Native Fish Fauna Research Articles

Effects of dam construction and fish invasion on the species, functional and phylogenetic diversity of fish assemblages in the Yellow River Basin

An understanding of the consequences of human-mediated disturbances from multi-facet diversity (i.e. species, functional and phylogenetic) perspectives is of great significance in biodiversity assessment and conservation planning. Most previous studies have concentrated on anthropogenic effects on species diversity in the Yellow River Basin (YRB) in China, but information on anthropogenic effects on phylogenetic and functional facets is still pending. Here, we identified the temporal changes in species, functional, and phylogenetic alpha diversity of fish assemblages in 18 reaches (i.e. 15 mainstream reaches and 3 tributaries) of the YRB under the background of long-term cascade hydropower construction and widespread introduction of non-native fish species. The results showed that native fishes experienced a sharp decline through time, with an average of 25.6 (extirpation rate 46.7%) native species extirpated per sub-region, and 89 of 182 (48.9%) native species extirpated across the whole basin during the period considered. However, the number of non-native fish species substantially increased, with an average increase of 8.6 species (invasion rate 26.9%) per sub-region. Furthermore, the percentage of non-native species showed a significant unimodal relationship with average altitude, with highest invasion rates (ca. 70%) in upstream reaches. The extirpation rate was negatively related to altitude, increasing from upstream to downstream reaches. Interestingly, the functional diversity indices (FEve, FDiv, FDis, RaoQ) and phylogenetic diversity indices (Δ+ and Λ+) of the entire fish fauna significantly increased through time, whereas these indices based on native fish fauna only did not change. Such increases in functional and phylogenetic diversities were mainly triggered by introductions of non-native species, which were functionally distinct and phylogenetically distant from native species, and extirpation of congeneric endemic species. In general, the present study revealed anthropogenic impacts on the multi-faceted diversity of fish assemblages in a large river and highlighted the negative effects of cascaded hydropower developments and non-native fish invasions on native fish. Moreover, evaluating the responses of multi-faceted diversity to anthropogenic disturbances is a suitable means to understand assemblage reorganization and to assess how such impacts lead to the decline of biodiversity. The complementary information derived from using the multi-faceted diversity approach indicate functional and phylogenetic diversity measures could be implemented in biodiversity planning in the sediment-laden and ecologically important Yellow River Basin.

First Scientific Record for Sivas Aquatic Systems Related to Alien Fish Species:Small-scaled Pacu; Piaractus mesopotamicus (Teleostei:Characidae)

In July 2017, three specimens of an alien fish species were caught by the amateur fishermen in Kızılırmak River at Sivas city center. One of the fish specimens was taken from the fishermen for ichthyologic examination. The morphological, metric (23 features) and meristic characters (13 features) of this specimen were determined. The alien fish is with ovoid shape and flattened laterally. Mouth is in a sub-ventral position. The tooth row is double. Teeth formula are 3,2 / 2,3 (at first row on maxil) and 2 / 2 (at second row on maxil), 3,3 / 3,4 (at first row on mandibul), 1,1 (at second row on mandibul). The number of rakers on the first gill arch is 33. The scale numbers in line lateral are 107 (on right side) and 103 (on left side). The number of branched rays of dorsal, anal, pectoral, and ventral fins are 14, 24, 14, and 7; respectively. As a result of the evaluation of morphological, metric and meristic characters, it was decided that the alien fish caught from Kızılırmak was Piaractus mesopotamicus (Holmberg, 1887) belonging to the Characidae family. This species is also called as the small-scaled pacu. P. mesopotamicus is not among to native fish fauna of Kızılırmak. It is a fish species which originated from South America and is a tropical freshwater fish. These alien fish specimens which were caught by the amateur fishermen, probably translocated from a hobbyist aquarium to this aquatic system. Both directly and indirectly, invasive fishes affect a wide range of native organisms from zooplankton to mammals across multiple levels of biological organizations ranging from the genome to the ecosystem. This study is the first scientific record for Sivas aquatic systems related to alien fish species.

