Environmental niche patterns of native and non-native fishes within an invaded African river system

To test ecological niche theory, this study investigated the spatial patterns and the environmental niches of native and non-native fishes within the invaded Great Fish River system, South Africa. For the native fishes, there were contrasting environmental niche breadths that varied from being small to being large and overlapped for most species, except minnows that were restricted to headwater tributaries. In addition, there was high niche overlap in habitat association among fishes with similar distribution. It was therefore inferred that habitat filtering-driven spatial organisation was important in explaining native species distribution patterns. In comparison, most non-native fishes were found to have broad environmental niches and these fishes showed high tolerance to environmental conditions, which generally supported the niche opportunity hypothesis. The proliferation of multiple non-native fishes in the mainstem section suggest that they form a functional assemblage that is probably facilitated by the anthropogenic modification of flow regimes through inter-basin water transfer. Based on the distribution patterns observed in the study, it was inferred that there was a likelihood of negative interactions between native and non-native fishes. Such effects are likely to be exacerbated by altered flow regime that was likely to have negative implications for native ichthyofauna.     

Life history responses of fishes to culture

The protected environment in culture permits fishes to reduce the proportion of energy normally channelled into the costs associated with competition for food, shelter and mates, avoidance of predators and counteracting parasites and diseases. The surplus energy so released is allocated to growth and reproduction, accelerating development through increased growth rate, earlier maturation and increased relative fecundity. Cultivators manipulate the rearing environment to remove seasonal variation in availability of resources, so that the fishes grow and develop through otherwise unproductive seasons. Such environmental manipulations exaggerate the basic accelerative effects. Since maturation deflects energy from growth, farmers also manipulate the fishes nutritionally, physiologically, hormonally and genetically to postpone maturation. As environmental regulators determine sex in many fish species, environmental manipulation in culture may have unintended effects on sex ratios. Mortality in culture should be very low, but survival of fishes released from culture is rarely as high as that of wild conspecifics. Finally, while short life‐cycles and simplified population age‐structures permit high rates of production in farms, they lead to ecological instability when the fishes are cultured for support of wild populations.     

The effects of environmental stress on outbreaks of infectious diseases of fishes*

Infectious diseases of fishes occur when susceptible fishes are exposed to virulent pathogens under certain environmental stress conditions. Very little research has been carried out to show the effect of pollution on outbreaks of infectious diseases of fishes. Therefore, examples taken from the literature were selected and reviewed to show the coincidence of infectious diseases with stress caused by temperature, eutrophication, sewage, metabolic products of fishes, industrial pollution, and pesticides.     

拉萨河流域外来鱼类的分布、群落结构及其与环境的关系

为揭示当前拉萨河流域外来鱼类的现状及其主要影响因素,于2010、2012及2014年对该流域的鱼类群落结构及水体环境进行了调查。共捕获4目6科17属25种鱼类,包括13种外来鱼类和12种土著鱼类。在42个采样点中的19个发现了外来鱼类,包括12处的湿地、6处的河流及1处水库采样点。外来鱼类基本都分布在下游,除了鲫（Carassius auratus）分布到了上游,鲤（Cyprinus carpio）、鳙（Aristichthys nobilis）和泥鳅（Misgurnus anguillicaudatus）分布到了中游。分布最广、数量最多的土著鱼类是拉萨裸裂尻鱼（Schizopygopsis younghusbandi younghusbandi）、东方高原鳅（Triplophysa orientalis）和西藏高原鳅（Triplophysa tibetana）,最常见的外来鱼类为泥鳅、鲫和麦穗鱼（Pseudorasbora parva）。典范对应分析表明,该流域的鱼类群落同时受局域和区域环境因素的作用,二者对鱼类群落变异的总解释量为33.9%。海拔、圆石的比例和沙的比例与鱼类群落结构的关系最为紧密。今后应当开展外来鱼类的监控和清除工作,减少人为活动对河流生态系统的干扰,以促进该地区外来鱼类的防控工作及土著鱼类的保护。     

