********************************
.capacity util
********************************
(001) BASE CAPACITY UTILIZATION=
1
Units: dmnl [0.75,1.25,0.05]
The normal rate of use of fishing gear and vessels.... The
default is 100% or 1.
(002) capacity utilization=
IF THEN ELSE(SWITCH ON OFF cpue affects capacity utilization=1, BASE CAPACITY UTILIZATION
*effect of cpue ratio on capacity utilization
, BASE CAPACITY UTILIZATION)
Units: dmnl
if switch is on then capacity utilization is determined by cpue
ratio. Other wise 100% use of existing capacity is assumed.
(003) effect of cpue ratio on capacity utilization=
LK effect of cpue ratio on capacity utilization(short term smooth of cpue ratio
)
Units: dmnl
The effect that recent catch per unit effort has on the actual
use of fishing vessels in the fishery.
(004) LK effect of cpue ratio on capacity utilization(
[(0,0)-(2,2)],(0,0.015),(0.2,0.5),(0.29106,0.674157),(0.4,0.8),(0.515593,
0.870786),(1,1),(1.19335,1.05056),(1.49272,1.11236),(1.98337,1.2))
Units: dmnl
A function describing how capacity utilization of vessels and
gear will change as catch per unit effort changes. \!cpue
ratio\!effect on capacity utilization
(005) short term smooth of cpue ratio=
SMOOTHI( cpue ratio, SHORT TERM CPUE SMOOTH TIME, 1)
Units: dmnl
The recent cpue ratio which affects how much fishing capacity
will be used.
(006) SWITCH ON OFF cpue affects capacity utilization=
1
Units: dmnl [0,1,1]
Switch to turn on and off the effect of cpue on fishing capacity
utilization. Default is on (=1).
********************************
.catch effect on mgmt politics
********************************
(007) effect of historical catch level on management mandate=
IF THEN ELSE( Switch ON OFF historical catch effect on mgmt=1, LK historical catch ratio effect on management lookup
(ratio of short to long term catch), 1)
Units: dmnl
The effect that historical changes in fish catches will have on
management. (Only in effect if switch is turned on).
(008) LK historical catch ratio effect on management lookup(
[(0,0)-(2,2)],(0,1.6),(0.5,1.25),(0.75,1.1),(1,1),(1.49647,0.846975),(2,0.75
))
Units: dmnl
A graphical description of the relationship between recent
catches compared to historical catches and the effect of this on
management's mandate. \!historical catch ratio .... is ....
short term / long term catch \!effect on management mandate
(009) long term smooth of catch=
SMOOTH(catch C, LONG TERM SMOOTH TIME)
Units: t/Year
A measure of catch levels (perceived by management) over the
long term.
(010) LONG TERM SMOOTH TIME=
20
Units: Year
length of time over which long term perception of catches is
determined
(011) ratio of short to long term catch=
IF THEN ELSE( long term smooth of catch>0, (short term smooth of catch/long term smooth of catch
) , 0 )
Units: dmnl
Ratio of short-term to long term perceptions of catch levels.
(012) short term smooth of catch=
SMOOTH(catch C, SHORT TERM SMOOTH TIME)
Units: t/Year
A measure of catch levels (perceived by management) over the
past few years.
(013) SHORT TERM SMOOTH TIME=
5
Units: Year
length of time over which short term perception of catches is
determined
(014) Switch ON OFF historical catch effect on mgmt=
0
Units: dmnl [0,1,1]
A switch to turn off (=0) and on (=1) the effect of historical
catch levels on management's mandate.
********************************
.Control
********************************
Simulation Control Paramaters
(015) FINAL TIME = 2100
Units: Year
The final time for the simulation.
(016) INITIAL TIME = 2000
Units: Year
The initial time for the simulation.
(017) SAVEPER = 0.25
Units: Year
The frequency with which output is stored.
(018) TIME STEP = 0.0625
Units: Year
The time step for the simulation.
********************************
.effect on ecosystem
********************************
(019) Ecosystem Capacity for Biomass of Unfished Stock= INTEG (
recovering capacity-losing capacity,
MAXIMUM ECOSYSTEM CAPACITY for this stock)
Units: t
Current capacity of ecosystem to support the fish stock
(020) ECOSYSTEM LOSS RATE PER UNIT=
0.0001
Units: 1/(Year*units) [0,0.0005,0.0001]
Fractional rate at which ecosystem capacity is lost for each
effective amount of fishing gear per year.
(021) effect on recovery time=
LK effect on recovery time multiplier(fraction of ecosystem capacity remaining
)
Units: dmnl
The recovery time becomes longer if the ecosystem capacity falls
well below the maximum capacity.
(022) effective biomass of unfished stock=
Ecosystem Capacity for Biomass of Unfished Stock
Units: t
Equlibrium biomass of stock if no fishing takes place... but
taking into account any damage done to the ecosystem by fishing
activity.
(023) LK effect on recovery time multiplier(
[(0,0)-(1,10)],(0,10),(0.0658824,8.22064),(0.155294,6.37011),(0.272941,4.48399
),(0.414118,3.02491),(0.524706,2.17082),(0.694118,1.35231),(0.9,1),(1,1))
Units: dmnl
A graphical function showing the relationship between the
capacity ratio and the effect on recovery time.\!\! Capacity
Ratio\!Effect on recovery time dmnl
(024) losing capacity=
Ecosystem Capacity for Biomass of Unfished Stock*ECOSYSTEM LOSS RATE PER UNIT
*effective fishing units
Units: t/Year
The loss of ecosystem capacity to support the fishery.
