The database and how it was created are fully described in: Boyce D.G., Petrie B. and Frank KT. 2021. Fishing, predation, and temperature drive herring decline in a large marine ecosystem. Ecology and Evolution. 
Tables 1 and 2 describe the data sources and indices that were created from them, and all associated metadata.
The columns in the database are as follows: 
Short_name: abbreviated name for the variable
Year: year of the timeseries
Y: data value
Long_name: full name for the variable, as described in Table 2
Category: descriptor for the variable, as described in Table 2
Datatype: denotes if value is imputed or not (I=imputed; R=raw)