Ben J. Labay

Assessing historical fish community composition using surveys, historical collection data, and species distribution models.

Accurate establishment of baseline conditions is critical to successful management and habitat restoration. We demonstrate the ability to robustly estimate historical fish community composition and assess the current status of the urbanized Barton Creek watershed in central Texas, U.S.A. Fish species were surveyed in 2008 and the resulting data compared to three sources of fish occurrence information: (i) historical records from a museum specimen database and literature searches; (ii) a nearly identical survey conducted 15 years earlier; and (iii) a modeled historical community constructed with species distribution models (SDMs). This holistic approach, and especially the application of SDMs, allowed us to discover that the fish community in Barton Creek was more diverse than the historical data and survey methods alone indicated. Sixteen native species with high modeled probability of occurrence within the watershed were not found in the 2008 survey, seven of these were not found in either survey or in any of the historical collection records. Our approach allowed us to more rigorously establish the true baseline for the pre-development fish fauna and then to more accurately assess trends and develop hypotheses regarding factors driving current fish community composition to better inform management decisions and future restoration efforts. Smaller, urbanized freshwater systems, like Barton Creek, typically have a relatively poor historical biodiversity inventory coupled with long histories of alteration, and thus there is a propensity for land managers and researchers to apply inaccurate baseline standards. Our methods provide a way around that limitation by using SDMs derived from larger and richer biodiversity databases of a broader geographic scope. Broadly applied, we propose that this technique has potential to overcome limitations of popular bioassessment metrics (e.g., IBI) to become a versatile and robust management tool for determining status of freshwater biotic communities.

Can Species Distribution Models Aid Bioassessment when Reference Sites are Lacking? Tests Based on Freshwater Fishes

Recent literature reviews of bioassessment methods raise questions about use of least-impacted reference sites to characterize natural conditions that no longer exist within contemporary landscapes. We explore an alternate approach for bioassessment that uses species site occupancy data from museum archives as input for species distribution models (SDMs) stacked to predict species assemblages of freshwater fishes in Texas. When data for estimating reference conditions are lacking, deviation between richness of contemporary versus modeled species assemblages could provide a means to infer relative biological integrity at appropriate spatial scales. We constructed SDMs for 100 freshwater fish species to compare predicted species assemblages to data on contemporary assemblages acquired by four independent surveys that sampled 269 sites. We then compared site-specific observed/predicted ratios of the number of species at sites to scores from a multimetric index of biotic integrity (IBI). Predicted numbers of species were moderately to strongly correlated with the numbers observed by the four surveys. We found significant, though weak, relationships between observed/predicted ratios and IBI scores. SDM-based assessments identified patterns of local assemblage change that were congruent with IBI inferences; however, modeling artifacts that likely contributed to over-prediction of species presence may restrict the stand-alone use of SDM-derived patterns for bioassessment and therefore warrant examination. Our results suggest that when extensive standardized survey data that include reference sites are lacking, as is commonly the case, SDMs derived from generally much more readily available species site occupancy data could be used to provide a complementary tool for bioassessment.

Population of variable platyfish (Xiphophorus variatus) established in Waller Creek, Travis County, Texas

Abstract The variable platyfish (Xiphophorus variatus), native to Gulf Coast drainages of northern Mexico, is a popular aquarium fish with a long history of introduction globally. We document the first Texas occurrence of this species, and its persistence in highly urban Waller Creek in the city of Austin since at least 2004. The population appears to be limited to Waller Creek, having not yet been found in neighboring creeks where similar habitat exists. We observed individuals in situ and in the lab surviving in 7°C water, well below published thermal minima, and report its persistence through one of the coldest winters in Austins recorded history. Its persistence may be due to a combination of its cold tolerance and the presence of thermal refuges. In the lab we found that individuals purchased in a local pet store and individuals from Waller Creek had the same cold tolerance.

American Eel in Texas – what we do, don’t, and need to, know

Copy of the oral presentation made by the first author to the January 2016 meeting of the Texas Chapter of American Fisheries Society in Kerrville, Texas. Presentation is provided in several file formats. Data mapped in the presentation are also included in kml format (Google Earth).

Year 1 report for ‘Conserving Texas Biodiversity: Status, Trends, and Conservation Planning for Fishes of Greatest Conservation Need’

State Wildlife Grant Program, grant TX T-106-1 (CFDA# 15.634), Contract No. 459125 UTA14-001402

Apparent Persistence of a Landlocked Population of Gulf Pipefish, Syngnathus scovelli

Abstract Though adults and older juveniles of some species are commonly encountered in freshwater reaches of coastal streams and rivers, pipefishes in general are believed to be either amphidromous or marine. In 1992, Gulf pipefish (Syngnathus scovelli) were reported in Lake Texana, a reservoir on the Navidad River near Edna, Jackson County, Texas. In June 2011, we collected an adult male with embryos and a juvenile from the same lake. This strongly suggests reproduction and persistence of the population at Lake Texana, which does not have access to saline waters. Though presence of a viable, reproducing population was not absolutely confirmed this appears likely to be the first known landlocked, freshwater population of any species of pipefish. Resumen Aunque adultos y juveniles mayores de algunas especies se encuentran comúnmente en aguas dulces de arroyos y ríos costeros, en general se considera que las especies de pez pipa son anfídromas o marinas. En 1992, el pez pipa del Golfo (Syngnathus scovelli) fue reportado en el Lake Texana, una presa artificial sobre el río Navidad cerca al poblado de Edna, condado de Jackson, Texas. En junio de 2011, colectamos un macho adulto con embriones y un juvenil en el mismo lago, hecho que sugiere la reproducción y persistencia de la población del Lake Texana, el cual no tiene acceso a aguas salobres. Aunque no se ha confirmado absolutamente, parece muy probable que esta población represente la primera población de pez pipa que puede reproducirse en agua dulce sin tener salida a agua salobre.