The reproductive biology of Pellonula afzeliusi Johnels,and Sierrathrissa leonensis thys Audenaerde in Lake Kainji,Nigeria

Aspects of the reproductive biology of the two species of clupeids known to occur in Lake Kainji, Pellonula afzeliusi Johnels and Sierrathrissa leonensis Thys Van Den Audenaerde were studied for a period of twenty eight months. Mature individuals were found in both species all the year round but with a prolonged peak of activity from December to May, more distinct in P. afzeliusi than in S. leonensis.There were no significant length differences between mature males and females in both species. The smallest mature individuals were 28 mm standard length female; 27 mm standard length male in P. afzeliusi, while the corresponding figures for S. leonensis were 18 mm standard length female and 19 mm standard length male.No sexual dimorphism was observed. There was a simple correlation between fecundity and fish standard body length as well as weight in both species.     

Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasuní National Park, Ecuadorian Amazonia1

We documented the floristic composition of pteridophytes (ferns and fern allies) and Melastomataceae in Yasuní National Park, Amazonian Ecuador. Our main questions were: (1) Are the density of individuals, species richness, and/or species diversity (measured with Shannon's H′) of the two plant groups related to edaphic differences? and (2) How many of the pteridophyte and Melastomataceae species are non–randomly distributed in relation to a soil base content gradient within terra firme (non–inundated forest). To answer these questions, we sampled 27 line transects of 500 × 5 m distributed in an area of ca 20 × 25 km. The study area included a permanent 50 ha plot established to monitor forest dynamics; thus, our results also provide information on landscape–scale floristic variability to which results from within the plot can be compared. A total of 45,608 individuals and 140 species of pteridophytes, and 4893 individuals and 89 species of the Melastomataceae, were counted in the transects. Both with pteridophytes and with Melastomataceae, a clear negative correlation was found between the amount of extractable bases in the soil and the number of plant individuals encountered in a transect. With Melastomataceae, species richness and species diversity also were negatively correlated with soil base content, but with pteridophytes they were not. More than 50 percent of the common species of both pteridophytes and Melastomataceae were nonrandomly distributed along the soil cation content gradient within terra firme. We conclude that while the species richness patterns observed in one plant group are not indicative of similar patterns in other plant groups, it seems likely that a substantial (but unknown) proportion of species belonging to other plant groups will be found to show distribution patterns that reflect edaphic preferences within terra firme forests.     

Similarities,differences, and seasonal patterns in the diets ofEulemur rubriventer andEulemur fulvus rufus in the Ranomafana National Park,Madagascar

I studied the diets of two sympatric species ofEulemur (E. fulvus rufus andE. rubriventer) in the Ranomafana National Part in southeastern Madagascar from July 1988 through August 1989. Both species were highly frugivorous throughout the year and devoted similar amounts of time to feeding daily; the composition of their diets were similar. Three aspects of both lemur species' diets were correlated with seasonal food availability: changes in interspecific dietary overlap, the length of feeding bouts, and the amount of time devoted to feeding daily. Throughout the year neither species had a more diverse or more folivorous diet than its sympatric congener. However, there were several consistent year-round differences between their diets.E. f. rufus initiated more feeding bouts daily that were shorter in duration than those ofE. rubriventer. E. f. rufus also consistently exploited more unripe fruits and mature leaves thanE. rubriventer did throughout the study.E. f. rufus migrated from the study site during a period of fruit scarcity. These dietary patterns are discussed here in regard to feeding patterns observed in other sympatric congeneric primate species, whether these dietary differences can contribute to these two species' ability to coexist, and how differences in diet may be influenced by differences in social structure. I suggest that subtle, consistent differences in diet and seasonal dietary differences are sufficient to allow these two species to coexist.     

