Halibut Stock Assessment

International Pacific Halibut Commission uses hook and line surveys to assess halibut stock.
It is important to know the hooking success of halibut by size. This frame supports four baited
hooks (16/0 Mustad circle hooks baited with ¼ lb of chum salmon) and is placed on the ocean
floor at depths between 20 and 100 fathoms (36 – 182 meters). It is repeatedly placed on the
ocean floor for approximately one hour then brought to the surface to assess what was caught.
The DIDSON monitors the device on the bottom to determine how many times fish (as a function
of size) attack the hook but are not caught. The advantage of a DIDSON over optical systems is
that DIDSON can monitor the device at the desired depths without regard to ambient light.

Courtesy of Steve Kaimmer, International Pacific Halibut Commission