The results of the pioneer research have been published on the journals Science of the Total Environment and Aquatic Toxicology, and are signed by the research group led by the experts Adolfo de Sostoa and Alberto Maceda-Veiga, from the Department of Animal Biology of the Faculty of Biology and from the Biodiversity Research Institute (IRBio), both affiliated with the campus of international excellence Barcelona Knowledge Campus (BKC).
What is the Conservation Status of Native Freshwater Fish Species in the Mediterranean Area?
Freshwater ecosystems are some of the most threatened in the world. According to the data collected by the International Union for the Conservation of Nature (IUCN), 52 % Mediterranean freshwater species are catalogued as endangered. Habitat degradation, hydrological alterations, pollution, exotic species and water abstraction have severely deteriorated the ecological status of Iberian aquatic fauna and Mediterranean rivers. Professor Sostoa, leader of the Consolidated Research Group on Vertebrate Biology of the UB and co-author of the description of Squalius laietanus, a new species of cyprinid, states that “fish and amphibians are the most threaten vertebrates. Moreover, the Iberian Peninsula has a high degree of fish endemicity, and that increases these species’ vulnerability”. The researcher Alberto Maceda Veiga considers that “taking into account the poor conservation status of many species, it is necessary to apply non-lethal diagnostic tools to evaluate health status in a precise way, and identify then the most vulnerable species”.
Fish as Bioindicators of Environmental Quality
The group led by Professor Sostoa was pioneer in evaluating the ecological status of Catalan rivers using fish species as bioindicators (IBICAT), within a project funded by the Catalan Water Agency (ACA) in 2003. Professor Sostoa explains that “this type of indexes are an effective diagnostic tool as they make an accurate selection of several characteristics , named metrics, of fish communities, by comparing many data from rivers”. “Nevertheless, these indexes —remarks Maceda Veiga— are subjective when categorizing some of these variables and not much effective when diagnosing sub-lethal effects. In other words, these indexes make a general diagnosis, as they determine that fish populations are impacted when drastic changes have already taken place in the community (for example, species decline)”. The researcher thinks that actions must be done before.
Improving Environmental Diagnostic Tools
The doctoral thesis of Alberto Maceda Veiga, led by Professor Sosta, received the special doctorate award in 2010-2011 academic year. It includes a first empirical work, published on Ecological Indicators in 2011, which categorizes quantitatively the tolerance of Catalan and Ebro basin ichtyofauna to water quality and habitat changes. His thesis also collects some works in which haematological variables are used to determine the effects of urban and industrial waste water on S. laietanus and B. meridionalis, carried out together with Professor Ginés Viscor, from the Department of Physiology.
About these works, Maceda Veiga explains that “they prove that sewage discharge in rivers has an effect on the health status of fish. Further research will be needed to determine the risk of metal pollution in this river and the relationship between metal bioaccumulation and the trophic ecology of these fish species”. The UB’s research group proves that metal concentrations in fish tissues exceeded the thresholds of European and Spanish legislation. “Metal concentrations in B. meridionalis —highlights Maceda Veiga— are higher than in S. laietanus, and pathological responses observed showed that S. laietanus seemed to be less sensitive than B. meridionalis to the effects of pollution on this river”.
Researchers warn that the water quality of many Mediterranean rivers do not reflect the improvements made in sewage treatment systems. Maceda Veiga highlights that “the ecological flow must be guaranteed in order to facilitate river self-purification process and fight against illegal discharges which continue to happen nowadays, even in natural parks”.
Invasive Species: A Serious Threat for Native Fish
Catalonia is a hotspot for exotic introductions into the Iberian Peninsula, remarked the UB’s research team on other paper published on Freshwater Biology in 2010. Professor Sostoa explains that “in Catalonia the number of census-taking exotic species is higher than native ones. If we do not improve conservation actions, native ichthyofauna may disappear in few decades. It is a slowly but implacable process, freshwater ecosystems may become globalized, as native species are being replaced by widespread exotic species, a phenomenon named biotic homogenization”.
How can we avoid species introductions and fight against the existent ones? Maceda Veiga considers that “complete eradication once exotics are established and widespread is a utopia and highly costly. Actions must be done when an introduction has just been detected, especially when they live in a small area, or expansion can be controlled. However, prevention and education programmes are the best way to avoid further introductions”. Professor Sostoa confirms these difficulties: “Solution is not trivial: an uncontrolled eradication may cause severe damages on other species conservation, or even native species may be more prone to predation”.
Exotic fish species may be vectors of pathogens that remain undetected until they cause clear symptomatic fish diseases or mass mortality. About this problem, the UB’s research group identified in 2009 one of the few cases of Ichthyophthirius multifiliis (commonly known as freshwater white spot disease) in wild freshwater fish. This disease, frequent in housed fish, is caused by an Asian ciliate protozoan and it has been spread due to aquaculture fish movement.
Future Freshwater Fish Conservation
Experts on environmental conservation consider that the conservation of ecological processes must be prioritized, especially in situ actions over ex situ ones (captive rearing). Maceda Veiga, who will continue his research with a Marie Curie grant at the University of Cardiff (United Kingdom), thinks that river recovery programmes benefit all the biological community, not only fish: “It is necessary to consider the sense of captive rearing programmes when we are not working for reducing anthropic pressures which produced a regression of a species”. Invasive species are one of these pressures. As he explains, “we are now researching on the role played by emerging sectors such as fishkeeping on increasing invasions, and how invasive species can alter ecosystem function”. Professor Sostoa concludes: “For the last years our research has focused on preventive diagnosis, so we hope that institutions and administrations will be able to apply findings and take measures to correct actions done in the management and conservation of aquatic fauna”.
Professor Mercè Durfort (Department of Cell Biology of the UB) and the professors Mário Pacheco (University of Aveiro, Portugal) and Maria José Ranzani de Pavia (Fishing Institute of São Paulo, Brazil) have collaborated in the works carried out by the ichthyology research group of the UB. These works have refined diagnostic tools based on haematological variables, and they will be developed further thanks to the doctoral theses on Lake Titicaca and Ripoll River in which Mario Monroy and Nicole Colin are working now, respectively.