Changes in fish assemblages in catchments in north‐eastern Spain: biodiversity, conservation status and introduced species

Abstract

1. North-eastern Spain is a hot spot for the introduction of alien fish species, and its native fish fauna is one of the most endangered worldwide. We used an extensive data set from 2002 to 2003 and historical information from the area to characterize fish diversity and establish conservation priorities in river catchments. 2. Diversity indices were used to characterize fish diversity at the basin scale. An index of conservation status was applied for each species, which considers the occurrence, abundance and endemicity of each taxon. We used indirect ordination methods to test the relationship among basin features and to identify those variables most correlated with each other. To identify physical, biotic and environmental characteristics that seem to make a basin particularly susceptible to invasion, we performed a step-wise multiple regression to examine the relationship between the number of native, translocated and introduced fish species (including the original native species richness of each basin), and landscape variables. 3. Over a period of approximately 50 years, the mean range size of native fish species has decreased by 60%. The greatest decline occurred in Gasterosteus gymnurus, Anguilla anguilla and Salaria fluviatilis, for which species over 75% of the original distribution area has been lost. The species with the highest conservation index were Gasterosteus gymnurus and Salaria fluviatilis. 4. Basin area and the catchment type explained 70% of variation in native species richness, whereas the number of dams and basin area accounted for more than 80% of variation in the number of introduced species. 5. The original native species richness and the number of introduced species at basin scale were not related, and thus there was no evidence of ''biotic resistance'' to invasion. The restoration of natural hydrologic processes and the development of specific management tools to protect native species, such as the prioritization of areas for fish conservation and the eradication of local populations of exotic species, are required to restore native fish fauna in these catchments.

Patterns of occurrence of semi-aquatic reptiles in highly invaded Mediterranean rivers

“…These changes have been associated with the collapse of native biotic communities in the coastal plain rivers (Doadrio 2001;Clavero et al 2009). In contrast, the headwaters of the rivers are subject to greater seasonality, have been colonised by fewer alien species and constitute important shelters for native fauna (Boix et al 2010;Maceda-Veiga et al 2010).…”

Effects of flow regulation on the establishment of alien fish species: A community structure approach to biological validation of environmental flows

“…The lower Ebro River is a Mediterranean large river that has undergone an ecosystem shift due to oligotrophication and flow regime alteration (Ibáñez et al, 2012a,b) and is severely impacted by the presence of alien fish species (Maceda-Veiga et al, 2010). Alien fish are likely to successfully establish and invade under modified flow regimes, regardless of the recipient biota (e.g.…”

First data on the freshwater fish fauna of Calabria (southern Italy)

“…During low flow conditions, we electrofished each station by passing once upstream, searching from one bank to the other following the methods outlined by Bohlin et al (1989), for a total length of almost 200 m. Single-pass qualitative electrofishing was conducted using a backpack electric fishing machine (SCUBLA ELT60, operated at 25-100 Hz and 300/550 V, depending on the water conductivity). Single-pass electrofishing is a suitable and common method for assessing the distribution of freshwater fishes in small and medium-sized lotic environments (Jowett & Richardson 1996;CEN 2003;Maceda-Veiga et al 2010). Fish were identified at species level based on Kottelat and Freyhof (2007), then were released.…”