Fisheries and biotic homogenization of freshwater fish in the Brazilian semiarid region

Hydrobiologia - The construction of dams in Brazilian semiarid regions has been a common governmental practice since the early 1900s, initially with the aim of providing water to meet the needs of...     

Effects of the freshwater aquarium trade on wild fish populations in differentially‐fished areas of the Peruvian Amazon

Base‐line data were collected to examine the possible effects of the aquarium trade on Amazon fish populations in differentially‐fished locations in the Departmento of Loreto, Peru. Fish abundance, species diversity (richness) and biomass were quantified at three locations with differential fishing pressure, including the Rio Nanay (high pressure), Rio Apayacu and Rio Arambassa (medium) and Rio Yanayacu –Pacaya‐Samiria National Reserve (low). Seining results indicated that the location with the highest fishing pressure had reduced fish abundance, species diversity and biomass compared to the other locations. A similar trend was seen using minnow traps. There was no significant difference in abundance, diversity and biomass between the medium and low fishing pressure locations. Habitat differences (pH and conductivity) among the three locations accounted for <13% of the observed variation, and thus it seemed possible that some of the decline in the Rio Nanay location could be tentatively attributed to increased fishing pressure. Although effects of pollution and habitat alteration could not be ruled out, this is one of the first studies to provide quantitative data on the effect of the freshwater aquarium trade on wild fish populations. While results suggest success in the protection of fishes for the aquarium trade in Pacaya‐Samiria National Reserve, it also may be sustainable to establish limited levels of fishing, as was found in the medium fishing pressure locations, in order to promote economic opportunities and incentives for habitat preservation for indigenous communities.     

Enemy at the gates: introduction potential of non-indigenous freshwater crayfish in Greece via the aquarium trade

Indigenous freshwater crayfish species (ICS) are important biodiversity components and desirable fishery targets. However, ICS populations are increasingly threatened by various anthropogenic stressors. Moreover, established populations of non-indigenous freshwater crayfish species (NICS) and new ‘waves’ of NICS introductions exert significant pressure on ICS populations at a pan-European level. These effects include direct competition for space and resources as well as crayfish ‘plague’ transmission from introduced North American species. Given low public knowledge of this problematic, considerable risk of future introductions exist as a result of conventional and internet-based aquarium trade, which often lead to deliberate and/or accidental releases of NICS into the wild. In 2011, we conducted a survey of freshwater crayfish species in eleven large-size pet shops located in three major cities and in three large internet-based aquarium companies in Greece. Overall, eight species belonging to three genera (Procambarus, Cherax and Cambarellus) were recorded, originating from the USA, Australia, New Guinea and Mexico. The invasion potential of the three most popular species was assessed using the Freshwater Invertebrate Invasiveness Scoring Kit (FI-ISK). Two species were determined to constitute a ‘very high risk’ of invasion. As such, regulatory measures need to be implemented to monitor the ornamental trade of NICS in Greece and a national framework developed for protecting ICS.     

Revealing the appetite of the marine aquarium fish trade: the volume and biodiversity of fish imported into the United States

The aquarium trade and other wildlife consumers are at a crossroads forced by threats from global climate change and other anthropogenic stressors that have weakened coastal ecosystems. While the wildlife trade may put additional stress on coral reefs, it brings income into impoverished parts of the world and may stimulate interest in marine conservation. To better understand the influence of the trade, we must first be able to quantify coral reef fauna moving through it. Herein, we discuss the lack of a data system for monitoring the wildlife aquarium trade and analyze problems that arise when trying to monitor the trade using a system not specifically designed for this purpose. To do this, we examined an entire year of import records of marine tropical fish entering the United States in detail, and discuss the relationship between trade volume, biodiversity and introduction of non-native marine fishes. Our analyses showed that biodiversity levels are higher than previous estimates. Additionally, more than half of government importation forms have numerical or other reporting discrepancies resulting in the overestimation of trade volumes by 27%. While some commonly imported species have been introduced into the coastal waters of the USA (as expected), we also found that some uncommon species in the trade have also been introduced. This is the first study of aquarium trade imports to compare commercial invoices to government forms and provides a means to, routinely and in real time, examine the biodiversity of the trade in coral reef wildlife species.     

