I don't think an accurate corelation between " catch rates " and " fish stocks " can be made from newspaper clippings reporting catches.
So many variables to contend with that I find it impossible to use any critical data sets to make remotely accurate assumptions.
The way to understand or report fish stocks is to count fish. That is impossible, so scientists use other means to produce results.
Catch rates over the years depend on many factors.
time spent fishing " fishing effort "
numbers of anglers
numbers of fish
distance to travel / area specific
habitat degredation and loss
floods and droughts ( this has a large bearing on recruitment of many species )
the actual reporting / recording
fishery legislation changes ( bag limits / size limits )
recruitment loss through commercial by-catch
envorinmental changes ( water temps )
loss or change to spawning areas
recreational and commercial fishing technics ( sounders, gps )
fishers attitudes ( C & R groups )
I would like to see the data used by Dr Ruth Thurstan and Professor John Pandolfi to make their assumption that the Snapper stocks have dropped by 90%. Using catch rates could possibly produce a result for a drop in catch rates, but what specifically are the catch rates based on ? Numbers of anglers ? Numbers of fish ? Fishing effort ?
Certainly an individual caught more Snapper in say 1960 than today, but then, there were no bag limits, size limits and certainly the species were more prevelant close to shore due to a number of factors including far less habitat destruction. And if we go further back, we would find the more bio-mass close to shore as the industrial and agricultural runoff was far less.
I understand that Qld Fisheries scientists have been monitoring the stocks for some time and believe we are at a specific level now relating to virgin bio-mass. What the vrigin bio-mass was, is really an unknown factor making any results from calculations an assumption.
What you will find through this research is that the attributal economic input into the Snapper fishery is far greater now than in years gone by. Meaning the numbers of fishers that fish for Snapper put more money into the economy in their pursuit for these brutes than ever before. A fair, but not statically accurate “ assumption “ would be to say in the year 1900 it would cost the average recreational fisher a lot less than 1 penny ( 1 cent ) per kilogram ( lbs , back then ) for each fish to catch and considering that would possibly be about 0.01% of their weekly pay ( income ), whereas today it is closer to $80 / kilo and about 6% of weekly pay.
In yesteryear and the same as this very day, there will always be the fisher that can catch their bag limit on any given day and there are fishers that will struggle. Ask the struggling fisher and they will tell you “ stocks are down “, ask the other one and they'll tell you “ no problems “. We need to ask the Fish...... I don't speak fish... do you ?
LP