Gravel Bottom Research Articles

Threatened fishes of the world: Parachondrostoma turiense (Elvira, 1987) (Cyprinidae)

Common names: Madrija (Spanish). Turia Nase (English). Conservation status: IUCN: Endangered [EN B2ab (i,iii,v), Crivelli 2006]; Spain: Endangered (EN B1+2c, Doadrio 2002). Identification: D III+8, A III+9, V II+8, P I+13-14, pharyngeal teeth 6-6 or 6-5, LL 44-51, gill rakers 21-27. Reaches 250 mm SL. A slender-bodied fish, with small head and blunt rounded snout. The mouth is ventral, arched from below, with a thin horny layer on the lower lip. Illustration by B. Elvira. Distribution: Restricted to the Turia and Mijares river basins in eastern Spain (Elvira 1987). Abundance: A rare species continuously declining in numbers and areas occupied (Crivelli 2006). Habitat and ecology: A rheophilic fish living in stretches with swift current, rich in submerged plants (Crivelli 2006). Reproduction: Moves in March-May to upper parts of rivers for spawning, which takes place in schools on gravel bottom (Kottelat and Freyhof 2007), laying 800–1,000 eggs that hatch in 5 days. Threats: The scarce populations are threatened by the introduction of exotic predatory fish, mainly largemouth bass Micropterus salmoides; agricultural pollution; water extraction, and drought (Elvira 1995). The extent of occurrence is less than 5,000 km. Conservation action: Protected at a regional level since 2004. Included in annex III of the Bern Convention and in annex II of the European Directive of Habitats. Two populations of the species are protected by the European Natura 2000 network. Artificial breeding produces about 1,000 juveniles per year which are stocked into the Turia River. Successful natural breeding of released fish occurred in 2008. Conservation recommendations: Effective correction of current threats is necessary. Remarks: Considered a distinct species by Elvira (1997), Doadrio (2002) and Elvira and Almodovar (2008). Doadrio and Carmona (2004) found that P. turiense showed a genetic divergence of 1.6–2.1% with respect to P. arrigonis, and of 1.1–1.3% with respect to P. miegii.

Small – but not easy: Evaluation of sampling methods in floodplain lakes including whole-lake sampling

We tested the efficiency of electrofishing and beach seining with several sampling strategies in small (<1 ha) floodplain borrow pits of the Dyje River (Danube basin). The study sites were characterized as rectangular-shaped with maximum depths of 2 m, having uniform habitat with minimal shelters and gravel bottom with organic sediment. We conducted point abundance sampling and continual electrofishing along the shoreline and also sampled in a zigzag pattern in the mid-zone from a boat. Sub-sampling and whole-lake sampling was conducted using a beach seine (40 m length, 10 mm mesh size). Each of the four sampling strategies (point sample electrofishing, continuous electrofishing, seining sub-samples, and whole-lake seining) was conducted on separate days in two sampling events in November 2005 and May 2007. A total of 22 species was registered in both sites. Electrofishing was more efficient for determining species richness in both sites compared to seining in the November sampling, but this finding was reversed in May 2007. Some species (chub, weatherfish) were recorded only by electrofishing, while other species (perch, bitterling, tench) were recorded mainly by electrofishing. Asp and blue bream were recorded only by seining. Pelagic species (bleak, bream, white bream) were highly underestimated by electrofishing in both sites and sample periods. The accurate representation of the fish community using just one sampling method and strategy is not feasible even in a small floodplain lake. Whole-lake seining through the entire borrow-pit site was more representative for pelagic species but less efficient for shelter-seeking species. Regarding the ability to capture representative samples, the behaviour of particular fish species seems to be a more significant factor than fish size.