The liver monooxygenase system of Brazilian freshwater fish

Content of cytochromes b5 and P-450, and activities of NADPH-cytochrome c (P-450) reductase (NCR) and 7-ethoxyresorufin O-deethylase (EROD) were measured in liver microsomes prepared from two South American endemic fish, Brycon cephalus and Colossoma macropomum, from tilapia, Oreochromis niloticus, and from Swiss mice, Mus musculus, which served as a control. Strong hemoglobin binding to fish liver microsomal membranes (FLM) altered visible spectra of microsomal cytochromes. Consequently, special precautions during FLM preparation, including liver perfusion followed by repeated washing of microsomes, were required in the study of microsomal cytochromes from these fish. FLM from all fish studied here had a significantly lower content of microsomal cytochromes but a similar level of NCR and EROD activities compared to mouse liver microsomes (MLM). Strong response of the monooxygenase system in O. niloticus to water pollution was detected with both specific cytochrome P-450 content and EROD activity increasing sharply. The optical spectra of hemoglobin from B. cephalus and C. macropomum were analyzed and some differences in shape and relative extinction were observed compared to known hemoglobins.     

Null model of biotic homogenization: a test with the European freshwater fish fauna

In recent years, there has been growing concern about how species invasions and extinctions could change the distinctiveness of formerly disparate fauna and flora, a process called biotic homogenization. In the present study, a null model of biotic of homogenization was developed and applied to the European freshwater fish fauna. We found that non-native fish species led to the greatest homogenization in south-western Europe and greatest differentiation in north-eastern Europe. Comparing these observed patterns to those expected by our null model empirically demonstrated that biotic homogenization is a non-random ecological pattern, providing evidence for previous assumptions. The place of origin of non-native species was also considered by distinguishing between exotic (originating from outside Europe) and translocated species (originating from within Europe). We showed that exotic and translocated species generated distinct geographical patterns of biotic homogenization across Europe because of their contrasting effects on the changes in community similarity among river basins. Translocated species promoted homogenization among basins, whereas exotic species tended to decrease their compositional similarity. Quantifying the individual effect of exotic and translocated species is therefore an absolute prerequisite to accurately assess the spatial dynamics of biotic homogenization.     

Introduction history of non-native freshwater fish in Okinawa-jima Island: ornamental aquarium fish pose the greatest risk for future invasions

We examined the introduction history of non-native freshwater fish in Okinawa-jima Island, Japan, to identify the pathway posing the greater risk for future invasions and to measure the strength of ornamental fish introductions as a vector of new invasions using all available records of freshwater fish introductions to date. At least 45 non-native freshwater fish have been introduced to Okinawa-jima Island. Of those, 22 species have successfully established in natural waters and, consequently, non-native fish species represent 76 % of the total freshwater fish fauna. The most important pathway was via the dumping of unwanted ornamental aquarium fish, which accounted for 71 % of the total introductions. The introduction of ornamental fish has occurred extensively in recent decades, and all fish introduced since the 1980s have been ornamental aquarium fish. The overall rate of establishment success was estimated at 51 %, although this is undoubtedly an overestimate because of unreported failed introductions. Establishment rates varied between stocked fish (100 %) and dumped ornamental fish (39 %), which may reflect the low propagule pressure of ornamental fish. From the observed trends in freshwater fish introductions, the dumping of ornamental fish into natural waters is expected to continue if no action is taken to reduce this most important pathway. We recommend regulations against the release of unwanted pet fish into natural waters, better programs for returning unwanted pet fish to stores or local zoos, educational programs for aquarists and retailers, and regulations against selling and trading ornamental fish that are judged to pose a high risk of causing economic or ecological harm.     

Invasion risks posed by the aquarium trade and live fish markets on the Laurentian Great Lakes

International trade is an important mechanism for global non-indigenous species introductions, which have had profound impacts on the biodiversity of aquatic ecosystems including the Laurentian Great Lakes. The best-documented vector by which non-indigenous species have entered the Great Lakes is ballast water discharged by transoceanic ships. A variety of potential alternative vectors exist, including the intentional release of aquarium or food organisms. To assess whether these vectors pose a significant invasion risk for the Great Lakes, we surveyed fish sold live in markets and fish, mollusks and macrophytes sold in pet and aquarium stores within the Great Lakes watershed. We evaluated invasion risk using information on species’ thermal tolerance, history of invasion elsewhere, and potential propagule loads as indicated by frequency of occurrence in shops. Our research suggests that both the aquarium industry and live fish markets represent potential sources of future invaders to the Great Lakes, including several aquarium fishes and macrophytes, as well as Asian carp species sold in fish markets. Currently, few regulatory mechanisms exist to control these potential vectors.     

The biotic resistance role of fish predation in fouling communities

Predation may often influence native species dynamics and so may be important for the control of introduced species as well. Here, we examine how predation can regulate fouling communities on artificial substrates in the coast of Brazil. Specifically, we tested whether predators limit colonization and establishment of introduced species. A predation experiment using plastic plates as experimental replicates (predator excluded and not excluded) was carried out in Ceará, Bahia, São Paulo and Santa Catarina, between 3°S and 27°S. Ninety-eight species colonized the plates, 14 of which were introduced. While species richness was similar among the treatments (except in Santa Catarina), community structure varied by treatment and introduced species were less abundant in the predation treatment at all sites. Also, predation was selective and controlled introduced, poorly defended, species, specifically ascidians. Thus, biotic resistance driven by predation was not ubiquitous but apparently targets one group of major economic and environmental impact. As a consequence, introduced barnacles were released from competition with dominant ascidians and thus the ecosystem service (biotic resistance) performed by fish alone was unable to completely avoid or control the introduction of non-native species. Control measures must rely on various approaches, but if we want fish to contribute in this control, it is very important to conserve the local native assembly of predators in order to reap their benefits in this ecosystem service.     

