Response of the riverine fish community to the construction and operation of a diversion hydropower plant in central Chile

• 1. Chilean rivers have a large potential for hydropower development, and they also contain a unique native fish fauna with a high level of endemism. Several diversion hydropower plants have recently been constructed in Chile; however, the response of fish communities to these new hydropower plant designs is not well known.
• 2. Responses of native and non‐native fish to the construction and operation of a new hydropower plant that diverts water from two rivers were quantified. The Laja River is highly regulated and manipulated with three older (40 yr) dam‐based hydropower plants and irrigation diversions located upstream from the new facility. In contrast, the Rucúe River has no other hydropower facilities and is comparatively undisturbed.
• 3. Prior to construction, the Laja River had a fish community with lower species richness compared with the Rucúe River. The fish community structure in the Laja River was dramatically altered after the new hydropower facility began operation. On the other hand, in the Rucúe River, even though abundance of fish declined, there was less of a change in the total fish community structure. The fish community in the Rucúe River exhibited greater resistance to change compared with the Laja River.
• 4. The species most affected were the introduced salmonids and an endangered native species Percilia irwini.
• 5. Although diversion hydropower designs may have less impact than traditional dam‐based hydropower facilities, results of this study indicate that diversion hydropower structures can cause large changes in the fish community.

Copyright © 2006 John Wiley & Sons, Ltd.     

Coupling stable isotope studies with food web manipulations to predict the effects of exotic fish: lessons from Cuatro Ciénegas,Mexico

• 1. Exotic species threaten native species worldwide, but their impacts are difficult to predict.
• 2. Stable isotope analysis was combined with field competition experiments to predict how an invasive African cichlid fish, Hemichromis guttatus, might affect native fish in the desert springs of Cuatro Ciénegas, Mexico.
• 3. Stable isotope analysis suggested diet overlap between the invader and juvenile endemic cichlids, and field experiments verified that the invader reduces growth rates of the juvenile endemics through competition, but has smaller effects on adults.
• 4. Competition between juvenile endemic cichlids and the invader was asymmetric, with the exotic out‐competing the native, suggesting the potential for competitive exclusion if the invasion is not stopped.
• 5. These results suggest that exotic removal programmes in Cuatro Ciénegas should focus on removing/reducing populations of the exotic cichlid in habitats where juvenile native cichlids are concentrated.
• 6. This approach could help focus efforts to manage exotic species before populations of native species have crashed, when it is too late to intervene.

Copyright © 2011 John Wiley & Sons, Ltd.     

Introduction of exotic fish species and decline of native species in the lower Po basin,north‐eastern Italy

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Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion,northern Australia

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Fish invading deserts: non‐native species in arid Moroccan rivers

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Constrained by aliens,shifting landscape,or poor water quality? Factors affecting the persistence of amphibians in an urban pond network

1. Freshwater communities and especially pond‐breeding amphibians are extremely vulnerable to land‐use change, alien species introductions and the use of pesticides or other toxic chemicals, as reflected in their worldwide decline. Effective conservation and management of ponds requires a better understanding of the biotic and abiotic factors that shape diversity patterns and species distribution, especially in cases of habitat loss
2. The present study aimed to reveal and classify which pond and landscape characteristics are the most important determinants for the occurrence patterns of amphibian species as well as for the overall amphibian species richness in an urban pond network. To achieve this aim, 17 biotic and abiotic variables were measured for 61 ponds and the dataset was analysed by means of a machine‐learning approach, suitability indices and co‐occurrence modelling
3. The highest probability of Triturus macedonicus occurrence was found at fishless artificial and semi‐natural ponds. The persistence of Lissotriton graecus in ponds was predicted by high pond connectivity and the absence of fish reflecting the species dispersive potential. Pelophylax kurtmuelleri showed a higher probability of occurrence with increased pond connectivity and macrophyte cover.
4. Amphibian species richness was higher in fishless ponds with well‐oxygenated waters located in sites with a low to intermediate road density network. Ponds categorized as ‘average’ in terms of newt suitability were more frequently inhabited by fish than Triturus macedonicus. Alien fish species showed negative associations with both newt species, while both newt species showed a positive association between them.
5. The results support the view that conserving a greater number of water bodies with increased landscape connectivity and without any fish presence could provide amphibian species with alternative habitat choices, especially in sites with human pressure where pond stability is at stake owing to continuous landscape changes.