Ecosystem consequences of fish parasites*

In most aquatic ecosystems, fishes are hosts to parasites and, sometimes, these parasites can affect fish biology. Some of the most dramatic cases occur when fishes are intermediate hosts for larval parasites. For example, fishes in southern California estuaries are host to many parasites. The most common of these parasites, Euhaplorchis californiensis, infects the brain of the killifish Fundulus parvipinnis and alters its behaviour, making the fish 10–30 times more susceptible to predation by the birds that serve as its definitive host. Parasites like E. californiensis are embedded in food webs because they require trophic transmission. In the Carpinteria Salt Marsh estuarine food web, parasites dominate the links and comprise substantial amount of biomass. Adding parasites to food webs alters important network statistics such as connectance and nestedness. Furthermore, some free‐living stages of parasites are food items for free‐living species. For instance, fishes feed on trematode cercariae. Being embedded in food webs makes parasites sensitive to changes in the environment. In particular, fishing and environmental disturbance, by reducing fish populations, may reduce parasite populations. Indirect evidence suggests a decrease in parasites in commercially fished species over the past three decades. In addition, environmental degradation can affect fish parasites. For these reasons, parasites in fishes may serve as indicators of environmental impacts.     

Environmental Variability, Historical Contingency, and the Structure of Regional Fish and Macroinvertebrate Faunas in Ouachita Mountain Stream Systems

In 1990–1992, the United States Forest Service sampled six hydrologically variable streams paired in three different drainage basins in the Ouachita Mountains, Arkansas, U.S.A. Fishes, macroinvertebrates, and stream environmental variables were quantified for each stream. We used these data to examine the relationship between regional faunas (based on taxonomy and trophic affiliation of fishes and macroinvertebrates) and measured environmental variables. Because fishes are constrained to their historically defined drainage basins and many insect taxa are able to cross basin barriers, we anticipated that both groups would respond differently to environmental variability. Fishes were influenced more by environmental variability that was unique to their historical drainage basins, but macroinvertebrates were associated more strongly with environmental variability that was independent of drainage basins. Thus, the individual drainage basins represented a historical constraint on regional patterns of fish assembly. For both fishes and macroinvertebrates, groupings based on taxonomy and trophic affiliation showed a similar response to environmental variability and there was a high degree of association between taxonomic and trophic correlation matrices. Thus, trophic group structure was highly dependent on the taxonomic make-up of a given assemblage. At the basin-level, fish and macroinvertebrate taxa were associated more strongly with environmental variability than the trophic groups, and these results have implications for basin-level studies that use trophic groupings as a metric to assess ecological patterns. Trophic categories may not be a useful ecological measure for studies at large spatial scales.     

The conservation and status of threatened fishes in southern Africa

The conservation status of 24 threatened freshwater fishes and seven estuarine fishes from southern Africa is discussed against the background of natural and anthropogenic environmental factors. The majority of threatened species are endemic temperate forms with restricted ranges. Major threats include introduced alien fishes and a wide spectrum of environmentally destructive causes. Research on threatened species includes distribution surveys, biological and ecological studies and methods of artificial propagation. Long-term remedies based on ecosystem conservation are also being promoted. The perceptions and attitudes of nature conservation authorities are adjusting to the new challenges offish conservation. The number of threatened fishes in Africa is likely to increase in the face of escalating problems of habitat destruction and degradation.     

Hormone als Schadstoffe?

Environmental estrogens Endocrine disrupters are environmental substances which interfere with the hormone system of organisms and thereby induce adverse effects. They exert their biological activity either by disrupting hormone metabolism or by imitating the biological action of the endogenous hormones. In the aquatic environment, an important group of endocrine disrupters is represented by the estrogen‐active compounds, which mimic the female sex hormone, 17β‐estradiol. Both laboratory experiments and field studies on fishes have demonstrated that already very low concentrations of environmental estrogens are able to induce disturbances in the hormone system and hormone‐regulated processes of fishes.     

