Habitat use,home range,movements and interactions of introduced Lepomis gibbosus and native Salmo trutta in a small stream of Southern England

Radio telemetry data were analysed to assess the microhabitat use, movement patterns, home range overlap and interspecific interactions of non‐native pumpkinseed Lepomis gibbosus (L.) and native brown trout Salmo trutta (L.) in a small English stream located immediately below a commercial angling lake from which pumpkinseed escaped. Although both species favoured pool habitats, brown trout preferred higher velocities and coarser substrata compared with pumpkinseed. Also, some individual brown trout preferred deeper waters than did pumpkinseed. Home range area of brown trout was substantially larger than that of pumpkinseed in spring and summer, and for both species, home range area in autumn was significantly smaller than in the other seasons. Range centre distribution analysis revealed that both species were distributed significantly nonrandomly within the stream during all seasons. There was substantial home range overlap between the two species in all seasons, the greatest being in spring. Overall distances moved were greatest during spring for both species, with brown trout moving greater distances relative to pumpkinseed. However, the absence of mutual attraction or avoidance between the species, as well as the lack of cohesion in preferred habitats and strong territorial fidelity, suggests little or no impact of introduced pumpkinseed on resident brown trout.     

Red operculum spots,body size,maturation and evidence for a satellite male phenotype in non‐native European populations of pumpkinseed Lepomis gibbosus

Carotenoid‐based pigmentation is a striking feature of many taxa, yet the function, if any, of colour traits is often unclear. Pumpkinseed Lepomis gibbosus, a widely introduced freshwater sunfish that exhibits alternative male mating strategies, express a striking, red operculum spot. To investigate the potential function of this red spot as a signal in this species' mating system, we determined the presence and measured the size of red operculum spots in fish collected from 12 populations in five European countries in which pumpkinseed is an established non‐native species. We subsequently related the presence and size of the red spot to body size and mating strategy, based on an analysis of relative gonad size (gonado‐somatic index, GSI), using a mixed modelling approach. The study demonstrated that the presence of a red operculum spot in pumpkinseed is associated with sexual maturation, with GSI frequency distributions suggesting that cuckolders in some non‐native populations comprised both sneaker and satellite males, the latter not having previously been reported for this species. Further, the size of red spot correlated strongly with body size in parental and cuckolder males, although there was no difference in the presence or size of the red operculum spot between male mating strategies. The function of a red operculum spot in females is not clear but may be partly mediated by pleiotropic genetic mechanisms. Red operculum spots appear to function as signals of male maturation and body size in pumpkinseed, irrespective of mating strategy.     

Salinity tolerance of non‐native suckermouth armoured catfish (Loricariidae: Pterygoplichthys) in south‐eastern Mexico: implications for invasion and dispersal

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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.     

Productivity and recovery of forage fish under climate change and fishing: North Sea sandeel as a case study

Forage fish occupy a central position in marine food‐webs worldwide by mediating the transfer of energy and organic matter from lower to higher trophic levels. The lesser sandeel (Ammodytes marinus) is one of the ecologically and economically most important forage fish species in the North‐east Atlantic, acting as a key prey for predatory fish and sea birds, as well as supporting a large commercial fishery. In this case study, we investigate the underlying factors affecting recruitment and how these in turn affect productivity of the North Sea sandeel using long‐term data and modelling. Our results demonstrate how sandeel productivity in the central North Sea (Dogger Bank) depends on a combination of external and internal regulatory factors, including fishing and climate effects, as well as density dependence and food availability of the preferred zooplankton prey (Calanus finmarchicus and Temora longicornis). Furthermore, our model scenarios suggest that while fishing largely contributed to the abrupt stock decline during the late 1990s and the following period of low biomass, a complete recovery of the stock to the highly productive levels of the early 1980s would only be possible through changes in the surrounding ecosystem, involving lower temperatures and improved feeding conditions. To that end, we stress the need for ecosystem‐based management accounting for multiple internal and external factors occurring within the broader context of the ecosystem in which forage fish species, such as sandeel, play an important and integral part.     

