Eric T. Tsakiris

Is False Spike, Quadrula mitchelli (Bivalvia: Unionidae), Extinct? First Account of a Very Recently Deceased Individual in Over Thirty Years

Abstract A recent survey of the San Saba River in San Saba County, Texas, has yielded the first record in >30 years of a very recently deceased individual (i.e., with tissue present within the shell) of the unionid mussel Quadrula mitchelli (false spike). This very recently dead individual suggests that living populations of Q. mitchelli might still exist in the San Saba River. Our results provide evidence that surveys in remote areas may help to locate populations of rare species of unionid mussels. Resumen Un muestreo recién del río San Saba en el condado de San Saba, Texas, ha dado el primer registro en >30 años de un individuo de mejillón unionido Quadrula mitchelli recientemente fallecido (es decir, con el tejido aún presente dentro de la concha). El encuentro sugiere que aún podrían existir más poblaciones actuales de Q. mitchelli dentro del río San Saba. Nuestros resultados rinden evidencia que muestreos realizados dentro de áreas remotas podrían ayudar a localizar poblaciones de especies raras del mejillón unionido.

False Spike, Quadrula mitchelli (Bivalvia: Unionidae), is Not Extinct: First Account of a Live Population in Over 30 Years

Abstract. During a recent survey a small population of Quadrula mitchelli (Simpson, 1895), a species thought to have been extinct, was discovered in Texas. In total, 7 live individuals were collected from the Guadalupe River near Gonzales, Gonzales County, Texas. Our finding represents the only known population for this species in Texas and the first record of live specimens in over 30 y, which is significant because this species is currently under review for protection under the Endangered Species Act.

New Distributional Records for Four Rare Species of Freshwater Mussels (Family: Unionidae) in Southwestern Louisiana

Abstract Recent studies of mussels have documented a gradient of extirpation that extends from Toledo Bend Dam to United States Highway 190 in the lower Sabine River. A similar pattern has been documented for the diversity and abundance of cyprinids. To evaluate whether impacts of the project have extended into nearby tributaries, we assessed the distribution and abundance of threatened species of mussels in Anacoco and Toro bayous, within Vernon and Sabine parishes, respectively. In total, 1,474 live mussels representing 15 species were collected during our survey. Of these, four are considered state-threatened: Fusconaia askewi (Texas pigtoe), Lampsilis satura (sandbank pocketbook), Obovaria jacksoniana (southern hickorynut), and Pleurobema riddellii (Louisiana pigtoe). In general, L. satura, O. jacksoniana, and P. riddellii appear to be rare in Anacoco Bayou and absent from Toro Bayou, whereas F. askewi is more abundant and widely distributed. Effects of backwater related to releases from impoundments, discharge from paper mills, and use of land within the watershed appear to be plausible factors contributing to the constrained distribution of freshwater mussels throughout both bayous. Resumen Estudios recientes de mejillones han documentado un gradiente de extirpación que se extiende desde Toledo Bend Dam hasta la Highway 190 en Estados Unidos en el bajo río Sabine. Un patrón similar ha sido documentado para la diversidad y abundancia de ciprínidos. Para evaluar si los impactos del proyecto se han extendido en las inmediaciones afluentes, evaluamos la distribución y abundancia de especies de mejillones amenazados en los pantanos Anacoco y Toro, dentro de los distritos Vernon y Sabine, respectivamente. Durante nuestro muestreo, se colectaron 1,474 mejillones vivos, representando 15 diferentes especies. De ellas, cuatro son clasificadas como amenazadas por el estado de Texas: Fusconaia askewi, Lampsilis satura, Obovaria jacksoniana, y Pleurobema riddellii. Por lo general, L. satura, O. jacksoniana y P. riddellii parecen ser raras dentro del pantano Anacoco y ausentes dentro del pantano Toro, mientras que F. askewi es más abundante y ampliamente distribuida. Efectos de remanso relacionado a la liberación de agua de embalses, descargo de agua por fábricas de papel, y uso de la tierra dentro de la cuenca parecen ser posibles factores que contribuyen a la limitada distribución de mejillones de agua dulce dentro de los dos pantanos.

A semi-arid river in distress: Contributing factors and recovery solutions for three imperiled freshwater mussels (Family Unionidae) endemic to the Rio Grande basin in North America

Freshwater resources in arid and semi-arid regions are in extreme demand, which creates conflicts between needs of humans and aquatic ecosystems. The Rio Grande basin in the southwestern United States and northern Mexico exemplifies this issue, as much of its aquatic biodiversity is in peril as a result of human activities. Unionid mussels have been disproportionately impacted, though the specific factors responsible for their decline remain largely unknown. This is problematic because the Rio Grande basin harbors one federally endangered unionid mussel (Popenaias popeii, Texas Hornshell) plus two other mussel species (Potamilus metnecktayi, Salina Mucket; and Truncilla cognata, Mexican Fawnsfoot), which are also being considered for listing under the U.S. Endangered Species Act. To date, surveys for these species have not corrected for variability in detection so current range estimates may be inaccurate. Using single occupancy-modeling to estimate detection and occupancy at 115 sites along ~800 river kilometers of the Rio Grande in Texas, we found that detection probabilities were relatively high, indicating that our survey design was efficient. In contrast, the estimated occupancy was low, indicating that our focal species were likely rare within the Rio Grande drainage. In general, the predicted occupancy of our focal species was low throughout their respective ranges, indicating possible range declines. A comparison of currently occupied ranges to presumptive ranges underscores this point. The best-approximating models indicated that occupancy was influenced by habitat, water quantity and quality, and proximity to large-scale human activities, such as dams and major urban centers. We also discuss a series of conservation options that may not only improve the long-term prognosis of our focal species but also other aquatic taxa.

