The Nature Conservancy's Emiquon Preserve: Fish and Aquatic Vegetation Monitoring Annual Report

The Nature Conservancy Grant/Contract No: C07-33Aquatic Vegetation Sampling and Gear Effort – Thompson Lake: We conducted aquatic vegetation sampling from 4/17/2008 to 10/17/2008 in littoral (within 15 m of the shoreline) and pelagic (>15 m of the shoreline) areas of Thompson Lake in 2008 (Table 1). We sampled aquatic vegetation monthly at 5 littoral and pelagic sites and at 20 littoral and pelagic sites each during the month of July. Additionally, three east/west fixed site transects were sampled monthly at 7 locations along each transect for aquatic vegetation from May-October. Aquatic Vegetation Collected and Observed Species – Thompson Lake: We collected and/or observed 14 aquatic vegetation species (submersed, emergent, and floating-leaved) at 76 out of 100 random littoral and pelagic sites at Thompson Lake in 2008. Community composition of the vegetated sites was dominated by submersed aquatic vegetation including coontail Ceratophyllum demersum (32.0%) , leafy pondweed Potamogeton foliosus (26.6%), American elodea Elodea canadensis (14.8%), bushy naiad Najas gracillima (6.3%), sago pondweed Stuckenia pectinata (6.3%), American pondweed P. nodosus (6.0%), curlyleaf pondweed P. crispus (2.2%), Eurasian water milfoil Myriophyllum spicatum (1.3%) and creeping water primrose Jussiaea repens (0.1%). Emergent aquatic vegetation composition at vegetated random sites was minimal, but included common arrowhead (Sagittaria latifolia) (0.1%), and narrow-leaved cattail Typha angustifolia (1.3%). One non-rooted floating-leaved vegetation family, Lemnaceae, was collected and was represented by duckweed spp. comprising 2.2% of the community composition at vegetated sites. Other species, such as softstem bulrush Scripus validus, heart-shaped water plantain Alisma subcordatum, and American lotus Nelumbo lutea were observed growing in the lake, but were not collected in our samples. Curlyleaf pondweed and Eurasian water milfoil were the only non-native species of aquatic vegetation observed. Aquatic Vegetation Sampling and Gear Effort – Flag Lake: We did not conduct aquatic vegetation sampling in Flag Lake in 2008 due to insufficient water levels for the majority of the sampling season, which inhibited navigation into the lake. However, aquatic vegetation was visually observed after water levels rose in late summer/early fall. The portion of the lake bed that was accessible (mainly the middle-northern portion) contained minimal to no aquatic vegetation (mostly flooded terrestrial vegetation); however, the remnant farm ditches running through the middle-northern portion of the lake contained abundant beds of coontail and duckweed species. Fish Sampling and Gear Effort-Thompson Lake: We conducted monthly fish sampling on Thompson Lake from 4/21/08 - 10/10/08 using a multiple gear approach (Table 1). Sampling consisted of 28 electrofishing runs (15 minutes each), 28 fyke net sets (24 hours each), 28 mini-fyke net sets (24 hours each), and 25 monthly minnow trap sets (24 hours each) at shoreline or pseudo-shoreline (used for shoreline gear) sites. Additionally, seven tandem fyke net sets (24 hours each) and seven tandem mini-fyke net sets (24 hours each) were deployed at open water sites. All gears were fished according to the protocols of Gutreuter et al. (1995), which are used for the Long Term Resource Monitoring Program. Total Fish Catch-Thompson Lake: We collected a total of 32,907 fish representing 15 species and 7 families from Thompson Lake in 2008. Overall, catches were dominated by centrarchids (mainly young-of-year Lepomis spp). Unidentified Lepomis spp. (bluegill L. macrochirus or pumpkinseed L. gibbosus with lengths <40 mm) dominated the catch with 25,177 fish comprising 76.5% of the total catch. Bluegill ≥40 mm followed with 4,456 fish totaling 13.5% of the catch and pumpkinseed ≥40 mm with 1,545 fish at 4.7% of the total catch. Largemouth bass Micropterus salmoides (1,026, 3.1%), black crappie Pomoxis nigromaculatus (415, 1.3%), unidentified Ameiurus spp. (bullhead catfish spp.) (134, 0.4%), warmouth L. gulosus (48, 0.1%), green sunfish L. cyanellus (43, 0.1%), goldfish Carassius auratus (23, 0.1%), black bullhead A. melas (16, <0.1%), western mosquitofish Gambusia affinis (10, <0.1%), bowfin Amia calva (7, <0.1%), white crappie P. annularis(2, <0.1%), and emerald shiner Notropis atherinoides, lake chubsucker Erimyzon sucetta, longnose gar Lepisosteus osseus, spotted gar L. oculatus, and unidentified cyprinid (Carassius or Cyprinus spp.) (1, <0.1% each) made up the remainder of the catch. (Table 4) Catch-per-Unit Effort (CPUE)-Thompson Lake We collected 10 fish species while electrofishing Thompson Lake in 2008, which comprised 3.5 % of the total catch by all gears. Largemouth bass dominated the catch with 100 fish/hour of electrofishing, followed by 30 unidentified Lepomis spp. (bluegill or pumpkinseed <40 mm), 27 bluegill (≥40 mm) per hour, three pumpkinseed (≥40 mm), black crappie, and goldfish per hour, and <1 warmouth, bowfin, green sunfish, white crappie, lake chubsucker, and unidentified cyprinid (Carassius or Cyprinus spp.) per hour electrofishing. Catch rates of different fish species varied by gear, but largemouth bass, bluegill, pumpkinseed and unidentified Lepomis spp. (bluegill or pumpkinseed <40 mm) dominated the catch by all gears. Goldfish were the only invasive fish species collected (23 fish), while the only undesirable species collected were green sunfish (43 fish) and black bullhead (19 fish). Fish Sampling and Gear Effort – Flag Lake: We did not conduct monthly fish sampling on Flag Lake due to insufficient water levels throughout the majority of the sampling season, which inhibited navigation into the lake. Abundant, flooded terrestrial vegetation inhibited proper gear fishing. However, water levels increased in late summer/early fall allowing for minimal fish sampling to be conducted. Two electrofishing runs (15 minutes each) were conducted in Flag Lake on 10/24/2008. Total Fish Catch – Flag Lake: We collected a total of 31 fish representing 2 species and 1 family from Flag Lake in 2008. Largemouth bass dominated the catch (27, 87.1%), followed by bluegill (2, 6.5%), and unidentified Lepomis spp. (bluegill or pumpkinseed