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CHAPTER II. Development of Fish Resources

2.1. Indicators Development, Values​​, and Weights in the Fish Resource Domain

The Fish Resources Domain is one of the tools in assessing the condition of fisheries management using an ecosystem approach. It is used to analyze the status of fish resources in inland waters ecosystems so that strategic steps can be taken to regulate fishing activity in inland waters. There are 5 (five) indicators in the Fish Resources domain, namely trends in fishing production, changes in the size of fish caught, the proportion of fry/brood fish caught not for aquaculture, catch composition, and presence of introduced and invasive species.

The ranking of indicators in each domain is a ranking to indicate the level of importance of an indicator in an inland water ecosystem. Meanwhile, the weights indicate the portion of each indicator in a domain.

2.2. Fishing Production Trends

The definition of trend in fishing production in this indicator is the change in quantitative Catch Per Unit Effort (CPUE) data or qualitative information on changes in the amount of fishing production in units of weight for most fishing business actors on average in recent years compared to previous years. According to Hubert & Fabrizio (2007) and Appelman (2015), CPUE is the catch of fish (in kg) per unit effort (number of fishing gear used, duration of fishing gear installation, or other units that can describe fisheries in a particular area).

Measuring trend indicators of fishing production is carried out to determine the abundance of SDI in an inland water ecosystem. A decrease in fishing production can indicate conditions of overfishing. Conversely, an unchanged trend in fishing production can indicate sustainable fishing practices.

In measuring trend indicators of fishing production, the parameters measured are the number of fish catchers and their experience level, total operating hours of fishing, number, type, and size of fishing gear used, total production of fish catches periodically (daily/monthly/yearly) in the last 5-10 years. Data/information can come from captured fisheries data in inland waters belonging to the Regional Organization (OPD) in charge of fisheries in the local province/regency/city. It can be supported by capturing fisheries data from other work units or related academics/researchers/experts.

Assessment of trend indicators of fishing production uses a Likert scale of 1 to 3. As for the value criteria for indicators of fishing production trends, namely a low score (1) is given if the trend of catches decreases by > 25%; a moderate value (2) if the trend of catches decreases by 25%, and a high value (3) the catch trend is stable or increasing.

The definition of change in the size of fish caught is an increase or decrease in the size of each type of fish caught. Measurement of indicators of changes in the size of fish caught is carried out to determine changes in the size of fish caught as an indicator of a decrease in fishery potential. In measuring indicators of changes in the size of fish caught, the parameters measured include the number, type, and size of fish caught. The catch size is the length of the fish, both the total length and the standard length (Figure 2). Each type of fish has a maximum length (Lmax, the longest size ever found). Data on the maximum length of fish can refer to the results of previous studies or available data on www.fishbase.org. Comparing data on the length of fish caught with Lmax can provide clues about the pressure on fish resources, namely a decrease in the size and selectivity of the fishing gear used. According to the theory of fishing down the food web, smaller catch sizes compared to previous years indicate overfishing. It means that fishing activities have resulted in the loss of large fish, and the mesh is getting smaller. In other words, the demographics of these fish are increasingly dominated by young and small fish. 

Figure 2. Fish Length Measurement Method

Source: https://www.fishbase.se/identification/MorphometricsAdvanced/centimeters/index.php

Description: SL = standard length, measured from the tip of the mouth to the middle of the base of the tail shaft, FL = fork length, measured from the tip of the mouth to the branching point of the tail fin; and TL = total length, measured from the edge of the mouth

The indicator assessment of the size change of the fish caught uses a Likert scale w. The value criteria for the indicator of change in the size of the fish caught, namely a low score (1) is given if the average size of the fish caught is smaller, medium value (2) if the average size of the fish caught is relatively constant, and high value (3) if the average size of fish caught increases.

Juvenile (juvenile) or fish fry can be defined as the growth phase of fish, in which its organs' shape and completeness resemble the adult phase but with smaller sizes, and the gonads are immature (Miller, 2009). This phase is often called juvenile fish or the stage before entering pre-adult age (young fish). Juvenile fish are recruits who will join the population to increase the population's number and biomass. The high or low proportion of recruits entering each year determines the ability to recover exploited fish populations.

