I'm tentatively putting my hand up to help with the marlin and tuna issue that's going around now (you all know I like to jump on the latest bandwagon).
http://www.afma.gov.au/fisheries/eastern%20tuna%20and%20billfish/workshop/datasum_1202.pdf
Take a look at the very last graph on page 9 - catch per unit effor for a few different species. It looks to me like the yellowfin tuna are in a much worse state than the marlin, so perhaps we should focus on this. The swordfish and bigeye are about ten years behind on the pattern but the catch per unit effort is already dropping. If the Australian catch is as small as some say then this graph gives a good indication of the number of fish left in the water. Thats assuming that before the peaks in the graphs they weren't targeted efficiently - or are the peaks down to shifting currents?
Why is the striped marlin graph on the same scale as the yellowfin? This makes it hard to gauge.
The average weight doesn't seem to be dropping which is usually the first sign of a fishery in trouble. Is this because they are fast growers like kingfish?