Since I would like to use the salinity data with lat/lon in the Gulf of St. Lawrence, Canada to compare with the fishing data. I'm trying to download the 2010-2019 average salinity data. As the table in this database showed. (https://www.arcgis.com/home/webmap/viewer.html?url=https%3A%2F%2Fgisp.dfo-mpo.gc.ca%2Farcgis%2Frest%2Fservices%2FFGP%2FTeleost_BottomTemperatureSalinityFond%2FMapServer&source=sd)
They have not enabled download through the ArcGIS Online, which would have been simplest. You need to add a link to their server in ArcGIS Pro.
If you click on the link in their open portal site:
It takes you to the metadata page, in the address bar is the server location:
Add that to ArcGIS Pro or ArcMap, ArcGIS Pro is much easier to use...
Drill down to your layer of interest and add to map so here is 2019 salinity
If you try to export the data it won't allow you, they have in their wisdom disabled that, not sure why one would share data and then not allow you to export it... They are also symbolizing this continuous surface as a polygon layer, a bit weird, would normally be raster. But the information you seek seems to be in the attribute table so you can export that using the table to table tool or table to Excel for example.