Fish species composition before and after construction of a main stem reservoir on the White River,Colorado

Synopsis The completion in the fall of 1984 of Taylor Draw Dam on the White River, Colorado, formed Kenney Reservoir — thus impounding the last significant free-flowing tributary in the Upper Colorado River Basin. Fishes were sampled above and below the dam axis prior to closure of the dam and in the reservoir and river downstream following impoundment. While immediate effects of the dam to the ichthyofauna included blockage of upstream migration to 80 km of documented range for endangered Colorado squawfish, the reservoir also proved to have profound delayed effects on the river's species composition. Pre-impoundment investigations in 1983–1984 showed strong domination by native species above, within, and below the reservoir basin. By 1989–1990, non-native species comprised roughly 90% of the fishes collected in the reservoir and 80% of the fishes collected in the river below the dam. Initially, fathead minnow, whose numbers quickly increased in the new reservoir, dominated all post-impoundment collections, but red shiner became the most abundant fish collected in the river below the dam by 1989–1990. While agency stocking programs for the reservoir sought to emphasize a sport fishery for salmonids, primarily rainbow trout, local enthusiasm for warmwater sport fishes resulted in illicit transfers of these species from nearby impoundments. Several species, formerly rare or unreported in the White River in Colorado, including white sucker, northern pike, green sunfish, bluegill, largemouth bass and black crappie, were present in the river following impoundment. Our investigation indicates smaller-scale, main-stem impoundments that do not radically alter hydrologic or thermal regimes can still have a profound influence on native ichthyofauna by facilitating establishment and proliferation of nonnative species.Cooperators are the U.S. Fish and Wildlife, the Colorado Division of Wildlife, and Colorado State University     

INFLUENCE OF FRESHWATER FLOW REGIME ON FISH ASSEMBLAGES IN THE GREAT FISH RIVER AND ESTUARY

Summary

Two and a half years of data were collected from the lower Great Fish River, head region and estuary to determine the fish species composition within these areas. Gilchristella aestuaria, Liza dumerilii, Rhabdosargus holubi and Pomadasys commersonnii were the four most abundant species captured, with riverine flow rate having an important effect on both species composition and numbers of fishes in the different regions. Most marine species displayed a strong inverse relationship between catch per unit effort and elevated freshwater inputs. Euryhaline marine species dominated the catches at all sampling sites during low flows but were less common during high flow periods when catadromous species were most abundant. Based on the available evidence it is suggested that for most marine species in the river this decline in abundance is related to low conductivity levels following floods rather than avoidance of elevated flows. The impact of elevated suspensoid concentrations and lowered dissolved oxygen concentrations on freshwater and estuarine fish populations during major river flooding is also discussed.     

Fish communities’ response to implementation of restoring measures in a highly artificialized estuary

Over the years, the Mondego estuary has undergone various anthropogenic impacts. One of the most serious was the closing of the communication between the two arms of the system (north and south), in the 1990s, which promoted eutrophication and a consequent water quality decline in the south arm. Several mitigation measures were subsequently implemented, in particular the re-establishing of the communication between the two arms in 2006, increasing water flow and reducing water residence time in the south arm. The present study aimed to evaluate the impact of management measures on the ecological and conservation condition of the Mondego estuary, through a longitudinal assessment of the structure and composition of the fish communities over a decade. The Mondego fish community showed important modifications over the years, in terms of structure, ecological quality and conservation value. The fish community status improved following the reconnection of both arms. In the south arm those changes appear to be more evident than in the other estuarine areas, where an inverse pattern was observed in the last few years. A redistribution of the fish species within the system may have been responsible for those unexpected alterations in the north arm and upstream area.     

Biodiversity in the Black Sea: effects of climate and anthropogenic factors

The Black Sea ecosystem and diversity underwent dramatic adverse changes during the 1960s and, especially, 1970s and 1980s of the last century. Anthropogenically-induced eutrophication increased through greater biogenic flow, dumping and pollutant discharge, in turn causing red tides, fish kills and oxygen depletion over the northwestern shelf. Anthropogenic pressures, associated with the economic situation of the Black Sea countries, has decreased during the last decade, allowing some improvement in the state and biodiversity of the ecosystem. The abundances of several native species have increased. However, mediterranization—the invasion by species from the adjacent basin and beyond—has continued. The conclusion is grounded, that biodiversity is not only inter- and intra-species diversity but also spatial–temporal variability, abundance and productivity dynamics, differences of the metabolic strategies providing sustainable existence in the changing environment. Biodiversity at the intra-species level expresses itself in spatial and temporal variations of the Black Sea biota. It has been shown, that рreservation of the Black Sea ecosystem’s biodiversity must be based on the measures which should be undertaken in national and social spheres, and be directed to the recreation, stabilization and conservation of this unique sea basin. Measures must be implemented nationally to conserve, stabilize or recreate the ecosystem biodiversity of this unique sea basin.     

