Review of the Edwards Aquifer Habitat Conservation Plan Report 3 (2018) / Chapter Skim
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2 The Listed Species
2 The Listed Species
Pages 29-66
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From page 29... ...
The indicator species are intended to represent the other listed species: the Comal Springs dryopid beetle, the Peck's Cave amphipod, the Edwards Aquifer diving beetle, the Texas troglobitic water slater, the Comal Springs salamander, the San Marcos salamander, the Texas blind salamander, and the San Marcos gambusia (EARIP, 2012, p.
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From page 30... ...
As will be evident from this chapter, much more is known about the life histories and habitat requirements of the indicator species compared to the others. FOUNTAIN DARTER Description and Life History The life history of the fountain darter has been described in many documents (Schenck and Whiteside, 1977; Brandt et al., 1993; Labay and 1 The use of the CSRB as an indicator of the other ESA-listed invertebrates is problematic because of a lack of information on the beetle's spatial distribution, range of potential habitats, and natural history.
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From page 31... ...
It is the latter; EAA treats the LTBG reaches as constituting the entire population of fountain darters when determining population abundance goals in each of the systems. Historically, the geographic extent of fountain darters in the San Mar
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From page 32... ...
However, the Committee notes that in its examination of the drop-net data for fountain darters, there were few to no fountain darter densities measured for Hydrocotyle, Ludwigia, Sagittaria, and Texas wild rice in the San Marcos system and for Potamogeton in both systems. For these SAV types, which were added to the goals by amendment of the HCP in 2016, fountain darter densities were estimated based on more recent observations (BIO-WEST and Watershed Systems Group, 2016)
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From page 33... ...
TABLE 2-1 Long-Term Biological Goals for Fountain Darters in the Comal and San Marcos Systems Comal Springs Fountain Darter Habitat, Submerged Aquatic Vegetation, m2 Study Reach Potamogeton Ludwigia Cabomba Sagittaria Bryophytes Vallisneria Upper Spring Run 25 25 850 1,750 Landa Lake 25 900 500 2,250 3,950 12,500 Old Channel 425 180 450 550 New Channel 100 2,500 150 TOTAL 25 1,450 3,205 3,550 6,400 12,500 Comal Springs Fountain Darter Median Density, number/m2 Potamogeton Ludwigia Cabomba Sagittaria Bryophytes Vallisneria 3.3 7 7 1 20 1 San Marcos Springs Fountain Darter Habitat, Submerged Aquatic Vegetation, m2 Study Reach Potamogeton Ludwigia Cabomba Sagittaria Hydrocotyle Zizania Spring Lake Dam 200 100 50 200 50 700 City Park 1,450 150 90 300 10 1,750 I-35 250 50 50 150 50 600 TOTAL 1,900 300 190 650 110 3,050 San Marcos Springs Fountain Darter Median Density, number/m2 Potamogeton Ludwigia Cabomba Sagittaria Hydrocotyle Zizania 5 7 7 1 4 5 SOURCE: BIO-WEST and Watershed Systems Group (2016)
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From page 34... ...
34 REVIEW OF THE EDWARDS AQUIFER HABITAT CONSERVATION PLAN A B FIGURE 2-1 Long-term biological goal and restoration reaches for the fountain darter in the Comal (A) and San Marcos (B)
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From page 35... ...
Fountain darters are associated with SAV, with different BOX 2-1 Calculation of Median Densities to Track Achievement of Biological Goals The method used to compute median fountain darter densities to show com pliance with the biological goals is insensitive to variation in observed densities, which is problematic. Presently, the Edwards Aquifer Authority (EAA)
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From page 36... ...
It shows that greater coverage of SAV in the drop-net sample allows for higher densities of fountain darters but does not guarantee higher densities. Figure 2-3 uses the same drop-net data and shows that fountain darter densities are generally higher in some SAV types over others, with a strong preference for bryophytes and filamentous algae.
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From page 37... ...
will always exceed 4.0 mg/L, and temperatures will be cooler than 25oC. The water quality objective is intended to ensure stable conditions for the fountain darter, which are associated with successful reproduction.
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From page 38... ...
and they are evaluating how to use the model to address questions about flow effects on habitat and fountain darter population dynamics. There are also process studies on fountain darters available as part of the Applied Research Program and other papers and theses.
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From page 39... ...
. Texas wild rice reproduces both sexually and asexually.
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From page 40... ...
found Texas wild rice to occur at sites with high water clarity. They also found that calcium and sulfur dioxide concentrations were elevated on non–wild rice transects and hypothesized that this was associated with suburban and urban runoff from the City of San Marcos and other nonpoint sources, including agriculture.
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From page 41... ...
It should be noted that flow can regulate both temperature and pH in the San Marcos system, highlighting the importance of maintaining minimum flows in the San Marcos River to Texas wild rice survival. The efficiency of carbon uptake is the foremost reason that C4 species outcompete C3 species when CO2 levels are low (and pH is high)
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From page 42... ...
3. To establish recreation awareness, with "control" in high-quality habitat areas when flow is below 100 cfs TABLE 2-2 Long-Term Biological Goals for Texas Wild Rice Reach Percentage of River Segment Areal Coverage, m2 Total Areal Coverage Spring Lake 1,000–1,500 n/a Spring Lake Dam to Rio Vista Dam 5,810–9,245 83–66 Rio Vista Dam to I-35 910–1,650 13–12 Downstream of I-35 280–3,055 4–22 TOTAL 8,000–15,450 100 SOURCE: EARIP (2012)
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From page 43... ...