Spatial assemblage and interference competition of introduced Brown Trout (Salmo trutta) in a Himalayan river network: Implications for native fish conservation

AbstractOften regarded as a potential threat to the native fish fauna worldwide, the Brown Trout (Salmo trutta), has successfully established its population in the majority of the Himalayan rivers post its introduction dating back to the eighteenth century. Over the years, the species has gained infamy as a sport fish and is considered a profitable source of income to the locals ensuing a heightened propagule pressure due to lack of appropriate management actions. No comprehensive study has been conducted to date in order to understand the mechanism by which the Brown Trout poses threat to the native fish populations. Through the present study, we could assess its competition with the native Snow Trout (Schizothorax richardsonii) to understand the spatial assemblage of both the species across space in Tirthan, a pristine high-altitude river of the western Himalaya. River Tirthan is one of the major tributaries of River Beas traversing for most of its stretch within the protected boundaries of the Great Himalayan National Park Conservation Area. A total of 108 sampling points were chosen from confluence to origin of rivers/streams, ranging from 989 to 3677msl. A total of 28 explanatory variables were recorded at each point. Overall, the Brown Trout adults were found to be greater in relative abundance (66.1%) than the Snow Trout adults (33.9%). The fingerlings of Snow Trout on the other hand, were distinctively high in relative abundance (61.9%) than those of the invasive Brown Trout (38.1%). Non-native trout showed higher abundance in the higher stream orders i.e. in the main streams while natives mostly restricted themselves to the lower order streams. Redundancy analysis (RDA) for species and environmental covariates resulted in 40.75% of constrained variance with higher eigen values for Redundancy analysis1 and Redundancy analysis2. Ward’s minimum variance clustering of Hellinger transformed data revealed sites agglomerating into six reasonable distinct subgroups with respect to species abundances. Immature individuals of non-native and native trout used similar habitat conditions, but they differed in using habitats at adult stage. Our results show a competitive dominance of Brown Trout in terms of higher abundance and maximum space utilization that highlight an urgent action for preventing its introductions to new areas. We recommend a national policy of ‘The Indian Invasive Species Act’ and management level interventions to control overstocking in the areas of established population.

Variation of stomach content and isotopic niche of puye Galaxias maculatus (Jenyns, 1842) in large river systems of southern Chile

Abstract Understanding of trophic structure and flow of energy within river systems is essential for informed management of these ecosystems and conservation of native fish fauna and fisheries resources. Food resources used by riverine fish depend on productivity within the main stem and adjacent floodplains, terrestrial inputs, and longitudinal and lateral hydrologic connectivity. Trophic ecology of puye (Galaxias maculatus Jenyns, 1842) in Chilean river systems remains poorly understood and studies that combine short‐term (stomach content) and long‐term (stable isotope analyses) analyses have not been performed to date. In this study, we assessed spatial variability in diet of puye based on both stomach content and analyses of stable isotopes of carbon and nitrogen in 10 river systems of southern Chile (including main stem, headwater lakes, and estuaries). Fish in the main stems of more northern rivers, with predictable flow regimes, were characterised by the most diverse diets, broad niche space, and high proportion of terrestrial prey items and zooplankton in diet. Fish collected in lakes were characterised by narrow isotopic niche space and diet dominated by zooplankton. Diet of G. maculatus in Chilean river systems is associated with characteristics of riverine habitats within each river system (lentic, lotic, and estuarine) and hydrologic connectivity among them. Indeed, connectivity with floodplain habitats and direct supply from headwater lakes appeared to be primary drivers of fish diet in systems where these are present. These supplies maintain fish populations of good condition and allow freshwater recruitment. Therefore, maintaining seasonal flow dynamics and connectivity is essential to preserve the natural function of these river systems and conserve native fish populations.

