I have fished the Forth for 75 years when stocks of sandeels and cod were plentiful there, and it is a fact that both species have practically disappeared almost overnight.
The herring stocks had already disappeared before the 1930s. Thankfully, we still have good stocks of young sprats, every September being chased inshore by shoals of mackerel making it easy to catch both from the beach.
Many years ago at a Kenmore seminar on salmon fishing, I mentioned the removal of sandeels at the Wee Bankie in the Forth by the Danes to the then-fisheries manager, David Dunkley. He stated the sandeels would be too big for the smolts to eat and not to bother! The sandeels were removed for their oil and cosmetics.
I said this would affect everything in the sea that depended on this food supply and I doubted very much if the stocks at the Wee Bankie could recover.
Global greed should be blamed for the disappearance of the cod from the Grand Banks off Newfoundland, and the efficiency of the Danish trawlers should be blamed for the sandeels’ disappearance from the Forth.