Broad-scale studies of climate change effects on freshwater species have focused mainly on temperature, ignoring critical drivers such as flow regime and biotic interactions. We use downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows and increased temperatures on four interacting species of trout across the interior western United States (1.01 million km2), based on empirical statistical models built from fish surveys at 9,890 sites. Projections under the 2080s A1B emissions scenario forecast a mean 47% decline in total suitable habitat for all trout, a group of fishes of major socioeconomic and ecological significance. We project that native cutthroat trout Oncorhynchus clarkii, already excluded from much of its potential range by nonnative species, will lose a further 58% of habitat due to an increase in temperatures beyond the species' physiological optima and continued negative biotic interactions. Habitat for nonnative brook trout Salvelinus fontinalis and brown trout Salmo trutta is predicted to decline by 77% and 48%, respectively, driven by increases in temperature and winter flood frequency caused by warmer, rainier winters. Habitat for rainbow trout, Oncorhynchus mykiss, is projected to decline the least (35%) because negative temperature effects are partly offset by flow regime shifts that benefit the species. These results illustrate how drivers other than temperature influence species response to climate change. Despite some uncertainty, large declines in trout habitat are likely, but our findings point to opportunities for strategic targeting of mitigation efforts to appropriate stressors and locations.

https://www.fs.fed.us/rm/pubs_other/rmrs_2011_wenger_s001.pdf

Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change [includes Supporting Information]

Many exploited fish and macroinvertebrates that utilize the coastal zone have declined, and the causes of these declines, apart from overfishing, remain largely unresolved. Degradation of essential habitats has resulted in habitats that are no longer adequate to fulfil nursery, feeding, or reproductive functions, yet the degree to which coastal habitats are important for exploited species has not been quantified. Thus, we reviewed and synthesized literature on the ecological value of coastal habitats (i.e. seagrass beds, shallow subtidal and intertidal habitats, kelp beds, shallow open water habitats, saltmarshes, mussel beds, macroalgal beds, rocky bottom, and mariculture beds) as feeding grounds, nursery areas, spawning areas, and migration routes of 59 taxa, for which the International Council for the Exploration of the Sea (ICES) gives management advice, and another 12 commercially or ecologically important species. In addition, we provide detailed information on coastal habitat use for plaice (Pleuronectes platessa), cod (Gadus morhua), brown shrimp (Crangon crangon), and European lobster (Homarus gammarus). Collectively, 44% of all ICES species utilized coastal habitats, and these stocks contributed 77% of the commercial landings of ICES-advice species, indicating that coastal habitats are critical to population persistence and fishery yield of ICES species. These findings will aid in defining key habitats for protection and restoration and provide baseline information needed to define knowledge gaps for quantifying the habitat value for exploited fish and invertebrates.

/pdf/ecological-value-of-coastal-habitats-for-commercially-and-4xgwz2az5r.pdf

Ecological value of coastal habitats for commercially and ecologically important species

Recent efforts to improve the survival of hydroelectric turbine-passed juvenile fish have explored modifications to both operation and design of the turbines. Much of this research is being carried out by power producers in the Columbia River basin (U.S. Army Corps of Engineers and the public utility districts), while the development of low-impact turbines is being pursued on a national scale by the U.S. Department of Energy. Fisheries managers are involved in all aspects of these efforts. Advanced versions of conventional Kaplan turbines are being installed and tested in the Columbia River basin, and a pilot scale version of a novel turbine concept is undergoing laboratory testing. Field studies in the last few years have shown that improvements in the design of conventional turbines have increased the survival of juvenile fish. There is still much to be learned about the causes and extent of injuries in the turbine system (including the draft tube and tailrace), as well as the significance of i...

