In a seasonal model with spawnmonth not set to the beginning of a season, the reported spawnbio was lower than expected.
Investigation found that there was no discrepancy with spawnmonth at beginning of a season.
And that the magnitude of difference was in accord with being off by exp(-z*seasdur)
The model output for spawntiming as shown in echoinput was:
2 N seasons
6 6 months/seas (fractions OK)
2 Number of subseasons (even number only; min 2) for calculation of ALK
0.5 0.5 processed season duration (frac. of year)
0.25 0.25 processed subseason duration (frac. of year)
processed subseason cumulative annual time within season
0 0.25
0 0.25
SPAWN month: 5.5; seas: 1; subseas_for_ALK: 2; timing_in_season: 0.75
Note that timing is as a fraction of the season. When the value gets used in internal calculations, season duration was not being taken into account:
SSB_pop_gp(y, p, GP4(g)) += fracfemale_mult * fec(g) * elem_prod(natage(t, p, g), mfexp(-Z_rate(t, p, g) * spawn_time_seas)); // accumulates SSB by area and by growthpattern
Solution will be to adjust spawn_time_seas by duration of the season.
To Reproduce
per what is shown above
Expected behavior
spawnbio calculation to decay by exp(-Z) within the season
Screenshots
No response
Which OS are you seeing the problem on?
No response
Which version of SS3 are you seeing the problem on?
This has probably been an error throughout the history of 3.30.
Describe the bug
In a seasonal model with spawnmonth not set to the beginning of a season, the reported spawnbio was lower than expected. Investigation found that there was no discrepancy with spawnmonth at beginning of a season. And that the magnitude of difference was in accord with being off by exp(-z*seasdur)
The model output for spawntiming as shown in echoinput was: 2 N seasons 6 6 months/seas (fractions OK) 2 Number of subseasons (even number only; min 2) for calculation of ALK 0.5 0.5 processed season duration (frac. of year) 0.25 0.25 processed subseason duration (frac. of year) processed subseason cumulative annual time within season 0 0.25 0 0.25 SPAWN month: 5.5; seas: 1; subseas_for_ALK: 2; timing_in_season: 0.75
Note that timing is as a fraction of the season. When the value gets used in internal calculations, season duration was not being taken into account:
SSB_pop_gp(y, p, GP4(g)) += fracfemale_mult * fec(g) * elem_prod(natage(t, p, g), mfexp(-Z_rate(t, p, g) * spawn_time_seas)); // accumulates SSB by area and by growthpatternSolution will be to adjust spawn_time_seas by duration of the season.
To Reproduce
per what is shown above
Expected behavior
spawnbio calculation to decay by exp(-Z) within the season
Screenshots
No response
Which OS are you seeing the problem on?
No response
Which version of SS3 are you seeing the problem on?
This has probably been an error throughout the history of 3.30.
Additional Context
No response