The announcement by the IPHC that halibut predicted by the stock model have gone missing in following years has led me to think about where they may have gone. When Doug Hoedel was on the NPFMC (and had a huge halibut PSC problem while trawling cod), he said, at an informal meeting in Kodiak, that trawlers needed 8,000 metric tons of halibut for their bycatch needs. Later, at another meeting, Julie Bonney of GFDB repeated the same number. Now I wonder how they both came up with that specific number?
Most people familiar with this fishery realize that the present 2,000 metric ton PSC cap on Gulf trawlers is nearly meaningless due to gaming of the observer program, potential sampling problems, and industry involvement in the generating of bycatch numbers that appear to always lead to reductions. Could it be that the 8,000 metric tons (17,600,000 pounds) of halibut bycatch desired by the GOA trawler is closer to the actual number that they know they catch? If it is true, 6,000 metric tons (13,200,000 pounds) of mortality would be missing from the IPHC management model each year from this one fishery in the Gulf of Alaska. Each year the model would recommend a directed catch that was substantially too high. The next year's survey and directed fishery CPUE data would see this but the model would produce a new harvest goal that was still wrong due to the unaccounted for mortality.
|Unaccounted for bycatch leads to poor modelling by stock managers.|
I would recommend to IPHC director Bruce Leaman that his staff retrospectively run the model calculations with 8,000 metric tons of gulf trawl bycatch to see if the model predictions are corrected. Knowing the magnitude of the "missing" halibut would be a good start to finding them.