# Predict spawning

#### Morgan Sparks, Bryan M. Maitland

# Introduction

hatchR has a built in function—`predict_spawn()`—which allows users to predict when a fish’s parent spawned based on the observation of either when a fish hatched or emerged. The function works almost exactly the same as `predict_phenology()` but walks backwards from the point of development (hatch or emerge) and outputs spawn date.

# Workflow

`predict_spawn()` works in essentially the same fashion as you learned about for `predict_phenology()` in the Predict fish phenology: basic vignette. First you have to select a developmental model. This will be determined by what life history stage from which you have empirical phenology data. For example, maybe you snorkeled a stream and observed bull trout emerging from a redd.

## Model selection

Because our empirical data are from observing juvenile bull trout emergence we will use the bull trout emergence model using `model_select()` and our `model_table`. However, if you have custom models those could be used in the same fashion.

    #select bull trout emergence model
    bt_emerge_mod <- model_select(author = "Austin et al. 2019",
                                          species = "bull trout",
                                          model = "MM",
                                          development_type = "emerge"
                                  )

## Predict spawning

We’ll use our `crooked_river` data set, which is temperature data from a reach of spawning bull trout. With model in hand we’ll predict spawn timing assuming we observed fish emerging March 21, 2015.

    #predict spawn timing using "2015-03-21" emergence date
    bt_spawn <- predict_spawn(data = crooked_river,
                  dates = date,
                  temperature = temp_c,
                  develop.date = "2015-03-21",
                  model = bt_emerge_mod
                  )

The outputted object has the exact same structure as a `predict_phenology()` output. They include the slots:

- `days_to_develop`: days from hatch or emergence to spawn

- `dev_period`: a 1x2 dataframe where `start`= predicted spawn time and `stop`=empirical developmental event used for prediction in the model.

- `ef_table`: a n x 5 tibble where n is the number of days from spawn to development. Note that the table is ordered from the development date and moves backwards in time. The columns are:

  - `index`: the row number in the temperature data set

  - `dates`: dates imported from your temperature data

  - `temperature`: daily average temperature imported from your temperature data

  - `ef_vals`: every day’s individual effective value

  - `ef_cumsum`: the cumulative sum of effective values moving backwards from 1, a fish hatches when `ef_cumsum` <= 0.

- `model_specs`: model specifications imported from the developmental model provided to `predict_phenology()`

A summary of the above output for `bt_spawn` is presented below.

    str(bt_spawn)
    #> List of 4
    #>  $ days_to_develop: int 188
    #>  $ dev_period     :'data.frame': 1 obs. of  2 variables:
    #>   ..$ start: POSIXct[1:1], format: "2014-09-15"
    #>   ..$ stop : POSIXct[1:1], format: "2015-03-21"
    #>  $ ef_table       : tibble [188 × 5] (S3: tbl_df/tbl/data.frame)
    #>   ..$ index      : num [1:188] 1572 1571 1570 1569 1568 ...
    #>   ..$ dates      : POSIXct[1:188], format: "2015-03-21" "2015-03-20" ...
    #>   ..$ temperature: num [1:188] 2.25 1.97 1.78 2 2.02 2.06 1.97 1.93 1.64 1.79 ...
    #>   ..$ ef_vals    : num [1:188] 0.00496 0.00479 0.00467 0.00481 0.00482 ...
    #>   ..$ ef_cumsum  : num [1:188] 0.995 0.99 0.986 0.981 0.976 ...
    #>  $ model_specs    : spc_tbl_ [1 × 5] (S3: spec_tbl_df/tbl_df/tbl/data.frame)
    #>   ..$ author          : chr "Austin et al. 2019"
    #>   ..$ species         : chr "bull trout"
    #>   ..$ model_id        : chr "MM"
    #>   ..$ development_type: chr "emerge"
    #>   ..$ expression      : chr "1/exp(5.590 - (x  * 0.126))"
    #>   ..- attr(*, "spec")=
    #>   .. .. cols(
    #>   .. ..   author = col_character(),
    #>   .. ..   species = col_character(),
    #>   .. ..   model_id = col_character(),
    #>   .. ..   development_type = col_character(),
    #>   .. ..   expression = col_character()
    #>   .. .. )
    #>   ..- attr(*, "problems")=<externalptr>

So we see, the fish took 188 days to emerge with a predicted spawning date of September 15, 2014.

    # development time
    bt_spawn$days_to_develop
    #> [1] 188

    # spawning date
    bt_spawn$dev_period$start
    #> [1] "2014-09-15 UTC"

Finally, because the model output is in essentially the same format as that from `predict_phenology()` it can be plotted using `plot_phenology()` .

    plot_phenology(bt_spawn)

### Compare to `predict_phenology()`

To demonstrate this provides the same information as `predict_phenology()` we can compare the outputs. Now we will use the predicted spawn date of `"2014-09-15"` as our input in `predict_phenology()`.

    bt_emerge <- predict_phenology(data = crooked_river,
                  dates = date,
                  temperature = temp_c,
                  spawn.date = "2014-09-15",
                  model = bt_emerge_mod
                  )

And we can compare `dev_period` to verify the outputs match.

    # are they the same (yes!)
    bt_emerge$dev_period == bt_spawn$dev_period
    #>      start stop
    #> [1,]  TRUE TRUE

    #print out values
    bt_emerge$dev_period; bt_spawn$dev_period
    #>        start       stop
    #> 1 2014-09-15 2015-03-21
    #>        start       stop
    #> 1 2014-09-15 2015-03-21

## Using multiple inputs for `predict_spawn()`

Like `predict_phenology()`, `predict_spawn()` can easily be mapped across multiple variable sets to automate the function. We can use a simple example of observing emerging fish across multiple months to demonstrate.

We’ll assume we observed fish emerging February 15, March 15, and April 15 in 2015. And then `map()` the function across those dates using the `purrr` package.

    library(purrr)

    #vector of dates
    emerge_days <- c("2015-02-15","2015-03-15", "2015-04-15")

    # object for predicting spawn timing across three emergence days
    bt_multiple_emerge <- map(emerge_days, # vector of emergence dates
                              predict_spawn, # predict_spawn function
                              # everything below are arguments to predict_spawn()
                              data = crooked_river,
                              dates = date,
                              temperature = temp_c,
                              model = bt_emerge_mod)

    # we can access just the dev_periods using map_df
    # the start column provides the predicted spawn dates
    bt_multiple_emerge |>
      map_df("dev_period")
    #>        start       stop
    #> 1 2014-08-29 2015-02-15
    #> 2 2014-09-11 2015-03-15
    #> 3 2014-09-27 2015-04-15

Based on our predictions, the fish spawned for our respective observed emergence dates on August 29, September 11, and September 27 in 2014.

`predict_spawn()` can be automated to greater extents just like with `predict_phenology()`. We recommend reading the Predict fish phenology: advanced vignette to review ways to map across multiple variables.