Fluoxetine results in misleading conclusions on fish behavior

Fluoxetine is an antidepressant medicine causing relaxation and mood improvement in people, with silencing certain personality traits in some cases. The question arise if such phenomena can be observed in nontarget organisms such as fish. Fluoxetine affects fishes behavior; however, it is not known if the medicine affects its “personality.” This study aimed to evaluate the reaction of the invasive Neogobius fluviatilis and native Gobio gobio individuals to fluoxetine at environmental concentration of 360 ng/L. We prepared three variants of the experiments: (a) behavioral trials with unexposed fishes, (b) behavioral trials with the same fishes after 21 days of fluoxetine exposure, and (c) behavioral trials with the same fishes after 21‐day depuration period, that is, without fluoxetine. The fishes reaction time (RT), that is, difference in time spent on reaching food with and without the necessity of overcoming the obstacle, was analyzed. Additionally, the personality, bold or shy, traits of each fish individual, was assigned. The results indicated that environmental concentrations of the antidepressant influenced RT. The average RT of the fishes cultured with fluoxetine was by 7‐min shorter in comparison with the nonexposed control. Share of individuals exposed to fluoxetine assigned as bold raised to 71.4% in comparison with 46.4% in nonexposed control. This sheds new light on wild fishes behavior caught from freshwater. Environmental concentrations of the antidepressant influenced the time of fishes reaction and share individuals assigned as bold. Moreover, 21‐day recovery lasting might be not enough to get fluoxetine effect on fishes.     

EVOLUTION OF PELVIC REDUCTION IN THREESPINE STICKLEBACK FISH: A TEST OF COMPETING HYPOTHESES

Reimchen hypothesized that pelvic reduction in threespine stickleback is favored by an absence of piscivorous fishes and the resulting increase in predation by insects, but Giles hypothesized that the predation regime is unimportant and that a low dissolved calcium concentration favors evolution of pelvic reduction. Substantial pelvic reduction in threespine stickleback sampled from 179 lakes around Cook Inlet, Alaska is strongly associated both with an absence of predatory fishes and a low calcium concentration. However, the association of pelvic reduction with low calcium concentration appears to be contingent on the absence of predatory fishes. These results emphasize the importance of interactions between seemingly unrelated environmental variables for selection of a single trait. However, these results also conflict with some observations elsewhere and do not rule out the possibility that other environmental factors are important for selection for pelvic reduction in threespine stickleback.     

Plagioscion squamosissimus (Sciaenidae) and Parachromis managuensis (Cichlidae): a threat to native fishes of the Doce River in Minas Gerais, Brazil

The middle section of the lake basin of the Doce River in Minas Gerais State, Brazil is plagued by grave environmental problems, including the introduction of non-native fish, which reduces the biodiversity of this region. This study reports the presence of two newly-detected non-native species in the Doce River Basin. Sampling efforts included gill nets with mesh size of 3 to 12 mm (measured diagonally) and trawling nets, both of which were used in independent field campaigns in 2002 and 2011. The two new invasive Perciform fishes, Plagioscion squamosissimus (Heckel 1840) and Parachromis managuensis (Günther 1867) were collected in Caratinga and Rio Doce municipalities. These records and other reports on non-native fishes suggest favorable environmental conditions for the establishment of invasive species in this drainage. These invasive species have behavior and diet observed in other wide distribution exotic fish of Rio Doce Basin representing a threat to the 77 native fishes of this region, 37 of which are endangered.     

