Edie Marsh-Matthews

Extirpation of red shiner in direct tributaries of lake texoma (Oklahoma-Texas) : A cautionary case history from a fragmented river-reservoir system

Abstract The effects of reservoirs on composition of fish assemblages are well documented in and downstream of reservoirs but are less well known upstream, especially in small tributaries. Here we report that a historically very abundant native minnow species (red shiner Cyprinella lutrensis) has been extirpated from several direct tributaries of Lake Texoma, a large impoundment of the Red and Washita rivers, Oklahoma-Texas. Using historical and recent data, we document the recent loss of or sharp declines in the red shiner from six of seven creeks that are direct tributaries of Lake Texoma. The red shiner is widespread, tolerant of harsh conditions, and highly invasive, so its demise is particularly noteworthy. The species remains common in direct tributaries of free-flowing reaches of the rivers that we sampled recently. Centrarchids that are potential predators of or competitors with the red shiner are now more abundant in Texoma-direct creeks than in tributaries to the rivers. Loss of the red shiner o...

Effects of maternal and embryo characteristics on post-fertilization provisioning in fishes of the genus Gambusia

Maternal provisioning of embryos in Gambusia (Poeciliidae) entails both production of large, yolky eggs and mother-to-embryo transfer of nutrients, the latter of which is readily quantified using injection of radiolabeled nutrients. We assayed patterns of nutrient transfer in broods of 26 Gambusia geiseri and 23 Gambusia affinis females, using injection of tritiated leucine. We examined maternal and embryo characteristics affecting the instantaneous rate of transfer and characterized the pattern of transfer to individual embryos within broods. Maternal (female size and condition) and brood characteristics (mean embryo size, developmental stage, brood size) did not predict the mean level of nutrient transfer to embryos in a brood for either species. Within broods, individual provisioning of embryos was not related to developmental stage, but was related to embryo mass in G. affinis with nutrient transfer higher to larger embryos. In addition, overall within-brood variation in nutrient transfer, measured as coefficient of variation in embryo radioactivity, was higher in G. affinis than in G. geiseri.

7 – SOUTHERN PLAINS RIVERS

The Arkansas and the Red—two large, separate river basins—drain the southern Great Plains region of the US south of the Kansas River and north of the Texas–Gulf coastal drainages. Rivers of the region flow through the Southern Plains, Central Prairie, Ozark Highlands, Ouachita Highlands, and Mississippi Embayment “freshwater ecoregions.” The rivers of the region fall into two different groups based on their upland versus lowland characteristics. The group including the Arkansas, Canadian, Red, Washita, and Cimarron rivers represents typical large to medium-size low-gradient prairie main stems with wide, shallow, braided, unstable sand-bed channels, often carrying heavy loads of large wood snags washed in by floods. Late-summer drying of streams in the region is a function of both evapotranspiration and lowered rainfall. Extreme rainfall events result in annual or more frequent bankfull spates and streambed scouring in many of the smaller tributaries to the main rivers. Clearing and snagging rivers for boat passage, contamination by salt water from oil production, and interbasin water transfers have altered the rivers over the years.

Resources and offspring provisioning: a test of the Trexler-DeAngelis model for matrotrophy evolution.

Theoretical models of the evolution of matrotrophy from a lecithotrophic ancestor suggest that resource availability plays a major role in selective scenarios favoring a change in offspring provisioning. We examined effects of feeding level on embryo provisioning in the livebearing fish Gambusia geiseri, a species with dual provisioning of embryos via both yolk sequestered in large eggs and post-fertilization mother-to-embryo nutrient transfer. Females were fed either once per day or once every three days for three months. Females fed daily had marginally larger brood size, significantly larger embryos, and a higher rate of nutrient transfer (assayed directly by injection of radiolabeled nutrients) than females fed every third day. There was no difference in the size of unfertilized eggs between the feeding treatments. Resource effects on matrotrophic provisioning in G. geiseri suggest that matrotrophy plays an important role in provisioning and allows females to adjust offspring size in response to resource availability.

Spatial variation in relative abundance of a widespread, numerically dominant fish species and its effect on fish assemblage structure.

Abstract. Collections of fish assemblages from streams in the midwestern United States were used to examine assemblage-level effects of spatial variation in relative abundance of the red shiner, Cyprinella lutrensis, a widespread and highly abundant minnow species. This species has been widely introduced outside its native range and is suspected to have impacted local assemblages where it has become established. Given its overall dominance of midwest fish assemblages, and its suspected impact on assemblage structure, we asked if structure of the residual fish assemblages (red shiners excluded) was a function of the relative abundance of red shiners throughout the native range of C. lutrensis in the USA. Although red shiner ranked first in abundance in half of the assemblages and numerically dominated 28% of the assemblages, red shiner relative abundance in an assemblage had no detectable effect on richness, diversity, evenness, or complexity of other (residual) species in the assemblage. Relative abundance of red shiners did have a positive effect on the abundance of benthic minnows in the residual assemblage, but not on water column minnows that are ecologically most like red shiners. Environmental factors did not explain a significant amount of the variation in relative abundance of red shiners, but did explain some variation in residual assemblage structure. Although widespread and numerically dominant at many localities, red shiners do not appear to have a strong impact on local fish assemblage structure within their native range. This is in sharp contrast to the reported negative effects of red shiners on fish assemblages where they have been introduced outside their native range.

