FISHGUARD: Impact assessment and remediation of anthropogenic interventions on fish populations

The disruption of longitudinal connectivity by man-made obstacles and the stocking of fish communities with non-indigenous species or genotypes may threaten the fish fauna of Belgian rivers to various extents. Obstacles impede migrations between habitats that are vital for populations, and they may restrict the gene flow between populations, thereby reducing the effective size and genetic diversity of populations and increasing the risk of local extinction. Restocking programs often involve the introduction of non-indigenous genotypes in native populations. Moreover, although stocking programs lead to the temporal and superficial enrichment of local fish communities or gene pools, they generally result in a loss of biodiversity on a regional or international scale through the homogenisation of communities and the breakdown of genetic differentiation between populations.
This project aims at assessing the impact of these factors and provide tools for priorisation and remediation, through a three-step approach:
(1)A descriptive FIELD SURVEY of fish diversity in the vicinity of various types of artefacts (circa 50 ‘model systems’), which are representative of the southern (upland) and northern (lowland) parts of Belgium. It comprises analyses at the fish community level and at the genetic level for target species that are representative of river systems and have undergone contrasting histories of restocking (brown trout, bullhead, roach and three-spine stickleback). Genetic analyses with hypervariable microsatellites will be conducted on specimens from the field and on stocks used for restocking in order to measure the impact of the stocking practices and of obstacles on the gene flow.
(2)The ECOPHYSIOLOGY OF MOVEMENT (swimming and leaping capacity of fish) will be determined under controlled conditions in the laboratory. The critical swimming speed of fish will be measured in respiratory swimming chambers. Theoretical leaping curves will be produced and evaluated in a large flume mimicking a culvert. The energy expenditure associated with swimming and leaping will be determined from measures of lactic acid and electromyography. Experimental data will be used to develop species-specific predictive models to be validated and evaluated in field situations.
(3)The CAPACITIES OF FISHES TO CROSS MAN-MADE OBSTACLES will be measured with telemetry (PIT and radio telemetry) in actual field conditions in a section of the river systems under study, both to test the predictions of laboratory models, and to cast light on how the obstacles eventually affect the gene flow. The monitoring of fishes tagged with EMG telemetry tags will provide further information on how much energy is invested in attempts to clear the obstacle. Fishes implied in the telemetry and energy studies will be genotyped to assess their origin and their status in the genetic structure of population.
Laboratory and field results will be integrated in order to produce tools (manual, software) for predicting the severity of obstacles and stocking practices, and determining the priorities for preservation and remediation. The principal objective is to make these tools user-friendly and efficient for the management of rivers and fish populations in Flanders and Wallonia.