The ecological and economic impact of non-native species introduction on local native biodiversity is often reported as undeniable scientific evidence on which to base management and sound policy. Here I used a combination of databases (Fishbase, FAO and IMPASSE) and an extensive review of existing literature to establish the proportion of non-native aquatic species introductions in Spain that are responsible for ecological and economic impacts. In Spain, aquaculture and angling are the two main ecosystem services responsible for introduction of non-native aquatic species. In total, forty two percent of all non-native aquatic introductions are intentional. Very little ecological impact resulting from these non-native species introductions has been demonstrated with some representing a benefit to Spanish ecosystem services. In 2007, the economic benefits to Spanish aquaculture arising from non-native aquatic species (n=9) was close to ˆ46.73 million (about U.S. $69 million) annually for an estimated average ecological risk for all introductions of 16.5% (SD=26.85). These results must be seen in the context of other environmental factors such as habitat destruction, water abstraction and pollution from agricultural farming which represent major environmental pressures on Spanish aquatic fauna.

The Iberian Peninsula contains a highly endemic freshwater ichthyofauna that is being homogenized and threatened by an increasing number of non-native fishes. Here, in this paper, I reviewed the literature on the impacts of fish introductions and translocations on the native Iberian ichthyofauna. The aims of the present review were (1) to provide an overview of the already studied and proven impacts as well as of the suggested potential impacts that remain to be tested, (2) to synthesize the current knowledge in the Iberian Peninsula and (3) to suggest future research approaches. Despite some well-documented impacts, an increasing number of non-native fish species and a wide range of diverse ecological situations uncover knowledge gaps which hamper conservation and management efforts. Since the introduction of species is often pointed out as a major cause of extinctions, I encourage research groups and funding agencies to devote more resources to the study of interactions between non-native and native fishes in order to develop evidence-based species-specific impact assessments.

This paper is the first attempt to compile a list of the non-indigenous aquatic invertebrate species currently known to occur in the Ebro River basin (Northeast Spain). A total of 23 exotic aquatic species have been recorded in this area, and one more (the branchiobdellida Xironogiton victoriensis) may also be present in this Iberian basin. Due to the negative impacts that biological invasions cause to ecosystems and to human activities, it is important to state the introduction pathways and prevent the spread of already introduced species. In order to fight against biological alien species invasions, development of national strategies on invasive alien species and international cooperation are considered essential.

This paper presents the distribution and the ecological parameters of Didymosphenia geminata in the Ebro River basin (North-East Spain) during the period 2006-2009. The presence of blooms in some rivers in 2009, as in Cinca River in Las Pilas bridge, is reported. D. geminata was found in summer at 24 localities, forming blooms in three of them. It prefers mountainous calcareous rivers, regulated or not, with oligotrophic waters, low flow conditions and well illuminated stretches. In order to prevent nuisance blooms of the species, it is necessary to study its ecology and establish a monitoring network for detecting early stages of blooms in order to take control measures.

This paper extends the knowledge of the geographical distribution of non-native freshwater fishes in the Ebro River basin (Spain). More than two hundred surveys were carried out since 2000, and thirteen non-native fish species were collected on fifty-eight occasions. The spread of most of the recorded non-native species seems to be a consequence of illegal introductions related to sport fishing activities and the subsequent natural dispersal. Their presence could impact natural populations of Iberian native –mostly endemic– freshwater fish species, through direct predation and competition for niche and/or trophic resources.

The pond slider (Trachemys scripta), an American species considered one of the most harmful invasives in the world, has spread worldwide to many regions, including the Iberian Peninsula, where it is able to reproduce. Therefore, many eradication campaigns are being held in several places and various methods of elimination and trap models have been tried. We present the Aranzadi Turtle Trap (ATT), which has been tested with great effectiveness in a fluvial backwater stretch of the Arga River in Pamplona. Along with the ATT other traps were utilized, but they did not yield any results, while the ATT captured at least 70% of the detected Trachemys. Other new records of pond slider in Navarre are reported.

During four years of project work (2006-2009), on the distribution and conservation of terrapins in the Castilla and León region (Spain), the majority of the rivers in this region were sampled. Datasets were obtained by compiling information after 2002, including citations by individuals and by field sampling, performed using visual linear transects (500-1000 m) and by live-capture using creels. The results reflect a significant increase in the number of records of non-native terrapins present. From more than 2000 points sampled a total of 67 positive results were obtained, distributed through nine provinces, in comparison with the six records and three provinces located in previous studies. These results allow us a more objective view of this problem and to determine with greater exactitude an action plan to manage it.

Dreissena polymorpha has invaded seven rivers in the Ebro basin (Spain) in the period 2001-2009. In this paper, we present a compilation of management strategies directed by the Ebro Hydrographic Confederation (CHE) with the aim of showing the different steps taken by this organisation to prevent the spread of this invader. These practical procedures are accompanied by diverse educational materials to inform and make people aware of the importance of this problem. The experience gained during these years has allowed the establishment of both an adequate sampling schedule and a sampling method for larval monitoring with the purpose of detection of zebra mussel populations. On the other hand, we have observed that mechanical cleaning and drying techniques are the physical control methods most frequently used by affected users in the Ebro basin, with use of chlorine as chemical method.

Pacifastacus leniusculus (an invasive species in European water bodies) was detected for the first time in the Andalusia Region (S. Spain) in the year 2000. Since 2005, a continuous control management programme has been carried out by the Environmental Regional Government. Management efforts aimed to reduce the population size, to contain the dispersal and reduce the probability of deliberate translocation into other rivers caused by illegal captures. A combination of techniques was used, including crayfish traps, manual removal from artificial refuges and electrofishing. In the 2005-2009 period, 31 374 specimens were captured. The mean catch rate per worker and day declined from 30.4 ± 3.2 specimens in the first year to 9.8 ± 1.7 in the fourth year, therefore suggesting a sharp decrease in population size. Summer was the period of mating and maximum yields, whereas minimum yields were obtained in Winter, coinciding with egg incubation in burrows. The results obtained and the experience gained will provide essential baseline information for the future management of non-native crayfish in the region.

The Chinese mitten crab Eriocheir sinensis was first recorded in the Guadalquivir Estuary in 1987. Management actions by the Andalusian Regional Government were implemented in 2001 to contain and reduce the population of this invasive crab in the estuary and also to prevent its dispersal to neighbouring natural protected areas. Our results showed a heterogeneous distribution of the mitten crabs in the estuary, concentrated in the Sevilla port area. The catch-per-unit-effort (CPUE) in traps was significantly higher in October-April. Annual CPUE decreased from 0.04 crabs net^-1d^-1 to minimum values of 0.006 crabs net^-1d^-1 in 2008, thus reducing the dispersal potential to neighbouring areas. However, given that a number of stochastic factors may be involved in fluctuations in population size and that ships´ ballast water remains uncontrolled, the management of E. sinensis needs to be continued. Based on the results obtained and the expected sequence of the invasion process in the Guadalquivir Estuary, we propose further management improvements. These results may help to optimize the management of this invasive species both in the Guadalquivir estuary and in comparable scenarios in different parts of the world.