Froghood: Postmetamorphic development of the rock river frog Thoropa miliaris (Spix, 1824) (Anura,Cycloramphidae)

Thoropa miliaris is a frog species endemic to the Brazilian Atlantic Rainforest, inhabiting wet rocky habitats. Males of this species present nuptial excrescences, which are keratinized spines on the surface of some fingers and internal metacarpal tubercles. Although these spines are usually associated with male adulthood, no details of their development are available. To investigate the sequence of spines' appearance, we correlated the number of spines with size and age, which was estimated by skeletochronology. We studied individuals collected from Rio de Janeiro, Brazil. There was significant correlation between size of individuals and number of spines and between age and number of spines in the callosities. The first spines appeared in metacarpal–phalangeal articulation of finger II, when specimens were 1 year old. The estimated growth curve did not show stabilization at any age. We considered the degree of development of the nuptial excrescences as a proxy for sexual maturity and so individuals may already be sexually active by 1 year of age. Estimated longevity of T. miliaris is similar to that estimated for other tropical species of frogs. Although growth in anuran species is considered to be undetermined, in T. miliaris, it seems to fit either undetermined or determined models.     

Evaluating Dispersal Limitation in Passive Bottomland Forest Restoration

Dispersal limitation can retard natural establishment of desirable species on restoration sites, especially where landscapes are fragmented, but dispersal limitation is assumed to become less critical with time as early colonists become reproductively mature. Distribution patterns of recruiting trees in a 20‐year‐old passively restored bottomland in northeast Louisiana suggested persistent dispersal limitation in some bottomland hardwood species and influence of dense shrub patches on colonization. To test these hypotheses, we measured seed rain as a function of distance to seed source and association with shrub cover. Seed rain of the wind‐dispersed Fraxinus pennsylvanica was highest near the forest edge, except where mature recruits occurred. Although shrub presence did not influence dispersal of F. pennsylvanica, its negative influence on probability of occurrence in the sapling layer suggests that shrub cover may limit its regeneration. The bird‐dispersed Crataegus viridis and Ilex decidua were found in the seed rain and as reproductive individuals within the field; neither had a positive relationship with shrub presence. Dispersal of heavy‐seeded Quercus spp. and Carya aquatica was limited to within 20 m of the forest edge. These results imply that dispersal limitation is diminishing in wind‐ and bird‐dispersed species with maturation of in‐field recruits and that shrub patches may influence these patterns. Heavy‐seeded species, however, remain restricted to field edges that directly abut a seed source. If canopy closure by wind‐ and bird‐dispersed species precedes dispersal of heavy‐seeded species into the field, establishment of Quercus and Carya spp. may remain low for the foreseeable future.     

Reproductive cycle of the oviparous lizard Sceloporus jalapae,from Zapotitlán Salinas,Puebla, Mexico

Reproductive patterns vary widely among species and populations of squamates. In general, patterns can be divided into cyclic and acyclic. Cyclic patterns are common in tropical and temperate species of seasonal environments, while acyclic ones are characteristic of tropical species that inhabit less variable environments. We studied the reproductive cycle of Sceloporus jalapae, one of the smallest species of Sceloporus, in an arid environment at Zapotitlán Salinas, Puebla, Mexico. Both sexes mature in the first year following hatching and exhibit a seasonal reproductive pattern with maximum activity in spring and summer that appears to be influenced by temperature. Unlike small species of Sceloporus that inhabit pine–oak and tropical forests, S. jalapae exhibits an extended period of reproductive activity that allows females to produce at least two clutches of 3–7 eggs each, and contrary to other species of Sceloporus, in this species there is no correlation between female length and clutch size. The reproductive pattern of S. jalapae is like that shown by other oviparous species of the genus; nevertheless, some life history traits of this species are shared with oviparous and viviparous species of small size.     