A fish-based biotic integrity index for assessment of lowland streams in southeastern Brazil

This study was carried out to develop and apply a fish-based biotic integrity index to assess lowland streams in a highly deforested region of the Upper Paraná River basin. Fifty-six first-order segments were randomly selected for environmental and fish evaluation. Because previous analysis had identified the main type of effect on the streams of the region as physical habitat degradation, 22 qualitatively biological attributes were selected and tested over a physical condition gradient between reference and degraded sites. Sensitivity and redundancy of each attribute revealed that five metrics were adequate for discriminating higher quality from degraded sites. Of the fifty-six streams assessed, one (2%) was classified as good, four (7%) as fair, ten (18%) as poor, and forty-one (73%) as very poor, indicating that, on a regional scale, many aspects of biological integrity are altered, indicative of serious degradation. Considering that first-order segments amount to 11,000 km in total, it is noticeable that 10,000 km of the stream segments have no more than half of the expected conditions, indicative of poor or very poor biotic integrity conditions. Possible strategies of mitigating this scenario are discussed. Handling editor: S. M. Thomaz     

Fish species richness and stream order in Washington State streams

Synopsis We sampled fish at pairs of sites of the same stream order on opposite sides of drainage divides in the Cascade Mountains and in the southwest portion of Washington state. Elevation, gradient, drainage area, and stream order were significantly correlated with number of fish species collected at a site. Elevation accounted for the greatest portion of the variation in number of species and stream order for the least, but in low gradient, low elevation streams, stream order was significantly related to number of species. Species richness was greatest in low elevation, low gradient, high order streams. Species richness of a site reflected species richness of the drainage: in paired comparisons, sites in a drainage with a richer ichthyofauna had more fish species than sites in a drainage with fewer species. Addition of species with increasing stream order occurred in most streams, but replacement was more frequent than in other studies relating fish to stream order. The apparently higher frequency of replacement in this study appeared to be a result of headwater introductions of brook charr, Salvelinus fontinalis, and a tendency for cutthroat trout, Salmo clarki, to occupy headwaters when in freshwater.     

Annotated checklist of marine fishes from the Sanctuary of Bahía Chamela,Mexico with occurrence and biogeographic data

An annotated checklist of marine fishes of the Sanctuary of Islands and Islets of Bahía Chamela in the central Mexican Pacific is presented. Records of fish species were obtained by different methods including visual census, sampling with anesthetics, fisherman-nets, and trawling with a biological dredge. Additional records were obtained from natural history collections and publications. The list comprises 196 species in 64 families and 141 genera. The Carangidae is the most speciose family with 11 species, followed by the Labridae with 10 and the Pomacentridae with nine. Fourteen species are endemic in Mexican Pacific waters, but none is restricted to Bahía Chamela. The most dominant species recorded during underwater surveys were Epinephelus labriformis, Stegastes flavilatus, and Halichoeres dispilus. Most species are of tropical affinities distributed throughout the tropical eastern Pacific (123), eastern Pacific (23), and Mexican Pacific (14). Other species are known from the eastern and Indo-Pacific regions (18), eastern Pacific and western Atlantic oceans (2), and some are circumtropical (9). A new record of the Gulf Brotula Ogilbia ventralis is provided for the Bahía Chamela and its geographical distribution is extended to Mexican central Pacific.     

珠江的鱼类区系及其动物地理区划的讨论

本文根据珠江水系实地调查的结果,对珠江淡水鱼类区系的组成、形成原因及其在动物地理区划中的位置进行了讨论,否定了前人将南岭山脉作为东洋区和古北区在东亚的分界线的观点,认为这两个大区的界线应向北推移到秦岭山脉,并且指出珠江水系的鱼类区系元大部分隶属于东洋区的南东亚亚区,而其西江上源的一小部分应划归南亚亚区。     

The fishes associated with three intertidal salt marsh creeks in a temperate southern African estuary

This study compares the fish assemblages in a range of intertidal salt marsh creeks in the Kariega Estuary, South Africa, as well as highlighting any differences between the ichthyofaunal structure of the creeks and adjacent Zostera bed habitats. The superimposition of environmental variables on the creek biotic groupings (60% similarity level) indicated consistent relationships between both the creek water depth and mouth area with the major creek fish clusters. Water temperature, salinity and turbidity did not display any pattern which could explain the disparity between the ichthyofaunal groupings. The results also indicated that intertidal creeks form a unique littoral habitat within the Kariega Estuary, with ichthyofaunal compositions very different to those found in nearby eelgrass beds. Furthermore, intertidal creeks in the Kariega system appear to be similar to creeks found elsewhere in the world in that their fish assemblages are dominated by 0+ juveniles, have a conspicuous marine transient and estuarine resident component, and very few piscivorous representatives. These results also give weight to the hypothesis that southern African salt marsh creek habitats serve as temporary refuges to juvenile fishes, a role that has also been proposed in other parts of the world.     

Impact of hurricane Firinga on fish community structure on fringing reefs of Reunion Island,S.W. Indian Ocean

Synopsis The reef flats of Saint-Pierre and Saint-Leu (Reunion Island, Indian Ocean) suffered badly from hurricane Firinga on 29 January 1989. The high degree of silting due to increased run-off killed the coral colonies. Fish communities were surveyed at four periods following the hurricane (March and September 1989, March and September 1990). An increase in both species richness (31 to 47 spp. per census) and abundance (169 to 265 individuals per census) of fishes was observed with time, along with changes in their trophic structure. This positive succession may be linked to the disappearance of the silt layer from reef flats since September 1989. Nevertheless, there were differences in fluctuations and trophic structure of the fish community between back-, inner- and outer-reef flats. Finally, differences in recovery between the two reefs are related to the overall environmental degradation of the Island, chiefly by human perturbation, prior to the hurricane.