(025) MAXIMUM ECOSYSTEM CAPACITY for this stock=
100000
Units: t
Maximum ecosystem capacity in the absence of fishing (or other)
damage
(026) possible recovery amount=
MAXIMUM ECOSYSTEM CAPACITY for this stock-Ecosystem Capacity for Biomass of Unfished Stock
Units: t
Amount of capacity that is still available for recovery.
(027) recovering capacity=
possible recovery amount/(RECOVERY TIME*effect on recovery time)
Units: t/Year
Recovery of the ecosystem's ability to support the fish
population.
(028) RECOVERY TIME=
10
Units: Year [0,60,1]
Time needed for ecosystem to recover from existing damage.
********************************
.fish pop
********************************
(029) additions=
delayed recruitment+growth additions
Units: t/Year
Amount of biomass added to the population each year.
(030) average rate of increase=
(modified rate of rec increase*fraction of additions from recruitment)+(modified rate of g increase
*(1-fraction of additions from recruitment
))
Units: 1/Year
The average rate of increase of the population (which is also
the basis of the average rate of population decrease without
fishing and other influences)
(031) catch C=
MIN(Current Fish Biomass B/TIME STEP,catch fraction*Current Fish Biomass B
)
Units: t/Year
Fish biomass being caught.
(032) catch fraction=
modified gear efficiency*effective fishing units
Units: 1/Year
Fraction of the current fish biomass caught by all fishing gear
units.
(033) cpue=
IF THEN ELSE( effective fishing units<=0, 0, catch C/effective fishing units
)
Units: t/Year/units
This is the catch obtained by each unit of fishing gear...
called catch per unit effort or CPUE.
(034) Current Fish Biomass B= INTEG (
additions-catch C-deaths,
INITIAL BIOMASS)
Units: t
The current biomass of catchable size fish in the fish
population.
(035) deaths=
Current Fish Biomass B*normal death fraction*ratio of current biomass to unfished biomass
Units: t/Year
Biomass of fish dying of natural causes.
(036) delayed recruitment= DELAY FIXED (
actual recruits, YEARS PRIOR TO ENTERING FISH STOCK, expected recruitment amount
)
Units: t/Year
Biomass of young fish ("recruits") entering the fish population
(037) expected recruitment amount=
IF THEN ELSE(SWITCH ON OFF constant recruitment option=0,
MAX(0, recruit additions+Pink Noise*recruit additions),
MAX(0, constant additions due to recruitment+Pink Noise*constant additions due to recruitment
))
Units: t/Year
Expected additions to the population biomass taking into account
random influences on "recruitment" (that is, the addition of new
young fish to the stock). Alternative is the constant
recruitment scenario with random fluctuations. Max functions
ensure recruitment, with variations, is not below zero.
(038) feedback effect of biomass on recruitment rate=
IF THEN ELSE(Switch to use Asymtotic recruitment=1,
0.5*(effective biomass of unfished stock+(k recru*effective biomass of unfished stock
))
/(Current Fish Biomass B+(p recru*k recru*effective biomass of unfished stock
) )
, 1)
Units: dmnl
The feedback effect of increasing stock biomass on the ability
of the stock to produce new recruits. As the stock size
increases the effect of increasing biomass becomes less. (When
these calculations are carried forward and multiplied by the
rate of increase and the current biomass then the result is
identical to a Beverton - Holt type recruitment curve).
(039) FEEDBACK EFFECT ON GROWTH=
0.3
Units: dmnl [0,0.6,0.05]
Maximum mutiplier that will increase rate of growth increase at
lower population levels and lower it at high population levels.
Perhaps in the range of .1 to .5
(040) growth additions=
Current Fish Biomass B*modified rate of g increase*(1-fraction of additions from recruitment
)*effect of ecosystem degradation on additions
Units: t/Year
Additions to the population biomass due to growth of existing
fish biomass
(041) INITIAL BIOMASS=
95000
Units: t [0,100000,1000]
Initial biomass of the fish population
(042) k recru=
1
Units: dmnl [0.2,2,0.05]
Fraction of max biomass determining the stock size which
determins asemtote for recruitment (in conjunction with r and
the fraction of additions from recruitment).
(043) modified rate of g increase=
RATE OF INCREASE r*effect of biomass on g rate of increase
Units: 1/Year
The effective rate of increase of growth additions to the
population biomass.
(044) modified rate of rec increase=
RATE OF INCREASE r*feedback effect of biomass on recruitment rate
Units: 1/Year
The effective fractional rate of recruitment additions to the
biomass of the population.
(045) normal death fraction=
average rate of increase
Units: 1/Year
This is the normal death fraction if the current fish biomass is
equal to the biomass of the unfished stock. In the standard case
it is the same as the rate of increase r. In the cases when
there is a feedback effect of biomass on growth and/ or
recruitment, then the normal death fraction is also modified.
