long-running data set for Moe Pond and notice any trends. The goal of the study was to compare current water quality with past as well as compare the fish community and abundance of largemouth bass to prior findings. Prior to 1998, seining in Moe Pond revealed that the only fish species in the water body were brown bullhead (Ictalurus nebulosus) and golden shiner (Notemigonus crysoleucas) (McCoy et al. 2001). In 1998 or 1999, largemouth bass (Micropterus salmoides) and smallmouth bass (M. dolomieu) were illegally introduced. The disappearance of the golden shiner population led to an increase in zooplankton mean size and abundance and increased algal grazing (Albright et al. 2004). Monitoring since has revealed conditions varying between dominance by algae and rooted macrophytes, presumably driven by trophic changes. 1 Robert C. MacWatters Internship in the Aquatic Sciences, summer 2013. Present affiliation: Department of Fisheries and Wildlife Technology, SUNY Agriculture and Technical College, Cobleskill, NY.
Figure 1. Topographic map showing the location of Moe pond and Otsego County, NY. METHODS AND MATERIALS On a weekly basis from 4 June 2013 to 3 July 2013, water quality was assessed at Moe Pond s deepest point (Figure 2). A YSI multiprobe was used to record temperature, conductivity, ph, oxidation-reduction potential (ORP), dissolved oxygen (%), and dissolved oxygen (mg/l) in profile. A Secchi disk reading was also taken each week. Water samples were collected and taken back to the lab for nutrient and chlorophyll a analysis. The fish community was evaluated via haul seine and electrofishing, as described below. A 200ft haul seine was deployed using a john boat in a teardrop shape with the bag at the top of the teardrop, furthest from shore. The net was pulled to shore, and the bag was lifted out of the water and the fish were transferred to totes. The study only focused on largemouth bass, and brown bullhead (Ameiurus nebulosus, the only other species collected) were returned to the pond immediately. The length of each largemouth bass was recorded. The first 10 fish over 150mm had a gastric lavage performed. A syringe with a 4in piece of aquarium hosing attached was filled with water. The hose was gently placed down the throat of the fish until resistance was felt. The fish was held inverted over the opening of a Whirl-Pak. The water was pushed from the syringe into the fish s stomach. This caused the fish to regurgitate any forage in to the Whirl- Pak. The bag was labeled with the date and fish s length, preserved with ethanol, and stored in the cooler until it was processed. Prior to being released, each fish received a caudal fin clip to identify it as having been collected. This was partly done to mark fish for an upcoming recapture effort to calculate an abundance estimate.
Figure 2. Water quality sampling location at Moe Pond, Otsego County, NY (modified from Sohaki 1972). A mark and recapture analysis was also performed at Moe Pond to further evaluate largemouth bass abundance. Using an electrofishing boat, courtesy of SUNY Cobleskill and Mark Cornwell, the entire perimeter of the pond was shocked on 14 July 2013 and all largemouth bass were netted using scap nets. The fish lengths were measured and recorded, a partial pelvic fin clip was performed and the fish were released back into the pond. On 24 July 2013 the same team of people shocked the entire perimeter of the pond again for the recapture for the same amount of seconds and the same number of amps and D/C volts. All largemouth bass were netted and put into the live well. The lengths were recorded and each fish was examined for the partial pelvic fin clip that was used to mark fish in the previous survey. A data sheet containing numbers of clipped and non-clipped fish was kept; data were used in the following formula (N = MC/R) to derive an estimate of the largemouth bass population within Moe Pond, where M = number of fish originally marked, C = the sample size at the time of recapture, R = number of marked fish at the time of recapture (Cornwell 2013).
