rearing_time_delta: Delta rearing time
In fishsciences/YoloBypassSBM: Yolo Bypass Salmon Benefits Model

Delta rearing time after adjusting for passage time and temperature

1	rearing_time_delta(water_year_string, date_index, passage_time, fork_length)

`water_year_string`	Water year (1997-2011) as a string
`date_index`	Index of date in a water year that cohort begins Delta rearing; in all years except WY1997, equivalent to day of water year
`passage_time`	Passge time
`fork_length`	Average fork length (mm) of cohort