Population prioritization for conservation of imperilled warmwater fishes in an arid‐region drainage

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Spatial extent and consequences of black bass (Micropterus spp.) invasion in a Cape Floristic Region river basin

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Heads you win,tails you lose: Life‐history traits predict invasion and extinction risk of the world's freshwater fishes

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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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Vulnerability of Cape Fold Ecoregion freshwater fishes to climate change and other human impacts

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Using occupancy models to assess the effectiveness of underwater cameras to detect rare stream fishes

1. Many conservation efforts for freshwater fishes have been undertaken; however, continuing the monitoring of both the distribution and the abundance of species to determine the effectiveness of these actions can be difficult. As species increase in rarity, they are more difficult to detect in the field, making inferences on occupancy less reliable.
2. Conventional sampling methods, such as electrofishing and seining, require the physical handling of rare fishes, which may cause stress and mortality and, consequently, compromise conservation goals and limit monitoring programmes. Non‐invasive surveillance methods, including underwater video, are playing an increasingly important role.
3. In this study, occupancy models were used to estimate the detection probability of underwater cameras as an alternative to the conventional sampling methods for rare stream fishes. Redside dace (Clinostomus elongatus), a small minnow listed as Endangered, was used as a model organism for rarity. A total of 69 historical redside dace sites were sampled using three sampling methods to determine the effect of gear type on detecting and identifying the habitat preferences of this rare minnow.
4. On average, using multiple underwater cameras is as effective at detecting a rare minnow as conventional sampling methods (backpack electrofisher and seine) and causes no harm.
5. The detection probability of both underwater cameras and backpack electrofishing were adversely affected by turbidity, whereas seining was positively affected by stream velocity. The probability of occupancy of redside dace is driven by open channels and sediment size, and this provides a strong basis for informing stream restoration projects.
6. The use of multiple underwater cameras over conventional sampling methods is recommended when sampling for rare and endangered minnows in systems with low turbidity.

     

From scientific obscurity to conservation priority: Research on angler catch rates is the catalyst for saving the hump‐backed mahseer Tor remadevii from extinction

1. The mahseer (Tor spp.) fishes of South and Southeast Asia are iconic megafaunal species that are highly valued by recreational anglers. Knowledge on their populations is limited owing to the challenges associated with sampling these large‐bodied fishes (>50 kg) in remote monsoonal rivers.
2. Despite its global iconic status among recreational anglers, the hump‐backed mahseer of the Cauvery River (South India) lacked a valid scientific name and was on a trajectory towards extinction until its rapidly declining population status was established by analyses of angler catch records.
3. Angling records from 1998 to 2012 showed that mahseer catch rates had increased in this period. The resulting publication in Aquatic Conservation (AQC) highlighted the positive role of catch‐and‐release angling in providing information on data‐poor species. However, further analyses showed that these catches comprised not one but two distinct phenotypes.
4. Before 1993, all mahseer captured were hump‐backed; since then, a blue‐fin phenotype appeared in catches and subsequently dominated them. These results triggered further studies indicating that the hump‐backed mahseer was the endemic Tor remadevii and that the blue‐fin was the invasive Tor khudree, introduced in 1976 and then stocked periodically from hatcheries.
5. The initial AQC publication successfully demonstrated the high value of organized angling as a monitoring tool for data‐poor fishes and its application to assessing the temporal population patterns of large‐bodied fishes in monsoonal rivers. It was also the catalyst for initiating subsequent studies on T. remadevii that, together, enabled its recent assessment as ‘Critically Endangered’ on the International Union for Conservation of Nature (IUCN) Red List. In the absence of the AQC paper, and the subsequent studies that it triggered, it is highly probable that the species would have remained on a trajectory towards rapid extinction. Instead, the first major steps to safeguarding its future have been taken.