Threatened fishes of the world: Triplophysa siluroides (Herzenstein 1888) (Balitoridae)

Common name: Catfish-like loach. Conservation status: Vulnerable, China Red Data Book of Endangered Animals (Yue and Chen 1998), and China Species Red List (Wang and Xie 2004). Identification: Body scaleless but densely covered with wart-like epidermal tubercles. Predorsal trunk depressed (SL≥ 200 mm) or laterally compressed (SL≤150 mm). Head depressed and tapering. D: iii, 8–9; P: i, 12–14; V: i, 7–8; A: ii, 5; C: 15–16 (branched rays). Irregular cloud-like bars present on the trunk in large individuals (SL>250 mm), while 8–15 regular bars in small ones (SL=104–191 mm) (Herzenstein 1888). Distribution: Endemic to the upper reaches of the Yellow River drainage in Qinghai, Sichuan and Gansu provinces in China (Zhu 1989; Ding 1994). Abundance: It is a commercial species in its distribution regions, with its populations declining dramatically in recent decades. Habitat and ecology: Inhabits bottom of the plateau rivers with gravel bottom, deep and swift current, or stays in slow current and static water with alluvial silt and lots of aquatic plants. It is a carnivorous fish with strong swimming ability. Reproduction: Spawning from June to August in the brooks with gravel bottom and slow flowing water, eggs are yellow and 2–3 mm in diameter. Larvae prefer to the riverside or adjacent small pools. Threats: Illegal fishing methods including poisoning, electrification and bombing. Overfishing resulted from tourists’ favorite of eating wild fishes has become one of the most harmful threats in recent decade. Conservation action: The lack of proper protection for this species has created some concern. The lack of protection has been related to poor public awareness and a lack of financial resources. Conservation recommendations: Strict fishing controls should be put into place and a natural reserve for this species created. Artificial propagation should be strengthened along with the release of artificial reared young fishes into the wild.

Laboratory Experiments on Artificial Reefs for American Lobsters

Abstract This laboratory study investigated design features for artificial reefs to be used as enhanced juvenile lobster habitat. These features included size of brick shelters, size of rocks in rock piles, and the character of the underlying substrate. Experiments using brick shelters tested the ability of two lobster sizes (50-59 and 82-89 mm CL) to enlarge shelters by digging in sand-gravel bottom. If the gravel size was 1-2 cm both lobster sizes occupied > 90% of shelters by 22 h and the difference between occupancy at 2 and 22 h was not significant. If gravel size was 3-5 cm or 6-8 cm fewer shelters were occupied and the excavation of the sand/gravel took longer. Piles of three sizes of rocks were each placed on hard bottom as well as sand/1-2 cm gravel bottom, and the number of lobsters occupying each rock pile noted after 2-days. Six times more 70-79 mm CL lobsters and 1.7 times more 50-59 mm CL lobsters occupied rock piles on sand/gravel than hard bottom. For all rock sizes and substrates combined...

New Record of Propappus volki (Annelida: Clitellata: Propappidae) from Japan

A species of freshwater oligochaete, Propappus volki Michaelsen, 1916, is newly recorded from sand and gravel bottoms of several unpolluted streams in Honshu, Japan. The present material agrees well with the previous descriptions of this species except that the spermathecal ampulla is shorter and the proboscis is more elomgate than those described earlier. This is the first record of the family Propappidae Coates, 1986 (New Japanese name: Kohimemimizu-ka) and the genus Propappus Michaelsen, 1905 (New Japanese name: Ko-himemimizu-zoku) in Japan. It provides evidence that the oligochaete fauna in Japan is more closely related to the Holarctic than to the Sino-Indian zoogeographical region. Propappus volki can be regarded as a good bio-indicator for unpolluted water.

