Fishing Dynamic and Stock Status of Endeavour Shrimp(Metapenaeus ensis de Haan)in Bombana Waters,South-East Celebes

The high market demand for endeavour shrimp(Metapenaeus ensis de Haan)has caused intensive fishing for this resource and tends to threaten their sustainability.Assessment of fishing dynamic and stock status of fisheries resource is the main point to formulate its proper sustainable management in the future.The purpose of this study was to determine the stock status of endeavour shrimp in the Bombana and its surrounding waters.The study was conducted from April to November 2021 using a survey method to analyze the length at first capture(L_(c)),length at first maturity(L_(m)),growth rate(K),maximum theoretical carapace length(Loo),and mortality rate such as total mortality rate(Z),fishing mortality rate(F)and natural mortality rate(M).The study results revealed that the endeavour shrimp growth pattern in Bombana was negative allometric and that the ratio of males and females was not balanced.The length at first capture(L_(c))was 29.83 mm(carapace length)and the length at first maturity(L_(m))was at a total carapace length of 31.67 mm.The growth rate(K)was 1.0 per year and maximum theoretical length(L_(∞))was 46.2 mm.The estimate total mortality rate(Z)was 2.52 per year,the fishing mortality rate(F)and natural mortality rate(M)were 0.91 per year and 1.61 per year respectively.The exploitation rate(E)was 0.36 per year,therefore the stock status is not categorized overfishing.In order to ensure the sustainability of the endeavour shrimp,then the effort must be increased by about 28%of the current effort.

OBSERVATION OF NONLINEAR VERTICUM-TYPE SYSTEMS APPLIED TO ECOLOGICAL MONITORING

In this paper the concept of a nonlinear verticumtype observation system is introduced. These systems are composed from several ＂subsystems＂ connected sequentially in a particular way： a part of the state variables of each ＂subsystem＂ also appears in the next ＂subsystem＂ as an ＂exogenous variable＂ which can also be interpreted as a con trol generated by an ＂exosystem＂. Therefore these ＂subsystems＂ are not observation systems, but formally can be considered as controlobservation systems. The problem of observability of such systems can be reduced to rank conditions on the ＂subsystems＂. Indeed, under the condition of Lyapunov stability of an equilibrium of the ＂large＂, verticumtype system, it is shown that the Kalman rank condition on the linearization of the ＂subsystems＂ implies the observability of the original, nonlinear verticumtype system. For an illustration of the above linearization result, a stagestructured fishery model with reserve area is considered. Observability for this system is obtained by applying the above linearization and decomposition approach. Furthermore, it is also shown that, applying an appropriate observer design method to each subsystem, from the observa tion of the biomass densities of the adult （harvested） stage, in both areas, the biomass densities of the prerecruit stage can be efficiently estimated.