     

Pushed to the edge: Environmental factors drive ecological responses of Aphanius fasciatus when in sympatry with invasive Gambusia holbrooki

1. Interspecific competition may be particularly exacerbated when occurring between native and invasive alien species, with environmental conditions affecting drivers of natural selection and shaping spatio-temporal dynamics of animal communities. The effects of invaders are particularly evident in aquatic ecosystems with delicate and complex balances, such as Mediterranean coastal wetlands, characterized by unpredictable water flows and variable reserves. Understanding how native species respond to human-induced biological invasions is of paramount importance for planning management measures aiming at conservation purposes.
2. This study investigated whether the occurrence of a competing invader species resulted in changes in the ecological adaptations of a native species by comparing two coastal wetland fish species: the invasive eastern mosquitofish Gambusia holbrooki and the native Mediterranean killifish Aphanius fasciatus of conservation concern. The hypothesis was tested by sampling fishes at a coastal Ramsar site in central Italy, over 2 years.
3. Generalized linear mixed models were used to examine the occurrence of killifish in relation to water parameters and the presence of its putative competitor. The aim was to determine whether salinity, temperature, and water depth influenced the presence and abundance of killifish when in sympatry with mosquitofish.
4. Both the probability of presence and abundance of killifish increased with water salinity, but this increase was stronger when mosquitofish was present. Increasing water temperature and water depth were associated with a higher probability of presence and abundance of killifish respectively, although the effect of water depth was small. Both salinity and the presence of the invader acted synergistically in characterizing and shaping the population structure of the native species.
5. Living in the most extreme and stressed environments, the killifish is potentially at higher risk of extinction. These results highlight the importance of considering the interplay between multiple abiotic stressors combined with comparative data between invasive and native species as increasingly critical to aid in conservation efforts.

     

Abiotic and biotic associations between the round goby Neogobius melanostomus and tubenose goby Proterorhinus marmoratus with the endangered northern madtom Noturus stigmosus in Canada

1. Quantifying habitat associations and threats to the persistence of imperilled species is a fundamental step for initiating species recovery efforts, but the traits associated with species imperillment (e.g. rarity and vulnerability to stressors) also limit the ability to empirically inform recovery strategies. Novel sampling designs and modelling approaches are therefore needed to quantitatively assess habitat associations and the threats to species persistence.
2. To improve the understanding of habitat associations and threats for one of the rarest endangered freshwater fish species in Canada, northern madtom (Noturus stigmosus), two‐species occupancy models were developed with two invasive gobies: round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus marmoratus). Models were parameterized with data from a multi‐year benthic trawling survey of two large Great Lakes tributaries in southern Ontario, Canada, and subsequently used to evaluate the need for reducing measurement error with future sampling efforts.
3. The probability of detecting northern madtom in the St. Clair (0.163) and Thames (0.194) rivers was low compared with round goby (St. Clair, 0.827; Thames, 0.833) and tubenose goby (St. Clair, 0.297). The best occupancy models indicated a negative association between northern madtom and round goby in the St. Clair River and the importance of gravel substrate for northern madtom.
4. Up to 16 repeated non‐detections using benthic trawls are needed to be 95% confident that northern madtom is absent at a site, indicating that current sampling approaches are likely inadequate.
5. Despite low detection probabilities, intensive trawling surveys combined with the two‐species occupancy modelling framework provided vital information for describing habitat associations for northern madtom and identified a significant negative association with round goby. Nonetheless, alternative sampling methods to improve the detection probability of northern madtom would allow a more robust evaluation of habitat associations and would provide more information on the negative association with round goby.

     

Predation on native fish eggs by invasive round goby revealed by species‐specific gut content DNA analyses

1. Conservation of riverine fish often aims to improve access to spawning grounds and restore longitudinal connectivity by removing migration barriers, and involves substantial investments. However, these investments also enable non‐native predators to invade upstream into spawning areas and potentially adversely affect the recruitment of threatened freshwater fish through egg or fry predation.
2. Detecting egg predation is often challenging. Visual inspections of fish gut contents may underestimate predation of soft materials such as eggs and fry, which limits the discovery of predators preying upon these life‐stages. DNA‐based detection assays may offer a more sensitive tool to assess predation of soft materials.
3. A conservation issue was confirmed by developing and applying a species‐specific DNA‐based detection assay: invasive round goby (Neogobius melanostomus) prey on the eggs or fry of the threatened common nase (Chondrostoma nasus) in Switzerland.
4. DNA‐based detection assays were also developed for five other valuable native fish species, including endangered salmonid and cyprinid river spawners. The applicability of the assays was confirmed in a series of laboratory and field feeding experiments involving eggs and fish tissue. In addition, this work provides a guiding framework for conservation managers regarding the use and applicability of different DNA‐based detection approaches for gut content analysis.
5. The results of this study could inform local conservation measures – such as temporary reductions in the density of round goby at spawning sites prior to spawning – and demonstrate how targeted application of species‐specific molecular markers may advance freshwater fish management.

