Knowledge of the ocean, the bottom, and what is in it, is very different from knowledge of commercial fish populations. Records of catch go way back and the met

Knowledge of the ocean, the bottom, and what is in it, is very different from knowledge of commercial fish populations. Records of catch go way back and the methods for inferring population are good enough. There is also an archaeological record of what coastal people ate thousands of years ago and these provide evidence of changes in fish populations over hundreds of years. c.f. https://en.wikipedia.org/wiki/Shifting_baseline https://en.wikipedia.org/wiki/Shifting_baseline