Historical distribution of freshwater fishes and the reference conditions concept in a large Mediterranean basin

Abstract The European Water Framework Directive 2000/60/EC (WFD) defines the ecological status of aquatic systems as the deviation between their present biological state and that which would be expected in the absence of any major human disturbance, referred to by the WFD as the ‘reference condition’ (RC). It assumes that their biotic composition should remain balanced and constant over time. This study tested both assumptions against an analysis of the historical distribution of the fish fauna in a large and highly disturbed Mediterranean basin. If fish communities change substantially over time, it will mean that the validity of the RC concept comes into question. Using presence/absence data for historical native fish fauna from the Guadalquivir Basin, distribution changes among sub‐basins were quantified by mapping between the nineteenth century and today. The range of two native species (Anguilla anguilla and Salmo trutta) has changed significantly. In addition, the diadromous species assemblage has almost become locally extinct, with the exception of the eel. Finally, most Guadalquivir sub‐basins (94.7%) have suffered major changes in the composition of their fish communities, either by losing native species or by adding new non‐native species. These results render the definition of any RC unlikely. In Mediterranean areas, the WFD objective of ‘good ecological status’ recovery based on the integrity of aquatic communities is a theoretical rather than a real goal. Nonetheless, the WFD provides an ecological guiding principle that can also be transferred to the conservation of freshwater ecosystems. As an alternative to the RC concept in Mediterranean lotic ecosystems, specific multimetric indices can be used, based on expert criteria, the metrics of which can also relate to the conservation value of water bodies, and not only to their ecological status.

Diversity of native larvivorous fish fauna during pre- and post-tsunami in Car Nicobar, Andaman & Nicobar Islands, India.

Malaria is a serious public health problem in Car Nicobar Island, Andaman & Nicobar Islands, India. Using larvivorous fishes has proved to be the cheapest method for vector management approach, with long suppression of mosquito population. This study aims to scale-up the diversity of larvivorous fishes and their potential larvivoracity to evolve an appropriate biological intervention strategy against the immature stages of malaria vectors. During 2003 (pre-tsunami) and 2014-2016 (post-tsunami), an ecological descriptive survey was carried out in the water bodies around Car Nicobar Island. Fishes were captured using fishing nets and cast nets; and placed in plastic jars and preserved in formalin solution. Fishes were identified and classified according to the available keys. Their abundance and data on the current conservation status was recorded and analyzed. Their potential larvivoracity was graded according to their feeding intensity. Pre-tsunami, a total of 27 larvivorous fish species belonging to 11 orders, 23 families and 23 genera were identified. Order Perciformes and the family Cyprinidae were the most ascendant group constituting 51.9 and 11.1%, respectively. While, 80.8% of species were preferred to inhabit the freshwater region, only 37% of species were surface feeders (SF). According to the conservation, assessment and management plan (CAMP, 1998), 44.4% species were at lower risk least concern (LRlc), while 55.6% species were at least concerned (LC) as per the IUCN, 2017 categorization. However, after the tsunami, 17 fish species had gone extinct and 10 fish species were found to remain alive in the local water bodies. Post-tsunami, the larvivoracity analysis indicated that Ophiocara aporos, Ophiocara procephala, Valamugil seheli, Channa punctata, Kuhlia rupestris, Khulia mugil, and Terapon jarbua possess high-level larvivorous potentiality in nature and are recommended for vector control in the study area. These fish species were facing several anthropogenic threats, such as human interference, loss of habitat, trade, overexploitation, and fishing. Therefore, it is important to protect the water bodies from external impact and implement the conservation strategies. Further, periodic fish fauna surveys, identification of breeding sites, scale-up of the larvivorous potentiality at the field level, creating public awareness through health education on establishment of larvivorous fish ponds and planning for mass rearing of the native fish species should be adopted as part of vector management approach in the endemic malarious region of Car Nicobar Island.

Seasonal feeding habits and ontogenetic diet shift of black bullhead (Ameiurus melas) in Lake Sava (Serbia)

The black bullhead is an invasive species that forms dense populations and has a negative impact on the native ichthyofauna. Recent studies indicate that it is one of the most dominant invasive fish species in Serbian waters. Feeding habits based on stomach contents of individuals caught in Lake Sava were analyzed as a first step towards evaluating its possible negative impact on the native fish fauna of the lake. The following indices for diet analysis were applied: vacuity index, frequency of occurrence, numerical abundance and prominence value. Trophic niche breadth and seasonal trophic diversity were calculated using the Shannon?s index. The diet spectrum comprised 16 different prey categories from five groups: Mollusca, Crustacea, Insecta, Teleostei and plants. Fish were the main prey in all seasons, followed by aquatic invertebrates. Plant material and terrestrial insects were used as food in relatively small quantities. Predation on fish eggs was also detected. Our research confirmed that this species is an opportunistic generalist. An ontogenetic diet shift was also detected. The lowest value of trophic diversity was found in age 1+ individuals (H=1.39), while the highest was found in age 3+ individuals (H=2.00). The widest niche breadth was recorded in spring 2011 (H=2.12).

