Evaluation of the impact of pre-baiting fishing practise and other activities on lake water quality

Description:

Monitoring of lake’s ecological status within the national monitoring framework shows that the status of Lake Bled and Lake Ledava is moderate or bad, due to the nutrients and organic matter overload. One of the nutrient sources represents the established pre-baiting angling practices for recreational fishery purposes. Attracting fish with food affects the ecological conditions/potential of stagnant water bodies, since it represents an additional source of organic matter and nutrients, which causes phytoplankton overgrowth and affects the entire food chain in the water body. The aim of this project is to evaluate the impact of the fisheries activity on the quality of lake water in comparison with other organic matter and nutrients sources in the River basin. For this purpose, a model of nutrient loads from the catchment and a model of nutrients cycling of Lakes Bled and Ledava will be developed, which will enable simulation of selected ecological and chemical variables in the lake depending on nutrients loads. Based on the results measures will be proposed and a Guideline for management of the lakes

Main goals:

1. Create an appropriate database suitable for modeling Lake Bled and Lake Ledava. The database will contain both sources of nutrient loads as well as their quantification and will be the basis for the use of the model. It will also contain basic data on the ecological and chemical state of the lakes, as well as measurements that will be carried out as part of this project. 2. Create a model of the load and state of the water bodies, Lake Bled and Lake Ledava, with the help of which we will carry out an analysis of the scenarios of various measures to reduce the load on the lakes and show the response of the lakes to the loads. With such an analysis, we will create an expert basis for the necessary measures to maintain the quality of water bodies. 3. Develop guidelines for the implementation of pre-baiting angling practices in inland stagnant waters with the aim of achieving a good ecological state in inland stagnant waters.

Project packages:

The project has 4 work packages (WP):
WP1: Definition of sources of organic matter and nutrients (dispersed and point)
As part of WP1, we will collect data on all known inputs of organic matter and nutrients in the water bodies of Lake Bled and Lake Ledava, both diffuse sources from different land uses and point sources. The data will be collected in a format that will allow the development of a load model of the contributing surfaces in the MapShed tool.

WP2: Data on the state of the lake and harmonization with other data
This work package includes (1) Processing of historical data on the chemical and ecological state of lakes from monitoring (ARSO) and other data that were measured in the context of other projects, such as molecular data on the occurrence of toxic cyanobacteria. The ecological and chemical state data will serve primarily to calibrate and verify the results of the model of the state of water bodies. (2) Measurements to determine parameters of lake models

WP3: Modelling: Model development and application
In this WP we will develop (1) Load model for lakes Bled and Leadava and (2) Water quality model for lakes Bled and Leadava

WP4: Analysis of results and development of guidelines
In WP4, we will use models to simulate different load scenarios and observe the response of the lakes to these loads. Based on the analysis of the scenarios and the discussion with the stakeholders, we will propose measures that will be evaluated according to how much they affect the improvement of the situation, their acceptability and feasibility. In particular, we will decide on the regime for the implementation of pre-baiting angling, in the sense of: what is the load share of this activity compared to the others and what the regulations of this activity contribute. Measures and proposals will be coordinated with stakeholders. This will be followed by the development of guidelines.