Coexistence of drosophilid flies: Aggregation, patch size diversity and parasitism

We carried out field experiments to investigate the coexistence of Drosophila species in domestic and forest areas on the basis of the aggregation model. Three cosmopolitan species Drosophila simulans Sturtevant, Drosophila melanogaster Meigen and Drosophila immigrans Sturtevant, and a native species, Drosophila auraria Peng, emerged abundantly from banana placed at the domestic station, while Drosophila immigrans and five native species, Drosophila lutescens Okada, Drosophila rufa Kikkawa and Peng, Drosophila bizonata Kikkawa and Peng, Drosophila sternopleuralis Okada and Kurokawa and Scaptodrosophila coracina (Kikkawa and Peng), were abundant at the forest station. The present analysis suggests that their coexistence was facilitated by the aggregation mechanism. In the cosmopolitan species, the density of individuals that emerged from patches increased with the increase of patch size, but the relationship between fly density and patch size was not clear in the native species. This difference in distribution patterns between the cosmopolitan and native species is likely to be due to the difference in the female visiting behavior. In the present analysis, however, it was not clear whether patch size diversity facilitated their coexistence or not. The effect of patch size diversity may have been masked, because the effect of aggregation was more prominent. The rate of parasitism by wasps was high in October at the domestic station, and in May and June at the forest station. The present result suggests that the rate of parasitism was density-dependent, at least at the domestic station, and therefore parasitism facilitates the coexistence of drosophilid species in domestic areas.     

Spawning season, ovarian development and fecundity of female Trichomycterus corduvense (Osteichthyes, Siluriformes)

We studied female reproductive biology of Trichomycterus corduvense. The study was carried out in the Anizacate River (Córdoba, Argentina). Samples were collected throughout one year on a monthly basis. Seven oocyte phases were identified. Five ovarian stages were described based on the macroscopic analysis of the oocyte phases. The spawning season for the species ranges from October to February; it was determined based on variations in GSI and the existence of mature females. The dynamics of oocyte development of T. corduvense, indicated the asynchronism of maturation. The correlation coefficient between fecundity and the individual weight was very low. Therefore, we suggest that this coefficient cannot be used to predict T. corduvense fecundity.     

Cropland edge,forest succession,and landscape affect shrubland bird nest predation

The effects of habitat edges on nest survival of shrubland birds, many of which have experienced significant declines in the eastern United States, have not been thoroughly studied. In 2007 and 2008, we collected data on nests of 5 shrubland passerine species in 12 early successional forest patches in North Carolina, USA. We used model selection methods to assess the effect of distance to cropland and mature forest edge on nest predation rates and additionally accounted for temporal trends, nest stage, vegetation structure, and landscape context. For nests of all species combined, nest predation decreased with increasing distance to cropland edge, by nearly 50% at 250 m from the cropland edge. Nest predation of all species combined also was higher in patches with taller saplings and less understory vegetation, especially in the second year of our study when trees were 4–6 m tall. Predation of field sparrow (Spizella pusilla) nests was lower in landscapes with higher agricultural landcover. Nest predation risk for shrubland birds appears to be greater near agricultural edges than mature forest edges, and natural forest succession may drive patterns of local extirpation of shrubland birds in early successional forest patches. Thus, we suggest that habitat patches managed for shrubland bird populations should be considerably large or wide (>250 m) when adjacent to crop fields and maintained in structurally diverse early seral stages. © 2011 The Wildlife Society.     

The effect of femel- and small scale clear-cutting on ground dwelling spider communities in a Norway spruce forest in Southern Germany

The early effects of femel-cutting (removing 20% of the trees) and small scale clear-cutting on ground-living spiders in a Norway spruce (Picea abies (L.) Karst.) forest in Southern Germany were investigated. The study was carried out as BACIP (before and after, control-impact, many paired samplings) study: Spiders were sampled during the pre-treatment year, the year of cutting, and the year after cutting. In total 7101 individuals were sampled, of which 4530 individuals were identified, 4468 were adult and 2633 individuals were juvenile. We identified 107 species, but a single species, Coelotes terrestris, dominated the control (spruce stand) comprising up to 49% of the total identified individuals. Clear-cutting changed the species composition in the traps, while the first step in femel-cutting preserved it. The number of individuals of the families Linyphiidae, Amaurobiidae, Agelenidae and Clubionidae decreased drastically within the 2 years after the clear-cutting, while the Lycosidae became numerically dominant in the clear-cut stands. The number of individuals with the following characterisation decreased significantly after clear-cutting: Small (<3.0 mm) and large spiders (>10.5 mm), web builders, ‘forest habitat species’, species favouring hygrophilic to medium moisture conditions, and preferences to live below ground or in and on the moss layer. On the other hand, middle-sized spiders, free hunters, ‘open habitat species’, spiders favouring dry conditions or that are euryoecious, preferring patterns covered by grasses or uncovered patches, increased in number. Clear-cut habitats with dense spruce regeneration showed a delayed and less pronounced response. With femel-cutting, species composition of ground-living spider communities may be preserved during the first step of regeneration of mature forest stands.     