Fish movements: the introduction pathway for topmouth gudgeon Pseudorasbora parva and other non‐native fishes in the UK

• 1. The contamination of fish consignments (for stocking or aquaculture) is a major pathway by which non‐native organisms, including fish, are introduced to new areas. One of the best examples of this is the topmouth gudgeon Pseudorasbora parva, which was accidentally imported into Romania and then throughout Europe in consignments of Asian carp species.
• 2. The introduction and spread of topmouth gudgeon in the UK has been linked to imports and movements of the ornamental variety (golden orfe) of ide Leuciscus idus. To examine this hypothesis, relationships between authorized movements of both native and non‐native fish species (in particular ide) and the occurrence in England of topmouth gudgeon were tested at the 10×10 km scale.
• 3. Topmouth gudgeon occurrence in the wild was significantly correlated with the trajectories of movements of ornamental fish species (ide/orfe, sunbleak Leucaspius delineatus) as well as a few non‐ornamental fish species (European catfish Silurus glanis, Atlantic salmon Salmo salar and grass carp Ctenopharyngodon idella).
• 4. These results highlight the mechanism by which non‐native fish species disperse from the point of first introduction, and especially that movements of fish within the country represent an important mechanism for accidental introductions of non‐native species. © Crown copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.

     

First application in Turkey of the European Non‐native Species in Aquaculture Risk Analysis Scheme to evaluate the farmed non‐native fish,striped catfish Pangasianodon hypophthalmus

The European Non‐native Species in Aquaculture Risk Analysis Scheme (ENSARS) was used to assess one of the most popular aquaculture species in the world, the striped catfish Pangasianodon hypophthalmus (Sauvage, 1878), in two locations of southern Anatolia (Turkey). The overall mean risk score generated for P. hypophthalmus by the ENSARS Organism module (which assesses the risks of introduction, establishment, dispersal and impact) indicated that the species poses a medium risk under current climatic conditions. All other ENSARS modules rendered scores that indicated a moderately low risk under current climatic conditions. However, the risks of introducing novel diseases and the actual use (e.g. deliberate introduction to the natural habitats or food market) of the species both attracted scores indicating a medium risk. Confidence levels were medium or high for all modules except the Socio‐economic, with low confidence values also attributed to the risks for farming process of the organism, and its overall risk of spread into the wild during farming procedures and to marketing impacts. Recommendations are provided for further use of the ENSARS scheme, especially for a a priori assessment of potential aquaculture species in Turkey, where the sector has been remarkably developing in the last decades.     

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

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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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Time‐series analysis of native and non‐native crayfish dynamics in the Thames River Basin (south‐eastern England)

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Changes in native bull trout and non‐native brook trout distributions in the upper Powder River basin after 20 years,relationships to water temperature and implications of climate change

Many bull trout populations have declined from non‐native brook trout introductions, habitat changes (e.g. water temperature) and other factors. We systematically sampled the distribution of bull trout and brook trout in the upper Powder River basin in Oregon in the 1990s and resampled it in 2013–2015, examined temperature differences in the habitats of the two species and analysed trends in temperatures in the light of possible increases associated with climate change. The species’ distributions are currently similar to those in the 1990s, except in one stream where bull trout declined. However, bull trout consisting of resident forms remain restricted to a few kilometres of habitat at the upper end of fish distribution. In streams where both species occur, the typical pattern was an intermediate zone of mixed bull trout, brook trout, and hybrids downstream of allopatric bull trout and allopatric brook trout extending farther downstream. Temperature differences between where bull trout and most brook trout occurred were small (0.5–1.0°C August mean). There were no statistical increases in water temperatures in nearby streams since the 1990s and no warming trends in air temperatures for the past 25–60 years. However, peak summer water temperatures are occurring about 3 weeks earlier than 25 years ago. Future effects of climate change, including possible increases in temperature, changes in timing and other factors (e.g. snowpack, flow and extreme events) remain a concern for the persistence of these populations. However, it is difficult to precisely predict where those changes will occur and what they will be.     