基于Maxent的两种入侵性鱼类(麦穗鱼和鲫)的全球适生区预测

受引种、贸易等人类活动的影响, 麦穗鱼(Pseudorasbora parva)和鲫(Carassius auratus)在全球范围内已经广泛分布并造成巨大的生态危害。根据野外采样和文献记录, 本文系统整理了麦穗鱼和鲫在世界各地的分布情况, 以高达2.5弧分分辨率的环境数据底图, 利用Maxent模型预测了麦穗鱼和鲫在全球的适生区, 以期为防控麦穗鱼和鲫的入侵提供早期预警。结果表明麦穗鱼和鲫在全球范围的分布区非常广泛, 除南极洲外的各个大洲均有其适生区, 因此这两种鱼还有继续扩散的潜力, 并可能在美国、巴西和阿根廷等国家出现由生物入侵导致的生态学问题。麦穗鱼的适生区主要集中在15º–55º N之间, 欧洲是麦穗鱼入侵的重灾区, 尤其是法国、荷兰周边的西欧国家和匈牙利、塞尔维亚周边的东欧国家; 而美国中部的密西西比河流域、东部及南部沿海, 以及西雅图至加拿大的温哥华之间是麦穗鱼潜在入侵风险性极高的区域。鲫自然分布于欧洲至东亚的广大地区, 目前已经在澳大利亚、加拿大、美国、马达加斯加、印度和越南等国家有分布, 未来还可能进一步扩散至大洋洲的新西兰和新喀里多尼亚, 北美洲的墨西哥至南美洲的阿根廷, 以及非洲的塞内加尔、几内亚和南非等国家; 尤其是南美洲的阿根廷和巴西, 非洲西部的几内亚、喀麦隆等国家将是鲫入侵风险极高的区域。     

Modeling the establishment of invasive species: habitat and biotic interactions influencing the establishment of <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis>

Bythotrephes longimanus is an invasive pelagic crustacean, which first arrived in North America from Europe in early 1980s and can now be found throughout the Great Lakes and in many inland lakes and waterways. Determining the suitability of lakes to Bythotrephes establishment is an important step in quantifying its potential habitat range and environmental risk. Lake environmental conditions, planktivorous fishes, sport fishes and Bythotrephes occurrence data from 179 south-central Ontario lakes were used in this study to model lake characteristics suitable for its establishment. The performance of principal component analysis and different predictive models was used to determine the habitats that are suitable for the survival of Bythotrephes and the factors that may regulate its spread. Four modeling approaches were employed: linear discriminant analysis; multiple logistic regression; random forests; and, artificial neural networks. Ensemble prediction based on the four modeling approaches was also used as an indicator for predicting Bythotrephes occurrence. Bythotrephes appears to establish more readily in larger, deeper lakes with lower elevation, that have more sport fishes. Bythotrephes occurrence can be best predicted by artificial neural networks when including the measures of fish data, in addition to lake environmental data. Lake elevation, surface area and sport fish occurrence were ranked as the most important predictors of Bythotrephes invasion. The inclusion of biotic variables (occurrence or diversity of sport or planktivorous fishes) enhanced cross-validated models relative to analyses based on environmental data alone.     

Transgenic fishes: modern state of the problem

Transgenic fishes are the object for the specialists in different research fields. It seems very promising to cultivate the rapidly growing objects resistant to diseases and negative environmental factors as well as the indicators of pollutions, models for oncological investigations etc. Some methodical, piscicultural, medical, ecological and others aspects of investigations of transgenic fishes as well as the legislative basis of Ukraine on this problem are discussed in the article.     

Conservation categories of siluroid fishes in North-East Sundarbans,India

In stock fishery of North-East Sundarbans, siluroid fishes hold a remarkable position owing to the culture potentiality of many of them. Scales in fishes play significant role in protection and resistance against environmental stresses and the lack of scalation in case of siluroid fishes is supposed to be one of the reasons for their decline in eco-degraded aquatic habitats. 11 species of fishes belonging to 9 genera, 8 families under the order Siluriformes have been recorded from different water bodies of North-East Sundarbans, India. Fish Magnitude Value (FMV) of those catfishes were recorded especially by information harvested from local fishermen community and stakeholders as well as from market survey on fish landing. The extensive damage to the population of catfishes in the area has placed the fishes under threat categories. Following the IUCN guidelines and also through Participatory Rural Appraisal (PRA) methods, an attempt has been made to assess the status of such fishes. Trend analysis, Fish Magnitude Value (FMV) and Rank Based Quotient (RBQ) revealed 1 catfish as Endangered, 5 as Vulnerable and 5 as Near Threatened species. The situation warrants immediate attention of ecologists, administrators, managers and entrepreneurs to propose remedial measures for revival of the fishes. The study also delineates distribution, present status and conservation measures for revival of the fishes in North-East Sundarbans wet-land environment of West Bengal, India.     

