# 2.8.6. Fishing parameters (Osmose >= 4.3)¶

## 2.8.6.1. Fishing mortality rates¶

In the Osmose versions >= 4.3, changes in the parameterization of fisheries have been implemented, although the spirit remains close to the one in versions 4.

Fisheries mortality time-series for each gear are now the product of three components:

• A vector of fishing mortality rates associated with fishing periods, $$F_{period}$$

• A vector of seasonality values, which provides the time-variation of the fishing effort during a given season, $$F_{season}$$

• A vector of multipliers, which provides a multiplication factor, $$F_{base}$$.

Therefore, for a given time-step $$t$$, the value of the fishing mortality for a given fleet would be:

$F(t) = F_{period}(t) \times F_{season}(t) \times F_{base}(t)$

Since the parameterisation is a bit tricky, a parameter (fisheries.check.enabled) allows to control whether the values of $$F$$, $$F_{period}$$, $$F_season$$ and : math:F_base should be saved. It allows to control that the given time-series are as expcted.

### 2.8.6.1.1. Fishing base ($$F_{base}$$)¶

The fishing base mortality multiplier is provided as regime shifts.

 fisheries.rate.base.fsh# Fishing base for the different regimes. fisheries.rate.base.shift.fsh# Years of the regime shifts. fisheries.rate.base.log.enabled.fsh# True if fisheries are provided in logscale.

If one value is provided in fisheries.rate.base.fsh#, this value will be used during all the simulation. If $$N$$ values are provided, then the fisheries.rate.base.shift.fsh# parameter must contain $$N-1$$ values, which are the years of the regime shifts.

### 2.8.6.1.2. Fishing period ($$F_{period}$$)¶

There is now the possibility to define a fishing period, i.e. a period when the fishery is active.

 fisheries.period.number.fsh# Number of fishing periods within one year ($$N_{per}$$) fisheries.period.start.fsh# Start of the active fishing period (fraction of year, default = 0, $$Y_{start}$$) fisheries.rate.byperiod.fsh# Fishing mortality rate. Must me in $$year^{-1}$$

Note that the number of values expected in the fisheries.rate.byperiod.fsh# parameter depends on $$Y_{start}$$.

If $$Y_{start} = 0$$, then $$N_{per} \times N_{year}$$ values are expected (one value for each fishing and non-fishing season).

If $$Y_{start} \neq 0$$, then $$N_{per} \times N_{year} + 1$$ values are expected.

Fig. 2.8 Fishing period for two values of $$Y_{start}$$

### 2.8.6.1.3. Fishing seasonality¶

In order to distribute the fishery mortality over the season, the user can define a seasonality vector, either as a file, or as a vector.

 fisheries.seasonality.fsh# Array of fishing seasonality. Must contain $$\frac{N_{step/year}}{N_{season}}$$ fisheries.seasonality.file.fsh# File containing the fishing seasonalities (must contain $$N_{step}$$ values)

In the first case, the same seasonality will be applied for each fishing season. Imagine that we have 24 time-steps per year and two fishing season (with no offeset, top of figure Fig. 2.8), then the seasonality provided should contain 12 values, which would apply for the active fishing period (green zone).

In the latter case, it is up to the user to generate the proper time series and to store it in a file.

Danger

The sum of fishing seasonalities must equal one over the fishing seasons! No automatic normalisation is performed by Osmose!

### 2.8.6.1.4. Case studies¶

fisheries.rate.base.fsh0;1
fisheries.season.number.fsh0;1
fisheries.rate.byperiod.fsh0;1
fisheries.season.start.fsh0;0
fisheries.seasonality.fsh0;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166;0.04166

fisheries.rate.base.fsh0;1
fisheries.season.number.fsh0;2
fisheries.rate.byperiod.fsh0;1, 0, 2, 0, 3, 0, 4, 0, 5, 0
fisheries.season.start.fsh0;0
fisheries.seasonality.fsh0;0.0;0.0;0.0;0.0;0.0;0.0;0.1666;0.1666;0.1666;0.1666;0.1666;0.1666;

fisheries.rate.base.fsh0;1
fisheries.season.number.fsh0;2
fisheries.rate.byperiod.fsh0;0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0
fisheries.season.start.fsh0;0.25
fisheries.seasonality.fsh0;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;

fisheries.rate.base.fsh0;1,2,3,10
fisheries.rate.base.shift.fsh0;1, 3, 4
fisheries.season.number.fsh0;2
fisheries.rate.byperiod.fsh0;0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0
fisheries.season.start.fsh0;0.25
fisheries.seasonality.fsh0;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;0.0833;

fisheries.rate.base.fsh0;1,2,3,10
fisheries.rate.base.shift.fsh0;1, 3, 4
fisheries.season.number.fsh0;3
fisheries.rate.byperiod.fsh0;0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7, 0, 8
fisheries.season.start.fsh0;0.25
fisheries.seasonality.fsh0;0.1,0.2,0.5,0.2,0,0,0,0