     

Change of fish fauna in ponds after eradication of invasive piscivorous largemouth bass,Micropterus salmoides,in north‐eastern Japan

• 1. The change in fish fauna was monitored in ponds within irrigation systems in Iwate prefecture, north‐eastern Japan to evaluate the effectiveness of eradicating the invasive piscivorous largemouth bass, Micropterus salmoides.
• 2. Eleven study ponds were categorized into three pond groups: bass‐dwelling (n=3), bass‐eradicated (n=3) and non‐invaded ponds (n=5).
• 3. Species richness and diversity, which temporally decreased in bass‐dwelling ponds, increased in bass‐eradicated ponds. Furthermore, in bass‐eradicated ponds, the mean numbers of topmouth minnow and freshwater goby were gradually restored, but in bass‐dwelling ponds the numbers decreased and both species eventually disappeared.
• 4. Although the eradication of piscivorous invaders is helpful for restoring fish species diversity in ponds, its effectiveness varies among species, and other alien fish such as the rose bitterling (Rhodeus ocellatus ocellatus) often invade and proliferate in the bass‐eradicated ponds.
• 5. To ensure successful restoration of native biota and avoid undesirable results, it is necessary to plan and implement continuous monitoring and adaptive management after eradication of alien predators. Copyright © 2010 John Wiley & Sons, Ltd.

     

The demography of introduction pathways,propagule pressure and occurrences of non‐native freshwater fish in England

• 1. Biological invasion theory predicts that the introduction and establishment of non‐native species is positively correlated with propagule pressure. Releases of pet and aquarium fishes to inland waters has a long history; however, few studies have examined the demographic basis of their importation and incidence in the wild.
• 2. For the 1500 grid squares (10×10 km) that make up England, data on human demographics (population density, numbers of pet shops, garden centres and fish farms), the numbers of non‐native freshwater fishes (from consented licences) imported in those grid squares (i.e. propagule pressure), and the reported incidences (in a national database) of non‐native fishes in the wild were used to examine spatial relationships between the occurrence of non‐native fishes and the demographic factors associated with propagule pressure, as well as to test whether the demographic factors are statistically reliable predictors of the incidence of non‐native fishes, and as such surrogate estimators of propagule pressure.
• 3. Principal coordinates of neighbour matrices analyses, used to generate spatially explicit models, and confirmatory factor analysis revealed that spatial distributions of non‐native species in England were significantly related to human population density, garden centre density and fish farm density. Human population density and the number of fish imports were identified as the best predictors of propagule pressure.
• 4. Human population density is an effective surrogate estimator of non‐native fish propagule pressure and can be used to predict likely areas of non‐native fish introductions. In conjunction with fish movements, where available, human population densities can be used to support biological invasion monitoring programmes across Europe (and perhaps globally) and to inform management decisions as regards the prioritization of areas for the control of non‐native fish introductions.

© Crown copyright 2010. Reproduced with the permission of her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Modelling effects of invasive species and drought on crayfish extinction risk and population dynamics

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Harvesting an invasive bivalve in a large natural lake: species recovery and impacts on native benthic macroinvertebrate community structure in Lake Tahoe,USA

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Long‐term changes in the fish assemblage of the Laja River,Guanajuato, central Mexico