Landsat TM inventory and assessment of waterbird habitat in the southern altiplano of South America

The diverse set of wetlands in southern altiplano of South America supports a number of endemic and migratory waterbirds. These species include endangered endemic flamingos and shorebirds that nest in North America and winter in the altiplano. This research developed maps from nine Landsat Thematic Mapper (TM) images (254,300 km2) to provide an inventory of aquatic waterbird habitats. Image processing software was used to produce a map with a classification of wetlands according to the habitat requirements of different types of waterbirds. A hierarchical procedure was used to, first, isolate the bodies of water within the TM image; second, execute an unsupervised classification on the subsetted image to produce 300 signatures of cover types, which were further subdivided as necessary. Third, each of the classifications was examined in the light of field data and personal experience for relevance to the determination of the various habitat types. Finally, the signatures were applied to the entire image and other adjacent images to yield a map depicting the location of the various waterbird habitats in the southern altiplano. The data sets referenced with a global positioning system receiver were used to test the classification system. Multivariate analysis of the bird communities censused at each lake by individual habitats indicated a salinity gradient, and then the depth of the water separated the birds. Multivariate analysis of the chemical and physical data from the lakes showed that the variation in lakes were significantly associated with difference in depth, transparency, latitude, elevation, and pH. The presence of gravel bottoms was also one of the qualities distinguishing a group of lakes. This information will be directly useful to the Flamingo Census Project and serve as an element for risk assessment for future development.

Effects of bottom substrate and presence of shelter in experimental tanks on growth and survival of signal crayfish,Pacifastacus leniusculus(Dana) juveniles

The effects of tank bottom substrates and presence of shelter on growth, survival and condition of cheliped in the juvenile (stage 2) signal crayfish, Pacifastacus leniusculus (Dana), with an initial stocking density of 200 individuals m−2 were investigated. In the first trial, three different tank bottom substrates with or without shelter were used. The three bottom types were loose gravel, glued gravel and bare bottom. The fastest growth both in terms of wet weight and carapace length was observed on loose gravel bottom. Also survival (range 30.1% to 49.8%) was affected by bottom type being higher on gravel bottoms than on bare bottom. Shelter improved survival only on loose gravel bottom. Bottom type influenced also the number of animals with cheliped injuries. The highest proportion of animals with no injuries (59.5%) was found on bare bottom and the proportion was about 12% and 13% units less on loose gravel and on glued gravel bottom. The presence of shelter had a marginal probability in increasing the number of animals without injuries. In the second trial, the substitution of ordinary gravel as tank bottom substrate with crushed limestone was studied. The mean final wet weights were 0.517 g on ordinary gravel bottom and 0.481 g on limestone bottom. The survivals were about 74% and 80% respectively. Limestone bottom decreased marginally final wet weight, and increased survival but did not affect the final carapace length that had a mean value of 13.6 mm. We conclude from the present experiments that the type of tanks and the rearing system used supported good growth of juvenile signal crayfish. The best growth results could be obtained by using loose gravel (or loose limestone) on the bottom of the tanks with a sufficient quantity of hiding places. However, there appears to be an increased risk for cheliped injuries on bottoms with loose materials.

ERODIBILITY OF URBAN BEDROCK AND ALLUVIAL CHANNELS, NORTH TEXAS1

ABSTRACT: Major erosion of urban stream channels is found in smaller basins in the North Texas study area with contributing drainage areas of less than ten square miles. Within these basins, four basic channel types are identified based on bed and bank lithologies: alluvial banks and bottoms, alluvial banks and gravel bottoms, alluvial banks with rock bottoms, and rock banks with rock bottoms. Most channels (75 percent) have alluvial banks with gravel or rock bottoms. Channel slopes are steep (.38 to.76 percent). Rock consists predominantly of shale and limestone. Channel cross sections are divided into the following four zones based on weathering, scour and entrainment mechanisms: soil zone, slake zone, rock zone and bed material zone. Erodibility of the channels is determined using multiple techniques including reach hydraulics and stream power computations, submerged jet testing, slab entrainment thresholds, and slake durability rates. Procedures are based on both empirical and modeled time series estimates of channel erosion. Field and modeled results support rates of erosion of up to four inches per year. Rates are tied to flow regime, climate, and type of channel bed and banks.