Effectiveness of a nonlethal method to quantify gamete production in freshwater mussels

Studies on the reproductive biology of freshwater mussels have contributed to conservation of this group, but methods to study early reproductive stages are either lethal (e.g., histological technique) or useful for only qualitative assessments (e.g., nonlethal syringe technique). Using 2 common mussels (Quadrula apiculata and Quadrula verrucosa) and 2 rare mussels (Quadrula petrina and Quadrula houstonensis) distributed across 3 sites in the Navasota River and San Saba River, Texas, we validated the effectiveness of the syringe technique to quantify gamete production by examining: 1) if estimates of gamete traits (sperm concentration, egg size, and egg concentration) obtained with the syringe technique were correlated to estimates of gamete traits (sperm density, egg size, and egg density) obtained with a histological technique; and 2) if survival, growth, and body condition of individual mussels sampled with the syringe technique were negatively affected in a 2-y mark–recapture field experiment. Pearson’s correlation analysis of gamete production measured over the 1st year of the study indicated sperm concentration and density and egg sizes were correlated between the 2 techniques; however, egg concentration and density were correlated in only some cases. Joint analysis of live and dead encounters from the mark–recapture experiment indicated the syringe technique had little to no effect on survival probability of mussels, and mixed models of shell growth and Fulton’s K body condition index failed to detect sublethal effects of the syringe technique on mussels. The syringe technique is relatively accurate and noninvasive and can be used to study the reproductive biology of threatened and endangered mussels quantitatively. In addition, it can provide the large sample sizes often needed to study the reproductive ecology of mussels.

Misidentification of sex for Lampsilis teres, Yellow Sandshell, and its implications for mussel conservation and wildlife management

Correct identification of sex is an important component of wildlife management because changes in sex ratios can affect population viability. Identification of sex often relies on external morphology, which can be biased by intermediate or nondistinctive morphotypes and observer experience. For unionid mussels, research has demonstrated that species misidentification is common but less attention has been given to the reliability of sex identification. To evaluate whether this is an issue, we surveyed 117 researchers on their ability to correctly identify sex of Lampsilis teres (Yellow Sandshell), a wide ranging, sexually dimorphic species. Personal background information of each observer was analyzed to identify factors that may contribute to misidentification of sex. We found that median misidentification rates were ~20% across males and females and that observers falsely identified the number of female specimens more often (~23%) than males (~10%). Misidentification rates were partially explained by geographic region of prior mussel experience and where observers learned how to identify mussels, but there remained substantial variation among observers after controlling for these factors. We also used three morphometric methods (traditional, geometric, and Fourier) to investigate whether sex could be more correctly identified statistically and found that misidentification rates for the geometric and Fourier methods (which characterize shape) were less than 5% (on average 7% and 2% for females and males, respectively). Our results show that misidentification of sex is likely common for mussels if based solely on external morphology, which raises general questions, regardless of taxonomic group, about its reliability for conservation efforts.

Abundance and Diversity of Arthropods in Nests of Lark Sparrows (Chondestes grammacus)

Abstract We examined abundance and diversity of arthropods in nests of lark sparrows (Chondestes grammacus). No true ectoparasite occurred in the nests sampled (n = 69) and no ectoparasite was found on nestlings. However, 67% of nests contained non-parasitic arthropods from ≥16 families. There was no significant difference in number of arthropods per gram of nesting material or diversity (at familial to higher taxonomic order) with height of nest (ground or arboreal), date of nesting, duration of activity per nesting attempt, mean or maximum temperature of nest, and frequency of prescribed burning of the habitat, or in relation to nest-building by two species of birds (lark sparrows and northern mockingbirds Mimus polyglottos). Resumen Examinamos la abundancia y diversidad de artrópodos en nidos de Chondestes grammacus. Ningún ectoparásito verdadero fue encontrado en la muestra de nidos (n = 69 nidos), tampoco se identificaron ectoparásitos en crías de C. grammacus. Sin embargo, 67% de los nidos tenían artrópodos no-parasitarios de ≥16 familias. No encontramos diferencias significativas en el número de artrópodos por gramo de material del nido ni diversidad taxonómica (al nivel de familia o más alto) en relación con la altura del nido (terrestre o arbóreo), fecha de anidación, duración de la actividad por intento de anidación, promedio o máxima temperatura del nido, y frecuencia de quema prescrita del hábitat, o en relación a la construcción de nidos de dos especies de aves (C. grammacus y Mimus polyglottos).