The role of anglers' perceptions and habits in biological invasions: perspectives from the Iberian Peninsula

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The introduction of the European bitterling (Rhodeus amarus) to west and central Europe

The European bitterling is considered to be a native species over much of its present range in Europe. A dramatic decline in its abundance from 1960 to 1980 in west and central Europe, attributed to aquatic pollution, led to the establishment of stringent national and international regulations for protection of the species. Here, we review the evidence that until AD 1100 the bitterling was restricted to the Ponto‐Caspian and Aegean regions (south‐eastern Europe and adjacent regions of Asia Minor) and only expanded into its present range during the 19th century. The earliest records of bitterling in west and central Europe are from regions where carp cultivation was common and the bitterling appears to have spread into this region in association with the gradual expansion of carp cultivation. After an initial period of expansion, between approximately 1150 and 1560 in regions with carp cultivation, the species virtually disappeared from Europe during the coldest period of the Little Ice Age. Bitterling reappeared at the end of the 18th century, initially in historical centres of carp cultivation, and was again abundant and widespread in Europe by around 1850. Its reappearance appears to have been through expansion of refuge populations as well as new invasions. The decline in abundance of bitterling during the period 1960–80 in west and central Europe appears not only to have been caused by pollution, as is generally believed, but may also be correlated with low spring temperatures. From approximately 1980 onwards the European bitterling once again expanded its distribution in many parts of Europe, particularly in eastern Europe. This recent expansion may be due to a combination of factors, including a rise in ambient temperature coupled with an increase in anthropogenic dispersal and changes to aquatic habitats favourable to bitterling. Thus, the bitterling, which is legally protected in Europe at a national and international level as an endangered indigenous species, is actually an invasive species and a parasite of freshwater mussels. Its current expansion in distribution could pose a hazard to freshwater mussel populations in regions where they are already threatened.     

A modelling approach to evaluate potential management actions designed to increase growth of white perch in a high‐density population

Abstract A deterministic, age‐structured population model was developed to simulate potential management scenarios designed to increase growth of individuals (quantified by maximum length) in a hypothetical population of white perch, Morone americana (Gmelin). Four scenarios were developed that included non‐selective mortality of adult white perch, increased mortality of age groups most influential on population growth, increased age‐0 mortality and inhibiting recruitment after spawning. The greatest increase in maximum length occurred with non‐selective adult mortality when population biomass was reduced by 97%; lesser increases in maximum length were achieved with the other management scenarios. Populations returned to their original state after control efforts ceased for each scenario.     

A country's response to tackling plastic pollution in aquatic ecosystems: The Chilean way

1. Marine plastic pollution is worse than expected, and we are starting to realize its full extent and severity. Solving the plastic pollution problem is not easy, as it requires the action and commitment of all sectors of our society. With a coastline extending over 4,000 km (from 18°S to 56°S), Chile is a maritime country, and since plastics are potentially harmful for marine and coastal ecosystems, food security, and public health, plastic pollution is a real threat.
2. Chile is the sixth-largest exporter of seafood (fish, invertebrates, and algae) in the world, but the extent of plastic contamination of marine organisms, its potential effects on commercial species and aquaculture, and its subsequent effects on human health are mostly unknown.
3. Chile has recently introduced some legislation to prevent plastics from reaching the environment and the coastal ocean. Governmental and non-governmental organizations have joined an informal alliance to take action against plastic pollution, both at a national and regional level, but stronger involvement of producers and commerce is required for effective measures.
4. Chilean scientists working on plastic pollution have created the Scientific Plastic Pollution Alliance of Chile network, aiming to promote collaborative and coordinated research focused on this pollutant. The wide geographical extent of Chile, with researchers working in diverse ecosystems, provides a unique opportunity to better understand the consequences of one of the most recent and severe threats to biodiversity.
5. Rather than solely presenting the plastic pollution problem from the scientific perspective, this paper includes views from different sectors of society. Mitigating plastic pollution is exceptionally complex, with this study highlighting the importance of local engagement, media, solving social inequities, new legislation, and law enforcement in order to advance on decreasing plastic pollution from a country-wide perspective.