On this basis, responsible fishing practices must be able to minimize the proportion of juveniles caught. The higher the ratio of juveniles caught, the greater the potential for reducing the success of the fish recruitment process. If these conditions continue, fishing can lead to growth overfishing. The age group (cohort) of juvenile fish that should contribute to an increase in the number of individuals and the biomass of a stock is decreasing.

The assessment of the proportion indicator of fry/brood fish caught not for cultivation uses a Likert scale with a scale of 1 to 3. The value criteria for the proportion indicator of fry/brood fish caught not for aquaculture, namely a low value (1) if the proportion of fry/broods fish caught >20% of the total catch; moderate value (2) the proportion of fry/brood fish caught <20% of the total catch; and a high score (3) if no fry/brood fish are caught.

This indicator's definition of catch composition is the composition of fish caught based on food chain groups, from herbivores, small carnivores, and large carnivores, to top predators. Catch composition indicators are measured to determine the health of the Fish Resources (SDI) population. The composition of the catch is an illustration of a balanced fish community structure and a stable ecosystem. The presence of top predators can be an indicator of the above conditions. If the catch still represents the completeness of the food chain between herbivores, small carnivores, large carnivores, to top predators. Then it can be assumed that the fish community structure in water is relatively stable. The presence of a top predator with a size above the length at first maturity (Lm) and an adequate number of catches can indicate the above conditions. In measuring catch composition indicators, the parameters measured include the number and size of groups of fish species caught (targeted and non-targeted).

The assessment of catch composition indicators uses a Likert scale of 1 to 3. The value criteria for catch composition indicators, namely a low value (1) if the catch composition is incomplete, dominance by certain species is high (> 30%); moderate value (2) if the composition of the catch is quite complete, dominance by certain species is low (<30%); high value (3) if the species composition is complete, diversity is high, not dominated by certain species.

 


The definition of the presence of foreign species in this indicator is the presence of fish species that enter the waters outside their original distribution area due to human activity. Invasive fish are foreign fish that have harmed both ecologically, economically, and human health (Lodge et al., 2006 in Dina et al., 2022). The translocation rate of aquatic biota continues to increase, and freshwater ecosystems are more at risk from the negative impacts of invasive foreign species, especially on the loss of biodiversity (Havelet al. 2005, Gherardi 2010, and Thomazet al. 2015 in Dayet al. 2022). Measurement indicators of foreign and/or invasive species are carried out to determine the level of biological pollution in an SDI community in an inland waters ecosystem. The presence of foreign species in mainland public waters can disrupt the existence of native/endemic species. Endemic fish species are types of fish that are only found in a certain place and are not found in other areas. Native fish species, also called indigenous, inhabit aquatic habitats or ecosystems that naturally inhabit waters without human intervention. As is known, native Indonesian freshwater fish species reach 1,248 species, of which 400 are endemic (Hubert et al., 2015; Widjaja et al., 2014; Dina et al., 2022). In measuring indicators of the presence of foreign and/or invasive species, the parameters measured include the number and type of fish caught by foreign species and the area of ​​fish caught by foreign species. As many as 50 foreign fish species have been found in Indonesian inland waters, and 18 are invasive fish, as attached in Appendix 1 (Dina et al., 2022). A list of fish species that are harmful from the Indonesian fishery management area, which is prohibited from being imported, cultivated, distributed, and released, can be seen in the Regulation of the Minister of Marine Affairs and Fisheries of the Republic of Indonesia Number 19/Permen-Kp/2020 (Appendix 2 ). 

 

Assessment of indicators of the presence of introduced and invasive species uses a Likert scale with a value of 1 to 3. The value criteria for indicators of the presence of introduced and invasive species are low values ​​(1) if there are introduced species and they have become invasive species; moderate value (2) if there is an introduced species, but not/has not become an invasive species; high value (3) if there are no introduced species.

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