Stephen T. Ross

Diversity, Distribution, and Conservation Status of the Native Freshwater Fishes of the Southern United States

Abstract The Southeastern Fishes Council Technical Advisory Committee reviewed the diversity, distribution, and status of all native freshwater and diadromous fishes across 51 major drainage units of the southern United States. The southern United States supports more native fishes than any area of comparable size on the North American continent north of Mexico, but also has a high proportion of its fishes in need of conservation action. The review included 662 native freshwater and diadromous fishes and 24 marine fishes that are significant components of freshwater ecosystems. Of this total, 560 described, freshwater fish species are documented, and 49 undescribed species are included provisionally pending formal description. Described subspecies (86) are recognized within 43 species, 6 fishes have undescribed subspecies, and 9 others are recognized as complexes of undescribed taxa. Extinct, endangered, threatened, or vulnerable status is recognized for 28% (187 taxa) of southern freshwater and diadromou...

Mechanisms structuring stream fish assemblages : are there lessons from introduced species?

SynopsisStream fish faunas are being increasingly subjected to non-native fishes. Successful establishment of non-native forms varies widely between geographic regions (38–77%), but is generally greater in areas that are either altered by man or initially depauperate in fish species. While such introductions have generally had undesirable effects on native fish species, they show no signs of decreasing. Thus, this essay is an attempt to determine if the introduction of non-native fishes may provide insights into processes structuring stream fish assemblages. There are, unfortunately, few detailed ecological studies documenting the response of stream fish assemblages to introduced fishes. Of the 31 studies included in my analysis, the majority (77%) documents a decline in native fishes following the introduction of exotic or transplanted forms. Only 10 studies examined shifts in resource use, of which 5 documented or suggested shifts in habitat. Overall, the responses of native stream fish assemblages to non-native fishes suggest that biotic interactions are important in structuring the impacted assemblages, being implicated in 62% of the studies. Proposed or demonstrated mechanisms are divided equally between competition and predation. Unfortunately, pre-disturbance data are generally lacking so that processes important in structuring native fish assemblages cannot be determined.

The Response of Fishes to Periodic Spring Floods in a Southeastern Stream

Movement of fishes onto a fringing floodplain was studied by seining and trapping during five spring floods. We collected 26 species from the inundated floodplain; the known channel fauna is 42 species. Species numerically dominant on the floodplain were Fundulus olivaceus, F. notti, Gambusia affinis, Notropis welaka, N. texanus, N. roseipinnis, Lepomis macrochirus, L. cyanellus and L. marginatus. Catch-per-effort in traps was generally greatest on the upper floodplain during the day and greatest nearer the channel at night. Night activity of fishes on the floodplain was apparently low. Several species, which we term flood-quiescent forms, were common in the channel (e.g., Lepomis megalotis and Percina nigrofasciata) but did not exploit the floodplain. Activity (as catch per trap-hour) of P. nigrofasciata was negatively correlated with floodinduced turbidity. A flood-exploitative species, Notropis texanus, had higher population abundance during 3 high-flow years than in 3 low-flow years, suggesting that spring flooding may exert significant control over fish community structure. INTRODUCTION Periodic flooding is characteristic of most lotic systems. Based on channel morphology and gradient, floods may be erosive and thus potentially destructive to the stream habitat, or depositional, exhibiting creeping flow and being generally nondestructive to channel morphology (Welcomme, 1979). Most studies of the effects of flooding on aquatic organisms have treated erosive floods (e.g., Paloumpis, 1958; John, 1963, 1964; Greenfield et al., 1970; Seegrist and Gard, 1972; Hanson and Waters, 1974; Hoopes, 1975; Harrell, 1978), in which severe faunal disruption often occurs. Adaptations of organisms to erosive floods are either for surviving high flow rates through behavioral or morphological modifications, or for life history characteristics allowing rapid recolonization. Few studies have addressed the effects of nondestructive flooding on North American streams. Such floods occur in low gradient systems in which floods are primarily characterized by lateral expansion rather than increases in depth (Welcomme, 1979). While lateral expansion of rivers onto floodplains is best developed in tropical areas (Welcomme, 1979), many North American streams, especially in the southeastern United States, also show (or showed prior to levee construction and channelization) well-developed fringing floodplains (Viosca, 1927; Gunter, 1957; Bennett, 1958; Guillory, 1979). Such natural floodplains may be seasonally inundated. Forbes (1925) pointed out the importance of inundated floodplains as breeding grounds and foraging areas for fishes and aquatic invertebrates. Wickliff (1945) recorded movement of fishes onto an inundated floodplain. Starrett (1951) determined that certain minnows spawn in backwater areas and suggested that flooding was an important factor controlling minnow populations. Bennett (1958) believed that periodic flooding of the Mississippi and Illinois rivers was beneficial to largemouth bass populations. Guillory (1979) found that a number of Mississippi River species used inundated floodplains as