Discussion of “Turbulent Open-Channel Flow in Circular Corrugated Culverts” by S. A. Ead, N. Rajaratnam, C. Katopodis, and F. Ade

The authors should be complimented for tackling one of the most challenging problems in hydraulic and fisheries disciplines, the determination of the flow conditions that allow unimpeded fish passage through culverts. Recently, this problem has received a lot of attention throughout the U.S. and Canada with the design and implementation of the stream simulation approach ~Maxwell and Papanicolaou 2001!. This approach requires the use of culverts with gravel bottoms, known as countersunk culverts that ‘‘mimic’’ the natural streambed conditions upstream or downstream of a road crossing. The objectives of the present discussion are: ~i! to elaborate on some of the results presented by the authors with respect to the habitat suitability index ~i.e., the index that relates fish behavior to flow characteristics ! and ~ii! to generate a discussion on the importance of turbulence and secondary flows in the design of culverts facilitating fish passage during periods of fish migration. The authors, based on their experimental findings, provide empirical equations @Eqs. ~5! and ~6!# that relate the local streamwise velocity, u, with the prolonged fish speed, u p . These equations can be used to draw the isovels ~i.e., the velocity contours! per cross section and delineate the regions through which fish may ascend. Eqs. ~5! and ~6! were developed by accounting for the ‘‘dip’’ observed in the streamwise velocity profile that was attributed to the presence of secondary currents.

Time/frequency spread for bistatic geometries

The overall goal of this work is to develop a functional characterization of, and empirical models for, high-frequency, broadband acoustic propagation through a shallow ocean channel. One important aspect of this characterization is the time/frequency spread, which quantifies how much signals spread in time and frequency as they propagate. Because time and frequency spread are random quantities which vary from pulse to pulse, time/frequency spread must be characterized using a second-order statistic, e.g., the scattering function, which is the expected value of the mean-square spreading function. The scattering function has been measured in the following ocean environments: sandy gravel bottom, isovelocity sound speed profile (SSP); rough rock bottom, slightly downward-refracting SSP; and mud bottom, upward-refracting SSP. A statistical model for the scattering function is being developed for these environments based upon radial basis function decompositions of the scattering function estimates. The ultimate use of a scattering function model will be with simulation to assess and optimize acoustic receiver performance. [Work is sponsored by the Office of Naval Research Ocean Acoustics Program.]

Importance of microhabitat characteristics in the macrobenthos microdistribution of a large river reach

1. The importance of microhabitat characteristics for macroinvertebrate microdistribution was studied within a reach of the main channel of the Upper Rhone River (France). 9 locations (3 on the left hand side, 3 across the middle, and 3 on the right hand side) were sampled twice on two dates (as duplicates in June and July 1982). From 19 variables, including substratum and hydraulic parameters, 14 were selected to describe the physical habitat of each location. 47 macroinvertebrate species were collected by means of dredging with a modified Rallier du Baty dredge. The habitat-fauna co-structure was studied using co-inertia analysis. 2. The river reach was transversally asymmetrical : shallow on one side (up to 2.80 m) with coarse sediments rich in periphyton, and much deeper on the other side (up to 4.80 m) with a gravel bottom rich in organic particles. In the middle of the channel these conditions were intermediate, but the current was stronger. Velocity and the other hydraulic parameters varied independently of the substratum characteristics. This independence is a consequence of old man-made impoundments (inherited structures) and perhaps of present paving of the substratum also. 3. The macroinvertebrate fauna was closely linked to this transverse asymmetry of the reach, with the highest richness and abundance to the shallow side of the channel and the lowest species richness in the rapid central part. The most significant faunistic differences were linked i) to water depth, acting on both hydraulic parameters and periphyton (by light transmission), ii) to the inherited old bottom substratum, and iii) to a lesser extent, to the present current velocity.