(046) p recru=
0.5
Units: dmnl [0.1,5,0.1]
Constant determining how fast recruitment will rise toward the
asyemtotic value as the fish population biomass increases. (Is
equal to the fraction of virgin stock at which recruitment =
0.5*r*virgin stock).
(047) Para effect of biomass on g rate of increase=
MAX(1-FEEDBACK EFFECT ON GROWTH,(-(FEEDBACK EFFECT ON GROWTH/0.5)*ratio of current biomass to unfished biomass
)+(1+FEEDBACK EFFECT ON GROWTH))
Units: dmnl
This represents a straight line of B/k (x) on Effect (y) where
the point 0.5,1 is the default value (effect is one at B/k=0.5).
Thus the effect is 1 at B/k=.5 and increases to 1 plus max
effect as B/k declines from the .5 to zero. Effect decreases
below 1 as B/k increases. MAX is used incase B exceeds k.
(048) RATE OF INCREASE r=
0.2
Units: 1/Year [0,1.5,0.05]
The intrinsic rate of growth in biomass.
(049) ratio of current biomass to unfished biomass=
Current Fish Biomass B/effective biomass of unfished stock
Units: dmnl
The effect of current fish biomass on the death fraction is the
ratio of the current fish biomass to the biomass of the stock of
fish if no fishing takes place (normall this is the original
fish stock also called the "virgin biomass"). However, herein it
it the maximum biomass that could be supported by the current
habitat conditions.
(050) recruit additions=
Current Fish Biomass B*modified rate of rec increase*fraction of additions from recruitment
Units: t/Year
Expected additions to the population biomass due the the entry
of new fish
(051) YEARS PRIOR TO ENTERING FISH STOCK=
1
Units: Year [0,10,1]
The time it takes for young fish to grow large enough to enter
the fishable stock.
********************************
.FISHERY MGMT final for posting
********************************
The purpose of this model is to provide a thinking tool for
those who are interested in the management of fisheries and the
factors that make management of even a simple fishery
complicated.
(052) actual recruits=
IF THEN ELSE(SWITCH on off seasonal recruitment=0, expected recruitment amount
*effect of ecosystem degradation on additions, released recruitment*effect of ecosystem degradation on additions
)
Units: t/Year
(053) BASE PRICE OF FISH=
1000
Units: $/t [100,5000,100]
(054) biomass out=
catch C+deaths
Units: t/Year
(055) Biomass Time= INTEG (
ton years entering-ton years leaving,
ton years entering*1/RATE OF INCREASE r)
Units: Year*t
(056) CATCH FOR PRICE SMOOTH TIME=
1
Units: Year [0.1,3,0.1]
(057) changing fish price=
(MIN(selling price of fish,MAX PRICE)-Recent Typical Fish Prices)/TIME NEEDED FOR PRICES TO BECOME TYPICAL
Units: $/t/Year
(058) constant additions due to recruitment=
IF THEN ELSE(Current Fish Biomass B<=max stock size where recruit relation exists
,
Current Fish Biomass B*modified rate of rec increase*fraction of additions from recruitment
,
max stock size where recruit relation exists*modified rate of rec increase
*fraction of additions from recruitment)
Units: t/Year
Additions due to recruitment if no stock vs recruitment
relationship exists above a minimum stock level. Below that
stock level the normal stock recruitment relationship (as
currently selected) is in effect.
(059) cumulative income per unit= INTEG (
current income per unit,
0)
Units: $/units
(060) cumulative value of catch= INTEG (
value of catch,
0)
Units: $
(061) current fraction of additions from recruitment=
LK fraction of additions from recruitment(mean age of biomass in the stock
)
Units: dmnl
The fraction of additions from recruitment can be estimated from
the mean age of biomass in the stock. For example when the mean
age is very low then most additions to the stock must come from
recruitment rather than from growth of existing biomass.
(062) current income per unit=
cpue*selling price of fish
Units: $/(Year*units)
(063) current income ratio=
ZIDZ(current income per unit, recent past income per unit)
Units: dmnl
A comparison of recent past income levels to current income level
(064) current time in months=
months per year*Time
Units: months
(065) effect of biomass on bh g rate of increase=
IF THEN ELSE(Switch to use Asymtotic growth=1,
0.5*(effective biomass of unfished stock+(k growth*effective biomass of unfished stock
))
/(Current Fish Biomass B+(p growth*k growth*effective biomass of unfished stock
) )
, 1)
Units: dmnl
If the switch is selected then the asyptotic function is used.
(066) effect of biomass on g rate of increase=
IF THEN ELSE(Switch to use ALT growth=1, Para effect of biomass on g rate of increase
, effect of biomass on bh g rate of increase)
Units: dmnl
Result of switch for selecting the appropriate feedback from
biomass to growth. 1 selects the alternate feedback, 0 selects
the BH style IF it is turned on with the other switch.
(067) effect of ecosystem degradation on additions=
IF THEN ELSE("SWITCH ecosys affects additions on-off"=1, LK eco effect on additions
(fraction of ecosystem capacity remaining),1)
Units: dmnl
The effect of ecological degradation on additions to the stock.
This effect is additional to any effect on the biomass carrying
capacity (k) of the ecosystem. That is, it is a special effect
on the additions to the stock.
(068) effect on acceptable cpue=
IF THEN ELSE(SWITCH to turn on effect of income on acceptable cpue=0, 1,
LK effect of recent realtive income on acceptable cpue(current income ratio
)
)
Units: dmnl
The effect that immediate relative income level has on the lower
range of acceptable cpue.
(069) expected rate new vessel entry=
effect of cpue on vessel entry*MAX POSSIBLE NEW VESSELS
Units: units/Year
New rate of vessel entry.... including the effect of current
catch per unit effort (cpue).
(070) FIXED FRACTION ADDITIONS FROM RECRUITMENT=
0
Units: dmnl [0,1,0.1]
If used this value will determine the fraction of additions to
the biomass that are from recruitment -- the addition of new
biomass in the form of new fish.
(071) fraction of additions from recruitment=
IF THEN ELSE(SWITCH to use fixed fraction=0, current fraction of additions from recruitment
, FIXED FRACTION ADDITIONS FROM RECRUITMENT)
Units: dmnl
(072) fraction of ecosystem capacity remaining=
Ecosystem Capacity for Biomass of Unfished Stock/MAXIMUM ECOSYSTEM CAPACITY for this stock
Units: dmnl
Fraction of ecosystem capacity still remaining
(073) FRACTION OF MAX POSSIBLE STOCK SIZE AND WHERE RECRUIT RELATION CHANGES
=
0.5
Units: dmnl
A fraction of the maximum possible stock size above which there
is recruitment affected only by environmental conditions and not
by stock size.
(074) income adjusted acceptable cpue=
UNDERLYING ACCEPTABLE CPUE*effect on acceptable cpue
Units: t/(Year*units)
The lowest catch per unit effort that is sufficient to make
participation in the fishery worthwhile.
(075) k growth=
1
Units: dmnl [0.1,2,0.1]
(076) LK eco effect on additions(
[(0,0)-(1,1)],(0,0),(0.128731,0.0394432),(0.216418,0.0881671),(0.311567,0.174014
),(0.406716,0.296984),(0.507463,0.440835),(0.597015,0.589327),(0.664179,0.726218
),(0.722015,0.816705),(0.79291,0.897912),(0.919776,0.981439),(1,1))
Units: dmnl
\!frac of ecosystem remaining\!effect on additions
(077) LK effect of recent realtive income on acceptable cpue(
[(0,0)-(2,2)],(0,0.3),(0.2079,0.516854),(0.45738,0.691011),(0.715177,0.865169
),(1,1),(1.49272,1.15169),(2,1.2))
Units: dmnl
effect of recent income levels on required cpue\!current
compared to recent past income\!effect on minimum desireable cpue
(078) LK effect that size of catch has on price(
[(0,0)-(8,4)],(0,2.5),(0.561331,1.54494),(1,1),(1.41372,0.730337),(1.96258
,0.52809),(2.66112,0.382022),(3.55925,0.292135),(4.93971,0.179775),(7,0.1)
)
Units: dmnl
\!ratio of catch level to recent levels\!effect on price
(079) LK fraction of additions from recruitment(
[(0,0)-(10,1)],(0,0.95),(1.64179,0.819026),(3.35821,0.693735),(5.11194,0.566125
),(6.90299,0.454756),(8.35821,0.37123),(10,0.3))
Units: dmnl
\!mean age of biomass\!est frac from recrt
(080) LK relation of cpue ratio to its effect on vessel replacement(
[(0,0)-(2,4)],(0,0),(0.4,0),(0.559702,0.482599),(0.783582,0.835267),(1,1)
,(1.26866,1.00232),(1.61194,1.00232))
Units: dmnl
A graphical function which takes as x the cpue ratio and
produces as y the effect on gear entry into the fishery.\!cpue
ratio ...... is equal to .... current cpue / acceptable
cpue\!effect on vessel entry dmnl
(081) MAX PRICE=
3000
Units: $/t [2000,5000,500]
Fish prices are limited if they rise above this value. For
example due to the availability of other similar products.
(082) max stock size where recruit relation exists=
FRACTION OF MAX POSSIBLE STOCK SIZE AND WHERE RECRUIT RELATION CHANGES*MAXIMUM ECOSYSTEM CAPACITY for this stock
Units: t
The stock size above which there is no defined relation between
new fish coming into the population (recruits) and the existing
stock size. Below this value stock size is the primary influence
on the biomass of recruited fish.
(083) mean age of biomass in the stock=
ZIDZ(Biomass Time,Current Fish Biomass B)
Units: Year
(084) month within year=
MODULO(current time in months, 12)
Units: months
(085) MONTHS OF SPAWNING=
2
Units: months [0.5,12,0.5]
(086) months per year=
12
Units: months/Year
(087) net growth of fish stock=
additions-catch C-deaths
Units: t/Year
total change in fish stock (for graphs)
(088) p growth=
0.5
Units: dmnl [0.1,1,0.1]
(089) Potential Recruitment= INTEG (
expected recruitment amount-released recruitment,
RATE OF INCREASE r*fraction of additions from recruitment*Current Fish Biomass B
)
Units: t
(090) ratio of current to recent catches=
XIDZ(catch C, recent catch levels, 0)
Units: dmnl
ratio of catch to catches in the very recent past.