Do steady state assemblages occur in shallow lentic environments from wetlands?

The Okavango Delta has an annual flood cycle that spreads slowly from the northwestern`panhandle' into a widening delta to the southeast. Rotifers were sampled from areas where the flood was active, and from other areas not yet reached by the flood. In still waters, the samples were dominated by euplanktonic rotifers, particularly of the genera Brachionus, Keratella and Hexarthra, with about 20 species per 1000 individuals at a station. Where the water was moving the samples were dominated by periphytic rotifers, with over 100 species per 1000 individuals at a single station. The periphytic species were dominated by the genus Lecane,with over 45 species, followed by Lepadellawith 24 species, and Trichocercawith 23 species. Comparison of the Okavango with six other tropical localities reveals fairly consistent ratios of the numbers of species in the periphytic genera Lecane, Lepadellaand Trichocerca,indicating that there may be assembly rules for communities of tropical periphytic rotifers.     

Caste differentiation and seasonal changes in Vespa velutina (Hym.: Vespidae) colonies in its introduced range

Since its introduction in France 10 years ago, the yellow‐legged hornet, Vespa velutina, has rapidly spread to neighbouring countries (Spain, Portugal, Belgium, Italy and Germany). It showed efficient social traits facilitating its invasive success. Only scarce and incomplete natural history studies were known from its native distribution area. Studying the biology of this species in its invasive distribution range was thus a prerequisite to the implementation of efficient control methods in a near future. During a 3‐year field survey, we collected 77 nests to investigate several of the species' key colony characteristics. Our results enabled us to accurately quantify each of the castes and to better understand their synchronicity throughout the season. Our study showed that mature nests are able to produce up to 13 000 individuals and that the size of mature nests is correlated to the number of individuals produced. This correlation enables the inference of one characteristic from the other. Furthermore, each mature nest can produce up to several hundreds of potential founder queens, a crucial datum in the light of today's unregulated spring queen trapping control campaigns. In addition, nest dissections enabled to record the incidence of nest relocation for the first time in this species. Results are discussed with regards to what is known in other Vespidae species, with a focus on Vespula species that are known to be invasive in many other countries worldwide.     

Distinctive vegetation communities are associated with the long‐lived conifer Agathis australis (New Zealand kauri,Araucariaceae) in New Zealand rainforests

The conifer Agathis australis (New Zealand kauri; Araucariaceae) has a significant influence on soil processes beneath its canopies, reducing soil pH, stalling nitrogen cycling processes, and sometimes forming podzols. Distinctive plant species assemblages have been anecdotally observed to occur in association with A. australis stands; however, the authenticity of these proposed associations has not been formally assessed. Owing to the effects of A. australis on its soil environment and the recorded vegetation patterns, we hypothesized that this species may act as a foundation species, playing a significant role in structuring plant community composition in its vicinity. To test this, we investigated the influence of proximity to A. australis on plant community composition at stand and individual tree scales. We also investigated compositional variation with distance from the conifer Dacrydium cupressinum (rimu, Podocarpaceae) within the same forests to directly compare A. australis effects to those of another large conifer. We examined changes in stand composition relative to the abundance of each of these conifers at two forests, and measured changes in environmental conditions and plant composition with increasing distance from mature individuals at one of the same and one other study site. The organic soil formed beneath A. australis individuals was highly acidic, with high levels of NH₄‐N, carbon and total nitrogen, but low levels of NO₃‐N. We recorded a difference in species composition in the vicinity of A. australis compared to forest without this species in the same environment, describing three groups of species: stress‐tolerant species dependent on the presence of A. australis within mature forest; those dependent on areas with A. australis absent; and those with distributions unaffected by A. australis presence. Such effects on the abiotic and biotic environments were not recorded in the vicinity of individuals of D. cupressinum. These results highlight the substantial effect that A. australis has in enhancing landscape‐scale habitat heterogeneity and influencing overall forest diversity.     

