FORMULAE IN SKEBUB 



Monthly Changes in Biomass 

 APEX PREDATORS 



The apex predators are divided into three g roups- -mamma 1 s , birds, and sharks. 

 Because of the high mobility of these predators, their biomasses are not computed 

 in this model. The mean annual biomass of each predator group is an input value. 

 Monthly deviations from this mean biomass are described by a simple harmonic 

 formula, (cosine), where the frequency and magnitude of the oscillations are input 

 values, and can be used to describe migrations in and out of the area. 



FISH SPECIES AND BENTHOS 



The following set of equations applies to benthos and all groups of fish 

 species with the exception of the squids. The data on the squids are insufficient 

 to enable the dynamic computation of their biomass, consequently, their biomass 

 is maintained in the same manner as the apex predators. Other species do prey on 

 the squids and the squids do prey on other species. 



The central formula for the monthly updating of biomass of a species grouping 

 (N) in month k is: 



^^N.k - ^^^N,k - ^''N,k - S,k 



^^N,k= ^^N,k-1 " ^ 



where GS,, , is the growth, CMS,, , the natural mortality excluding predation, 



N ,k N ,k 



FP.. , the fishing mortality, and C , the consumption of N by other species. 



IN J K iN J K 



An iterative procedure is used to update this equation: 



a) an initial, and approximate, computation uses the previous month's (k-1) 

 values of growth, natural mortality, fishing mortality, and predation. This 



