CHAPTER II Indicators, Weights, and Rankings in the Environmental Domain of Fish Resources

The Environmental Domain of Fish Resources is one of the tools used in assessing fisheries management conditions with an ecosystem approach. It is used to analyze the environment of fish resources related to fisheries management in an inland waters ecosystem. It aims to determine the condition of the inland waters environment as a viable habitat for fish resources, damaging or already damaged. So strategic steps can be taken to maintain or improve the environmental conditions of fish resources in inland waters. There are 7 (seven) indicators of Fish Resources Environmental Domain, namely fluctuations in water level, pollution, boundaries and/or littoral areas, habitat reserves, environmental modification, siltation or reduction of water area, and important habitats.

The indicator ranking in each domain is a ranking order to indicate the level of importance of an indicator in an inland waters ecosystem. Meanwhile, the weight shows the portion of each indicator in a domain.

2.1. Water Level Fluctuations

The definition of water level fluctuation in this technical guide is a change in the volume of water in inland waters. In the environment of fish resources in inland waters, fluctuations in the water level are generally related to seasonal changes, namely the rainy and dry seasons, which are marked by the ebb and flow of the water level. Fluctuations in the water level in inland waters are closely related to the concentration of pollutant substances and the carrying capacity of the waters. Thus, indicators of water level fluctuations are measured to determine the quality and productivity of waters that support the growth of fish resources in inland waters. In addition, fluctuations indicator of the water level determines the extent of fish habitat in the littoral and the bio-chemical cycles of the waters.

In addition to human activities (anthropogenic), river and swamp fish resources are also heavily influenced by changes in natural habitat caused by changes in river water volume, fluctuations in water levels, and the availability of natural food. These changes contribute directly or indirectly to the abundance of river fish resources and affect the amount fishermen catch.

Swamp fish are abundant during low water levels (low tide). Food distribution can also affect it, such as the abundance of phytoplankton and zooplankton during low tide. According to Kahl et al. (2008), changes in water level, especially in lakes or rivers, can affect the abundance of phytoplankton and zooplankton, affecting the abundance and distribution of fish resources. For example, Baran et al. (2001)) reported that fluctuations in the water level of the Mekong River had been shown to have a strong positive correlation with fishery production in the Mekong River. Also, It found that there are very sensitive fish toward the changes in the water level that impact the number of fish caught by the fisherman, such as Henicorhynchus sp. on the Mekong River. A positive correlation between water level fluctuations and catches also occurs in inland waters in Indonesia. For example, fishermen's catch in the Mahakam rivers and swamps is high at low tide (Kasim et al., 2015; Aisyah et al., 2016). Studies on the Lubuk Lampam flood exposure show that the water level also affects the number of juvenile fish species (Prianto, 2018).

The indicator assessment of water level fluctuation uses a Likert scale of 1 to 3. If the water level fluctuations during high and low water seasons are high in the last 5-10 years, then the value will also be high (3). Otherwise, the value is low if the water level fluctuations decrease (1). Then, a value of 2 is given if the water level fluctuation is constant.

2.2. Pollution

The definition of physical and chemical pollution in this technical guide is the value of several physical and chemical parameters or key parameters of water quality. Measurement of physical and chemical pollution indicators are measured to determine the total pollution on the waters that can affect the sustainability of fish resources. In measuring indicators of physical and chemical pollution, the parameters measured include watercolor, light intensity, turbidity, oxygen, temperature, total dissolved solids (Total Suspended Solid, TSS), biological oxygen demand (Biochemical Oxygen Demand, BOD), chemical oxygen demand (Chemical Oxygen Demand, COD), phosphorus, heavy metals, detergents, and ammonia. One guideline that needs to be considered in measuring physical and chemical pollution indicators is PP No. 22 of 2021 concerning the Implementation of Environmental Protection and Management.

The definition of biological pollution in this technical guideline is the measurement result of the increasing number of aquatic plants, bacteria, and microalgae caused by excess nutrients. The increasing number of aquatic plants can be used to indicate the poor quality of the aquatic environment. It is because too fertile waters can disrupt the sustainability of fish resources. Biological pollution indicators measure the area covered by aquatic plants in water. The area of water cover is closely related to the availability of dissolved oxygen due to aquatic biota's chemical and biological processes. Aquatic plants that are generally used as indicators of the quality of the aquatic environment include water hyacinth (Eichhornia crassipes), watercress (Pistia stratiotes), and ganepo (Salvinia natans).

Assessment of pollution indicators using a Likert scale with numbers 1-3. A value of 1 (lowest) is given if water is heavily polluted or smells and has dark in color or causes mass death of fish. Then, value two is given if the water is moderately polluted or unfit for drinking but still suitable for bathing. Meanwhile, 3 (highest) is given if the water is lightly polluted or still suitable for drinking.

2.3. Demarcation and/or littoral areas

The definition of demarcation and/or littoral area is a certain area around waters that has important benefits to maintain the sustainability of water functions. Determining river and lake demarcation lines is an effort to protect, use and control the resources in rivers and lakes per their objectives. Determination of river demarcation lines and lake demarcation lines aims to:

The function of rivers and lakes is not disturbed by the activities that develop around them;
The utilization activities and efforts to increase the benefits and value of existing resources in rivers and lakes can provide optimal results while maintaining the preservation of the functions of rivers and lakes; and
The destructive power of the river and lake water on the environment can be limited.