ORIENTATION OF CARBONATE LAMINATIONS IN GRAVELLY SOILS ALONG A WINTER/SUMMER PRECIPITATION GRADIENT IN BAJA CALIFORNIA, MEXICO

We observed, along a north-to-south transect in central Baja California, that the positioning(top vs. bottom) of pedogenic carbonate on gravel in Holocene soils was related to the proportion of winter versus summer/early fall precipitation. Carbonate coatings were found on gravel bottoms at sites where precipitation occurs predominantly in winter but on gravel tops at sites where summer/fall precipitation is dominant. The positioning of carbonate coatings co-varied with other ecosystem properties such as floral distribution, oxygen isotope composition of carbonate, and depth to the top of the Bk horizon in response to precipitation patterns. The processes responsible for the orientation of carbonate on gravels are unknown. We proposed that the nature of soil thermal gradients during major precipitation events or periods may influence carbonate solubility and, therefore, the loci of deposition. While the deposition of carbonate on gravel tops is apparently unique and restricted to areas of summer/fall precipitation in Baja California, the positioning of carbonate coatings in gravelly soils in this region may also provide some insight into long-term climate patterns in the perarid regions of the Sonoran Desert.

High-frequency reverberation in shallow water

Monostatic reverberation measurements were collected in shallow water, over a coarse gravel and cobble bottom, 100 m deep, off the coast of Nova Scotia. Data were collected at frequencies of 21, 28, and 36 kHz using linear FM pulses of 2-kHz bandwidth and 0.160-s duration. An anchored, high-frequency active sonar array deployed at a depth of 42 m was used to collect the data. The reverberation measurements were compared with estimates computed with the NUWC generic sonar model (GSM). The data were reasonably well modeled for times greater than 0.2 s after pulse transmission by neglecting surface reverberation and using Lambert's rule for bottom backscattering with a scattering coefficient of -27 dB, independent of frequency. At all three frequencies, the data and model show a peak approximately 0.9 s after pulse transmission. This peak results from a focusing effect that the downward-refracting sound-speed profile has on the interaction of the rays with the bottom.

Foraging Rates of a Vertebrate and an Invertebrate Predator in Stream Enclosures

We compared prey consumption by brown trout (Salmo trutta) and leeches (Erpobdella octoculata) when they occurred together and alone in stream enclosures. One density of trout was compared with three densities of leeches during 24-h-long experiments. Separate experiments were conducted with two prey taxa, Gammarus pulex and Baetis rhodani, using two types of substrate, fine gravel and fine gravel plus cobbles. We found that trout had a higher foraging rate over fine gravel bottoms than over cobble bottoms, whereas leeches were more effective over cobble bottoms. Prey type also affected foraging rates, with trout consuming more Baetis than Gammarus, and leeches consuming more Gammarus than Baetis. A direct comparison of foraging rates of trout and leeches when alone showed that trout consumed more prey than the highest density of leeches, except when Gammarus occurred over cobble bottoms; then trout consumed prey at the same rate as the lowest leech density. When leeches and trout were together, trout foraging was unaffected by leeches, but leech foraging was affected by trout when feeding on Baetis but not Gammarus. These results show that one leech consumes much less than one trout, but at representative densities, leeches can have similar impacts on prey per area of stream, suggesting that the role of invertebrates in structuring benthic communities can be similar to that of fish.

創出した水域における空間と生物群集の対応関係の把握 国営みちのく杜の湖畔公園分流池を事例として

The authors tried to clarify the relationships between space units and biotic communities of man made off-stream ponds by a case study. An experimental pond excavated in the reed wetland located in Mitinoku Lakewood National Government Park, Miyagi Prefecture, north-east part of Japan. The construction work completed in March of 1996. Both aboitic and biotic condition data were collected from July 1996 toFebruary 1997. Consequently, four different types of space units were identified as followings.(1) type 1; shallow, high speed stream, gravel bottom(2) type 2; shallow, low speed strem, sand botto(3) type 3; shallow, extremly low speed stream, mud bottom(4) type 4; deep, extreamly low speed stream, mud bottom.These four types of space units were identified mainly by stream velocity and depth of water. And each types had their own species composition of benthic fauna classified by life forms. Identification andmapping of physio-bio (phyisiological and biological) space units are useful for management or recreation of ponds and streams for benthic fauna.