. Every reach of the San Marcos River appears to have gained Texas wild rice.
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From page 44... ...
Description and Life History At the initiation of the HCP, very little was understood about the life history and population biology of the CSRB, its optimal water quality conditions, and general distribution within the Comal Springs system. Hence, in an effort to better understand the habitat, ecology, and population biology of the CSRB, the Applied Research Program has focused several projects on the beetle (see Table 5-3 in NASEM, 2017, for a recent review; BIO-WEST, 2016, 2017; Nowlin et al., 2016a,b)
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From page 45... ...
THE LISTED SPECIES 45 erations and asynchronous emergence not associated with seasonal changes in weather (Bowles et al., 2003; Cooke, 2012)
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From page 46... ...
As with the other listed species, the biological objectives for achieving the long-term biological goals for the CSRB have three components. The flow component of the objective is to maintain a long-term average total Comal Springs discharge above 225 cfs with a minimum of 30 cfs that is not to exceed six months in duration, followed by at least 80 cfs for three months (the same as for the fountain darter)
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From page 47... ...
Monitoring CSRB populations are monitored in the three study reaches of the Comal Springs system shown in Figure 2-4: Spring Run 3, the western shoreline of Landa Lake, and the Spring Island area. The populations are collected periodically each year using a cotton-lure approach that provides qualitative estimates of both larvae and adults, but cannot provide true density estimates (as discussed at length in NRC, 2015, and NASEM, 2017)
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From page 48... ...
For each monitoring event in 2016, it was reported that ten lures per study reach were placed downstream of ten individual flowing spring orifices with visible flow and then incubated for approximately four weeks (BIO-WEST, 2016)
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From page 49... ...
These are important questions that influence how the data generated from each sampling event should be analyzed and interpreted for compliance purposes. Finally, while using median values to define the biological goals is adequate given the qualitative nature of sampling and zero-abundant data, a well-designed and articulated approach to calculating the annual median values is needed.
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From page 50... ...
. San Marcos salamanders are one of approximately 15 closely related species (a single monophyletic lineage)
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From page 51... ...
They inhabit spring outflows throughout Spring Lake and they also occur in the San Marcos River a short distance downstream from the Spring Lake Dam spillway (with both areas being designated by the FWS [1978, 1995] as critical habitat)
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From page 52... ...
. Biological Goals and Objectives The long-term biological goals for the San Marcos salamander address habitat quality and population density.
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THE LISTED SPECIES 53 FIGURE 2-6 Long-term biological goal reaches for the San Marcos salamander: hotel site, riverbed site, and Spring Lake Dam site.
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From page 54... ...
regulation of human recreation activity at the spillway site -- are odd because as stated they are virtually identical to certain M&M measures. A third, flow-related objective is the same as for Texas wild rice: a long-term average of 140 cfs and a minimum of 45 cfs.
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From page 55... ...
To supplement the current sampling, an additional protocol that uses occupancy estimation could be designed for the San Marcos salamander. Such a protocol would provide estimates of proportion of area occupied as well as detection probability and allow inference of salamander population trends across more of their potential habitat within Spring Lake.
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From page 56... ...
OTHER COVERED SPECIES Other covered species include the Comal Springs dryopid beetle, Peck's Cave amphipod, Edwards Aquifer diving beetle, Texas troglobitic water slater, Texas blind salamander, Comal Springs salamander, and San Marcos gambusia. Description of the Organisms The Comal Springs dryopid beetle (Stygoparnus comalensis)
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From page 57... ...
. This species is restricted to the subterranean waters of the Edwards Aquifer in Hays and Comal Counties, where it has been collected from artesian wells and from Comal Springs (EARIP, 2012)
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From page 58... ...
. Biological Goals and Objectives Ecological knowledge of the Comal Springs dryopid beetle, the Peck's Cave amphipod, the Edwards Aquifer diving beetle, and the Texas troglobitic water slater is lacking, while relatively more research on the Texas blind salamander and the Comal Springs salamander is available.
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From page 59... ...
. The Comal Springs dryopid beetle and the Edwards Aquifer diving beetle were rarely captured in drift nets, whereas Texas troglobitic water slaters and especially Peck's Cave amphipods were collected in high numbers during the 12-year study period.
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From page 60... ...
There are still some questions about relative competition of Texas wild rice versus other native and nonnative SAV, which could be addressed with mesocosm studies. The long-term biological goals for Comal Springs riffle beetle density should be updated during Phase 2 of the HCP to reflect more quantitative and standardized monitoring methods.
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From page 61... ...
Finally, the San Marcos salamander would benefit from additional studies on its life history, particularly using refugia populations, similar to what has been done for the fountain darter, CSRB, and Texas wild rice and other SAV. The EAA should continue to collect data as possible on all other nonsentinel species with the goal of eventually being in position to test the hypothesis that the sentinel species do indeed serve as viable proxies for protecting all Edwards Aquifer species.
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From page 62... ...
2016. Habitat Conservation Plan Biological Monitoring Program Comal Springs/ River Aquatic Ecosystem.
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From page 63... ...
Methods in Ecology and Evolution 6:543-556. EAHCP (Edwards Aquifer Habitat Conservation Plan)
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From page 64... ...
2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2.
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From page 65... ...
2004. Carbon use by the endangered Texas Wild Rice (Zizania texana, Poaceae)
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