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Comment by nosuchthing | Hacker News Reader

https://sites.uw.edu/bevanseries/2018/02/28/data-is-in-the-e...

"Dr. McClenachan used photographs taken between 1956 and 1985 to document the loss of the large trophy fish in the Florida Keys, and compared them with photographs that she took in 2007. She found a major shift in species composition across reef communities through time, with larger predatory fish being fished first, followed by a steep decline in the sizes and weights of fish caught more recently. Historically, catches were dominated by large sharks and goliath groupers, but today, the catches are almost exclusively small snappers. Interestingly, Dr. McClenachan found that the cost of fishing trips did not decrease, meaning customers paid approximately the same price for a ~20 kg trophy fish as they do for a ~2 kg trophy fish now, some 50 years later."

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Thanks. I still have issues though.

We don't know how representative those picture were. The 1950s pictures have survived over a half century, they were taken at a time when photography was harder work than today. I could go fishing, photograph my meagre catch, and put it on instagram for the world to see easily.

Plus these seem to be tourist photos? Maybe its a symptom of (inexperienced) amateurs going to Florida Keys spending big bucks for the experience, whereas in the 50s it was actual fishermen going out to catch big fish, and the very best would take photos of their catch.

Again I'm not denying the phenomenon, just how much we can actually rely on it to tell us something useful. You can't from this array of photos definitively state that populations of x,y and z have dropped i%.

Isn't that conclusion 100% the wrong way round?

If it were so difficult for photos to survive half a century wouldn't it be hard to show catches tended to bigger? After all the ancient 1950s photos of large catches have been lost through not surviving such unimaginable eons. Sorry for the tone, but seriously, by 1950s photography was not the rare and specialist thing it was in the 1910s. Sure, it might be just the unrepresentative ones that survived into modernity, but...

With millions of photos being taken daily today, shouldn't it be trivial to find some examples of enormous catches among them? Yet we don't find them. Yeah, yeah, I know, absence of evidence is not evidence of absence.

Reports of 2m, 100kg cod are from history, today both size and catch has plummeted.

My point was more that today I have a phone in my pocket permanently, digital photos are free so ill take a picture of anything. In the 50s there were financial and convenience barriers to photography, however small.

Plus these photos have survived. My modern photo of an un notable thing probably wont survive, a picture of a notable thing probably will.

I find it´s best to make a mental note, and talk to Uncle´s friends. There is an intergenerational information transfer band if you pay enough attention to it. Plus your own memory will inform you after a while.

I remember growing up and there being 3-4 weeks of snow around January and putting on multiple pairs of socks to play in it. My mother remembers there being a couple of feet of snow up into March, and getting trapped once driving across Dartmoor.

Perhaps your children will ask you what snow was.

Agreed, but that isn't science.

You could use it as a prompt to start doing more research to see if there actually is less snow. I'm not sure what else you could do with that information though, a tool for raising awareness of climate change?

Photos are better, they're useful for things like measuring glacier retreat. But even in your example there would be issues, if snow becomes noteworthy more people will take photos of it, so already you can only be confident of looking at the most extreme examples.

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