The spread of exotic fish species in Italian rivers and their effect on native fish fauna since 1990

ABSTRACT The introduction of exotic fish species into Italian river systems presents an additional threat to freshwater native fish species, a wildlife group already under conservation pressure from myriad other anthropogenic factors. Few large-scale and long-term monitoring programmes exist that adequately describe the impact of exotic fish species on native fish. To fill this gap, we analysed the bulk of available data (1985–2014) on fish collected at a national level within the BioFresh Project with the aim of investigating the effects of human-introduced exotic fish species on native species. The results showed that both the Continental and Mediterranean biogeographic regions are home to fish communities which, in conservation terms, are a cause for concern, while Alpine Regions are less so. Generally, the richness of exotic species is still growing in Italy, with about 50% of them having a positive trend while native species’ trends are in the opposite direction – that is, the spread of many exotic species is positively correlated with the decline in many co-occurring native species. Key policy insights Worrying increase in the richness of exotic species between the 1985 and the 2014. A large segment of the current exotic fish contingent is self-sustaining. Common bream, Black bullhead, Goldfish, Largemouth bass, Rainbow trout, Roach, Pike perch and European catfish negatively affect the presence probability of at least 50% of co-occurring native species over time. The restoration of habitat characteristics and native fish assemblages as well as more rigorous controls during population reinforcement for recreational fishing are needed to prevent or counteract the further spread of exotic fishes.

Ecological impacts of an invasive top predator fish across South America

Peacock bass Cichla ocellaris is a piscivorous cichlid native from the Amazon and Orinoco river basins, which has been broadly introduced into tropical areas worldwide, leading to several adverse local effects. However, predictors of its invasibility and assessments of its ecological impacts over large spatial scales are still lacking. The importance of different environmental factors in explaining the relative abundance of peacock bass in 62 sites across South America (30 native and 32 invaded systems) was investigated. The impacts of peacock bass on fish assemblages were appraised, using years since introduction as a proxy of its cumulative impacts and modern statistical techniques, such as random forests, and negative binomial regression models. Random forests highlighted maximum depth, introduced status, and ecosystem type as the best predictors of the peacock bass relative abundance, which ranged 0.01–26.0%, increased with maximum depth, was highest in invaded reservoirs but decreased with depth in native riverine populations. Other factors such as climate or limnological features were less important in explaining C. ocellaris abundance, which did not vary markedly with years since introduction. Introduction year was not related to latitude but varied among hydrographic regions, indicating invasion pathways not linked to geographical proximity. Variation partitioning of different fish assemblage metrics showed that hydrographic region followed by limnological and reservoir features accounted for most explained variation, indicating a strong historical and local influence. Introduction time accounted for 5–8% of variation in species composition and diversity, independently of limnological features. Our results suggest that the ecological effects of introduced C. ocellaris on native fish fauna are likely but small compared to large geographical and environmental gradients. Although experiments and before-after designs are probably more sensitive in detecting the ecological impacts of invasive species, large-scale compilations of available data are more feasible and can provide invaluable information, especially for large-sized invaders that are often illegally introduced.

Interpopulation Variability in Dietary Traits of Invasive Bleak Alburnus alburnus (Actinopterygii, Cyprinidae) Across the Iberian Peninsula

The bleak Alburnus alburnus is native to most of Europe. This cyprinid fish is a successful invader in the Iberian Peninsula. No studies exist on its foraging strategies on a large scale for this ecoregion. The aim of the present study was to compare dietary traits of invasive bleak among the main Iberian rivers and a ‘reference’ native bleak population from France. Bleak were sampled during May–June 2019 from the Iberian Rivers Ebro, Tagus, Guadiana, Segura and Guadalquivir and the River Saône (France). Diptera larvae and zooplankton were common food categories in the River Saône. Insect nymphs were more important in the River Ebro. The intake of plant material was higher in the River Tagus. Flying insects were more consumed in the River Guadiana. Nektonic insects were important in the River Guadalquivir. Detritus was a frequent food category for all populations, in terms of occurrence and mass. Dietary parameters followed a unimodal response in relation to the latitudinal gradient, with the maximum values for the Tagus and Guadiana populations. Overall, results suggest that this wide interpopulation variability will contribute to the species’ successful establishment throughout Mediterranean Europe, which poses a serious risk to its highly valuable native fish fauna.