The aquarium trade as a potential source of fish introductions in southwestern Europe

The aquarium trade has been identified as an important vector of aquatic invasive species but this question has mostly been investigated in North America. We investigated the variation in diversity and species composition in different trade types in southwestern Europe (three major international wholesalers, different retail store types, and local internet forums), mostly in Spain and Portugal. As in previous studies, the diversity of fishes in the aquarium trade was vast, with a total of 20 orders, 79 families, and 1,133 fish species detected in the trade types analyzed. 248 species were observed in a single metropolitan area (Barcelona), with estimates of about 294 species being present. International wholesalers had higher species richness and evenness, with a single one having over 700 species. General pet stores had much lower evenness but due to high turnover had a total richness of over 200 species. Internet forums had the lowest evenness but similar richness. The different commerce types varied significantly in relative species abundance with about a dozen of popular fish species (e.g., goldfish, Siamese fighting fish, common carp, guppy, swordtails) dominating the retail stores, particularly the general pet stores. Our results imply that frequency in the trade varies strongly among species and commerce types and although general pet stores have usually low diversity, this is compensated with a higher species turnover. Many of the most popular species are well known invasive species and some of the species available are temperate species that might establish in Europe, reinforcing the need for more careful implementation of education programs, regulation and monitoring of trade, and internalization of environmental costs by the industry.     

An approach to the prediction of temperate freshwater fish communities

The organization and structure of temperate fish communities is discussed. A measure of organization based on the Shannon measure of entropy is applied. It is concluded that the way organization changes with species number reflects the underlying structure of the community. The prediction of fish assemblages by the analysis of individual species requirements is also investigated using fish data sets from regions considered to be undergoing acidification. The species set within a habitat is generated by a set of rules termed the operational niche. It was concluded that an analysis based on physico-chemical conditions within the habitats gave reasonable correspondence between observed and predicted.     

Completeness of national freshwater fish species inventories around the world

The aim was to discriminate the countries with relatively comprehensive inventories of freshwater fishes from those with insufficiently prospected inventories. We used a data set of 16,734 freshwater fish species with a total of 1,373,449 occurrence records. Accumulation curves relating the increase in the number of species to the number of records, and completeness values obtained after extrapolating these curves to estimate the total number of predicted species were calculated for each country using the RWizard application KnowBR. Using the final slope values of the accumulation curves, the obtained completeness values, and the ratio between the number of records and the observed species, maps and plots representing the location of good, fair and poor quality inventories at country level were obtained. Inventory completeness ranged from 5.3% (Guinea-Bissau) to 108.4% (United Kingdom), with a pooled mean of 65.9%. We observed that a completeness higher than 90%, a slope lower than 0.02 and a ratio of records/species observed greater than 15 were good thresholds for identifying countries with good quality inventories; only 26 countries met these requirements, mainly located in Europe and North America. However, more than 71% of countries worldwide have inventories that can be categorised as of poor quality. Furthermore, even those countries with relatively accurate national inventories possess a high variability in the completeness of their provincial or regional inventories.     

Assessing the potential for biotic communities to recolonise freshwater wetlands affected by sulfidic sediments

1. The formation of sulfidic sediments in response to factors such as secondary salinisation and fertiliser usage is an emerging concern for the management of many freshwater wetlands. However, fundamental knowledge regarding the influence of sulfidic sediments on the aquatic biota is still lacking. 2. This study investigated the potential for biota to recolonise wetlands affected by sulfidic sediments, by assessing zooplankton hatching and aquatic plant germination following inundation with freshwater. Sediment samples were collected from 16 wetlands in the southern Murray‐Darling Basin, Australia, that ranged in condition from non‐impacted to possessing a known history of sulfidic sediments and/or acidification. 3. Principal Components Analysis indicated that the wetlands separated out into five different groups based on their sediment chemistry: non‐impacted, sulfidic, sulfidic and highly saline (sediment EC 46 800–209 000 μS cm^?1), sulfidic and potentially acidic (sediment pH 5.81–6.45 and ANC 0.07–0.31% CaCO₃), and sulfidic and acidic (sediment pH 4.37 and ANC 0.00% CaCO₃). 4. A viable dormant propagule bank was present in all wetlands, but the taxon richness of zooplankton and aquatic plants was significantly lower in wetlands affected by sulfidic sediments compared with those that were non‐affected. 5. This suggests that zooplankton and aquatic plants will be capable of recolonising wetlands that have accumulated sulfidic sediments via their propagule banks if the appropriate remediation measures are undertaken, although the communities developing are likely to be less diverse compared with those in non‐affected wetlands.     