Dynamics of Littoral Fishes and Decapods Along a Coastal River-Estuarine Gradient

Abstract We examined community dynamics of nekton along a coastal river-estuarine gradient in Old Fort Bayou Mississippi, U.S.A. Distribution, abundance and similarity of nekton varied spatially and seasonally along the gradient in concert with varying physical-chemical conditions. The tidal freshwater (TFW) and oligohaline (OH) habitats had greater diversity and evenness than the mesohaline (MH) habitat, due to the interfacing of the dominant freshwater and the estuarine/marine faunas. Stepwise multiple regression indicated that water temperature was the most important predictor of species richness within TFW and MH when the entire species complement was considered. However, separation of freshwater and estuarine/marine species suggested that water temperature (positive relationship) and salinity (negative relationship) were the best predictors of freshwater species at TFW while the estuarine/marine species complement was best predicted by salinity and water temperature at TFW and MH. Models based on abundance data indicated that there was a significant negative relationship between salinity and turbidity and freshwater species abundance while a positive relationship was documented between estuarine/marine species abundance and salinity and turbidity. The dynamic nature of saline marsh nekton depends, in part, on the species complement, the salinity, and the rate of salinity fluctuation within various sections along the estuarine gradient. Although it is dogmatic that many estuarine habitats are physiologically ‘harsh’ due to fluctuating physical-chemical conditions, low-salinity nekton were found to tolerate greater fluctuations in salinity and pH than higher-salinity nekton. These habitats act as conduits between freshwater and estuarine habitats and serve a nursery function for estuarine-dependent fishes and decapods; they are thus functional components of the estuarine system.

Seasonal and diel variation in the standing crop of fishes and macroinvertebrates from a Gulf of Mexico surf zone

Abstract To determine the relative importance of surf zones as habitats for fishes and macroinvertebrates, compared to other inshore marine environments, seasonal and diel abundance patterns were studied for one year. Both study sites were located on the south shore of Horn Island, a barrier in the northern Gulf of Mexico. At each site a 300 m 2 area was sampled, using a 50-m seine set around steel poles. Capture efficiency of the seine, determined from escapement tests, averaged 82%. While 59 species were captured during the study, only six species, Harengula jaguana, Anchoa hepsetus, A. mitchilli, Callinectes sapidus, A. lyolepis and Menticirrhus littoralis , comprised 90% of the total catch by number. Summer macrofaunal standing crop (mean = 9·8 gm −2 , wet weight) was significantly greater than other seasons. The lowest values for both density and standing crop were those obtained in the winter. Both standing crop and average weight of the fishes increased significantly in night samples; a similar pattern did not occur for blue carbs. This primarily reflects the movement of larger, but generally rarer, fish species into the shallow surf zone after dark. Principal components analysis indicated that the standing crop of fishes was lowest during periods of reduced water volume and wave activity. However, seasonal factors appear, overall, to be more important in influencing fish abundance. Compared to a wide range of inshore marine habitats, surf zones appear intermediate in standing crop. Thus, at least during the summer, such habitats are important contributors to inshore standing crops of fishes.

Spatial and Temporal Resource Utilization by Southeastern Cyprinids

MIGITA, M., AND V. HASHIMOTO. 1949. On the digestion of higher carbohydrates by zsuanhi (Ctenopharyngodon idella). Bull. Jap. Soc. Scient. Fish. 15. NEUDECKER, S. 1977. Transplant experiments to test the effects of fish grazing on coral distribution. Proc. Third Int. Coral Reef Symp. 1:317-323. . 1979. Effects of grazing and browsing fishes on the zonation of corals in Guam. Ecology 60: 666-672.

