West Coast Groundfish Observer Program Manual, Part2 - NOAA

CHAPTER 5
Pacific Halibut in the Composition Sample
Pacific halibut are tallied at the same time as all other
species but the method used for determining their weight is
often different than for any other species. Pacific halibut
are often too large to obtain an accurate weight with the
scales provided and large individuals may not be brought
on board the vessel at all. If the fish are small enough to
weigh, it is preferred that individuals be collected for an
average weight sample and applied to the tallied number.
For situations where this is not possible, the IPHC has
developed a length to weight table that lists approximate
weights of Pacific halibut based on the length in
centimeters (see Appendix J). It is acceptable to estimate
the weight of Pacific Halibut in tally samples using this
table. If actual lengths cannot be obtained, it is permissible
to use visually estimated lengths.
The following suggestions will help with estimating the
length of Pacific Halibut (See Figure 5-16):
• Measure the distance from the roller to weld marks
on the side of the vessel or the waterline, if weather
permits.
• Measure the distance between the gangions on the
groundline and measure the length of the gangions
themselves. On most longline vessels, the distance
between the gangions and the length of the gangions
are consistent. Under normal operations the Observer
will be able to see the fish being pulled by the
groundline and gangion. Estimate the length of the
Pacific Halibut in reference to the length of
groundline between the gangions or the length of the
gangion itself.
• Use the length of the gaff or the pole gaff to compare
to the lengths of the Pacific Halibut.
5-48 1/30/2004