     

Population crash in Lesotho's endemic Maloti minnow Pseudobarbus quathlambae following invasion by translocated smallmouth yellowfish Labeobarbus aeneus

1. A genetically distinct population of the Maloti minnow Pseudobarbus quathlambae (Lesotho's only endemic fish) is known only from the Mohale catchment, and was formerly abundant in the Senqunyane, Bokong and Jorodane rivers which flow into Mohale Reservoir.
2. Situated ~4 km downstream of Mohale Reservoir, the Semongkoaneng waterfall has historically prevented larger fish species from moving upstream into areas inhabited by P. quathlambae. After the filling of the Mohale Reservoir in 2003, an inter‐basin transfer (IBT) linking it to Katse Reservoir was opened and in 2006 the smallmouth yellowfish Labeobarbus aeneus, a larger more aggressive species, was recorded in the reservoir, presumably introduced via the IBT.
3. The objectives of the present study were to: (1) establish whether any additional non‐native fish species were present in the Mohale catchment; (2) ascertain whether L. aeneus has dispersed into the rivers flowing into Mohale Reservoir; and (3) gauge whether the Mohale population of P. quathlambae is in decline. Twenty‐eight sites situated on major rivers flowing into the reservoir, and four sites in the reservoir itself, were surveyed to evaluate changes in fish populations and habitat quality.
4. Results indicate that P. quathlambae has all but disappeared from its natural range: only five individuals were recorded in the Jorodane and Bokong rivers, and none were recorded in the Senqunyane River – a former stronghold for the species. On the other hand, L. aeneus was recorded in all three rivers and is probably responsible for the decline of the P. quathlambae population, given that there does not appear to have been major deterioration in habitat conditions. Another non‐native fish, the Orange River mudfish Labeo capensis, was recorded in the Mohale catchment for the first time. Urgent conservation action is required to prevent the Mohale lineage of P. quathlambae from becoming extinct.

Copyright © 2016 John Wiley & Sons, Ltd.     

Nearshore fish assemblages associated with introduced predatory fishes in lakes

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Essential fish habitats and hotspots of nekto‐benthic diversity and density in the western Mediterranean

1. Since the 1990s, most currently assessed Mediterranean nekto‐benthic stocks have been exploited above maximum sustainable yield and have declined. This study explores the co‐occurrence of essential fish habitats for the most important nekto‐benthic resources exploited by bottom‐trawl fisheries in the western Mediterranean and areas of importance for nekto‐benthic communities.
2. Fishery‐independent data obtained from Mediterranean scientific bottom‐trawl surveys were used to identify persistent hotspots of recruitment for the most important nekto‐benthic species around the Iberian Peninsula and the Balearic Islands between 2002 and 2016, as an indicator of their essential fish habitats. Likewise, hotspots of nekto‐benthic community diversity and density were also determined, as an estimate of key areas for nekto‐benthic communities.
3. Areas of overlap of persistent hotspots of recruitment and of community species richness and density were mainly found on the deep shelf and the upper slope (100–200 m and 200–500 m deep respectively).
4. These overlapping areas could be of particular interest in the development of fishery management plans aiming to implement an ecosystem approach to fisheries. Protection, through temporary or permanent closures, of the overlapping areas identified would contribute to improving both the sustainable exploitation of the main target species of bottom‐trawl fisheries and the conservation of nekto‐benthic communities.

     

Potential impacts of non‐native channel catfish on commercially important species in a Japanese lake,as inferred from long‐term monitoring data

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