Annual monitoring of Moe Pond in conjunction with bio-manipulation Zachary R. Diehl 1 and Nicholas J. Muehlbauer 2 Introduction Moe Pond (Figure 1) is a 38 acre man-made polymictic pond located near Cooperstown, New York, and is owned by the State University of New York College at Oneonta Biological Field Station (BFS). Due to high nutrient concentrations and frequency of algal blooms, Moe Pond has historically been considered to be eutrophic (Sohacki 1972). Moe Pond has been surveyed intermittently since 1972 (Sohacki 1972). A survey done in 1994 found that brown bullhead (Amerius nebulosus) and golden shiners (Notemignous crysoleucas) were the only fish species present (McCoy et al. 2001). The abundance of golden shiners caused low abundances of large zooplankton, which resulted in frequent algal blooms and decreased transparency (Wilson et al. 1999). In 1998 or 1999 largemouth bass (Micropterus salmoides) and smallmouth bass (M. dolomieu) were illegally introduced into Moe Pond where they completely altered the trophic balance in the pond. By 2007 the largemouth bass had out competed smallmouth bass and had decimated golden shiner populations leaving little to no forage for this newly established predator (Reinicke and Walters 2007). The disappearance of the golden shiner population lead to an increase in the zooplankton abundance and mean size and increased algal grazing (Albright et al. 2004). Monitoring since has showed conditions fluctuating between dominance by rooted macrophytes and by algae, likely driven by trophic changes (Stowell 2013). Trophic changes led to an altered ecosystem in Moe Pond and caused largemouth bass populations to become stunted in recent years. During the summer of 2016, the long-term dataset from Moe Pond, with regards to the fish community, the zooplankton community and limnology has continued. As in 2015, largemouth bass were culled from Moe Pond via a haul seine or angling to reduce numbers and determine impacts on fish growth. Likewise, tiger muskellunge (Esox masquinongy x Esox lucius) were stocked as an apex predator to reduce the abundance of bass in Moe Pond. Tiger muskellunge were provided by New York State Department of Conservation (DEC). This project can be used as a model for future studies dealing with similar problems. 1 Robert C. MacWatters Internship in the Aquatic Sciences, summer 2016. Present affiliation: Department of Fisheries, Wildlife and Environmental Science Technology, SUNY Agriculture and Technical College, Cobleskill, NY. 2 Oneonta Biological Field Station intern, summer 2016. Current affiliation: SUNY Oneonta.
MATERIALS & METHODS Figure 1. United States Geological Survey (USGS) map of Moe Pond in relation to the SUNY Oneonta biological field station (BFS) Limnology: Water quality sampling took place on 3, 16, 21 and 29 June, and on 5 and 14 July 2017. Sampling took place at the deepest point in the pond, at about 2.8 m. On 3 June a depth sounder was used to find the deepest point of Moe Pond and an anchor buoy was deployed to ensure sampling took place in the same location. A YSI multi-probe was used to measure temperature, conductivity, ph and dissolved oxygen (mg/l and % saturation) (Table 1). YSI measurements were taken at the surface, 1m, 2m and the bottom. Finally a Secchi disk was used to gauge the transparency of the water. Zooplankton Community: The zooplankton community was sampled each time water quality was sampled. Zooplankton were sampled using a Wildco zooplankton net dragged behind the boat at a depth of about one meter below surface. All samples were stored in 500 ml bottles and diluted with ethanol. IMAGE PRO PLUS software was used with an Axioskop 40 microscope to identify and measure the first 100 zooplankton found, 1 ml at a time. Fish Community: A 200ft. haul seine and angling were used to collect largemouth bass from Moe Pond. All largemouth bass collected were euthanized with a lethal dose of MS-222. Fish collected were brought back to the lab and assigned an ID number. Once a fish was assigned an ID number, length (mm) and weight (grams) were recorded for each fish.