Seasonal movements of non‐native lake trout in a connected lake and river system

Abstract Non‐native lake trout, Salvelinus namaycush (Walbaum), threaten native salmonid populations in the western United States. Effective management of lake trout requires understanding movements within connected lake and river systems. This study determined the seasonal movements of subadult lake trout in the Flathead River upstream of Flathead Lake, Montana, USA using radio telemetry. The spatiotemporal distribution of lake trout in the river was related to water temperature. Lake trout were detected in the river primarily during autumn, winter and spring, when water temperatures were cool. By contrast, fewer were detected when temperatures were warmest during summer and during high spring flows. Downriver movements to Flathead Lake occurred throughout autumn and winter when water temperature decreased below 5 °C, and in late spring as water temperature rose towards 15 °C and river discharge declined following spring runoff. Upriver movements occurred primarily in October, which coincided with migrations of prey fishes. These results suggest that lake trout are capable of moving throughout connected river and lake systems (up to 230 km) and that warm water temperatures function as an impediment to occupancy of the river during summer. Controlling source populations and maintaining natural water temperatures may be effective management strategies for reducing the spread of non‐native lake trout.     

Underwater evaluation of habitat partitioning in a European river between a non‐native invader,the racer goby and a threatened native fish,the European bullhead

We conducted underwater surveys using SCUBA gear to examine habitat and microhabitat competition between the Ponto‐Caspian racer goby Babka gymnotrachelus and native European bullhead Cottus gobio to assess the potential for competitive displacement of the native species by the invading species. In summer, 88 surveys were made in a tributary of the River Vistula within defined benthic areas across the entire width of the river bed. The occurrence of fish by total length class (small: <6 cm; large: >6 cm) and environmental conditions (depth, water velocity, substratum type, plant cover, shelter type) was recorded. We found a substantial separation between the species and size classes in relation to substratum, shelter type and water velocity. European bullheads were limited to lotic areas with stony bottoms, whereas racer gobies also occupied lentic areas over sand or mud. European bullheads usually took refuge under stones in contrast to a wider range of shelters used by racer goby, including tree roots and rubbish. In general, the breadth of habitat used by the racer goby was wider than that of the European bullhead, although habitat overlap between the species was not statistically significant except for the type of shelter occupied by small fish, selecting smaller stones. An inverse relationship was observed between small European bullheads and all racer gobies in areas where they co‐occurred, suggesting that invader may be having an adverse effect on the distribution and habitat use of small native bullheads, particularly in areas of moderate water velocities over small stones and gravel.     

Prey and non‐native fish predict the distribution of Colorado pikeminnow (Ptychocheilus lucius) in a south‐western river in North America

Colorado pikeminnow (Ptychocheilus lucius) has been extirpated from a large portion of its historical range in the Colorado River basin, USA. A repatriation effort via stocking of juvenile P. lucius in the San Juan River, NM, CO and UT has resulted in limited recruitment of individuals into an adult population. Understanding biotic and abiotic factors that limit their persistence in the Colorado River basin will be a critical step in providing for their recovery. To elucidate potential recruitment barriers in the San Juan River, we assessed relationships between the numbers of two age classes of P. lucius and prey, competitors and predators collected at a 1.6 km reach scale between 2003 and 2012. We used an information theoretical approach to rank candidate models testing the relative importance of these biotic conditions in predicting the spatial distribution of P. lucius. We found positive relationships between the numbers of P. lucius ≤200 mm total length (TL) collected and catch per unit effort (CPUE) of native prey among reaches. For P. lucius >200 mm TL (individuals that are likely completely piscivorous), we found positive associations between the numbers of P. lucius collected and CPUE of total prey and CPUE of potential non‐native competitors in each reach. Our data suggest size‐specific affinities of P. lucius for native and non‐native prey as well as the potential for negative interactions between P. lucius and non‐native competitors may contribute to limited recruitment of juvenile P. lucius into an adult population in the San Juan River.     