Reproduction in the Mediterranean endemic gorgonian Spinimuricea klavereni (Anthozoa,Octocorallia, Plexauridae)

Spinimuricea klavereni is a Mediterranean endemic gorgonian that is rarely encountered, probably because it typically occurs at depths below 50 m. It is exceptionally common in the northern Marmara Sea, with an unusually shallow upper depth limit of ~20 m. The reproductive biology of this species was studied during a one year period off Büyükada, in the northeastern Marmara Sea. Spinimuricea klavereni is a gonochoric broadcast spawner with an almost even sex ratio. Colonies were ~15 cm in height at first reproduction. Gametogenesis was continuous, characterized by high male and female fecundities year‐round. Oocytes and sperm sacs of all developmental stages were found throughout the year, with small‐sized oocytes and sperm sacs dominant throughout the year. The reproduction of S. klavereni did not seem to exhibit any marked seasonal pattern, unlike most other studied Mediterranean octocorals. Modest variation in gamete output was probably related to slight alterations in food availability and temperature. The non‐seasonal reproductive pattern we observed may be related to the low intra‐annual variation in temperature in the Marmara Sea, and the fact that the mesotrophic‐eutrophic level of productivity in the Marmara Sea can support the energetic requirements of continuous gametogenesis in this gorgonian. Whether these patterns are local adaptations or intrinsic characteristics for this Mediterranean endemic species remains to be studied.     

Life history of the talitrid amphipod Macarorchestia remyi (Schellenberg, 1950) on a Tyrrhenian sandy beach, Italy

In this study, we analysed the life cycle and some aspects of the reproductive biology of the talitrid amphipod Macarorchestia remyi (Schellenberg, 1950) on a sandy beach in central Italy (Tyrrhenian Sea). The species is strongly associated with rotting wood carried by the sea. The animals were sampled once a month by hand over 1 year (May 2006–April 2007) and a total of 3,484 individuals were collected. Results showed the occurrence of intersexes in addition to males and females (n = 268) and a sex ratio always in favour of females. Breeding peaked twice during the year and the number of eggs in the ventral brood chamber ranged from 3 to 19. Linear regression analysis showed a positive correlation between total length of ovigerous females and the number of eggs they carried. The mean length of both mature males and mature females was 6 mm, while the maximum length was 13 mm. The presence of two cohorts during the year was also identified. Our results suggest that, despite the ephemeral habitats where the species lives, the population is stable over time and its life cycle does not differ in relation to other talitrid species that live on beaches.     

Onion thrips colonization of onion fields bordering crop and non‐crop habitats in muck cropping systems

Onion thrips, Thrips tabaci Lindeman, colonization of onion fields may be influenced by bordering crop and non‐crop habitats. Identifying habitats adjacent to onion fields associated with high T. tabaci infestations would be valuable for improving scouting efforts and management decisions. A 3‐year study examined adult T. tabaci colonization patterns within onion fields early (June through early July) and late in the season (August) in three muck regions in New York (USA). We hypothesized that early‐season adult densities would be greater in onion fields bordering other crops (e.g. carrot, corn and potato) and non‐crops (e.g. woods) than those bordering other onion fields and that more adults would occur along onion field edges than field centres. Results indicated similar adult densities in onion fields regardless of bordering crop and non‐crop habitats in seven of nine muck region × year data sets; exceptions were more adults in onion fields bordering potato (Elba region only) and corn (Potter region only) than those bordering other onion fields. Adult densities decreased as distance into onion fields increased in only four of nine muck region × year data sets; in these cases only 38% more adults were found along field edges than field centres. Later in the season, we hypothesized that adult densities would be greater in non‐mature onion fields bordering mature onion fields, and densities would be greater along field edges than field centres. Results indicated that adult densities in non‐mature onion fields bordering mature onion fields were 54 times greater than those bordering other non‐mature onion fields, and four times more adults occurred along field edges than field centres; adult densities were similar along field edges and centres in non‐mature onion fields bordering other non‐mature onion fields. Implications for T. tabaci management in onion based on these colonization patterns are discussed.     