Direct Evidence for Mother-to-Embryo Transfer of Nutrients in the Livebearing Fish Gambusia geiseri

Abstract We present direct experimental evidence of maternal-to-embryo nutrient transfer in largespring gambusia, a species in which embryonic development was believed to depend solely on nutrients and energy sequestered in the egg prior to fertilization. Thirteen pregnant females were injected with tritiated leucine, and developing embryos of those individuals were assayed for radioactivity two hours postinjection. In eight females, one to all embryos in the developing brood showed significant uptake of labeled leucine. This finding suggests that matrotrophy may be an important maternal investment strategy for this species.

Matrotrophy in the cave molly: An unexpected provisioning strategy in an extreme environment

Maternal provisioning of animal embryos may be entirely through yolk deposited in the unfertilized egg (lecithotrophy) or may include post-fertilization nutrient transfer (matrotrophy) in varying degrees. Current theory suggests that the extent of post-fertilization provisioning is resource-dependent, with higher levels of matrotrophy being advantageous in more productive environments. In this study, we investigated post-fertilization embryo provisioning in a livebearing fish, Poecilia mexicana, from two different habitats (a toxic cave and a non-toxic surface habitat) that impose different energetic demands and therefore differ in resources available for reproduction. We predicted that fish in the benign habitat would be more matrotrophic than those from the toxic cave. We used two different techniques for this assay: (1) the matrotrophy-index analysis (MI) for field-collected fish and (2) both MI and radio-tracer assay for laboratory-reared females. According to the interpretation of the matrotrophy index, both populations are purely lecithotrophic, while the radio-tracer assay found females from both populations to actively transfer nutrients to developing embryos at approximately the same rate. Our results suggest that P. mexicana, which was traditionally classified as lecithotrophic, is capable of incipient matrotrophy, and that matrotrophy can contribute to embryo provisioning even in populations from resource-limited environments. Furthermore, the analysis of laboratory-reared animals provides evidence for a genetic component to the large offspring size in cave mollies, which had so far only been described from the field. Specifically, our results suggest matrotrophy occurs in species interpreted as lecithotrophic using the MI approach. Hence, to avoid misclassification, both techniques should ideally be employed in concert, rather than individually. Finally, our results provide further insights into the possible evolutionary pathway from lecithotrophic oviparity to matrotrophic viviparity.

Conservation and status of the fish communities inhabiting the Río Conchos basin and middle Rio Grande, México and U.S.A.

The Chihuahuan Desert region contains a numberof unique aquatic environments, but with fewexceptions, these have been little studied. Because of the dearth of information aboutthese environments and because many of the fishin the region are threatened with extinction orhave gone extinct, we sampled the RíoConchos basin and adjoining aquatic habitats inthe Rio Grande to assess the status of the fishof this region. Most sites showed some degreeof human-induced impacts. A number ofpotentially threatened fish were eitherabundant at only a few sites or rare or absentthroughout the localities sampled. Withoutconcerted binational efforts to conserve thefish of the region, further deletions to thenative fish fauna will likely occur.

Density-Dependent Overwinter Survival and Growth of Red Shiners from a Southwestern River

Abstract The red shiner Cyprinella lutrensis is the most widespread and abundant minnow (Cyprinidae family) in central and southwestern North America, occurring at very high local densities in streams from northern Mexico to Nebraska and Iowa. The streams in which red shiners occur are typically harsh, unpredictable environments with temperature extremes and episodes of low oxygen, floods, and drought. In outdoor experimental streams, red shiners stocked at densities typical of natural streams showed moderate density effects on overwinter survival and strong effects on growth from October to May. At lower densities a higher percentage (>70% on average) of individuals survived winter, and most grew to adult size the next spring. At higher densities survival and average growth were lower, and the distribution of final body size was highly skewed, with a few individuals reaching sexual maturity and most remaining at the juvenile stage. The apparent growth of the cohort in the Washita River, Oklahoma, from wh...

Can a highly invasive species re-invade its native community? The paradox of the red shiner

Red shiners (Cyprinella lutrensis) are among the most widespread, ecologically general, and environmentally tolerant fish species in North America, and are highly invasive where they have been introduced outside their native range. However, long-term data on fish assemblages showed that red shiners gradually (1980s to 2006) disappeared from creeks that are direct tributaries of Lake Texoma (Oklahoma, USA) where they are native and historically had been numerically dominant. Following a major flood in 2007, red shiners were detected anew in some of these creeks, but repeatedly disappeared and re-appeared through November 2009. Given their invasive abilities where they are not native, their failure to become re-established prompted us to examine factors that affect their apparent inability to re-invade their native habitat. We established assemblages of five common fish taxa native to Brier Creek in 12 large, outdoor mesocosm stream units. Subsequently, we introduced red shiners at two densities of 10 or 30 per unit, six replicates each, to examine potential effects of propagule pressure on establishment success. Approximately six months later, we ended the experiment and recovered all fish. Red shiners failed to become established in the experimental units, regardless of initial stocking density. They also exhibited much lower survival than other species in the native community, which not only survived well but exhibited some recruitment. Red shiner survival was significantly negatively related to the number of sunfish (Lepomis spp.) that grew to adult size in experimental units, suggesting that predation can inhibit early stages of invasion by red shiners.