     

Renibacterium salmoninarum bar forms: characterization, occurrence, and evidence of a host response to a R. salmoninarum infection

Unique-staining Renibacterium salmoninarum (Rs) cells, termed bar forms, first observed in a coho salmon, Oncorhynchus kisutch (Walbaum), in 1983, could not be cultured, making their characterization difficult and significance obscure. They can be detected only by the fluorescent-antibody technique (FAT) and their numbers estimated only by a quantitative FAT (QFAT). Data collected over a 10-year period showed that bar forms were observed only in vivo and appeared associated with a host response. Bar forms were observed in 10 salmonid species from five countries and in fish from < 1 g to spawning adults. They were observed in 50.1% of kidney smears prepared from 10,061 Rs positive chinook, O. tshawytscha (Walbaum), coho, and Atlantic salmon, Salmo salar L. Bar forms were shown to be Rs cells based on absorption studies, their reaction with an Rs-specific FAT and enzyme-linked immunosorbent assay, and a transition from 'typical' Rs cells to bar forms in naturally and experimentally infected fish. Bar forms were determined to be non-virulent, damaged or dead Rs cells, based on fluorescence and electron microscopy observations, the inability to culture them, and mortality data. Bar forms appeared to represent visual markers of recovery from an Rs infection.     

Hierarchical faunal filters: an approach to assessing effects of habitat and nonnative species on native fishes

Abstract –  Understanding factors related to the occurrence of species across multiple spatial and temporal scales is critical to the conservation and management of native fishes, especially for those species at the edge of their natural distribution. We used the concept of hierarchical faunal filters to provide a framework for investigating the influence of habitat characteristics and nonnative piscivores on the occurrence of 10 native fishes in streams of the North Platte River watershed in Wyoming. Three faunal filters were developed for each species: (i) large-scale biogeographic, (ii) local abiotic, and (iii) biotic. The large-scale biogeographic filter, composed of elevation and stream-size thresholds, was used to determine the boundaries within which each species might be expected to occur. Then, a local abiotic filter (i.e., habitat associations), developed using binary logistic-regression analysis, estimated the probability of occurrence of each species from features such as maximum depth, substrate composition, submergent aquatic vegetation, woody debris, and channel morphology (e.g., amount of pool habitat). Lastly, a biotic faunal filter was developed using binary logistic regression to estimate the probability of occurrence of each species relative to the abundance of nonnative piscivores in a reach. Conceptualising fish assemblages within a framework of hierarchical faunal filters is simple and logical, helps direct conservation and management activities, and provides important information on the ecology of fishes in the western Great Plains of North America.     

Using a topological approach to identify keystone species of fish in eutrophic lake ecosystems: A case of Zhushan Bay,Taihu Lake

Eutrophication is a global aquatic environmental problem. Traditional biomanipulation targeting keystone species has been effective for restoring eutrophic lakes. In this study, we conducted monthly fishery assessments and identified keystone species in Zhushan Bay of Taihu Lake, the most representative lake in the middle and lower reaches of the Yangtze River. We built the topological structure of Zhushan Bay's food web based on feeding relationships and calculated network indices of fish groups in the food web using network analysis, combined with Key Player Problem operation. Culter mongolicus, Culter alburnus, Protosalanx hyalocranius and Salangichthys tangkahkeii were the keystone species in Zhushan Bay's food web. Culter mongolicus and Culter alburnus had the greatest impact on the food web after removal. Protosalanx hyalocranius had the fastest speed of transmitting information. Salangichthys tangkahkeii was the key baitfish with the strongest ability to determine structure of species in higher trophic levels. Our study provided a reference for scientific management of shallow lake ecosystems and biological solutions for restoration of eutrophic lakes.     

The immune response in rohu,Labeo rohita (Actinopterygii: Cyprinidae) to Argulus siamensis (Branchiura: Argulidae) infection: kinetics of immune gene expression and innate immune response

Argulus siamensis is a major pathogen in freshwater aquaculture. The immune responses of Indian major carp, Labeo rohita to experimental infection of A. siamensis was evaluated by quantitation of immune‐relevant gene expression in head kidney and skin, and serum innate immune parameters through the course of infection. In skin of infected fish, antioxidant genes like natural killer cell enhancing factor (NKEF‐B) and superoxide dismutase (MnSOD) were significantly up‐regulated in addition to lysozyme G and β₂ microglobulin (β₂M). Both tumour necrosis factor α (TNFα) and toll‐like receptor 22 (TLR22) genes were significantly down‐regulated in skin during early phases of the infection. Most of the genes exhibited significant down‐regulation in head kidney; immunoglobulin (IgM) and β₂M genes being the exceptions which were significantly up‐regulated at 12 h and 3 days post infection. Most of the innate immune parameters like serum complement activity and ceruloplasmin levels showed significant reduction in infected fish. The observed results are indicative of A. siamensis modulating the immune response of rohu by down‐regulation of many immune factors which may explain the susceptibility of rohu to A. siamensis infection. The interaction of this parasite with the host need to be further explored to understand its pathogenesis.