The relationship between the snowmelt flood and the establishment of non‐native brown trout (Salmo trutta) in streams of the Chitose River,Hokkaido, northern Japan

Flow regime is one of the major determinants of establishment success for non‐native aquatic organisms. Here, we examine the influence of flow variability associated with snowmelt flood on the establishment success of non‐native brown trout in 10 streams in northern Japan. We regarded the presence of Age‐0 brown trout as the index of the successful establishment. The emergence of Age‐0 brown trout in our study region begins in May, a time that overlaps with the occurrence of snowmelt flood. The presence of Age‐0 brown trout was negatively associated with flow variability, and it was also negatively associated with summer water temperature. Our results indicate that the non‐native brown trout tends to establish in the streams with smaller snowmelt floods and lower summer water temperatures. Brown trout is an invasive, non‐native species that is problematic all over the world, and effective management strategies for preventing their further expansion are urgently needed. This study suggests that river managers should recognise that stable streams such as spring‐fed streams (i.e., low flow and summer water temperature) and flow‐regulated streams, have a higher potential risk of brown trout invasion.     

Managed and natural inundation: benefits for conservation of native fish in a semi‐arid wetland system

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Immune responses of Litopenaeus vannamei to non‐ionic ammonia stress: a comparative study on shrimps in freshwater and seawater conditions

To investigate the effect of non‐ionic ammonia (NH₃‐N) stress (0.1 and 0.5 mg L^?1) on the immunity of Litopenaeus vannamei cultured in long‐term freshwater, the total haemocyte count (THC), the activity of phenoloxidase (PO), nitric oxide synthase (NOS), superoxidase dismutase (SOD) and the content of malondialdehyde (MDA) were determined and further compared with those of seawater shrimps. The results showed that NH₃‐N stress significantly reduced THC and the activity of PO and SOD (P < 0.05). Under 0.1 mg L^?1 NH₃‐N stress, NOS activity increased first and then decreased significantly, while it dropped dramatically under 0.5 mg L^?1 NH₃‐N stress (P < 0.05). During NH₃‐N stress, MDA content increased continuously, and the MDA content in hepatopancreas of freshwater shrimps was higher than that of seawater shrimps. It was concluded that NH₃‐N stress significantly influenced the non‐specific immunity and could also upset the balance of antioxidant system of L. vannamei in both freshwater and seawater shrimps. Compared with in seawater, the shrimps in freshwater were more vulnerable to NH₃‐N stress because of higher lipid peroxidation and lower immunity.     

Recruitment,distribution boundary and habitat temperature of an arcto‐boreal gadoid in a climatically changing environment: a case study on Northeast Arctic haddock (Melanogrammus aeglefinus)

Climate change is expected to have major effects on the distribution and abundance of fish. In spite of extensive research on the topic in high‐latitude marine ecosystems, the mechanistic understanding of how temperature impacts recruitment and distribution of arcto‐boreal fish stocks remains elusive. Exemplified by an arcto‐boreal gadoid in the Barents Sea, the Northeast Arctic (NEA) haddock (Melanogrammus aeglefinus), we investigate the effect of ecosystem temperature (here temperature from a fixed reference section) on abundance and distribution boundaries between 1981 and 2008. During this time interval there has been a trend of increasing temperature in the ecosystem. We compare the ecosystem temperature with the species habitat temperature of NEA haddock (i.e., ambient temperature of the population) – two temperature approaches representing the indirect and direct environmental impacts on fish, respectively. In addition to the temperature effects, density‐dependent effects on distribution boundaries are considered. The study is based on swept area density estimates and spatial temperature data collected annually in winter surveys. We found a positive relationship between ecosystem temperature and abundance, a connection related to both direct and indirect mechanisms with short‐term and long‐term pathways. Distribution boundaries are, on a year‐to‐year basis, more related to abundance than ecosystem temperature. The long‐term trends, however, indicate a north‐eastward shift in distribution boundaries, probably indirectly related to the coinciding ecosystem temperature increase. In spite of the gradual increase in ecosystem temperature, the abundance of 4‐ to 7‐ year old NEA haddock expanded into colder waters. Thus, our results show how different the two temperature approaches may be.     

Reserve site selection for data‐poor invertebrate fisheries using patch scale and dispersal dynamics: a case study of sea cucumber (Cucumaria frondosa)

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