Dynamics of ships running aground

A comprehensive dynamic model is presented for analysis of the transient loads and responses of the hull girder of ships running aground on relatively plane sand, gravel, or rock sea bottoms. Depending on the seabed soil characteristics and the geometry of the ship bow, the bow will plow into the seabed to some extent. The soil forces are determined by a mathematical model based on a theory for frictional soils in rupture and dynamic equilibrium of the fluid phase in the saturated soil. The hydrodynamic pressure forces acting on the decelerated ship hull are determined by taking into account the effect of shallow water. Hydrodynamic memory effects on the transient hull motions are modeled by application of an impulse response technique. The ship hull is modeled as an elastic beam to determine the structural response in the form of flexural and longitudinal stress waves caused by the transient ground reaction and hydrodynamic forces. A number of numerical analysis results are presented for a VLCC running aground. The results include bow trajectory in the seabed, time variation of the grounding force, and the maximum values of the sectional shear forces and bending moments in the hull girder.

La biologie du suceur cuivré (Moxostoma hubbsi) comparée à celle de quatre autres espèces de Moxostoma (M. anisurum, M. carinatum, M. macrolepidotum et M. valenciennesi)

The copper redhorse, Moxostoma hubbsi (Legendre), which was discovered in 1942, is a threatened and endemic fish species of the lowlands around Montréal (Quebec). A survey of historical data, an investigation of the preserved specimens, and a comparison of selected biological characteristics of the five Quebec Moxostoma species living in sympatry in the Richelieu River show that this redhorse has a unique combination of life history characteristics. Compared with the other redhorses, it is among the most long-lived (more than 20 years), has the highest growth rate and fecundity, and is the latest spawner, its reproduction probably taking place at the end of June or at the beginning of July. The copper redhorse shows a high degree of specialization in the use of alimentary resources and feeds almost exclusively upon molluscs. The comparison of the stomach contents of the different species living in sympatry shows little diet overlap. This may be due to the specialization of their pharyngeal apparatus and to a certain degree of spatial segregation. Similar to its congeners, the copper redhorse shows a predilection for lowland rivers of medium size characterized by abrupt banks and uniformly deep channels (4–7 m) flowing over a solid clay, sand, or gravel bottom. The most populated sections of river have rather slow currents; they are interspersed by sections of rapids suitable for spawning. In the St. Lawrence system, the range of the copper redhorse is much more restricted than that of other redhorses, and this species appears much more vulnerable to habitat degradation.

Aggregation and spawning by lampreys (genus Ichthyomyzon) beneath cover

Lampreys are generally reported to spawn in shallow water on open, gravel bottoms. During surveys in Wisconsin and Minnesota, we regularly observed aggregations of adult Ichthyomyzon c.f. gagei, I. castaneus, and I. fossor beneath such cover objects as boulders, woody debris, and, at one site, vegetation. In some cases, observations of eggs or rapid quivering by individual lampreys indicated that spawning was occurring. The literature includes scattered anecdotal reports of similar behavior in other populations of Ichthyomyzon. Our data for I. c.f. gagei suggest that aggregations beneath cover objects occur at a greater range of depths than those in the open, but that aggregations in the open can contain greater numbers of individuals. Facultative spawning beneath cover objects may permit lampreys to spawn in deep waters with swift current where spawning could not otherwise occur. Moreover, this behavior may reduce the vulnerability of spawning lampreys to some types of predators.