The Development of Advanced Hydroelectric Turbines to Improve Fish Passage Survival

The successful establishment and expansion of invasive species may be linked to the behavior and dispersal tendency of individuals within an introduced population. To test the prediction that the boldest individuals, with the greatest dispersal tendency would be concentrated in the area of active range expansion, we compared the behavior, dispersal tendency, and metabolic rate of male round goby (Neogobius melanostomus) sampled from the expanding edge of their range with those sampled from an established area in the Trent–Severn Waterway, Ontario, Canada. Behavior and dispersal tendency were assessed in an artificial flume at 2 different water velocities using individuals caught in the spring and autumn of 2013, while resting metabolic rate (RMR) was determined using intermittent flow-through respirometry on fish collected in the autumn only. Round goby from the edge of their expanding range emerged from a shelter sooner, moved farther and faster in the flume, and had higher RMRs than individuals from established areas within the river. Neither water velocity nor season of capture was important in explaining the variation in time of emergence or movement. The higher proportion of bold individuals with high dispersal potential at invasion fronts facilitates further dispersal of round goby populations, and could help explain the rapid expansion of this species in North America and Western Europe. However, the benefits of bold phenotypes in terms of dispersal may be offset by increased energetic costs while at rest.

To boldly go where no goby has gone before: boldness, dispersal tendency, and metabolism at the invasion front

Freshwater ecosystems constitute only a small fraction of the planet's water re‐ sources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians or reptiles. Fresh waters are, however, par‐ ticularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, pollution and biological invasions. This environmental degradation, com‐ bined with unprecedented rates of biodiversity change, highlights the importance of robust and replicable programmes to monitor freshwater fish. Such monitoring programmes can have diverse aims, including confirming the presence of a single species (e.g., early detection of alien species), tracking changes in the abundance of threatened species, or documenting long‐term temporal changes in entire communi‐ ties. Irrespective of their motivation, monitoring programmes are only fit for purpose if they have clearly articulated aims and collect data that can meet those aims. This review, therefore, highlights the importance of identifying the key aims in monitor‐ ing programmes and outlines the different methods of sampling freshwater fish that can be used to meet these aims. We emphasize that investigators must address is‐ sues around sampling design, statistical power, species’ detectability, taxonomy and ethics in their monitoring programmes. Additionally, programmes must ensure that high‐quality monitoring data are properly curated and deposited in repositories that will endure. Through fostering improved practice in freshwater fish monitoring, this review aims to help programmes improve understanding of the processes that shape the Earth's freshwater ecosystems and help protect these systems in face of rapid environmental change.

/pdf/effective-monitoring-of-freshwater-fish-1z7mzxnke0.pdf

Effective monitoring of freshwater fish

Key-words: Gobiidae, Danube, Rhine, range expansion, drivers Five Gobiid fish species have recently increased their ranges along the Danube/Rhine river corridor. Studies to date, however, have tended to be local, site specific and reactive, examining just one or few species. As such, overall range has tended to be assumed based on a summary of patchy, and sometimes contradictory, data. This study provides an upto-date literature review of first records of occurrence for all five species along their expansion route. In addition, available shipping data are examined to identify possible proximal causes of introduction. Three main discontinuous population centres were identified; all at or near important container ports: Vienna, Duisburg and Rotterdam. Shipping is confirmed as an important factor in the rapid national and international expansion of Ponto-Caspian Gobiids, with downstream drift, rip-rap and heavy boat traffic contributing to rapid spread on the Rhine. Geopolitical factors, however, such as the fall of communism and the Balkan conflict, have been key in influencing where, when, and by which route gobies first appear. Rapid expansion of Gobiids in the Rhine raises the possibility of establishment throughout mainland Europe via two new potential invasion corridors across Germany/Poland and France.

/pdf/a-review-of-gobiid-expansion-along-the-danube-rhine-corridor-zhvp96jvha.pdf

A review of Gobiid expansion along the Danube-Rhine corridor – geopolitical change as a driver for invasion

1.
After re-introduction in 1991 of Eurasian otters Lutra lutra (L.) to the River Lee catchment (England), changes in range were assessed from spraint collections in the periods 1991–1994, 1995–1997 and 1998–2000. Diet, assessed from concerted spraint sampling within the first two periods, was compared between 1992–1994 and 1996–1997, with dietary preferences assessed for the initial phase using available fish stock data for that period.

