“Ocean Life in Olden Days”

Earlier this week, the Census of Marine Life put out a press release summarizing their findings of their History of Marine Animal Populations (HMAP) division.  Some of those findings can cause you to catch your breath a little bit.

In 1995, in a one-page postscript [PDF] in the journal Trends in Ecology and Evolution, fisheries biologist Daniel Pauly came up with a name for an illness he saw afflicting fisheries science: Shifting Baseline Syndrome.  The problem, he wrote, was that each new generation of scientists forms a new idea of what things “ought” to be like. Because of a lack of trustworthy historical data and formal records, each new cohort assumes as a matter of course that the way things are when they begin their careers is more or less how it always has been, and measures any changes occurring in their lifetimes against that level. In this way, truly staggering decreases in abundance and diversity can take place almost unnoticed over several generations.

Photos of trophy fish from Florida in (a) 1957, (b) the 1980s sometime, and  (c) 2007.  These were dug up by Loren McLenachan, of the Scripps Institute of Oceanography.

Photos of trophy fish from Florida in (a) 1957, (b) the 1980's sometime, and (c) 2007. These were dug up by Loren McLenachan, of the Scripps Institute of Oceanography.

This problem, of course, is not limited to scientists, or to the abundance and diversity of marine animals. It is a manifestation of the general human tendencies to forget things easily and disregard the wise advice of our elders. It is particularly widespread and serious in the context our changing environment, where a lack of records and a thinning cultural memory leave most people utterly unaware of how different nature looks today compared with our parents’, grandparents’, or great-grandparents’ time.

The HMAP of the Census of Marine Life has been doing their damnedest to rectify this problem. They’ve gone back in time, using sources ranging from genetic analysis to whaling logbooks to fishing tournament photos from Florida* (at right). The story emerging from their work appears to be that our impact on the oceans started a lot earlier than we generally think it did, and that the size and abundance of animals today is much less than it was at the beginning of that impact. A few examples from HMAP:

  • Before whaling, there were 27,000 right whales living around New Zealand—30 times what are there today.
  • Cornwall, GB, had huge pods of blue whales, orcas, and sharks living offshore.
  • The size of freshwater fish caught by Europeans started declining far back in the middle ages. Around 1100, Europeans shifted from local freshwater fish to those caught in the open ocean.
  • The European herring fishery suffered a collapse in the early 19th century, followed by an explosion of the jellies the herring had been eating.

Those are the ones I found most interesting. The release can be found here.

* I read the paper behind these photos (McLenachan, Loren, “Documenting the loss of large trophy fish from the Florida Keys with Historical Photographs,” Conservation Biology v. 23 n. 3 pp 636-643) and it’s not clear to me what role stricter regulations/size limits have played in the decreasing size of the keepers. Still, this little montage is pretty impressive.

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