(091) recent catch levels=
SMOOTHI(catch C, CATCH FOR PRICE SMOOTH TIME, catch C)
Units: t/Year
(092) recent past income per unit=
SMOOTH(cpue*selling price of fish, RECENT PAST INCOME SMOOTH TIME )
Units: $/Year/units
(093) RECENT PAST INCOME SMOOTH TIME=
5
Units: Year
(094) Recent Typical Fish Prices= INTEG (
changing fish price,
BASE PRICE OF FISH)
Units: $/t
(095) released recruitment=
spawning period*(Potential Recruitment/time over which recruitment occurs
)
Units: t/Year
(096) revised replacement rate=
Expected Rate of Vessel Replacement*LK relation of cpue ratio to its effect on vessel replacement
(smooth of cpue ratio)
Units: units/Year
At low cpue the replacement rate declines
(097) SHORT TERM CPUE SMOOTH TIME=
0.25
Units: Year
(098) spawning period=
IF THEN ELSE(month within year <=MONTHS OF SPAWNING, 1, 0)
Units: dmnl
(099) "SWITCH ecosys affects additions on-off"=
1
Units: dmnl [0,1,1]
Switch to turn off the effect of the ecosystem on additions to
the stock
(100) SWITCH ON OFF constant recruitment option=
0
Units: dmnl [0,1,1]
Switch to turn on ( =1) or off (=0) the option for constant
recruitment above a certain stock size.
(101) SWITCH on off seasonal recruitment=
0
Units: dmnl [0,1,1]
switch to turn on (=1) and off (=0) seasonality of recruitment
(addition of new fish to the stock). DEFAULT is off
(102) SWITCH to turn on effect of income on acceptable cpue=
1
Units: dmnl [0,1,1]
Switch to turn on the effect of income on the acceptable cpue
level. Default is on (=1)
(103) Switch to use ALT growth=
0
Units: dmnl [0,1,1]
On off switch to turn on the alternated growth function. Default
= 0 - off
(104) Switch to use Asymtotic growth=
1
Units: dmnl [0,1,1]
On off switch to turn on Beverton Holt type recruitment
function. 1=on.
(105) Switch to use Asymtotic recruitment=
1
Units: dmnl [0,1,1]
On off switch to turn on Beverton Holt type recruitment
function. 1=on
(106) SWITCH to use fixed fraction=
0
Units: dmnl [0,1,1]
Switch to turn it on the use of a fixed fraction of editions
from recruitment. Otherwise the fraction of editions from
recruitment is determined by the mean age of biomass in the
stock.
(107) TIME NEEDED FOR PRICES TO BECOME TYPICAL=
5
Units: Year [0,10,0.5]
(108) time over which recruitment occurs=
MONTHS OF SPAWNING/months per year
Units: Year
(109) ton years entering=
Current Fish Biomass B
Units: t
(110) ton years leaving=
biomass out*mean age of biomass in the stock
Units: t
(111) value of catch=
catch C*selling price of fish
Units: $/Year
Value of catch
********************************
.gear efficiency
********************************
(112) BACKGROUND FRACTION OF IMPROVEMENTS IMPLEMENTED=
0.05
Units: dmnl [0,1,0.05]
Fraction of possible improvements that are incorporated into
fishing gear efficiency regardless of CPUE or other influences.
Default is zero.
(113) changing typical gear efficiency=
recent changes/TIME FOR FISHING GEAR CHANGES TO BECOME TYPICAL
Units: 1/(Year*units)/Year
changing efficiency of typical fishing gear.
(114) CPUE RATIO AVERAGING TIME=
0.5
Units: Year [0,4]
The time over which cpue ratios are smoothed.
(115) effect of cpue on improvements=
LK effect of cpue on implementation of improvements(Smooth of Recent CPUE Ratios
)
Units: dmnl
As catch per unit effort drops below some accetable level
fishermen are forced to make whatever additional improvements
they can to their fishing techniques. These improvements are in
addition to any baseline improvements that might also affect
fishing gear effectiveness.
(116) implemented improvements=
(SWITCH on off effect of cpue on gear improvement*effect of cpue on improvements
+BACKGROUND FRACTION OF IMPROVEMENTS IMPLEMENTED)*(possible improvement)
Units: 1/(Year*units)
improvements incorpoarated into fishing gear effectiveness
(117) INITIAL GEAR EFFICIENCY q=
0.001
Units: 1/units/Year [0.0001,0.01,0.0001]
Fraction of the current fish biomass caught by each fishing gear
unit.
(118) LK effect of cpue on implementation of improvements(
[(0,0)-(1,1)],(0,0),(0.0001,1),(0.141176,0.97153),(0.251765,0.918149),(0.352941
,0.843416),(0.435294,0.75089),(0.56,0.487544),(0.625882,0.330961),(0.708235
,0.206406),(0.790588,0.124555),(0.875294,0.0604982),(1,0))
Units: dmnl
A graphical dfunction describing the effect that changes in cpue
will have on the incorporation of fishing gear improvements.
\!cpue ratio\!effect on implementation of improvements Dmnl
(119) modified gear efficiency=
Typical Recent Fishing Gear Efficiency+implemented improvements
Units: 1/(Year*units)
Efficiency of a single unit of fishing gear. This is the
fraction of the fish biomass that can be caught by a single unit
of fishing gear in a year.