Scale samples and otoliths were also taken to estimate age of each fish. All scales and otoliths were placed into scale envelopes until they were ready to be aged. Finally, stomachs were taken from each fish and stored in ethanol and placed into Whirl-Pak until they were analyzed. Largemouth bass stomachs were emptied and then everything was identified where possible. Once identified, total count and frequency of occurrence were calculated. We estimated abundance of the largemouth bass population in Moe Pond by extrapolating haul seine densities to the whole pond. The area of the haul seine is 300m 2. The average number of bass collected per haul seine was multiplied by 155,800m 2, the total area of Moe Pond. Tiger muskellunge were stocked into Moe Pond in an attempt to control largemouth bass abundance through trophic manipulation. All tiger muskellunge stocked were implanted with passive integrated transponder (PIT) tags, for later estimation of growth and survival. Ninety eight tiger muskellunge were stocked, with all fish stocked being 225-300mm (Figure 2). Tiger muskellunge-moe Pond 2016 Frequency 40 35 30 25 20 15 10 5 0 0 25 50 75 100 125 150 175 200 225 250 275 300 325 Length (mm) Figure 2. Length frequency histogram of tiger muskellunge stocked in Moe Pond during summer 2016.
RESULTS AND DISCUSSIONS Limnology: There were no major changes in water quality parameters in Moe Pond throughout the summer of 2016 (Table 1). Conductivity is a measure of the ability of water to carry an electric current, and is the most important water quality parameter for electrofishing. Conductivity levels in Moe Pond were relatively low; this is believed to be because Moe Pond is at the top of the watershed and has no inflowing water sources and is fed by rain water. The local bedrock is low in limestone (McCoy et al.2000) (which generally influences conductivity). The temperature in Moe Pond stayed consistent throughout the summer. Largemouth bass are considered warmwater fish and average temperatures in Moe Pond fall within that range for optimal growth (25-31 C). For most of the summer dissolved oxygen levels were within optimal ranges (>5ppm), although near the bottom it was relatively anoxic for much of the summer. Secchi disk readings (meters) stayed relatively the same throughout the summer. Secchi disk readings help gauge how far sunlight can penetrate the water column, with high Secchi disk readings potentially favoring the growth of rooted plants. Moe Pond. ph readings stayed relatively basic for the duration of the summer. Table 1. Water chemistry parameters for Moe Pond, NY. Summer 2016 Date Depth (m) Temperature Conductivity (ms/cm) ph DO % DO ppm Secchi Disk (m) 6/3/2016 0 23.34 0.052 9.47 111.80 9.52 2.3 1 22.56 0.061 8.61 128.40 11.34 2 19.62 0.093 7.02 27.60 2.53 2.8 19.31 0.095 7.01 13.10 1.16 6/16/2016 0 24.17 0.006 8.51 105.90 8.84 2.5 1 24.14 0.004 8.73 101.60 8.64 2 23.51 0.003 8.58 88.10 7.52 2.8 22.96 0.001 8.32 45.22 2.34 6/21/2016 0 24.73 0.057 9.09 119.50 9.95 2.3 1 25.92 0.057 9.21 123.00 10.39 2 23.62 0.062 8.91 97.40 8.76 2.8 20.46 0.063 8.89 67.89 3.45 6/29/2016 0 25.67 0.053 9.03 120.60 9.63 2.2 1 24.38 0.057 9.34 125.40 10.11 2 20.38 0.062 8.87 94.30 8.93 2.8 19.82 0.067 8.91 54.86 2.89 7/5/2016 0 24.66 0.052 9.02 121.70 9.54 2.5 1 23.86 0.052 9.45 124.90 10.23 2 19.82 0.061 8.72 96.80 8.84 2.8 19.14 0.068 8.67 45.88 3.46 7/14/2016 0 25.63 0.059 9.07 120.80 9.67 2.5 1 24.58 0.061 9.48 123.90 10.34 2 19.42 0.063 8.37 97.80 8.94 2.8 18.68 0.069 8.26 56.14 4.16
