DINAMICS OF SUSTAINABLE WELFARE FISHERIES BASED ON TUNA FISH SENDANG BIRU, MALANG (DINAMIC SYSTEM APPROACH).

This study was developed as a dynamics system model which is integrated tuna stocks, social economic and policy sub models. This model was developed based on historical data, than development into three development scenarios: with fish cact limitation, limitation by sustainable yield (MSY) limitation by maximum economic yield (MEY) and open access equilibrium (OAE). System dynamic modeling was conducted to analyze sustainable tuna and sustainable income of tuna fishermen based on various points of view to get the better management of sustainable tuna fisheries.

This study was developed as a dynamics system model which is integrated tuna stocks, social economic and policy sub models. This model was developed based on historical data, than development into three development scenarios: with fish cact limitation, limitation by sustainable yield (MSY) limitation by maximum economic yield (MEY) and open access equilibrium (OAE). System dynamic modeling was conducted to analyze sustainable tuna and sustainable income of tuna fishermen based on various points of view to get the better management of sustainable tuna fisheries.

…………………………………………………………………………………………………….... Introduction:-
Indonesia is the largest archipelagic country in the world, with 2/3 of its territory being a sea area with a total of around 17,504 islands and a coastline of 81,000 km. The vast potential of marine resources is stored in the content of biological and non-biological resources starting from inland waters to the Indonesian exclusive economic zone. The biggest potential of marine biological resources is fisheries. In the last 10 years, it has been shown that fisheries exploitation and exploration in Indonesia shows a very significant increase, but not followed by an increase in catch, this has an impact on the welfare of fishermen kicked in blue While the relationship with a negative sign indicates an increase in a variable will result in a decrease in the other variables and vice versa. Causal loop diagram consists of 3 sub-models that are sub population model, sub-model of catch and ship and sub-economic model in this study illustrated in Figure. 2.

Picture. 2:-Causal Loop Diagram
Input -Output Diagram:-Input -output diagram is used to describe the input and output variables of the system schematically, in inputoutput diagrams, variables are classified into controlled inputs and uncontrolled inputs, controlled output, uncontrolled output and environment. Input -output diagram describes the desired output from modeling, inputs that can be changed to achieve optimal output and other factors that cannot be changed but can affect the desired output.

Stock and Flow Diagrams Organization:-
Organizing stock and flow diagrams begins with a reference to the causal loop diagram that has been made before, Stock and Flow is made to describe the interaction between variables according to the logic of structure in dynamic modeling software. Stock and Flow is a tool that can be used to simulate the dynamic behavior

Result:-And AnalysisFish Population Sub-Model:-
In the sub-model of fish stocks, the main focus is the fish stock response variable which is an ecological aspect of sustainability indicators. On graph 4, It can be seen that tuna stocks tend to decrease every year this is because the effort has increased every year, an increase in effort can be seen in graph 4. Which has an impact on the decrease in the number of obtained CPUE? Growth follows the pattern of tuna stock, when the stock moves down, growth also falls, followed by the number of catches that also drop until the last year of the simulation.

Catch and Ship Sub-Models:-
In the sub-fishing model, the main focus of the response variable is CPUE (catch per unit effort). In graph 4. It can be seen that the CPUE value always decreases every year. Decreasing CPUE caused by an increase in effort can indicate overfishing in these waters.

Fisherman Economic Sub-Model:-
The main focus of the fisherman's economic sub-model variable is profit which is an indicator of the economic aspects of sustainable fisheries. A small or minus profit can be interpreted as overfishing in that area. With a large effort, the costs required are also large while the resulting catches are small so it is not comparable between the cost of fishing and the results obtained. In graph 4.it can be seen that even though the number of catches decreases each year, the profit of fishermen actually increases, this is inseparable from the influence of the price of fish that continues to rise every year.

Conclusions:-
In the simulation of the existing conditions the profit obtained by fishermen has decreased every year. Because the number of fish stocks and CPUE has decreased due to fishing businesses that continue to increase throughout theyear. To keep fish stocks from decreasing every year it is necessary to limit fishing efforts, in sustainable fisheries management there are three approaches to catching effort as follows: