If you need proof that something is drastically wrong with our sea fish populations you need look no further than the British sea fish angling records.
These records will give you little indication of the size of fish prior to large scale commercial exploitation (archaeological records show that cod in medieval times could be several meters long), but for a look at the modern state of our marine environment it is enlightening.
If you take an average of the years in which the record fish were caught, the heyday for catching big fish in UK waters in modern times was roughly in the mid-1980's, and it's been pretty much downhill ever since.
No British sea fish record has been officially broken since 2002 (Couch's sea bream) and the oldest record still standing is from 1933 (Atlantic bluefin tuna - they left us when the N. Sea herring fishery collapsed).
Taking a closer look and accounting for commercial fish species only, the picture looks even bleaker.
The largest bass was caught in 1988, cod in 1992, haddock in 1978, halibut in 1979, herring in 1973, ling in 1989, mackerel in 1984, monkfish in 1984, skate in 1986 and plaice in 1989. (Source: British Record Fish Committee). It would be extremely surprising if any of these records are ever broken again.
Whilst this comparison can in no way be described as a definitive account of the state of the UK's seas, it is, for a person who grew up in the 1970's and was used to frequently seeing a 40lb cod or ling adorning the cover of the sea angling press, a sobering reminder of what we have lost beneath our surrounding seas.