Patterns of Resource Partitioning in Searobins (Pisces: Triglidae)

Eight species of searobins are common on the West Florida Shelf between Tampa and Fort Myers. All have the same mouth shape; the principal differences between species are relative mouth size and adult body size. Cluster analysis of searobins based on prey similarity indicated two principal species groups corresponding, in part, to inshore and offshore distribution patterns. Searobins showed two adult feeding modes based on prey size utilization. A scitulus mode was shown by Prionotus scitulus, Bellator militaris, P. martis and P. roseus, in which at least 70% of the adult diet was made up of prey 10 mm or smaller. A tribulus mode was shown by P. alatus, P. tribulus, P. ophryas and P. salmonicolor, in which prey larger than 10 mm made up 66% of the adult diet. Scitulus mode predators had significantly greater percent relative abundances than tribulus mode predators. The dominant method of resource partitioning was macrohabitat partitioning. At high levels of overlap there was evidence of partitioning by prey size.

Spawning and Associated Movement Patterns of Gulf Sturgeon in the Pascagoula River Drainage, Mississippi

Abstract Gulf sturgeon Acipenser oxyrinchus desotoi are federally listed as threatened, the principal reasons for population declines being habitat loss due to dams, overfishing, and water quality deterioration. The timing of freshwater migration and the locations and habitat features of spawning areas are undocumented for Gulf sturgeon in the Pascagoula River drainage. Our objectives were to identify and characterize spawning areas, determine spring movement patterns, and document homing fidelity by gill netting and radio-tracking. Through collection and rearing of Gulf sturgeon eggs, we verified that the Bouie River north of Hattiesburg, Mississippi (250 river kilometers upstream from the mouth of the Pascagoula River), is a spawning area. We also documented homing fidelity in the Bouie River using radiotelemetry and capture data. Prolonged residence and overwintering of Gulf sturgeon were observed near the Bouie River spawning area. This behavior may be caused by the modified nature of this portion of ...

Reproduction, Age, and Growth of the Bayou Darter Etheostoma-rubrum (Pisces,Percidae) - An Endemic of Bayou Pierre

-The life history of the bayou darter, a threatened darter endemic to Bayou Pierre, Mississippi, was studied over 18 mo during 1986-1987. Spawning, as determined by ovarian staging as well as a gonadosomatic index, occurred from April through August, with peak activity in May. Although some variation in the initiation and extent of spawning occurred between seasons, these differences were in part attributed to water temperatures. The simultaneous occurrence of females in the three reproductively active ovarian stages, and the presence of at least two distinct ova size classes, indicate that this species may spawn multiple clutches. The mean adjusted clutch size of 40 is among the lowest reported estimates for species of Nothonotus; however, assuming multiple clutch spawning, fecundity was estimated to be at least two times mean clutch size. Longevity was 3 yr, most older individuals being males, as determined from both scale analysis and length-frequency distributions. Approximately 60% of the average size of age 3 fish was achieved after the 1st growing season and 80% after the 2nd. Length-frequency analyses corroborated back-calculation results based on scale data.

Ecology and population structure of the bayou darter, Etheostoma rubrum: disjunct riffle habitats and downstream transport of larvae

The bayou darter, Etheostoma rubrum (Percidae), is endemic to the Bayou Pierre system in Mississippi. Adult and juvenile E. rubrum occupy swift, shallow riffles or runs over coarse gravel and pebble substrata. Habitat requirements of larval and post-larval stages, and the role of downstream dispersal of larvae in colonizing riffles are poorly known. The potential for movement and the high level of habitat specificity for the discontinuous riffle habitat suggest that E. rubrum may comprise a metapopulation of linearly arranged local populations. The greatest population densities of E. rubrum occur in the upper reaches of Bayou Pierre. We hypothesized that metapopulation structure of E. rubrum may include source–sink dynamics, whereby downstream areas are a sink for larvae/early juveniles originating upstream. We tested hypotheses that a transport mechanism, larval drift, occurred in E. rubrum, and that downstream riffles showed characteristics of population sinks. We captured larval stages of E. rubrum in cross-sectional and longitudinal drift nets, and rates of drift tended to increase during the day. Larval E. rubrum (n=19) occurred in samples above and below riffle areas, with no differences among longitudinal drift nets placed above and below riffles. Thus, larval drift is a viable transport mechanism. Relative abundance of adults and juveniles declined from upstream to downstream, and inter-riffle distances increased with cumulative downstream distance. However, both predictions of the source–sink hypothesis were not supported. The distribution of size classes did not change between upstream and downstream riffles nor did the mean size-adjusted body mass.