My bet is that this is probably the first evidence of indeterminate growth [1] in the species. Increasing skeletal size is a pretty tell tale sign. With all the conservation programs working, they’ve started to get old enough that we can see enough of a difference to overcome individual variance in their growth cycle.
Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos [2]. If a mammal were to acquire this adaptation, it makes sense that it would be a marine one - I think whales and dolphins exhibit it too
These photos might not support the claim, but it is well known in fishing communities that many species of fish have gotten smaller. For instance, the size of lake trout in the great lakes has decline greatly. People used to catch 100+ lb lake trout. That's unfathomable to me.
> Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos
My reading of the article is that the pictures don't show a particular species getting smaller over time, but that the species of fish that grow large aren't caught anymore. Yes the fish in the pictures got smaller over time, but they also changed species.
From the article:
> Yes. This really isn’t a story about shifts in size within a particular species. I didn’t find that. What I did find is that the big species just aren’t there anymore.
My comment said exactly the same. This photos don't support the claim that fishes are reducing its size.
1) Photos show a mix of pelagic and coastal species. There was an incredibly stupid extinction of 10-20 years old local groupers the first year. Those were probably the fishes saved by World War II. Men killing themselves was a blessing for fishes. After removing all the big coastal species, if you have pelagic species your average size increases, otherwise is the last photo (with fishes that aren't small in fact, More or less on the average for the species shown).
2) The big pelagic species are seasonal migrators, and the migrations don't overlap exactly with the holiday season. This Carangidae could decide to travel one week before of after holidays, or pass at 50 Km more far of the coast and neither this giant fishes nor its even bigger predators will appear in the photo. This does not mean that they were extinct. Warming sea temperatures changed the migration patterns also.
Are fishes reducing its size when the predatory pressure increases? yes. Some Mediterranean fishes are also maturing much faster than before. But the proofs are in the scientific journals, not here. When the predator pressure skyrocket we have this escape response when the animals became giants or dwarfs. We can see the same effect on elephant tusk being shorter when they are hunted too much.
Having this in mind, we can understand better why we have a problem here with the sealions.
Size change in male sealions suggest that the predatory pressure over seals was alleviated. This is bad news.
It means that Killer whales and white sharks are silently [1] vanishing. Either they are being hunted by us (or killed by our machines), and/or their preys disappeared by a climatic event, and/or we can suspect a major disease.
If this disease extends to the functional category "predator" instead to the taxonomic category "Dolphinidae" the problem lies most probably in the trophic chain, and we can suspect bioaccumulation also.
If the big predators that eat fish are going locally extinct, we have a problem, because we are big predators that eat fish.
If predators are not anymore to do their jobs, we can safely predict that next-in-list group of preys will start suffering from major epidemics... that lead us directly to summer 2022:
"More than 150 sea lions have been found sick or dead along Oregon’s coast due to a bacterial outbreak of Leptospirosis this summer" [2].
"Hundreds of dead or dying sea lions have washed up on the beaches of Peru since January 2023 affected by bird flu" [3]
So it seems that what we have here is an ecosystem eroding and collapsing over the next lower level like a house of cards. Probably because there is a serious problem with the trophic chain that lead animals unable to trigger a good immune response. The wave will travel slowly toward the basis until eventually losing momentum and stopping. If the most affected seals were the older ones and the sample was focused in stranded animals, we would have a direct alternative explanation for the bigger skulls: Bad sampling.
[1] As they are pelagic and just sink on open sea most of the effect was silent and missed.
There is also selectivity for smaller fish for those that are caught using gillnets since they target a specific size. Smaller fish can swim right through and thus are advantaged at avoiding being fished.
Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos [2]. If a mammal were to acquire this adaptation, it makes sense that it would be a marine one - I think whales and dolphins exhibit it too
[1] https://en.m.wikipedia.org/wiki/Indeterminate_growth
[2] https://psmag.com/environment/fish-stories-the-ones-that-got...