Gerlinde Van Thuyne

An Index of Biotic Integrity characterizing fish populations and the ecological quality of Flandrian water bodies

A multimetric fish Index of Biotic Integrity (IBI) was composed to assess the biotic integrity of Flandrian water bodies. As fish communities differ substantially between standing waters, running waters of the bream zone and running waters of the barbel zone, eight candidate metrics for each of these water types or zones were identified, representing three major classes of biological attributes. These are species richness and composition, fish condition and abundance, trophic composition. The metrics were tested and modified where needed. The IBI was applied throughout Flanders on 104 locations in standing waters, 500 locations in waters of the bream zone and 257 locations in waters of the barbel zone. Standing waters scored substantially different from running waters. Standing waters rarely contained no fish at all, but their fish communities were very often poor to very poor. Waters of the bream and barbel zone were often fishless (respectively 40% and 35% of all locations contain no fish), but the locations with fish usually scored reasonable to poor. Only 18.5% of all locations were classified as reasonable to excellent (IBI classes 4 or lower on a scale from 1 to 9) and were considered to satisfy the basic ecological quality demands. The Leie-, Dijle-, Dender- and Schelde-basins had a very poor quality (more than 50% of the locations contained no fish). The Maas-, Grote and Kleine Nete-basins scored rather well, with respectively, 44%, 48% and 68% of the locations achieving an IBI of 4 or lower. The IBI is a valuable and complementary tool to assess the ecological quality of water bodies as suggested in the proposal for a Water Framework Directive by the European Commission.

Are persistent organic pollutants and metals in eel muscle predictive for the ecological water quality

Relationships between the presence of PCBs, OCPs and metals in aquatic ecosystems and the ecological water quality were investigated by combining datasets of long-term monitoring of chemicals in European eel (Anguilla anguilla, N = 1156) in Flanders (Belgium) and the Ecological Quality Ratio (EQR), based on the assessment of fish assemblages at 185 locations. For most pollutants, EQR scores were lower when pollutant levels were higher. Threshold concentrations for a good quality could be formulated for PCBs, most metals and OCPs. Mixed models suggested that the ecological water quality was significantly correlated with the presence of PCBs. However, the low R(2) indicates that other environmental pressures may significantly influence the biotic integrity of fish communities. Empirical data and their analyses are essential to enable defining threshold values of bioaccumulated levels to allow better protection of the aquatic environment and its biota through associated food webs as demanded by the Water Framework Directive.

The distribution of an invasive fish species is highly affected by the presence of native fish species: evidence based on species distribution modelling

Topmouth gudgeon (Pseudorasbora parva) is one of the most invasive aquatic fish species in Europe and causes adverse effects to ecosystem structure and functioning. Knowledge and understanding of the species’ interactions with the environment and with native fish are important to stop and prevent the further spread of the species. Creating species distribution models is a useful technique to determine which factors influence the occurrence and abundance of a species. We applied three different modelling techniques: general additive models, random forests and fuzzy habitat suitability modelling (FHSM) to assess the habitat suitability of topmouth gudgeon. The former two techniques indicated that the abundance of native fish (i.e. biotic variables) was more important than environmental variables when determining the abundance of topmouth gudgeon in Flanders (Belgium). Bitterling (Rhodeus amarus), stone loach (Barbatula barbatula), three-spined stickleback (Gasterosteus aculeatus) and predator abundance were selected as the most important biotic variables and implemented in the FHSM to investigate species interactions. Depending on the preferred food source and spawning behaviour, either coexistence or interspecific competition can occur with bitterling, stone loach and three-spined stickleback. In contrast, the presence of predators clearly had a top down effect on topmouth gudgeon abundance. These findings could be applied as a biological control measure and implemented in conservation strategies in order to reduce the abundance of earlier established populations of topmouth gudgeon.

VIS – A database on the distribution of fishes in inland and estuarine waters in Flanders, Belgium

Abstract The Research Institute for Nature and Forest (INBO) has been performing standardized fish stock assessments in Flanders, Belgium. This Flemish Fish Monitoring Network aims to assess fish populations in public waters at regular time intervals in both inland waters and estuaries. This monitoring was set up in support of the Water Framework Directive, the Habitat Directive, the Eel Regulation, the Red List of fishes, fish stock management, biodiversity research, and to assess the colonization and spreading of non-native fish species. The collected data are consolidated in the Fish Information System or VIS. From VIS, the occurrence data are now published at the INBO IPT as two datasets: ‘VIS - Fishes in inland waters in Flanders, Belgium’ and ‘VIS - Fishes in estuarine waters in Flanders, Belgium’. Together these datasets represent a complete overview of the distribution and abundance of fish species pertaining in Flanders from late 1992 to the end of 2012. This data paper discusses both datasets together, as both have a similar methodology and structure. The inland waters dataset contains over 350,000 fish observations, sampled between 1992 and 2012 from over 2,000 locations in inland rivers, streams, canals, and enclosed waters in Flanders. The dataset includes 64 fish species, as well as a number of non-target species (mainly crustaceans). The estuarine waters dataset contains over 44,000 fish observations, sampled between 1995 and 2012 from almost 50 locations in the estuaries of the rivers Yser and Scheldt (“Zeeschelde”), including two sampling sites in the Netherlands. The dataset includes 69 fish species and a number of non-target crustacean species. To foster broad and collaborative use, the data are dedicated to the public domain under a Creative Commons Zero waiver and reference the INBO norms for data use.