Zooplankton community: Table 2 shows the mean lengths and percent composition for all the zooplankton collected throughout the summer 2016 surveys. Daphnia were the most frequent zooplankton identified, second being calanoid and cyclopoid copepods. Moe Pond appears to be dominated by larger crustaceans. Nauplius larva, calanoid and cyclopoid copepods and daphnia make up 83% of the total percent composition. Polyartha rotifers were observed for the last two consecutive years, before that they had not been seen since 2008 (Finger 2009). Eight trichocera were collected this summer, which marks the second year in a row that they have been collected. Prior to this no trichocerca have been reported in recent years (Busby and Casscles 2015). Table 2. Average length (mm) and percent composition of zooplankton species in Moe Pond, NY during summer 2016. Average plankton samples-moe 2016 Species: Mean length (mm) Frequency of occurrence Cladocerans: Daphnia 1.362 36% Bosmina 0.160 6% Leptodora 2.671 1% Copepods: Cyclopoid 0.426 20% Calanoid 0.646 10% Nauplius 0.138 17% Rotifers: Asplancha 0.132 4% Keratella spp. 0.108 6% Polyartha 0.128 1% Trichocerca 0.298 1%
Fish community: A total of 200 largemouth bass were collected from Moe Pond via haul seine or angling. Throughout the study, angling proved to be a more successful means of collecting specimens. All fish collected were less than 380mm (15 inches). The length frequency histogram (Figure 3) shows a bottleneck shape with most fish being of similar relative size. There was one fish that was collected (360 mm) that was able to get past the 125-275mm size range. Largemouth bass collected from Moe Pond were aged two ways; using both scales and otoliths (Figure 4 and 5). Neither method resulted in a large number of fish that were over age 3. This is suspected to be due to the lack of a forage base for the population of largemouth bass. There were many young-of-year largemouth bass collected this year via haul seine. In 2014 no young of the year largemouth bass were collected throughout sampling (Picante 2015). 60 50 Largemouth bass-moe Pond 2016 Frequency 40 30 20 10 0 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 Length (mm) Figure 3. Length frequency histogram of largemouth bass in Moe Pond during summer 2016.
Length (mm) 400 350 300 250 200 150 100 50 0 Length (mm) vs. Sclae Age of Largemouth bass 0 1 2 3 4 5 6 Age Figure 4. Length (mm) vs. scale age of largemouth bass in Moe Pond during summer 2016. Figure 5 suggests that there are distinct classes of bass in Moe Pond, based on age and length. Out of the 200 fish collected, only one fish was over 4 years in age (360 mm). This stunting of fish in Moe Pond appears to be due to the lack of a food source. Length (mm) Length (mm) vs. Otolith Age of Largemouth bass 400 350 300 250 200 150 100 50 0 0 1 2 3 4 5 6 Age Figure 5. Length (mm) vs. otolith age of largemouth bass in Moe Pond during summer 2016.
The most abundant food source identified in largemouth bass stomachs by far was Daphnia (Table 3). There were 1344 individual Daphnia found throughout all fish collected, comprising 47% of total composition by number. Other dominant food sources includes organisms from the Zygoptera suborder (dragonflies), Anisoptera suborder (damselflies), and Amphipods order (scuds), which also made up a majority of the total composition. There is no optimum food source for the largemouth bass in Moe Pond, after decimating the golden shiner populations they were left with a diet of zooplankton and macroinvertebrates. Table 3. Stomach contents of 200 largemouth bass from Moe Pond 2016. Content # of individuals Total count Frequency of occurrence (%) Amerius nebulosus 1 2 <1% Amphipod 48 568 20% Anisoptera 51 158 6% Chironimid 8 91 3% Coleoptera 10 22 1% Cranefly larva 2 3 <1% Daphnia 25 1344 47% Emphemeroptera 1 1 <1% Empty 34 0 <1% Hirudinea 12 78 3% Lepidoptera 1 12 <1% Platyhelminthes 1 2 <1% Plecoptera 1 2 <1% Tricoptera 21 68 2% True Flies 14 107 4% Zygoptera 84 391 14%