Multiscale effects on freshwater fish distribution in a highly disturbed Mediterranean-type basin: community-level and species-level responses

Fish–habitat relationships are a key element for conservation and management strategies, especially in highly disturbed areas where fish communities are subjected to many human pressures. In this regard, multiscale studies help to improve the knowledge of the spatial components and identify local (e.g. water width) and regional (e.g. elevation) key variables in species distribution. We examined local and regional requirements to study freshwater fish assemblage and occurrence at 216 locations in a highly disturbed basin, the Guadalquivir River Basin (S Spain). Fifteen environmental variables were considered at local scale and twenty at regional level. A total of eighteen species were captured during field sampling. The global prevalence for introduced species was 25%, which can be considered a high value. The most extended introduced species were eastern mosquitofish (Gambusia holbrooki) and pumpkinseed (Lepomis gibbosus), with around 10% prevalence. Regional and local scales showed different relevance according to the level-study approach (community or species). At the community level, the local, regional and shared components revealed similar influence on the fish assemblage, while at individual species level the local component was the main factor to explain most of fish occurrences. Moreover, variables’ interaction was scarcely selected and almost no introduced species distribution was affected by the interaction of any variable. Our results highlight the poor conservation status of the native fish fauna of the Guadalquivir River Basin as well as the importance of analyzing fish–habitat relationships at different scales and approach. These results provide useful information to assess and design conservation strategies in Mediterranean-type basin.

Зміни основних біологічних показників та живлення окуня звичайного (Perca fluviatilis linnaeus, 1758) в умовах спеціального товарного рибного господарства

Зміни основних біологічних показників та живлення окуня звичайного (Perca fluviatilis linnaeus, 1758) в умовах спеціального товарного рибного господарства

Сучасні знахідки головня європейського Squalius cephalus (Linnaeus, 1758), карася звичайного Carassius carassius (Linnaeus, 1758) та хроміста плітки звичайної Rutilus rutilus (Linnaeus, 1758) в пониззі Дніпра

The article presents the materials on the detection of two very rare species of fish: the European chub Squalius cephalus (Linnaeus, 1758) and the crucian carp (the golden carp) Carassius carassius (Linnaeus, 1758) in the waters of the lower estuary of the Dnipro river in recent years. C. carassius is listed in the Red Book of Ukraine (2009). The article also describes the first encounter in these waters with the khromist of the common roach Rutilus rutilus (Linnaeus, 1758), which has a yellow-golden colour of the whole body. The basin of the Lower Dnipro includes the Kakhovske reservoir, the Ingulets river, several small tributaries and the lower unregulated part of the Dnipro riverbed along with the straits. Over the entire period of observation, up to 72 species of the round-mouthed fish and the fish from 59 genera and 19 families have been spotted in the fish fauna of the Lower Dnipro basin. According to some data, it is stated that within the migratory and freshwater species of the round-mouthed fish and the fish of the Lower Dnipro's ichthyocenosis only 21 out of 47 species of the native fish fauna have survived here. In general, the current fish fauna of the unregulated part of the Lower Dnipro amounts to 51 species of fish. The habitat of 28 species of fish in the lower estuary of the Dnipro river was confirmed in 2019.

