# fisheries and reserves

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breed [fishers fisher] breed [herrings herring] globals [ starvations kills boat-deaths drag-factor safe mean-energy ] patches-own [ plankton zone ] turtles-own [ energy cruise-speed wiggle-angle turn-angle metabolism birth-energy age ] fishers-own [ fisher-field-of-view fisher-sight-range ] to setup ;; (for this model to work with NetLogo's new plotting features, ;; __clear-all-and-reset-ticks should be replaced with clear-all at ;; the beginning of your setup procedure and reset-ticks at the end ;; of the procedure.) __clear-all-and-reset-ticks set safe 1 create-herrings herring-population [ setxy random-xcor random-ycor set color grey set cruise-speed 1 set shape "fish" set wiggle-angle 5 set turn-angle 10 ;herring-turn-angle set birth-energy 25 ;herring-birth-energy set energy random-float 100 set age random 200 grow ] repeat fisher-population [make-fishers random-xcor random-ycor] ask patches [ set plankton random 3 ] ;; smooth out the plankton so the distribution is more homeogenous repeat 5 [diffuse plankton 1 ] ask n-of zone_no patches [ set zone safe let targets patches in-radius zone_size ask targets [set zone safe] ] ;; scale the color of the patches to reflect the quantity of plankton on each patch ask patches [ set pcolor scale-color turquoise plankton 0 5 ] ;set fisher-deaths 0 ;set starvations 0 set drag-factor 0.5 set kills 0 set mean-energy 0 end to go ;; main procedure ;; plankton growth. If there is less than the threshold amount of plankton on a patch regrow it with a particular probability determined ;; by the growth rate. We also diffuse the plankton to allow for the fact that plankton drift. ask patches [ if (plankton < 5) [ ;if ((random-float 100) < plankton-growth-rate) [ ; set plankton plankton + 1 ] set plankton plankton + 1 ;plankton-growth-rate ;growth rate on slider between 0 and 2 maybe ] ] diffuse plankton 1 ;; scale the color of the patches to reflect the quantity of plankton on each patch ask patches [ ifelse (zone = safe) [ set pcolor green ] [ set pcolor scale-color turquoise plankton 6 0 ] ] ;; main minnow procedures ask herrings [ swim feed ] ;if (herring-dynamics?) [ ask herrings [ birth ] ;death ] ;] ;; main boat procedures ask fishers [ hunt ] ;if fisher-dynamics? [ ask fishers [ birth death ]] do-plots if kills > 2000 [stop] tick end ;; create boats with the following paramter values. These values could be set with sliders ;; but it would make for crowded interface to make-fishers [x y] create-fishers 1 [ set heading random 360 setxy x y set size 4 set shape "boat" set wiggle-angle 5 set turn-angle 10 set fisher-sight-range 10 set fisher-field-of-view 120 set cruise-speed 1.5 set energy 100 set metabolism 0.3 set birth-energy 25 ;fisher-birth-energy set color red ] end ;; main minnow procedure governing movement and loss of energy to swim set energy energy - metabolism let danger fishers in-cone sight-range field-of-view ifelse ((any? danger) and escaping?) [set turn-angle herring-turn-angle * 3 ;; the turn angle for escaping is larger than normal by a factor of 3 avoid min-one-of danger [distance myself ] fd escape-speed set energy energy - escape-speed * drag-factor ] [ifelse schooling? [school][cruise] ] end ;; minnow or boat procedure which determines random motion when no predators or prey are near. to cruise rt random wiggle-angle lt random wiggle-angle fd cruise-speed set energy energy - cruise-speed * drag-factor end to hunt set energy energy - metabolism let prey herrings in-cone fisher-sight-range fisher-field-of-view ifelse (([zone] of patch-here) = safe) [ cruise ] [ ifelse ( any? prey ) [ let targets prey in-radius 2 ;; minnows are eaten if they are with a radius of 2 ifelse any? targets [ let totcatch sum [energy] of targets set kills kills + count targets ask n-of (count targets) targets [die] set energy energy + totcatch * 0.5 set mean-energy mean-energy + sum [energy] of fishers] [ ifelse hunting? ;; if minnows are not close enough head towards them [ approach min-one-of prey [distance myself] fd hunt-speed