Population dynamics of Bythotrephes cederstroemii in south-east Lake Michigan 1995–1998

1. Population characteristics (density, size, reproductive patterns) of the predatory cladoceran Bythotrephes cederstroemii in south-east Lake Michigan were monitored at an offshore station (110 m) in 1995–98 and at a nearshore station (45 m) in 1997–98.
2. The mean density of B. cederstroemii at the offshore station was generally highest in July–September (145–914 m⁻²) and at the nearshore station in October–November (168–1625 m⁻²). In 1995 and 1998, density was also high at the offshore station in November (211–284 m⁻²). Fish predation may limit B. cederstroemii in nearshore regions in the summer. The maximum annual densities of B. cederstroemii for 1995–98 were generally similar to those reported from the late 1980s, when the species arrived in Lake Michigan.
3. Body size increased rapidly each year to a maximum in August. Thereafter, body size declined and converged for stage-2 and 3 individuals, suggesting food scarcity or size-selective fish predation was affecting large individuals.
4. Most reproduction occurred asexually (90%), and by stage 2 or 3 females (99%). Asexual brood size was highest when B. cederstroemii first appeared each year, and decreased in August, when larger neonates were produced. There appeared to be differences in reproductive mode for stage 2 and 3 females, with a higher percentage of stage 2 females reproducing sexually.     

Molecular Phylogeny and Species Identification of Pufferfish of the Genus Takifugu (Tetraodontiformes, Tetraodontidae)

The phylogenetic relationships and species identification of pufferfishes of the genus Takifugu were examined by use of randomly amplified polymorphic DNA (RAPD) and sequencing of the amplified partial mitochondrial 16S ribosomal RNA genes. Amplifications with 200 ten-base primers under predetermined optimal reaction conditions yielded 1962 reproducible amplified fragments ranging from 200 to 3000 bp. Genetic distances between 5 species of Takifugu and Lagocephalus spadiceus as the outgroup were calculated from the presence or absence of the amplified fragments. Approximately 572 bp of the 16S ribosomal RNA gene was amplified, using universal primers, and used to determine the genetic distance values. Topological phylogenic trees for the 5 species of Takifugu and outgroup were generated from neighbor-joining analysis based on the data set of RAPD analysis and sequences of mitochondrial 16S rDNA. The genetic distance between Takifugu rubripes and Takifugu pseudommus was almost the same as that between individuals within each species, but much smaller than that between T. rubripes, T. pseudommus, and the other species. The molecular data gathered from both analysis of mitochondria and nuclear DNA strongly indicated that T. rubripes and T. pseudommus should be regarded as the same species. A fragment of approximately 900 bp was amplified from the genome of all 26 T. pseudommus individuals examined and 4 individuals of intermediate varieties between T. rubripes and T. pseudommus. Of the 32 T. rubripes individuals, only 3 had the amplified fragment. These results suggest that this fragment may be useful in distinguishing between T. rubripes and T. pseudommus. Received September 29, 2000; accepted February 26, 2001.     

