I’ve been thinking a lot about how fishing and fisheries science are so intertwined. Gordon Miller, the wonderful librarian at the Pacific Biological Station in Nanaimo, sent me this photograph of my friend, Jergen Westrheim, sampling fish on a boat somewhere off British Columbia. And I do believe that’s a rockfish of some kind that Jergen is sorting.
Sampling is at the core of fisheries science. In order to see what fishermen are catching, scientists go to sea, , just as Lee Alverson described. In the days before dedicated research ships, they hitched a ride with fishermen. The at-sea job was to see what came up in the net, sort out the fish, measure some of them, and take scale samples, which they used to try to come up with basic data about the fish. How many males? How many females? Where were they caught, at what depth, with what kind of gear? They would take scales, and back at the laboratory, study them to see how many growth rings (fish are like trees, they lay down daily growth rings). The is the raw data that goes into calculating the CPUE, or Catch per Unit Effort, which is most basic fisheries calculation: how many fish are being caught by each fisherman on each tow? A decline in CPUE is considered a sign that a fishery may be headed for trouble.
Here’s William F. Thompson, writing about sampling halibut in 1915:
The fish were examined on the deck as they were brought in. The decks were always so slippery and slimy that it was necessary to lash the fish down ‘fore and aft’ to guard against the rolling movements of the vessels as they lay in the trough of the seas. Also, of course, the place chosen to work on could not be in the way of the fishermen at their work, and it was, therefore, necessarily distant from the ‘checkers’ or pens of fish, despite the difficulty of handling heavy fish on a slippery deck. Care was likewise necessary that no cuts were made which could injure the market value of the fish. As a result of these conditions it was possible to examine less than a hundred fish in a day, save in exceptional cases where the fish were small. It need only be said that accurate work under such conditions was time consuming.
Boats have gotten better since Thompson wrote those words, but it’s still challenging and difficult to do work at sea.
 J. Richard Dunn, “William Francis Thompson (1888-195) and his pioneering studies of the Pacific Halibut, Hippoglossus stenolepis. Marine Fisheries Review. 63 no. 2 (2002): 8.