Habitat Use of Two Darter Species in Glover River, Oklahoma

Channel darters have generally been reported to inhabit areas of moderate current over bedrock substrate (Cross, 1967), gravelly sections of slow-flowing streams (Miller, 1973; Miller and Robison, 1973), and deeper water in larger streams (Blair, 1959). Logperch have been reported to prefer clear streams with gravel and rocky bottoms and to be found in deep water in or at the base of riffles near pools (Lachner et al., 1950; Thomas, 1970). Generally these species occupy permanently flowing streams. They are, however, resident in Glover River which in the summer is often reduced to isolated pools kept fresh by subsurface flow (Orth and Maughan, 1982). It was hypothesized that habitat use in this stream might differ from use in more typical habitats occupied by this species. Darters were collected by electroshocking quarterly from 1978 to 1980 at 14 sites of known area (Jones et al., 1984) along the Glover River. Measurements were made on depth, velocity and substrate at each individual capture location and on habitat measurements along several transects at each site once each quarter, using techniques outlined by Orth and Maughan (1982). Frequencies were divided in each interval of water depth, water velocity, and substrate type by available area within each respective interval to obtain an estimate of relative density. Logperch were captured most frequently in pools, although they were occasionally taken in deeper riffles and runs in spring. Captures were made

Aspects of the Life History of the Stippled Darter Etheostoma punctulatum

Aspects of the life history of the stippled darter Etheostoma punctulatum were studied in the Spring River in SW Missouri. Females attained a maximum standard length of 85 mm and males 83 mm. Both sexes lived slightly more than 4 years. Sparvning began in early February and continued through late May. Males were mature at 1 year of age while only those yearling females at least 49 mm long produced mature ova. Females contained an average of 447 ova2-0.55 mm in diam in two distinct size modes and a group of smaller developing ova. The presence of these distinct size groups of ova throughout the spawning period indicates that two or more clutches of eggs were produced by each mature female. The fertilized eggs were 1.6 mm in diam and hatched in 11 days at 16 C. The diet was made up primarily of crustaceans and aquatic insect larvae. INTRODUCTION The stippled darter Etheostoma punctulatum is a robust darter and the largest in the subgenus Ozarka, reaching 88 mm SL (Kuehne and Barbour, 1983). This darter is distributed throughout the Ozarks where it is most often found in small creeks and spring branches having clear water with permanent flow and silt-free bottoms. Pflieger (1975) indicates it may be found in quiet pools and backwaters where it hides around large rocks or in beds of organic debris. Although not uncommon within its known range of distribution, there are very few populations large enough to permit taking the numbers necessary for life history analysis. Fishes restricted to small headwater streams are frequently subjected to wide fluctuations in environmental conditions. This study was begun with samples being taken in two streams but was terminated in Weaubleau Creek in Hickory Co., Missouri, when dry weather reduced the stream to a few isolated pools and destroyed the darter population. The danger faced by darter populations in headwater locations is also increased by human activity. The second stream location is immediately downstream from a troutrearing facility through which nearly all water in the stream passes. Cleaning of the trout pools in February 1983 produced silt which covered the gravel bottom of the sampling area to a depth of 0.5 m in many places. This site is also 2-km upstream from a well-publicized source of dioxin contamination in the watershed and fishes in the area are known to be concentrating this substance. Activities affecting this stream section may eliminate the desirable habitat which sustains populations of Etheostoma cragini, E. microperca and E. punctulatum among others. Important contributions on life history and ecology of other members of the subgenus Ozarka have been made, but a basic study of the stippled darter has been lacking. Life history features of the threatened paleback darter Etheostoma pallididorsum were determined from preserved museum specimens by Hambrick and Robison (1979). Taber et al. (1986) discussed several aspects of the life history of E. cragini; Boschung (1979) commented on the life history and distribution of E. boschungi, and Etnier (1970) made significant contributions to the known distribution of E. trisella. More recently Ryon (1986) studied the life history and ecology of E. trisella. Information gained by studying the stippled darter is important to the information base which could be used in conservation of this and other less abundant species of its subgenus.