RESULTS AND DISCUSSION The water quality values from the YSI from 4 June 2013 to 3 July 2013 are shown in Table 1. Data show that the temperature steadily increased from the beginning to June to the beginning of July. Conductivity and ph stayed fairly constant at around 0.068 ms/cm and 7.6, respectively. Dissolved oxygen near the bottom occasional was <1.0 mg/l, likely following calm periods during which mixing was not entraining oxygen as fast as it was being lost through respiration. In Table 2, results from the analyses of nutrients, chlorides, calcium and chlorophyll a are shown. All parameters are in line with values of recent years. The Secchi disk readings were all greater than 2 meters. Compared to previous years of studies conducted on Moe Pond, transparency has greatly increased since 1992 (Table 3). This was likely a direct result of the absence of golden shiners. Larger zooplankton, such as daphnia, effectively graze on algae. Therefore, prevalence of planktivorous fish in the waterbody can greatly influence algae, which in turn effects transparency. Initially, golden shiner reduced daphnia abundance, while more recently daphnia have been a major food item in young largemouth bass in Moe Pond (i.e., VanDerKrake 2013). Table 1. Water quality parameters of Moe pond between 4 June 2013 and 3 July 2013. Date Depth Temp. Sp. Cond. ph ORP DO DO TURB. Secchi ( o C) (us/cm) (% sat.) (mg/l) (NTU) (m) 6/4/2013 0 21.39 0.053 8.75 91 101.1 8.91 3 N/A 1 21.38 0.053 8.29 90.4 100.2 8.85 3.1 2 16.47 0.056 8.26 87.1 92.3 9.01 4.9 2.5 15.32 0.143 7.27-177.1 26.8 2.68 4 6/12/2013 0 18.93 0.056 7.77 154.1 87.1 8.08 3.7 2.3 1 18.72 0.056 7.61 164.6 84.1 7.86 3.6 2 18.34 0.056 7.54 167.3 85.6 8.04 3.7 2.5 18.46 0.055 7.36 128.5 84.9 9.57 3.9 6/20/2013 0 20.95 0.055 8.15 152.6 98.1 8.75 N/A 2.3 1 20.05 0.054 7.63 165.8 94.4 8.57 N/A 2 19.71 0.054 7.43 137.8 89.8 8.27 N/A 2.3 19.54 2056 6.97 131.4 68.4 6.17 N/A 6/27/2013 0 25.73 0.055 7.32 33.4 91.2 7.52 0.6 2.5 1 24.45 0.055 8.18 83.3 94.5 7.7 0.4 2 22.18 0.064 7.5 102.7 15.3 1.26 27.2 2.7 20.08 0.151 6.99-194 4.2 0.36 5.7 7/3/2013 0 24.66 0.051 8.03 106.9 73.6 6.11 N/A 2.3 1 23.59 0.054 7.34 124.4 51.2 4.3 N/A 2 21.87 0.083 6.65-84.4 3.2 N/A N/A 2.3 21.39 0.098 6.41-106.6 2.6 0.23 N/A
Table 2. Nutrient Data of Moe pond between 4 June 2013 and 27 June 2013. Date Nitrite+nitrate Total nitrogen Total phosphorus Chlorophyll a (mg/l) (mg/l) (µg/l) (µg/l) 6/4/2013 < 0.02 0.32 22 6/12/2013 < 0.02 0.30 21 6/20/2013 < 0.02 0.27 17 2.16 6/27/2013 < 0.02 0.36 20 6.85 7/3/2013 < 0.02 0.23 23 2 7/12/2013 < 0.02 0.36 46 7.77 Table 3. Average values of Secchi depth, total phosphorus, nitrate+nitrite, and chlorophyll a (bd=below detectable limits) (Modified from VanDerKrake 2013). 1972 1994 2000 2001 2002 2003 2004 2005 2006 2007 2008 2012 2013 Secchi Depth (m) NA 0.85 1.2 1.1 2.2 2.33 1.26 1.26 2.2 2.62 1.35 2.24 2.33 Total Phosphorus (µg/l) 40-70 36.7 NA NA 26.4 29.05 42.29 56.64 26.91 20.5 28.95 26.33 20 Nitrate+nitrite (mg/l) NA <.05 NA NA 0.14 0.11 0.1 0.01 0.01 <.01 0.003 bd bd Chlorophyll a (ppb) NA 2.2 0.2 8.1 2.4 2.49 4.4 2.41 19.4 2.75 3.94 4.99 4.69 The stomach contents of 40 largemouth bass collected with the haul seine were analyzed in the lab (Table 4). The most common forage found in the stomachs was daphnia. This could suggest that the pond s Secchi disk readings would start to decrease as more bass forage on daphnia. Other popular forage for the bass was damselfly larvae and pupae as well as amphipods. Three stomachs on 20 June 2013 contained brown bullhead fry (Table 4). Brown bullhead spawn in late spring early summer and incubate for roughly 20 days before hatching (Werner 2004). Because bass are piscivorous, one would expect to encounter more bass containing other fish in the stomach. Overpopulation of the pond likely plays a major role in such omnivorous diets for the bass of Moe Pond.
