fish models Flashcards
CPUE
measures abundance
uses q,f
q=proportion of stock captured per fishing effort
Fish surveys
measure abundance
uses A,a,x,n
CMR peterson
measures abundance
R- number of recaptured
T-population in first captire
C-number of tagged in first capture
generic tags-fin clips
individual marks-PIT tags
assumes:
-no immigration no emmigration
-no recruitment no mortality
-small,closed population
depletion method
measures abundance
Nt,Ninf,Ct,q
Y-CPUE X-cummulative catch
q= -slope,
Ninf= (-intercept/q)
sumCadj= catch/2 + sumC
assumes:
-no change in I,E,R,D
-ignores stock size (all fish are equally catchable)
-fishing reduces CPUE significantly
Mass-Length regression
measures growth
M,a,L,b (often 3)
Y-weight
X-Length
or
Y-ln Weight
X-Ln Length
(this makes b=slope, can solve for a)
Von Bertalanffy model
measures growth
Lt,to,Linf,K
Y-Length
X-Age
Scales
Measures growth
Lx,Lp,Sx,Sp
x-previous
p-present
Beaverton holt
measures recruitment
a,b
S
R
Y-recruitment
X-Spawning stock
reaching asymptote K because inc competition from inc density .: recruit decreases (DD)
smaller a, more DD affects it
Ricker
measures recruitment
a,b
S
R
equation with exp
Y-recruitment
X-spawning stock
recruitment reaches a max then decreaswes as stock increases (canbilism, disease .: DD)
smaller b, the greater recruitment max
Shepherd
measures recruitment
a,b,k,s
equation with K
Y-recruitment
X- spawning stock
b<1 weak DD
b=1 beavterton holt
b>1 ricker
a influence until K where threshold for b is
Mortality from catch curve
No,e,z
lnNt=lnNo-zt
Y-Ln N
X-Age
solve for Z from formula and graph (linear dec in example)
Mortality from effort data
Z=M+F
or
Z=M+qf
Y-N
X-fishing effort
M=intercept
MSY
used for stock assessments
Bt,r,C
Fmsy-effort to produce MSY
graph 1:
Y-Biomass
X-Time
makes S shape, middle of S is biomass/2 i think, top of S is K asymptote
graph 2:
Y-growth rate
X-Biomass
rainbow shape, max growth &MSY in middle of rainbow
Schaefer Surplus production model
used for stock assessments
same original formula for MSY, but also
CPUE=a+bf
Fmsy= -a/2b
MSY= -a^2/4b
Y-CPUE
X-fishing effort
assumes:
-biomass added=biomass removed and CPUE~N
- Assumes perfect rainbow relationship between stock biomass and biomass addition (ignores +/- DD)
-ignores size and age structure
Populations additions with stock size
measures recruitment
compensation: beaverton holt
Over compensation: ricker
depensation:U shape and then rainbow