Impact of the non-native locariid fish Pterygoplichthys pardalis in native fish community on a seasonal tropical floodplain in Mexico

The present study reports the seasonal dynamics of the fish community structure in the presence of a non-native fish (Pterygoplichthys pardalis) in tropical waterbodies of southern Mexico. The studied floodplain existed in both connected pools and disconnected pools “to the Palizada river”. Local fish fauna showed consistent assemblages across seasons, but among the 17 local fish species recorded, the non-native species P. pardalis showed the highest percentage of contribution to the fish community (ca. 20%). Conversely, the frequency of occurrence and density of the non-native species showed variation in relation to the type of waterbody and seasonality; its density was approximately four times higher in disconnected pools than in connected pools in the rainy season and its predominant size class in both pool types was 21-30 cm in standard length. Interestingly, the diversity of the native species was negatively related to the density of the non-native species, indicating that the presence of P. pardalis can be a factor involved in the decline of native fish diversity in these local communities. Currently, the possible impacts of the presence of P. pardalis on local fish diversity at the regional scale are unknown, but our results suggest that hydrological dynamics regulate the establishment of the non-native species in this region. However, future studies are needed to provide insights into the actual scenario of P. pardalis distribution in Yucatan Peninsula and the possible impacts on the native fish fauna in southern Mexico.

Pınarbaşı Deresi (Burdur, Türkiye)’nde Yabancı Balık Türü Hemichromis letourneuxi (Cichlidae)’nin İlk Kaydı

Freshwater habitats of Anatolia have been subject to the impacts of many invasive alien fish species. African jewelfish, Hemichromis letourneuxi Sauvage, 1880 is an ornamental freshwater fish which is widely distributed throughout northern half of Africa. In this study, H. letourneuxi was collected from Pınarbaşı Creek, Burdur Province, Turkey. Introduced specimens of H. letourneuxi in this area may be the result of escapes from fish farms, intentional releases from nearby ornamental fish farms or aquariums. This study discusses the potential ecological impacts of H. letourneuxi upon native fish fauna and ecosystem in the area.

An invasive species, Carassius gibelio, alters the native fish community through trophic niche competition

Carbon and nitrogen stable isotope analyses were used to determine isotopic niche width of the invasive fish species Carassius gibelio to help assess the niche overlap and potential impact of this species on the native fish fauna in the Karamenderes River, northwest Turkey. C. gibelio had the highest niche area of the coexisting species. The greatest overlap of isotopic niche was between C. gibelio and Mugil cephalus in the river mouth. The freshwater species displayed similar patterns when taking into consideration their relative abundance and isotopic overlap. While C. gibelio is likely to outcompete some species at some localities, the species was found co-occurring with others by maximum tolerable overlap degree and apparently utilised vacant niche space at some stations. Overall our results indicate that C. gibelio has extensive niche overlap with the native fish species making it a strong competitor, and because of its high abundance and high niche width this invasive species represents a serious threat to the native fish fauna, particularly in the river mouth.

River science and management issues in Chile: Hydropower development and native fish communities

AbstractThe magnitude of hydropower developments in emerging regions threatens the sustainability of their riverine landscapes. Fragmentation of river networks by multiple barriers and the imposition of new hydrological regimes influences the ability of these river ecosystems to absorb and adapt to these developments and other stressors. Direct transfer of paradigms built from a restricted geographical base to a global context is fraught with issues because of regional differences in eco‐hydro‐geomorphology, biological communities, and nonlinear interactions between the two. In this manuscript, some impacts of hydropower development on Chilean riverine ecosystems are presented. To understand the context of hydropower, we provide the political context of energy development in Chile. Interactions between hydropower generation and Chilean river ecosystems with special reference to native Chilean fish fauna are outlined. Three case studies are presented that considers: (a) habitat alteration downstream of the Rucúe Dam, (b) the effects of daily hydropeaking in the Biobío River, and (c) mitigation strategies to reduce habitat alteration upstream of the San Pedro Dam. These case studies illustrate the expanding scientific knowledge on Chilean riverine landscapes. Finally, new measures to reduce ecosystem impacts of hydropower development on native Chilean fish communities are outlined. Although specific scientific information is available, developing regional ecohydrological models and improving knowledge of ecosystem and sustainability science is required. The scientific approach on which solutions are sought to address present and future river ecosystem problems in Chile are inherently interdisciplinary nature.