(120) new maximum possible gear efficiency=
Typical Recent Fishing Gear Efficiency+(Typical Recent Fishing Gear Efficiency
*POTENTIAL GEAR IMPROVEMENT FRACTION)
Units: 1/(Year*units) [0.0005,0.01,0.0005]
New maximum efficiency of fishing gear possible.
(121) possible improvement=
new maximum possible gear efficiency-Typical Recent Fishing Gear Efficiency
Units: 1/(Year*units)
The amount of possible improvement to current fishing gear.
(122) POTENTIAL GEAR IMPROVEMENT FRACTION=
0.1
Units: dmnl [0,0.5,0.01]
At any given time there is a technical potential for gear
improvement. This is indicated as a fraction of the existing
gear efficience. Thus .05 would mean that current gear
efficiency could be improved by 5% if a full effort was made.
(123) recent changes=
modified gear efficiency-Typical Recent Fishing Gear Efficiency
Units: 1/(Year*units)
recent changes to fishing gear efficiency.
(124) Smooth of Recent CPUE Ratios=
SMOOTHI(cpue ratio, CPUE RATIO AVERAGING TIME, 1)
Units: dmnl
A smooth of recent cpue (catch per unit effort) ratios comparing
the desired cpue to the current cpue.
(125) SWITCH on off effect of cpue on gear improvement=
1
Units: dmnl [0,1,1]
Switch to turn off the effect of cpue on gear imporvement.
Normall is on (=1), and cpue will effect how much possible
improvement is implemented. When turned off (=0) the effect is
influenced only by the "background gear improvement rate."
(126) TIME FOR FISHING GEAR CHANGES TO BECOME TYPICAL=
2
Units: Year
The time needed for changes in the efficiency of fishing gear to
become incorporated into normal fishing gear.
(127) Typical Recent Fishing Gear Efficiency= INTEG (
changing typical gear efficiency,
INITIAL GEAR EFFICIENCY q)
Units: 1/(Year*units)
Typical gear efficiency incorporating changes in the recent
past. The fraction of the fish stock caught by one unit of gear
in one year (other things being equal).
********************************
.Management efforts
********************************
(128) actual vessel entry rate=
MIN((industry's desired entry rate*(1-realized strength of management views
))+(managements proposed vessel entry rate
*realized strength of management views),industry's desired entry rate)
Units: units/Year
This is the weighted mean of the two proposed entry rates where
weighting is based on the strength of managments view. If the
industry rate is lower than the negotiated rate then the
industry rate is used .... i.e. management can't force vessels
to enter the fishery.
(129) biomass ratio when ecosystem changes are not known=
Current Fish Biomass B/MAXIMUM ECOSYSTEM CAPACITY for this stock
Units: dmnl
This is the biomass ratio comparing the current fish biomass to
the original unfished biomass. If managers are unaware of damage
to fish habitat then they will continue to use this value in
determining the stock status.
(130) change in perception=
difference in status perception/TIME NEEDED TO CHANGE PERCEPTION
Units: dmnl/Year
Changing perception of the fishery
(131) difference in status perception=
new perception of stock status-Management's Perception of the Fish Stock
Units: dmnl
The difference between the current perception of the fishery and
the new perception.
(132) effect of differences on management acceptability=
IF THEN ELSE("switch - lobbying feedback"=1, LK lobbying effectiveness lookup
(ratio of vessel entry difference to fleet size), 1 )
Units: dmnl
The effect that the size of the differences in the proposed
entry rates proposed by management and industry will have on the
overall effectiveness of management... if lobbying is in effect.
Larger differences will increase cause lobbying to be more
effective.
(133) effect of perception on proposed gear numbers=
LK perception of stock vs fishing gear change lookup(Management's Perception of the Fish Stock
)
Units: dmnl
The effect that the management entity's perception has on their
recommendation for fishing gear numbers.
(134) EXPECTED IMPLEMENTATION TIME=
1
Units: Year [0.5,3,0.5]
Expected time needed to make changes in fishing gear numbers
(135) LK lobbying effectiveness lookup(
[(0,0)-(1,1)],(0,1),(0.08,0.98),(0.145522,0.944316),(0.201493,0.904872),(
0.251866,0.858469),(0.296881,0.794382),(0.386194,0.668213),(0.5,0.5),(0.615672
,0.38051),(0.708955,0.308585),(0.828358,0.243619),(1,0.2))
Units: dmnl
A graphical function describing how ( depending on the strength
of lobbying) large differences between management's and
industry's desired vessel entry rate can have an effect on the
strength of management. If industry's desired entry rate is very
high compared to that of management and send the management
mandate will be decreased. \!difference in new vessels over
current number in fleet\!effect on strength of management's
views.
