Preliminary Study On Short Term Prediction And Model Selection Of Surplus Production Model

Based on the development history of our coastal fisheries, this paperuses Monte Carlo simulation method to model two kinds of over-exploitedfisheries, which is also called predatory fisheries. Then, two kinds ofstock assessment models are applied to the two simulated fisheries undertwo different white noise levels, during which process three modelselection criterions are used to select the more appropriate one for stockassessment.In addition, from two different perspectives (input control andoutput control), this paper sets4fisheries management measures whichmight be adopted to manage over-exploited fisheries. Fisheries managementmeasure1: maintain the fishing effort at certain level, permitting slightchanges. Fisheries management measure2: reduce certain amount of fishingeffort per year. In this paper, the reduced amount of fishing is definedas1.25percent of the fishing effort of the current year. Fisheriesmanagement measure3: maintain annual catch at certain level, allowingslight changes. In this paper, annual catch is defined as80percent ofthe fishing catch of the current fisheries. Fisheries management measure4: in short period (about2–5years) fishing catch will be controlledto increase year by year or enjoy a linear increase. In this paper, theinitial allowing catch for management measure4is defined as80percentof the fishing catch of the current fishery and increased catch has firstorder linear relationship with years. After that, apply selected stock assessment model to two kinds ofsimulated fisheries at two different white noise levels under the controlof4pre-set fisheries management measures, respectively. By predictingthe changing trends of the two simulated fisheries at different whitenoise levels under the management of4pre-set fisheries measures,simulate the changes of allowable stock biomass and thereby make riskassessment for the responded fisheries management measures so that toprovide necessary theoretical basis for the design of fisheriesmanagement policy and laws.Result shows, it is quite impossible for the conservation ofover-exploited fishery1or2if fisheries management measure1or2wasseparately implemented. Even worse, it might result in further depletionof the fishery stock. Otherwise, under the control of fisheries managementmeasure3, the two simulated over-exploited fisheries will probably enjoysome extent restoration, although during the process its implementationmight encounter much trouble. What’s more, under the control of themeasure, the stock biomass of the two simulated fisheries in the futurefive years only has slight fluctuation, which indicates this fisheriesmanagement measure has relatively stable effect on fisheries stockconservation. Admittedly, fisheries management measure4has somepotential risk factors, however, under the control of this measure, twosimulated over-exploited fisheries at different white noise levels allenjoy conservation, to some extent. In conclusion, when design fisheriesmanagement measures or policies, the potential advantages anddisadvantages should be fully considered. Input control, like fisheriesmanagement measure1and2, is much more feasible, but their effect onfisheries stock conservation is quite hard to predict and therefore largeamount of following investigation and assessment work should be needed. For output control, its good influence on stock conservation could beexpected, with relatively less need for lots of following work, while itsimplementation process might be necessarily faced with many difficulties.