Differentiation and maintenance of topo-community patterns with reference to regeneration dynamics in mixed cool temperate forests in the Chichibu Mountains,central Japan

Topo-community structure and dynamics were studied in mixed cool temperate forests, using the regeneration dynamics, to clarify the maintenance mechanisms of community patterns along a microtopographic gradient. The 76 stands studied were classified into two groups (i.e. convex slope and concave slope stands). The soil surface was more eroded on the concave slope than on the convex slope, while water potential was not significantly different between topographies. On the convex slope, even-aged patches alternated between young phase patches dominated by shade intolerant species, such asAcer rufinerve andBetula grossa, and mature phase patches, withTsuga sieboldii andFagus crenata. A slower lateral growth rate ofTsuga canopy trees and the absence of suppressed saplings in the mature phase may prolong the gap phase, which provides a favorable situation to shade-intolerant species. On the concave slope, patch structure was less clear, and process of replacement of canopy species by previously suppressed individuals of the same species was seen in the mature phase, which was mainly composed ofF. crenata, Fagus japonica, Acer sieboldianum andStewartia pseudo-camellia. Gaps on the concave slope were formed frequently but were generally closed within 10 years by lateral growth of deciduous canopy trees and by upgrowth of suppressed trees, and thus some individuals underwent recurrent periods of suppression until they reached the canopy. We concluded that soil surface stability and gap encroachment pattern are critical to the maintenance of the community pattern along a microtopographic gradient.     

Habitat use and population characteristics of potentially spawning shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820), blue sucker (Cycleptus elongatus (Lesueur, 1817), and associated species in the lower Wisconsin River, USA

The goal of this study was to compare the possible locations, timing, and characteristics of potentially spawning shovelnose sturgeon (Scaphirhynchus platorynchus), blue sucker (Cycleptus elongatus), and associated species during the spring of 2007–2015 in the 149‐km‐long lower Wisconsin River, Wisconsin, USA, a large, shallow, sand‐dominated Mississippi River tributary. A 5‐km index station of two pairs of rocky shoals surrounded by sandy areas was electrofished for shovelnose sturgeon and blue sucker in a standardized fashion a total of 40 times from late March through mid‐June, the presumed spawning period. On one date in 2008 and two dates in 2012, all rocky shoals and adjacent sandy areas in the lowermost 149 km of the river were also electrofished for both species. Shovelnose sturgeon and blue sucker appeared to spawn in the limited rocky areas of the river along with at least four other species: mooneye (Hiodon tergisus), quillback (Carpiodes cyprinus), smallmouth buffalo (Ictiobus bubalus), and shorthead redhorse (Moxostoma macrolepidotum), usually at depths of 0.8–2.0 m and surface velocities of 0.4–1.0 m/s. However, apparently spawning shovelnose sturgeon were found only on mid‐channel cobble and coarse gravel shoals within a single 7‐km segment that included the 5‐km index station, whereas apparently spawning blue suckers were encountered on these same shoals but also more widely throughout the river on eroding bluff shorelines of bedrock and boulder and on artificial boulder wing dams and shoreline rip‐rap. Both species showed evidence of homing to the same mid‐channel shoal complexes across years. Blue sucker tended to concentrate on the shoals earlier in the spring than shovelnose sturgeon, usually from late April through mid‐May at water temperatures of 8.0–15.5°C along with quillback and shorthead redhorse. In comparison, shovelnose sturgeon usually concentrated on the shoals from mid‐May through early June at 13.5–21.8°C along with mooneye and smallmouth buffalo. Based on recaptures of tagged fish, at least some shovelnose sturgeon and blue sucker returned to the shoals at one‐year intervals, although there was evidence that female blue sucker may have been more likely to return at two‐year intervals. Most shovelnose sturgeon could not be reliably sexed based on external characteristics. Spawning shovelnose sturgeon ranged from 487 to 788 mm fork length, 500–2400 g weight, and 5–20 years of age, whereas spawning blue sucker ranged from 495 to 822 mm total length, 900–5100 g weight, and 5–34 years of age, although age estimates were uncertain. Females were significantly larger than males for both species although there was overlap. Growth in length was negligible for tagged and recaptured presumably spawning shovelnose sturgeon and low (3.5 mm/y) for blue sucker, suggesting that nearly all growth may have occurred prior to maturity and that fish may have matured at a wide range of sizes.