• 1. The structure and composition of fish communities in rivers of central Mexico have been altered as a result of water over‐exploitation, habitat fragmentation, introduction of exotic species, and pollution. However, the specific pattern and degree of change are poorly documented.
• 2. Long‐term information from the Laja River (Guanajuato, Mexico) in the Lerma River basin was used to explore trends in fish species richness and community composition (species origin, trophic niche, tolerance, and preferred habitat) from the 1960s to the present in both river and reservoir sites.
• 3. Declines in native, sensitive, benthic native and carnivore species ranging from 11% to 30% per decade, and increases in the number of tolerant and exotic species by 9–20% per decade, are documented. Repeated measures ANOVA and sign tests revealed significant declines in the number of benthic, native, carnivore and sensitive species. Species richness, number of exotics, tolerant species and omnivore species did not change statistically, though statistical power was low. Some important changes occurred in these variables, such as the expansion and establishment of exotics such as Xiphophorus variatus and Micropterus salmoides, which pose a serious potential threat to native species.
• 4. The changes in fish community composition for the Laja portray how the fish communities in other rivers in central Mexico, for which long‐term data do not exist, have changed or could change if environmental deterioration continues.

Copyright © 2006 John Wiley & Sons, Ltd.     

Long‐term changes of marine subtidal benthic communities in North East Asia (Yellow and Japan seas) in a global change context: A review

1. A review of the long‐term changes and variations in benthic communities and the current status of the marine invasive species (MIS) in shallow waters of the Yellow Sea (Chinese sector) and the Sea of Japan (Russian and partly Korean sectors) is presented. This paper reflects on the progress and lessons learned, recommending actions for the future about the conservation of biodiversity.
2. In the Bohai Sea, the benthic ecosystem has been degenerating due to anthropogenic activities such as overfishing and pollution since the 1950s. The dominant position of K‐strategy species is gradually being lost and replaced by R‐strategy species. In the Yellow Sea, the macrobenthic community is different from other areas due to the Yellow Sea Cold Water Mass. Many economic species have been destroyed, and the biotic structure has changed significantly due to overfishing and climate change.
3. In the Russian sector of the Sea of Japan, the macrobenthic communities in the shallow‐water soft bottom have generally been in a stable condition for the last decades, except for some heavily polluted or disturbed areas due to dredging operations. The abundance of select large invertebrate species has changed considerably due to commercial fishing and poaching. Variations in macro? and meiobenthic communities under aquaculture conditions have occurred on a local scale during the last five decades.
4. MIS show obvious differences between China and Russia in the following aspects: introduction pathways of MIS, composition and number of non‐native species, threats and impacts of MIS to native communities and ecosystems, and economic and public health impacts.
5. Long‐term monitoring programmes should be developed to reveal future biotic changes and to separate the effects of cyclic variations of benthic communities from the impacts of pollution and eutrophication. Standardization of sampling procedures is required to compare changes/alternations in benthos across various regions worldwide.

     

The status and distribution of a newly identified endemic galaxiid in the eastern Cape Fold Ecoregion,of South Africa

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Comparison of traditional and environmental DNA survey methods for detecting rare and abundant freshwater fish

1. Detecting rare species is often a necessity for conservation and management, yet challenging for many field survey methods. Environmental DNA (eDNA) is a highly promising solution that has been shown to outperform many established survey methods.
2. Macquarie perch (Macquaria australasica) is an endangered native species that has declined significantly in range and abundance. Detection of M. australasica was compared with an abundant alien fish species (Oncorhynchus mykiss) using eDNA and three conventional survey methods: gill nets, electrofishing and fyke nets.
3. eDNA occupancy estimates for both fish species were compared using four different models to investigate what effect these differences have on false positives and false negatives for the rare and common fish species. These models used unadjusted eDNA detections in water samples, eDNA detections that have been screened using a limit of detection method to remove potential false positives, eDNA data supplemented with a second survey method, or eDNA data augmented with sequencing of positive polymerase chain reaction replicates.
4. eDNA surveying as a single detection method was found to be more efficient and sensitive compared with each capture method separately and combined. Occupancy estimates for the common and rare species did not vary significantly between the four site occupancy-detection models, suggesting that supplementary data may not have as much effect on occupancy estimates compared with other approaches such as temporal or spatial sampling.
5. We conclude that eDNA outperforms the three established survey methods for both a rare and common freshwater fish species. Although there was no significant effect of augmenting eDNA survey methods with other survey data, additional data may improve confidence in detection, and provide confirmatory evidence for unexpected or new detections of a species.

     

Fragmentation and drying ratchet down Great Plains stream fish diversity

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Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream

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