2.
In 1991–1994, range encompassed much of the catchment, but reduced in 1995–1997 to a small area around the initial release site, when the otters were joined/replaced by natural immigrants presumed to come from a contiguous catchment. Range expanded in 1998–2000 to upper reaches of the catchment's major tributaries.

3.
Fish, mainly cyprinids, were the major prey taken in 1992–1994 and 1996–1997. In 1996–1997, fish abundant near the initial release site became more prominent, in particular chub Leuciscus cephalus, and (upstream) species characteristic of the initial range decreased in importance.

4.
Despite confirmed and unconfirmed sightings of females with cubs, it remains unclear whether the presence and apparent expansion of otters in the Lee catchment is the result of the re-introduction or of natural immigration/recolonization.



Copyright © 2003 John Wiley & Sons, Ltd.

Range and diet of Eurasian otters Lutra lutra (L.) in the catchment of the River Lee (south-east England) since re-introduction

Diet of two invading gobiid species (Proterorhinus semilunaris and Neogobius melanostomus) during the breeding and hatching season: No field evidence of extensive predation on fish eggs and fry

Bones were obtained from three fish species (brown trout Salmo trutta m. fario, grayling Thymallus thymallus and Carpathian sculpin Coitus poecilopus) for regression analysis. Bones used were chosen based upon frequency of occurrence in spraint samples and diagnostic value. Relationships between the length of diagnostic bones and fish length, fish length and weight, and standard length to total length, were assessed for the three fish species. Polynomial regression was deemed most suitable for the relationship between bone length and fish standard length, multiplicative between fish standard length and fish weight, and linear (brown trout) or polynomial (grayling and Carpathian sculpin) for standard length against total length. All calculated regressions were highly significant and displayed high coefficients of determination, ranging between 93.9 and 99.8 %. The uses of the bones examined, and the equations produced, are discussed in the light of their future use in estimating prey numbers, length and biomass in otter diet analysis.

On the use of diagnostic bones of brown trout, Salmo trutta m. fario, grayling, Thymallus thymallus and Carpathian sculpin, cottus poecilopus in Eurasian otter, Lutra lutra diet analysis

The round goby Neogobius melanostomus has recently invaded several major freshwater systems in Europe and North America. Despite numerous studies predicting an impact on native fish assemblages, few have attempted to demonstrate it. In this case study, we monitored the effect of N. melanostomus colonisation on abundance and habitat utilisation of both young-of-the-year (YOY) native fish and YOY western tubenose goby Proterorhinus semilunaris in a typical, medium-sized European river. Colonisation by N. melanostomus had no apparent effect on either native fish abundance and species richness or P. semilunaris abundance. Moreover, after colonisation, both native fish and P. semilunaris occupied similar niches (i.e. microhabitats) to those occupied before colonisation. While niche use of YOY N. melanostomus and P. semilunaris overlapped significantly, YOY native fish utilised different habitats from the gobiids. We suggest that N. melanostomus did not compete for resources with YOY fish in our study area due to lack of niche overlap and/or surplus resources. As N. melanostomus rapidly dominated the fish assemblage at our site, we further suggest that utilisation of an empty niche, rather than competitive superiority, was the main factor facilitating its success.

Kevin Roche

Papers

A review of Gobiid expansion along the Danube-Rhine corridor – geopolitical change as a driver for invasion

Range and diet of Eurasian otters Lutra lutra (L.) in the catchment of the River Lee (south-east England) since re-introduction

Diet of two invading gobiid species (Proterorhinus semilunaris and Neogobius melanostomus) during the breeding and hatching season: No field evidence of extensive predation on fish eggs and fry

On the use of diagnostic bones of brown trout, Salmo trutta m. fario, grayling, Thymallus thymallus and Carpathian sculpin, cottus poecilopus in Eurasian otter, Lutra lutra diet analysis

No effect of round goby Neogobius melanostomus colonisation on young-of-the-year fish density or microhabitat use