Effects of spatial distance,physical barriers,and habitat on a stream fish metacommunity

Hydrobiologia - Metacommunity structure depends on environmental and spatial factors. Stream fishes are constrained to disperse within dendritic networks and waterfalls and other barriers add...     

云南李仙江流域水电开发中的鱼类资源保护

水电工程的开发对江河道鱼类资源产生了诸多不利影响,在保护和恢复日益增多的濒危鱼类种群的实践中,孕育和逐渐形成了保护水产学.该文对李仙江流域水电开发与流域内珍稀鱼类异鱲、越鳠、软鳍新光唇鱼和暗色唇鱼人工增殖保护实践中的实施效果和存在问题进行了分析.李仙江水电开发与鱼类增殖保护为河流鱼类的增殖保护提供了一个参考模式.但是增殖放流不是简单地一项任务,要保证整个过程得以顺利进行,需要提前进行繁育规划,提前委托,监测和增殖技术研究先行,资源保护与当地经济发展相结合.     

Complete and rapid reversal of the body color pattern in juveniles of the convict surgeonfish Acanthurus triostegus at Moorea Island (French Polynesia)

Coral Reefs - Color polymorphism is widespread in animals and can be associated with temporary adjustments to environmental variables (phenotypic plasticity). In teleost fishes, one of the most...     

Climate-driven changes in abundance and distribution of larvae of oceanic fishes in the southern California region

We examined climatic effects on the geographic distribution and abundance of 34 dominant oceanic fishes in the southern California region using larval fish data collected from the 50‐year long California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys. The oceanic species responses to environmental changes in their geographic distributions were not very pronounced, perhaps because they lived in the deep layer where temperature change was relatively small or because the environmental variation of the CalCOFI region is not strong enough (with an average temperature gradient of the upper 100 m around 91 km °C^?1). Among the 34 taxa, 16 showed a significant distributional shift (median latitude or boundaries) in relation to environmental variables, and eight species significantly shifted their geographic distribution from the 1951–1976 cold period to the 1977–1998 warm period. Interestingly, the vertically migrating taxa more often showed a significant response to environmental variables than the nonmigrating mesopelagic taxa, reflecting the more significant increase in heat content of the upper ocean (<200 m), compared with the deeper zone (300–500 m) where the mesopelagic fishes typically remain. Climate change has significant effects on the abundances of oceanic fishes. Twenty‐four taxa exhibited a significant change in abundance in relation to environmental variables, and 25 taxa, including both warm and cold‐water taxa, showed a significant increase in abundance from the cold to warm period. Analysis of physical data indicated that the surface‐layer (20–200 m) warmed significantly and the isotherms approached shoreward from the cold to the warm period. We further show that the spatial distribution of coastal–neritic fish retreated shoreward and oceanic fish extended shoreward from the cold to warm period. Our results suggest intensified stratification of the southern California region during the warm period may create a suitable habitat for the oceanic species. Moreover, such an unfavorable condition (e.g. changes in food habitat) for coastal–neritic species might result in competitive release for the oceanic fishes to flourish.     

Effects of a hurricane on fish parasites

Hurricanes, also called tropical cyclones, can dramatically affect life along their paths, including a temporary losing or reducing in number of parasites of fishes. Hurricane Katrina in the northern Gulf of Mexico in August 2005 provides many examples involving humans and both terrestrial and aquatic animals and plants. Fishes do not provide much of an indicator of hurricane activity because most species quickly repopulate the area. Fish parasites, however, serve as a good indicator of the overall biodiversity and environmental health. The reasons for the noted absence or reduction of parasites in fishes are many, and specific parasites provide indications of different processes. The powerful winds can produce perturbations of the sediments harboring intermediate hosts. The surge of high salinity water can kill or otherwise affect low salinity intermediate hosts or free-living stages. Both can introduce toxicants into the habitat and also interfere with the timing and processes involved with host-parasite interrelationships. All these have had a major influence on fish parasite populations of fishes in coastal Mississippi, especially for those parasites incorporating intermediate hosts in their life cycles. The length of time for a parasite to become re-established can vary considerably, depending on its life cycle as well as the associated biota, habitat, and environmental conditions, and each parasite provides a special indicator of environmental health.