(136) LK perception of stock vs fishing gear change lookup(
[(-10,0)-(10,2)],(-10,0.1),(-8.54985,0.482456),(-6.85801,0.745614),(-4.98489
,0.868421),(-1,0.97),(0,1),(1,1.03),(4.96471,1.15),(10,1.32))
Units: dmnl
A graphical function describing the relationship between the
current perception of the fishery and the effect on fishing gear
numbers.\!\! Perception\!effect on fishing gear numbers
(137) LK stock vs perception lookup(
[(0,-10)-(1,10)],(0,-10),(0.0996979,-5),(0.247734,-2.19298),(0.338369,-0.789474
),(0.425982,-0.263158),(0.5,0),(0.58006,0.263158),(0.655589,0.789474),(0.752266
,1.92982),(0.897281,4.91228),(1,10))
Units: dmnl
A graphical lookup function describing the relationship between
biomass ratio and perception of fishery status.\!Biomass Ratio
B/K\!perception of resource
(138) Management's Perception of the Fish Stock= INTEG (
change in perception,
LK stock vs perception lookup(perceived stock ratio))
Units: dmnl
The currently held perception of the fishery by the management
entity.
(139) management's proposed adjustments to gear numbers=
((Units of Fishing Gear E*effect of perception on proposed gear numbers)-
Units of Fishing Gear E)/EXPECTED IMPLEMENTATION TIME
Units: units/Year
The change in fishing gear numbers proposed by the management
entity.
(140) managements proposed vessel entry rate=
revised replacement rate+management's proposed adjustments to gear numbers
Units: units/Year
The number of new fishing vessels proposed by management,
accounting for expected replacement of retiring old vessels
(141) new perception of stock status=
LK stock vs perception lookup(perceived stock ratio)
Units: dmnl
The management entity's perception of fishery status as based on
the perceived biomass ratio.
(142) perceived stock ratio=
ratio to use*STOCK ASSESSMENT INACCURACIES
Units: dmnl
The stock comparison (current to max possible) used by managers.
(143) ratio of vessel entry difference to fleet size=
ZIDZ((industry's desired entry rate-managements proposed vessel entry rate
), Units of Fishing Gear E)
Units: 1/Year
The difference between industry's proposed entry rate and that
of management expressed as fraction of the fishing gear
currently in the fishery.
(144) ratio to use=
IF THEN ELSE("switch - use which ratio?"=1, ratio of current biomass to unfished biomass
, biomass ratio when ecosystem changes are not known)
Units: dmnl
Default is the second option. .. the original value of unfished
biomass. If managers regularly refit the model to the fishery
data then the other option is likely to be more realistic.
(145) realized strength of management views=
MIN(1, STRENGTH OF MANAGEMENT MANDATE*effect of differences on management acceptability
*effect of historical catch level on management mandate)
Units: dmnl
Management views are fully implemented if this value is 1. The
strength of management's MANDATE is affected by differences
between fishers and management regarding fishing gear levels,
and by the effect of historical catch rates.
(146) STOCK ASSESSMENT INACCURACIES=
1
Units: dmnl [0.5,1.5,0.1]
Multiplier changing the perceived stock ratio due to stock
assessment inaccuracies or biases. Default is 1 = no effect.
This was included for testing ideas.
(147) STRENGTH OF MANAGEMENT MANDATE=
0
Units: dmnl [0,1,0.1]
Has values from 0 to 1. A value of one means that management's
efforts are fully accepted.
(148) "switch - lobbying feedback"=
0
Units: dmnl [0,1,1]
A switch to turn the lobbying effect on or off (off=0).
(149) "switch - use which ratio?"=
0
Units: dmnl [0,1,1]
A switch to determine which measure of max biomass managers are
using. The default is that they assume the actual virgin biomass
is the maximum possible. The alternative (=1) assumes that
managers use analysis based on current observable stock size and
that their estimate of max possible stock size is closer to the
actual value as influenced by fishing activity effects on the
eco-system and possible variations in natural productivity.
(150) TIME NEEDED TO CHANGE PERCEPTION=
2
Units: Year [0.5,3,0.5]
The time needed for the management entity to change its
perception of the fishery status.
********************************
.noise component
********************************
(151) Change in Pink Noise = (White Noise - Pink Noise)/Correlation Time
Units: dmnl/Year
Change in the pink noise value; Pink noise is a first order
exponential smoothing delay of the white noise input.
(152) Correlation Time=
1
Units: Year [0,6,0.1]
The correlation time constant for the pink noise.
(153) Mean=
0
Units: dmnl
The mean of the pink noise process.
(154) Noise Seed=
2
Units: dmnl [1,25,1]
The noise seed determines which sequence of realizations for the
random process are used. Simulations with the same noise seed
will yield the same sequence, so different simulations can be
compared. Changing the see changes the realizations.
(155) Pink Noise= INTEG (
Change in Pink Noise,
Mean)
Units: dmnl
Pink Noise is first-order autocorrelated noise. Pink noise
provides a realistic noise input tomodels in which the next
random shock depends in part on the previous shocks. The user
can specify the correlation time. The mean and standard
deviation are specified by the user. (based on information from
Sterman 2000)
(156) Standard Deviation for pink noise=
0
Units: dmnl [0,1,0.1]
The standard deviation of the pink noise process.
(157) White Noise=
Mean + Standard Deviation for pink noise*((24*Correlation Time/TIME STEP)
^0.5*(RANDOM UNIFORM(-0.5, 0.5, Noise Seed)
))
Units: dmnl
White noise input to the pink noise process. The user specified
the mean, standard deviation, and noise seed. The white noise
input is drawn from a uniform distrib ution, then scaled to
yield the correct standard deviation for the pink noise.