A population estimate of Moe Pond was done using an aerial extrapolation method (Table 4). For summer 2016 it was estimated that there were 10,500 largemouth bass in Moe Pond. This is significantly greater than the last two s years Moe Pond has been sampled (2014, 2015). Decline in populations of golden shiner and smallmouth bass are also diagrammed in this table. A total of 306 largemouth bass were euthanized via haul seine or angling. It is hoped with removing largemouth bass and the introduction of tiger muskies that within the coming years a decrease in largemouth bass populations will be observed. Table 4. Changes in the populations of golden shiner, largemouth bass, and smallmouth bass from 1994-2016 in Moe Pond (modified from Busby & Casscles 2016). Year Golden shiner Largemouth bass Smallmouth bass 1994 (McCoy et al. 2000) 7,154: +12,701;-6,356 0 0 1999 (Wilson et al. 2000) 3,210+/-1,760 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 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 (Stowell 2014) 0 13,560 0 2013 (Stowell 2014)* 0 4,205 0 2014 (Picante 2015) 0 6,361+/-1,676 0 2015 (Casscles & Busby 2016) 0 35,015+/-5,329 0 2015 (Casscles & Busby 2016)* 0 8.109 0 2016 (Diehl & Muehlbauer 2017) 0 10,500 0 *Indicates where abundance estimates were conducted using electrofishing mark/recapture surveys rather than areal extrapolation. CONCLUSION The water quality of Moe pond has remained fairly consistent throughout the time it has been monitored. Alternatively, the dynamics of fish, both types and amounts, has fluctuated throughout the time of monitoring. These changes in the fish community have contributed to the changes in the zooplankton community. After the reduction of the golden shiners with the introduction of large and smallmouth bass, zooplankton populations were able to recover. Aiding the recovery of the zooplankton community was the low recruitment rate of largemouth bass in recent years, most likely due to intra-specific competition among largemouth bass.
Introduction of tiger muskellunge to the system will hopefully continue to reduce the number of largemouth bass and bring greater balance to the system. These fish were chosen for two factors; 1) for their tolerance to higher temperatures and 2) their hybrid vigor. Hybrid vigor can be explained as getting the best genes from each of your parents and essentially growing faster, although the will not grow as large as their predecessors. Moe pond has been a one-species system for several years and the addition of a predator to balance the system will allow for a more healthy water body. Due to the infertility of tiger muskellunge, a continued stocking program is needed to keep the system balanced. With predation of the largemouth bass and continued population culling through haul seining and angling, a balance will be achieved. This will hopefully allow for the reintroduction of forage species, increasing diversity and stopping cannibalism between largemouth bass. With balanced numbers of fish within the pond, it will allow for an increase in zooplankton and potentially reduce or eliminate the annual algal blooms. Looking ahead to future studies, monitoring to determine growth and mortality rates of the tiger muskies and bass populations to see how the introduction progresses will shed light on the changes. This will also allow for future decisions as to the feasibility of introduction of forage species. Continuing the monitoring procedures that have been carried out each year will provide the information to make informed management decisions. REFERENCES Albright, M.F., W.N. Harman, W.T Tibbits, M.S. Gray, D.M. Warner, and R.J. Hamway. 2004. Biomanipulation: A classic example in a shallow eutrophic pond. Lake and Reserve Management. 20(04):263-269. Busby, D. and J.B. Casscles. 2016. Continued monitoring of the Moe Pond ecosystem in conjunction with biomanipulation (2015). In 48 th Annual Report (2016). SUNY Oneonta Biol. Fld. Sta., SUNY Oneonta. Finger, K.M. 2009. Continued monitoring of the Moe Pond ecosystem following the introduction of smallmouth and largemouth bass (Micropterus dolomieu and M. salmoides, respectively). In 41 st Annual Report (2008). SUNY Oneonta Biol. Fld. Sta., SUNY Oneonta. McCoy, C.M. III, C.P. Madenjian, J.V. Adams, and W.N. Harman. September 2001. The fish community of a small impoundment in Upstate New York. Journal of Freshwater Ecology, 16(3):389-394.
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