Hi, here is a beverton and holt function. It gives the monthly recruitment in each zone as a function of the spwaning biomass in the zone. prepro refers to the monthly reproduction distribution. I used Reproduction rate is used to model the proportion of mature in each poulation group //bevethon and holt applied in each reproduction zone //R(zone,month)=prepro(month) *SSB(zone) / (alpha*SSB(zone)+beta) double ssb = 0.0; double alpha=0.5; double beta=5; for(Zone zr : zoneRepro){ ssb=0; for (PopulationGroup cr : groups){ ssb+=N.getValue(cr,zr)*cr.getMeanWeight()*cr.getReproductionRate(); //Reproduction rate is used as a maturity ogive } double value=prepro*ssb/(beta+alpha*ssb); result.setValue(zr, value); } return 0; Viktoria Kahui a écrit :

Hi

I am trying to define a beverton-Holt recruitment reproduction equation (based on values of virgin mature biomass and ‘steepness’ I have) for orange roughy in ISIS. Does anyone have an example of such an equation? I am not sure how to write the program.

Thanks Viktoria

Viktoria Kahui │ Post Doktor

Dept of Economics │NFH

University of Tromsø │ 9037Tromsø│Norway

Tel. +47 776 46386

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