Table 5. Stomach Contents of 40 Largemouth Bass from Moe pond between 4 June 2013 and 27 June 2013. 4-Jun-13 Length (mm) Brown Bullhead fry Crayfish (Pieces) Copepod Daphnia Midge Amphipod Aquatic Worm Mayfly Larvae Dragonfly Larvae Beetle Damselfly Pupae Damselfly Larvae Grasshopper Fly Backswimmer 215-1 6 1 - - - - - - - - - - - 214 - - 2-4 1 - - - - - - - - - 226 - - - - 1 2 2 - - - - - - - - 110 - - - 182 2 1 - - - - - - - - - 204 - - - - - 6-1 - - - - - - - 219 - - 2 2-1 - - - - - - - - - 269 - - - - 1 - - - 1 - - - - - - 276 - - 1 - - - - - - 1 - - - - - 264 - - - - 1 - - - - - 1 1 - - - 262 - - 1 2 1 - - - 1 - - - - - - 12-Jun-13 Length (mm) Brown Bullhead fry Crayfish (Pieces) Copepod Daphnia Midge Amphipod Aquatic Worm Mayfly Larvae Dragonfly Larvae Beetle Damselfly Pupae Damselfly Larvae Grasshopper Fly Backswimmer 250-1 - - 1 - - - 1 1 1 3 - - - 223 - - - 1 1 - - - 1 - - 1 - - - 212 - - 2 - - - - - - - 3 - - - - 211 - - - - - - - - - - 8 2 - - - 237 - - - - 2 - - - - - - 2 - - - 251 - - 1-1 - - - - - 3 - - - - 239 - - - - - - - - 2 - - 12 - - - 218 - - 1-2 - - - 1 - - 1 1 - - 171 - - - - - - - - - - - - - - - 184 - - - - - - - - - - 1 - - - - 20-Jun-13 Length (mm) Brown Bullhead fry Crayfish (Pieces) Copepod Daphnia Midge Amphipod Aquatic Worm Mayfly Larvae Dragonfly Larvae Beetle Damselfly Pupae Damselfly Larvae Grasshopper Fly Backswimmer 151 - - - - 4 63 - - - - 6 - - - - 189 - - - 31 - - - - - - 2 - - 2-192 - - - 213 - - - - 3-6 - - - - 179 1 - - - - - - - - - - 1 - - - 264 13 - - - 5 - - - - - 3 3 - - - 219 - - - 67-3 - - - - - 1 - - - 206 1 - - 113 4 - - - - - 3 - - - - 221 - - - 11 - - - - - - - - - - - 169 - - - 6 - - - - - - 3 - - - - 187 - - - 7-9 - - - - 4 3 - - - 27-Jun-13 Length (mm) Brown Bullhead fry Crayfish (Pieces) Copepod Daphnia Midge Amphipod Aquatic Worm Mayfly Larvae Dragonfly Larvae Beetle Damselfly Pupae Damselfly Larvae Grasshopper Fly Backswimmer 210 - - - - - - - - - - - 2 - - - 212 - - - 6 1 - - - - - - - - - - 114 - - - - - - - - - - - - - - - 135 - - - 3 5 - - - - - 3 - - - - 189 - - - - - - - - - - - 2 - - - 147 - - - 13 3 - - - - - - - - - - 132 - - - - - 10 - - 1 - - - - - 1 209 - - - - - 3 - - - - - 2 - - - 147 - - - - - - - - - - - - - - 1 134 - - - - - - - - - - - 1 - - - Totals 40 15 2 16 658 39 99 2 1 11 2 47 37 1 2 2
In past years, largemouth bass abundance was estimated through the area extrapolation method. The area seined was estimated to be 300 m². The number of bass caught per seine was divided by the area seined, and that number of fish per m² was then multiplied by 155,800m², the area of Moe Pond (Reinicke 2006). Though this method is not considered to accurately estimate abundance, it was considered a proxy of abundance (Lopata 2004). For this study, a comparison between the area extrapolation method and the mark and recapture method was evaluated to see how the two methods compared. Table 5 shows that after finding the number of bass in Moe Pond based on each haul seine, an average was taken and the population estimate was 13,560 Largemouth bass in Moe Pond. Table 5. Area extrapolation methods for haul seines on Moe Pond between 4 June 2013 and 27 June 2013. Date 4-Jun 12-Jun 20-Jun 24-Jun 24-Jun 24-Jun 25-Jun 25-Jun 27-Jun Total bass caught in Seine 81 22 36 12 19 15 13 24 13 Area of Seine (m2) 300 300 300 300 300 300 300 300 300 Fish per m2 0.27 0.07 0.12 0.04 0.06 0.05 0.04 0.08 0.04 Area of Moe Pond (m2) 155800 155800 155800 155800 155800 155800 155800 155800 155800 # of bass in Moe Pond/seine 42066 11425 18696 6232 9867 7790 6751 12464 6751 Average # of Bass in Moe Pond 13560 A second population estimate used for comparison was mark and recapture. Ninety six largemouth bass received a caudal fin clip after being caught in the haul seine. From the 96 fish clipped, only 2 were recaptured while using the electrofishing boat. The Peterson mark and recapture formula N = MC/R was used to estimate a population of 21,600 largemouth bass in Moe pond (Table 6). This number was about 7000 fish higher than the area extrapolation number. However, the low number of recaptured fish (about 2%) provides results having low precision and high potential error (Quinn and Deriso 1999). Table 6. Population estimate of Moe pond through the Peterson mark and recapture method, using the haul seine (mark) and electrofishing boat (recapture). Peterson Mark and Recapture (Haul Seine) # of fish originally marked(m) 96 Sample size taken at time of Recapture(C) 450 # of marked fish at time of recapture(r) 2 Estimate of population in Moe Pond 21600
