B0 |
is the virgin biomass (often expressed in terms of the biomass
of mature females) - see also K. |
BMSY |
is the biomass at which MSY is achieved. |
Bt |
is the (exploitable) biomass at the start of year
t. |
|
is the catch by all gear-types during year t. |
|
is the catch by gear-type g during year
t. |
Depletion |
is the ratio of the biomass in a given year to that in a
virgin state. |
|
is the fishing mortality at which the slope of the
yield-per-recruit curve is 0.1 of that at the origin. |
|
is the ith hypothesis (the combination of a model and a
set of values for its parameters). For cases in which the model is assumed
known, corresponds solely to a set of
values for the model parameters. |
|
is the index of abundance for year t. |
K |
is the environmental carrying capacity - see also
B0. |
|
is the likelihood of the data given a parameter vector (see
Section 1.3.1). |
|
is the instantaneous rate of natural mortality. |
MCMC |
Markov Chain Monte Carlo - a numerical method for computing
posterior distributions. |
MSY |
is the Maximum Sustainable Yield. |
MSYR |
is the ratio of MSY to
BMSY. |
|
is the number of fish of age a and sex s at the
start of year t. |
N(x,y2) |
is the normal distribution with mean x and standard
deviation y. |
|
is the recruitment (
is the recruitment during year t). |
|
is the recruitment in a virgin state. |
|
is the average recruitment. |
|
is the spawner stock size
( is the spawner stock size at the
start of year t). |
SIR |
Sample-Importance-Resample - a numerical method for computing
posterior distributions. |
Steepness |
is the ratio of the recruitment expected at 20% of
B0 to the recruitment expected at B0 (see
also h). |
U[a,b] |
is the uniform distribution on the range a to
b. |
|
is the value of some function f of the model
parameters. For example, f could simply involve selecting one of the
parameters or some more complicated function such as projecting the model and
computing the current biomass. |
|
is the product of the likelihood function and the prior
evaluated at the parameter vector
. |
h |
is the steepness of the stock-recruitment relationship (the
ratio of the expected recruitment at 20% of B0 to the expected
recruitment at B0). |
k |
is a (constant) harvest rate. |
|
is the prior probability of the parameter vector
. |
q |
is the catchability coefficient - the parameter which relates
catch rate to exploitable biomass. |
|
is the intrinsic growth rate parameter for a biomass dynamics
model. |
s |
is the annual survival rate. |
|
is the relative selectivity of the gear used by gear-type
g on fish of age a and sex s during year
t. |
|
is the exploitation rate on fish of age a and sex
s by gear-type g during year t. |
|
is the weight of a fish of age a and sex s
during year t. |
|
is the slope of the stock-recruitment relationship at the
origin (or the logarithm of this slope). |
|
is the parameter that determines the carrying capacity for a
stock-recruitment relationship. |
|
is a multiplicative factor to adjust the output of the
stock-recruitment relationship for year t. |
l |
is the intrinsic growth rate parameter (also referred to as
r). |
|
is the vector of model parameters;
is the jth element of
. |
|
is the posterior probability of the parameter vector
. |
|
is the importance function. |
|
is the amount of temporal autocorrelation in assessment
error. |
|
is the amount of temporal autocorrelation in process
error. |
|
is the standard deviation of the extent of assessment
error. |
|
is the standard deviation of the extent of implementation
error. |
|
is the standard deviation of the process error. |
|
is the standard deviation of the inter-annual variation in
catchability. |
|
is the standard deviation of the noise about the
stock-recruitment relationship. |
|
is the standard deviation of the variation in biomass due to
environmental fluctuations. |
|
is relative fecundity as a function of age. |