River banks are areas along a river's left and right sides, including artificial rivers/canals/primary irrigation canals, which have important benefits for maintaining the sustainability of river functions. The canal is the outer demarcation line of river safeguards that limits the construction of buildings on the banks of the river, and it is designated as river protection. The distance can be different in each river, depending on the river's depth, the presence of embankments, and the position of the river. River demarcation is often misinterpreted as river banks. If the river bank, it only shows the riverbank area when it floods (flood plain). Then the river demarcation shows the riverbank area plus the riverbank avalanche area and river erosion areas that may occur. This demarcation was created to ensure sustainability. Then it has the river's function and protects the community from disaster hazards around the river, such as floods and landslides. In spatial planning, river demarcation lines are regulated in local protected areas and included in additional special provisions. River border protection is carried out to protect the function of the river from cultivation activities that can disturb and damage the river's condition and secure the river's flow.

River demarcation has several buffer functions between river and land ecosystems, so that river functions and human activities are not mutually disturbed. River demarcation is virtual lines to the riverbed's left and right, designated as river protection boundaries. The lake demarcation is the area of land that surrounds and is a certain distance from the edge of the lake body, which functions as a lake protection area, public facilities, the community, and environmental aspects. The lake demarcation line is determined to encircle the lake at least 50 (fifty) meters from the edge of the highest water level that has ever occurred. The highest water level that has ever occurred becomes the demarcation of the lake body. The lake body is a space that functions as a water container.

River demarcation and lake riparian areas must be maintained to protect rivers and lakes from human activities that can disturb and damage the water quality in rivers and lakes, the physical condition of the banks and rivers bed, and secure river basins. Demarcation indicator measurements are carried out to determine the condition of the demarcation in water. The parameters measured in the assessment of the border indicator are the area of vegetation that covers the border. In assessing the indicators of riparian areas and/or littoral areas, paying attention to the river criteria for determining the demarcation lines contained in PUPR Ministerial Regulation number: 28/PRT/M/2015 concerning Determination of River Demarcation lines and Lake Demarcation lines. Demarcation indicator assessment uses a Likert scale of 1 to 3. The value criterion for the border indicator is given a value of 1 if the border does not exist (transfer of function), a value of 2 if the border has a distance of 1-15 m, and a value of 3 if the border distance is more than (>) 15 m.

2.4. Fisheries Restricted Areas

The definition of a fisheries-restricted area is a protected area for fish resources to carry out their life cycle and/or reproduce naturally. Fisheries-restricted areas are also known by local names such as reserves, lubuk larangan, lebak lebung, and others with the same role and function. Indicators measurement of fisheries restricted areas is carried out to determine the natural potential for recovery of fish resources in an inland waters ecosystem.

In measuring indicators of fisheries-restricted areas, the parameters measured include fisheries-restricted regions' existence and fishery reserve areas' management. Assessment indicators for fishery reserve areas use a Likert scale of 1 to 3. As for the value criteria for indicators of fishery reserve areas, namely, if there is better management of fishery reserve habitat, gain the highest score (3) and vice versa (1). If there is an area where fishing is prohibited but has not been appropriately managed, the score is 2.

2.5. Environment Modification

Environmental modification is humans' physical change of waters, causing flow changes, disruption of fishing routes, and/or damage/loss of demarcation areas. Environmental modification indicators are measured to determine the status of environmental modifications that impact the sustainability of fish resources in an inland waters ecosystem. The parameters measured in measuring environmental modification indicators include location, type, and impact of environmental modification. Assessment of environmental modification indicators uses a Likert scale of 1 to 3. The value criteria for environmental modification indicators, namely, if an environmental modification disrupts the fish life cycle, is given a value of 1. Then if an environmental modification does not disturb the fish cycle, the value is 2. Then, if there is no environmental modification, the value is 3 (high).

2.6. Siltation

The definition of siltation is the reduction of the water-holding capacity of a body of water, either due to natural factors (natural disasters, landslides, etc.) or man-made factors (human activities). Siltation generally occurs due to sedimentation, while the reduction in water area is caused by using water areas for non-fishery purposes. Measuring indicators of siltation or reduction of water area is carried out to determine the condition of living space or habitat for fish resources. In measuring indicators of siltation or reduction of water area, the parameters measured include average water depth, average water area, and the location and causes of siltation or reduction of water area. The assessment of indicators of siltation or reduction of water area uses a Likert scale with a value of 1 to 3. The value criteria for indicators of siltation or reduction of water area, namely, the higher the percentage (> 20%) of siltation, the smaller the value, and vice versa.

2.7. Important Habitats

Important habitats are spawning grounds, nursery grounds, and feeding grounds for natural and hereditary fish resources. Important habitat indicators are measured to determine the number and distribution of important habitats in an inland water ecosystem. This important habitat is closely related to the local knowledge of the local community in conducting effective fishing. In measuring important habitat indicators, the parameters measured include the number of important habitats, physical conditions, and the environment's carrying capacity in supporting the survival of fish resources. Assessment of important habitat indicators uses a Likert scale of 1 to 3. The value criteria for important habitat indicators are seen from the condition of the important habitat and the possibility of recovery. If the condition of the important habitat has changed/decreased and cannot be restored, it is given a value of 1. If the condition of the important habitat has changed/decreased but can still be restored, it is given a value of 2. If the condition of the important habitat has not changed/decreased, the highest score is given, namely, 3.