The third method used to derive a population estimate of Moe pond was the use of the electrofishing boat to both mark and recapture fish. On the first night of shocking, 14 July 2013, 450 largemouth bass were shocked, given a pelvic fin clip, and released back to the water. The second night shocking, 24 July 2013, focused on recaptures. The same route around the pond was taken, but shocking was done for only 2180 seconds, and a total of 271 fish were shocked. Of those 271, 29 had a pelvic fin clip from the previous week s shocking. Using the same Peterson mark and recapture formula, N = MC/R, a population estimate of ~4205 largemouth bass was calculated for Moe pond (Table 7). Table 7. Population estimate of Moe pond through the Peterson mark and recapture method, using the electrofishing boat only. Peterson Mark and Recapture (E-Boat) # of fish originally marked(m) 450 Sample size taken at time of Recapture(C) 271 # of marked fish at time of recapture(r) 29 Estimate of population in Moe Pond 4205 The total fish population of Moe Pond has been estimated for several years. Table 8 shows that golden shiners were extirpated around 2001 and smallmouth bass around 2006. Largemouth bass populations grew from 1999 to around 2007 and then decreased significantly. This could be due to the high competition and lack of forage. Further studies with determine if the population of largemouth bass continues to decrease.
Table 8. Populations of golden shiner, largemouth bass, and smallmouth bass for 1994, 1999-2008, and 2012-2013. Year golden shiner largemouth bass smallmouth bass (Notemigonus crysoleucas) (Micropterus salmoides) (Micropterus dolomieu) 1994 (McCoy et al., 2000) 7,154: +12,701;-6,356 0 0 1999 (Wilson et al., 2000) 3,210+/-1760 1,588+/-650 958+/-454 2000 (Tibbits, 2001) 381+/-296 2,536+/-1,177 945+/-296 2001 (Wojnar, 2002) 1,708+/-1,693 3,724+/-3,447 504+/-473 2002 (Hamway, 2003) 3 206 20 2003 (Hamway, 2004) 2 318 1 2004 (Lopata, 2005) 0 6,924+/-2,912 0 2005 (Dresser, 2006) 0 12,019+/-3,577 223+/-257 2006 (Reinicke & Walters, 2007) 0 11,555.17+/- 0 2007 (Underwood, 2008) 0 13,373+/-249 0 2008 (Finger, 2009) 0 46,740+/-13,220 0 2012 (VanDerKrake 2013) 0 6,480+/-1,533 0 2013 (current, seining) 0 13,560 0 2013 (current, mark-recap) 0 4205 0 CONCLUSION Through comparisons of long running data sets, 2013 Moe Pond water quality was fairly consistent with 2012 averages. Phosphorus and chlorophyll a were lower than 2012, hinting that there has been less algal growth in 2013. The large mats of Elodea sp. could also be taking up the nutrients first and leaving less in the water samples tested. Related to decreased algae, Secchi disk readings increased from 2012, as expected with the greater abundance of zooplankton resulting from less predation. The fish of Moe Pond have changed significantly since studies of the pond began in 1994. The pond was dominated by golden shiners and brown bullhead until the illegal introduction of largemouth and smallmouth bass somewhere around 1999. As the bass populations took hold, the golden shiner population decreased to all but extinct in just 3 years. The largemouth bass have since out-competed the smallmouth bass and now dominate the pond, with few brown bullhead trolling the bottom. Since the bass have taken over the pond, their diet has switched from mostly forage fish to primarily zooplankton and invertebrates. Only 3 out of 40 stomachs had fish in them, showing that the bass aren t consuming fish for forage, and seem to be stunted as a result.
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