Transmission of parasites from introduced tilapias: a new threat to endemic Malagasy ichthyofauna

Invasive species are a major threat to biodiversity. In Madagascar, one quarter of freshwater fish fauna consist of introduced species. The introduction of non-native species affects native biota by means of direct interactions but also through indirect interactions including those mediated by parasites, as parasites are usually co-introduced with their hosts. Almost nothing is known about the parasites co-introduced with their fish hosts into Madagascar and their potential impact on native endemic fish fauna. We studied the metazoan parasites of native and introduced cichlid fishes (and some non-cichlids) in the northern part of Madagascar. Using parasite data we evaluated the effect of fish introduced from mainland Africa on native Malagasy cichlid fauna. We documented the co-introduction into Madagascar of parasite species from mainland Africa and also probably from Eurasia. Malagasy cichlids and some other species living in sympatry with non-native cichlids acted as competent hosts for generalist parasites and also for host-specific parasites of African mainland cichlids. However, African mainland cichlids were not susceptible to infection by parasites specific to Malagasy cichlids. The different compositions of parasite communities and infection parameters in endemic and non-native cichlids in the regions investigated may be potentially explained by the different sources and timings of fish introductions. In addition, native endemic parasite fauna even seem to be outcompeted by introduced parasites, which cross the barriers of host specificity. The transmission of non-native parasites associated with the introduction of non-native freshwater fishes may represent a serious risk to endemic freshwater fish and parasite fauna in Madagascar.

Rapid expansion and biodiversity impacts of the red devil cichlid (Amphilophus labiatus, Günther 1864) in Lake Sentani, Papua, Indonesia

Ohee HL, Sujarta P, Br Surbakti S, Barclay H. 2018. Rapid expansion and biodiversity impacts of the red devil cichlid (Amphilophus labiatus, Günther 1864) in Lake Sentani, Papua, Indonesia. Biodiversitas 19: 2096-2103. The red devil cichlid (Amphilophus labiatus, Günther 1864) is one of ten exotic fish species inhabiting Lake Sentani. It is believed to be one of the most important threats to the native fish of Lake Sentani. This study aimed to document the distribution of red devil cichlids and the impacts of this species on native fish fauna. Fish were sampled in six locations in Lake Sentani using gill nets during February and March 2018. Fish species and abundance were recorded and used to calculate the relative abundance, dominance, species evenness, Shannon Wiener Index (H’) and the correlation between introduced and native fish species. A total of 836 fish belonging to 12 species were recorded across Lake Sentani. Mean fish diversity (H’=0.57) and evenness (E= 0.25) were low. The red devil cichlid is the most abundant fish recorded during our surveys (87.2% of total fish collected) and is now the most dominant fish in the lake (C=0.76). Moreover, it has colonized all areas sampled within the lake because of its ability to colonize new habitat and to successfully exploit a large diversity of trophic niches. However, Amphilophus labiatus was not found to be significantly correlated to native fish between different sites in Lake Sentani. The existence of endemic and native fish in Lake Sentani is now seriously threatened by the presence of the red devil cichlid throughout this lake.

The role of introduced species in the decline of a highly endemic fish fauna in Central Mexico

Abstract Central Mexico, home to a unique and imperilled freshwater fish fauna, high in endemism, is also a very densely populated region with considerable human activity. Aquatic systems in the region have been heavily disturbed by human activity in the form of species introductions, pollution, and habitat modification, which has resulted in the extirpation of native fishes and the alteration of the native fish fauna. An analysis of the roles of these factors in the decline of the fish fauna and an overview of its conservation status are presented. Both current and historic fish assemblages were characterized and water physicochemical parameters recorded at 62 localities within the region. Water quality, hydrological modification, and the presence of introduced species were used as variables in a linear model to explore their respective influence on the integrity of local fish assemblages. Analyses suggest that both water quality and the presence of introduced species have had adverse impacts of similar magnitude on the conservation status of native species, whereas hydrological modification has had no statistically significant effect. This survey revealed the profound alteration of the fish fauna. Only 40% of the expected native populations were found, and only 30% of the sampled assemblages were free of introduced species. As little as 17% of the sampled assemblages were taxonomically intact. The mean species richness per locality was only half of that indicated by historical records. The conservation value of springs, where many threatened microendemics can still be found, is highlighted, and we argue that their small size and isolation make them key targets for conservation efforts.