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

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Seasonal dynamics of riverine fish communities using eDNA

As fish communities are a major concern in rivers ecosystems, we investigated if their environmental (e)DNA signals vary according to the sampling period or hydromorphological conditions. Three rivers were studied over a year using eDNA metabarcoding approach. The majority of the species (c. 80%) were detected all year round in two rivers having similar hydromorphological conditions, whereas in the river affected by an upstream lake waterflow, more species were detected sporadically (42%). For all the rivers, in more than 98% of the occasional detections, the reads abundance represented <0.4% of the total reads per site and per sampling session. Even if the majority of the fish communities remained similar over the year for each of the three rivers, specific seasonal patterns were observed. We studied if the waterflow or the reproduction period had an effect on the observed dynamics. Waterflow, which influences eDNA downstream transportation, had a global influence in taxonomic richness, while the fishes' reproductive period had only an influence on certain species. Our results may help selecting the best sampling strategy according to research objectives. To study fish communities at local scale, seasons of low waterflow periods are recommended. This particularly helps to restraint effects of external eDNA coming from connections with other aquatic environment (tributaries, lakes, wetlands, sewage effluents, etc.). To obtain a more integrative overview of the fish community living in a river basin, high waterflow or breeding seasons are preferable for enhancing species detection probability, especially for rare species.     

Mechanisms of maintenance of tropical freshwater fish communities in the face of disturbance

Community resistance to, and resilience from, perturbation will determine the trajectory of recovery from disturbance. Although selective timber extraction is considered a severe disturbance, fish communities from headwater streams around Danum Valley Field Centre, Sabah, Malaysia, showed few long-term changes in species composition or abundance. However, some species showed short-term (< 18 months) absence or decrease in abundance. These observations suggested that both resistance and resilience were important in maintaining long-term fish community structure. Resistance to perturbation was tested by monitoring fish communities before and after the creation of log-debris dams, while resilience was investigated by following the time-course of recolonization following complete removal of all fish. High community resistance was generally shown although the response was site-specific, dependent on the composition of the starting community, the size of the stream and physical habitat changes. High resilience was demonstrated in all recolonization experiments with strong correlations between pre- and post-defaunation communities, although there was a significant difference between pool and riffle habitats in the time-course of recovery. These differences can be explained by the movement characteristics of the species found in the different habitats. Resilience appeared to be a more predictable characteristic of the community than resistance and the implications of this for ensuring the long-term persistence of fish in the area are discussed.     

Barcoding and border biosecurity: identifying cyprinid fishes in the aquarium trade

Background

Poorly regulated international trade in ornamental fishes poses risks to both biodiversity and economic activity via invasive alien species and exotic pathogens. Border security officials need robust tools to confirm identifications, often requiring hard-to-obtain taxonomic literature and expertise. DNA barcoding offers a potentially attractive tool for quarantine inspection, but has yet to be scrutinised for aquarium fishes. Here, we present a barcoding approach for ornamental cyprinid fishes by: (1) expanding current barcode reference libraries; (2) assessing barcode congruence with morphological identifications under numerous scenarios (e.g. inclusion of GenBank data, presence of singleton species, choice of analytical method); and (3) providing supplementary information to identify difficult species.

Methodology/Principal Findings

We sampled 172 ornamental cyprinid fish species from the international trade, and provide data for 91 species currently unrepresented in reference libraries (GenBank/Bold). DNA barcodes were found to be highly congruent with our morphological assignments, achieving success rates of 90–99%, depending on the method used (neighbour-joining monophyly, bootstrap, nearest neighbour, GMYC, percent threshold). Inclusion of data from GenBank (additional 157 spp.) resulted in a more comprehensive library, but at a cost to success rate due to the increased number of singleton species. In addition to DNA barcodes, our study also provides supporting data in the form of specimen images, morphological characters, taxonomic bibliography, preserved vouchers, and nuclear rhodopsin sequences. Using this nuclear rhodopsin data we also uncovered evidence of interspecific hybridisation, and highlighted unrecognised diversity within popular aquarium species, including the endangered Indian barb Puntius denisonii.

Conclusions/Significance

We demonstrate that DNA barcoding provides a highly effective biosecurity tool for rapidly identifying ornamental fishes. In cases where DNA barcodes are unable to offer an identification, we improve on previous studies by consolidating supplementary information from multiple data sources, and empower biosecurity agencies to confidently identify high-risk fishes in the aquarium trade.