********************************
.old age in stock
********************************
********************************
.output
********************************
(158) Sum of Catch= INTEG (
catch C,
0)
Units: t
Accumulation of catch over the course of the simulation.
********************************
.price and cost
********************************
(159) selling price of fish=
Recent Typical Fish Prices*LK effect that size of catch has on price(ratio of current to recent catches
)
Units: $/t
********************************
.recruitment loop
********************************
********************************
.vessel entry
********************************
(160) actually retiring from fleet=
MAX(normally retiring from fleet*effect of cpue on retirement, 0)
Units: units/Year
Number of vessels retiring from the fishery.
(161) AVERAGE VESSEL LIFE SPAN IN FLEET=
10
Units: Year [1,20,1]
Life-time of vessels in the fishery (not necessarily the life of
the vessel).
(162) cpue ratio=
cpue/income adjusted acceptable cpue
Units: dmnl
The ratio of the current cpue to the acceptable cpue.
(163) CPUE SMOOTH TIME=
3
Units: Year [0,5,0.1]
The the number of years taken into account when fishers are
deciding if fishing has been good enough to convince them to
enter the fishery.
(164) effect of cpue on retirement=
LK relationship of cpue to increasing vessel retirement(smooth of cpue ratio
)
Units: dmnl
The effect that different catch rates (cpue) have on the rate of
vessel (fishing gear) retirement from the fishery.
(165) effect of cpue on vessel entry=
LK relation of cpue ratio to its effect on vessel entry(smooth of cpue ratio
)
Units: dmnl
The effect that the cpue ratio has on the entry of gear units
into the fishery. When this ratio is 1 there is a neutral effect
on vessel entry. New vessels are more likely to enter the
fishery when cpue is higher than normal. When cpue is very high
all available vessels will join the fishery.
(166) effective fishing units=
Units of Fishing Gear E*capacity utilization
Units: units [0,500,25]
The number of fishing gear units in use adjusted by the capacity
utilization (if implemented)
(167) entering fleet=
actual vessel entry rate
Units: units/Year
number of vessels (or gear units) entering the fishery. Can be
negative in extreme circumstances.
(168) expectation smooth time=
2
Units: Year
smooth time determining replacement fishing gear entry into
fishery
(169) Expected Rate of Vessel Replacement=
SMOOTH3( normally retiring from fleet, expectation smooth time)
Units: units/Year
The rate at which units of fishing gear enter the fishery when
the fishery is in approximate equlibrium.
(170) industry's desired entry rate=
expected rate new vessel entry+revised replacement rate
Units: units/Year
The desired number of new vessels on the part of the fishing
industry
(171) INITIAL NUMBER OF FISHING UNITS=
25
Units: units [0,300,5]
The number of fishing gear units (e,g, vessels) in the fishery
at the start of the simulation.
(172) LK relation of cpue ratio to its effect on vessel entry(
[(0,0)-(10,1)],(1,0),(2.45322,0.0955056),(3.40956,0.162921),(4.34511,0.244382
),(5.44699,0.342697),(6.38254,0.452247),(7.0894,0.567416),(8.06653,0.794944
),(8.79418,0.91573),(9.27235,0.969101),(9.56341,0.985955),(10,1))
Units: dmnl
A graphical function which takes as x the cpue ratio and
produces as y the effect on gear entry into the fishery.\!cpue
ratio ...... is equal to .... current cpue / acceptable
cpue\!fraction of vessels which will enter dmnl
(173) LK relationship of cpue to increasing vessel retirement(
[(0,0)-(1,10)],(0,10),(0.039501,6.88202),(0.0893971,5.22472),(0.168399,4.01685
),(0.257463,3.22506),(0.404851,2.4594),(1,1))
Units: dmnl
A graphical relationship describing the effect that cpue has on
vessel retirement. As cpue ratio drops below 1 the retirement
rate of vessels increases\!smooth of cpue ratio\!effect on
retirment of vessels
(174) MAX POSSIBLE NEW VESSELS=
500
Units: units/Year [0,1000,5]
The physical maximum number of new vessels that can be purchased
or transferred into the fishery (i.e. limited by construction or
other constraints). This value is important in determining how
many vessels can enter when fishing is good. This includes
vessels transfering from other fisheries.
(175) net change in unit numbers=
entering fleet-actually retiring from fleet
Units: units/Year
Net change in fishing gear numbers
(176) normally retiring from fleet=
Units of Fishing Gear E/AVERAGE VESSEL LIFE SPAN IN FLEET
Units: units/Year
Number of vessels normally retiring from the fishery
(177) smooth of cpue ratio=
SMOOTH(cpue ratio, CPUE SMOOTH TIME)
Units: dmnl
cpue ratio perceived by fishers is a view accumulated over a
period of time
(178) UNDERLYING ACCEPTABLE CPUE=
35
Units: t/(Year*units) [0,100,5]
This is the approximate minimum acceptable, or minimum target,
CPUE of each fishing gear unit (e.g. a fishing boat).
(179) Units of Fishing Gear E= INTEG (
entering fleet-actually retiring from fleet,
INITIAL NUMBER OF FISHING UNITS)
Units: units [0,300,10]
Number of units of fishing gear in the fishery.