set energy energy - hunt-speed * 4 ] [ cruise ] ;; if you are not hunting cruise around ] ] [ cruise ] ;; if you can't see any minnows just cruise around ] end ;; minnow procedure governing schooling behaviour to school let schoolmates herrings in-cone sight-range field-of-view with [distance myself > 0.1 ] ifelse any? schoolmates ;; minnows you can see [let buddy min-one-of schoolmates [distance myself] ;; closest minnow you can see ifelse distance buddy < safety-range [ set turn-angle herring-turn-angle ;; avoid minnow if it is too slose avoid buddy ] ;; if nobody is too close then turn towards each of the schoolmates in turn, by an angle that exponentially ;; decrease with distance. This ensures that the minnow is more influenced by closer minnows. After making these turns ;; then try to align to the headings of each of the schoolmates in turn by an angle that exponentially ;; decreases with distance. [ foreach sort schoolmates [ set turn-angle herring-turn-angle * exp( ((distance buddy) - (distance ?) ) ) approach ? align ? ] ] fd cruise-speed set energy energy - cruise-speed * drag-factor ] ;; after making adjustements in heading move [cruise] ;; if you can't see any other minnows just cruise around end ;; boat or minnow procedure to turn in the direction of a target turtle by at most the specified turn angle to approach [target] let angle subtract-headings towards target heading ifelse (abs (angle) > turn-angle) [ ifelse angle > 0 [right turn-angle ][left turn-angle] ] [ right angle ] end ;; minnow procedure to turn in the direction of the heading of a target turtle by at most the specified turn angle to align [target] let angle subtract-headings [heading] of target heading ifelse (abs (angle) > turn-angle) [ ifelse (angle > 0) [right turn-angle ][left turn-angle] ] [ right angle ] end ;; minnow procedure to turn in the direction away from a target turtle by at most the specified turn angle to avoid [target] let angle subtract-headings ((towards target) + 180) heading ifelse (abs(angle) > turn-angle) [ ifelse (angle > 0) [right turn-angle ][left turn-angle] ] [ right angle ] end ;; minnow procedure. If there is plankton on the patch eat it to gain energy and reduce the plankton count on the patch. to feed if (plankton > 1) [ set energy energy + 1 ; herring-food-energy set plankton plankton - 3 ] end ;; minnow and boat procedure if your enery exceeds a threshold hatch an offspring with energy = birth energy and ;; reduce your energy accordingly to birth if (energy > 2 * birth-energy) [ set energy energy - birth-energy hatch 1 [ set energy birth-energy set heading random 360 fd cruise-speed ] ] end ;; minnow and boat procedure for removing turtles with energy below zero to death ;; first check for random deaths let mort_rate 0.0 let mort_check random-float 1 ifelse (breed = herrings) [set mort_rate herrings_mort_rate] [set mort_rate herrings_mort_rate] if (mort_rate > mort_check) [ die ] ;; now check for metabolic death if energy < 0 [ if (breed = herrings) [set starvations starvations + 1] ; [set fisher-deaths boat-deaths + 1] die ] end ;; minnow procedure to color and size the minnows so that their age and energy are visually apparant to grow ifelse (age > 300 ) [set size 2 ] [set size 1 + age * 0.003 ] set color scale-color color (energy ) 0 (200 + birth-energy) end to do-plots set-current-plot "Population" set-current-plot-pen "herrings" plot count herrings set-current-plot-pen "fishers" plot count fishers ;set-current-plot-pen "plankton" ;plot sum [plankton] of patches set-current-plot "energy" set-current-plot-pen "energy" plot sum [energy] of fishers set-current-plot-pen "kill" plot sum [energy] of herrings set-current-plot-pen "pen-1" plot 0 end

There is only one version of this model, created about 11 years ago by Stuart Kininmonth.

## Attached files

File | Type | Description | Last updated | |
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fisheries and reserves.png | preview | Preview for 'fisheries and reserves' | about 11 years ago, by Stuart Kininmonth | Download |

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