## 2.8.6.2. Size selectivities¶

 fisheries.selectivity.tiny.fsh# Selectivities values below which selectivity if forced to 0 ($$\epsilon$$) fisheries.selectivity.type.file.fsh# File containing the selectivity types fisheries.selectivity.type.shift.fsh# Array containing the selectivity periods fisheries.selectivity.type.fsh# Selectivity types (one value per shift period). Must be 0, 1 or 2 fisheries.selectivity.a50.file.fsh# File containing the age selectivities. fisheries.selectivity.a50.shift.fsh# Array containing the $$A_{50}$$ shift periods fisheries.selectivity.a50.fsh# Age selectity (one value per shift period). If set, assumes that fishery selectivity is age-based fisheries.selectivity.l50.file.fsh# File containing the $$L_{50}$$. fisheries.selectivity.l50.shift.fsh# Array containing the $$L_{50}$$ shift periods fisheries.selectivity.l50.fsh# $$L_{50}$$ (one value per shift period). fisheries.selectivity.l75.file.fsh# File containing the $$L_{75}$$ fisheries.selectivity.l75.shift.fsh# Array containing the $$L_{75}$$ shift periods fisheries.selectivity.l75.fsh# $$L_{75}$$ (one value per shift period).

Note that type, a50, l50 and l75 are parameterized in the same way. If the .file parameter is defined, then it is used. If it is not set, then values are defined by using the other two parameters. The shift array contains thresholds, where the values are to change.

The selectivity type must contain 0 (knife-edge), 1 (sigmoid), 2 (Gaussian) or 3 (log-normal).

If one of the a50 parameter, it is assumed that age selectivity is used.

Warning

Only knife-edge selectivity can be used with age.

Note

If only knife-edge selectivity is used, then the l75 parameters are not used.

### 2.8.6.2.1. Knife-edge selectivity¶

Knife-edge selectivity is computed as follows:

$S(L) = 1\ if\ L \ge L_{50}$

### 2.8.6.2.2. Sigmoid selectivity¶

Sigmoid selectivity is computed as follows:

\begin{align}\begin{aligned}S(L) = \frac{1} {1 + exp^{S_1 - S_2 L}}\\S_1 = \frac{L_{50} \times \ln 3}{L_{75} - L_{50}}\\S_2 = \frac{S_1}{L_50}\end{aligned}\end{align}

### 2.8.6.2.3. Gaussian selectivity¶

Gaussian selectivity is computed as follows:

\begin{align}\begin{aligned}S(L) = \frac{F(L)}{F(L_{50})}\\F(L) = exp\left(-\frac{L - L_{50}}{2 \sigma^2}\right)\\\sigma = \frac{L_{75} - L_{50}}{q_{75}}\end{aligned}\end{align}

with $$q_{75}$$ is the inverse cumulative standard normal distribution for the 75th percentile.

## 2.8.6.3. Catchability¶

Fishery cathabilities are parameterized in a similar way as predation accessibility matrix.

 fisheries.catchability.file Name of the catchability file fisheries.catchability.file.cat# Name of the catchability file fisheries.catchability.years.cat# List of years when the catchability should be used. fisheries.catchability.initialYear.cat# First year when the catchability matrix should be used (if year list not provided) fisheries.catchability.finalYear.cat# Last year when the catchability matrix should be used (if year list not provided) fisheries.catchability.steps.cat# List of steps within a year when the catchability should be used.

Fishery catchabilities should be provided as a CSV file, with fisheries as column (predators) and species (background and focal) as rows (preys). If the first parameter (fisheries.catchability.file) is found, then this catchability matrix will be used over the entire simulation.

If this parameter is not found, Osmose will assume that catchability matrixes may vary over time. It will therefore look for all the fisheries.catchability.file.cat# parameters. Each catchability matrix should be associated with time-indications, which specifies on which year (interannual variability) and which time-steps (seasonal variabillity) this catchability matrix should be used.

Warning

Note that the # here is not related to the one of fisheries.

## 2.8.6.4. Discards¶

There is also the possibility to define fisheries discards. It is defined in the same way as catchabilies (cf above for a detailed description of the parameters).

 fisheries.discards.file Name of the catchability file fisheries.discards.file.dis# Name of the catchability file fisheries.discards.initialYear.dis# First year when the catchability matrix should be used fisheries.discards.finalYear.dis# Last year when the catchability matrix should be used fisheries.discards.years.dis# List of years when the catchability should be used. fisheries.discards.steps.dis# List of steps within a year when the catchability should be used.

Fishery discards should be provided as a CSV file, with fisheries as column (predators) and species (background and focal) as rows (preys).