Fig. 17.8 Halibut hooks. The two designs on the left were used before 1982. The
circle hook on the right was introduced in 1982–1983.
(^) (After IPHC 1998.)
In fact, CPUE as a measure of stock size has received extended criticism early and
late, as reviewed by Maunder et al. (2006). There turn out to be a many biases. A
partial list includes:
(^1) a tendency to excessively high values early in a fishery as the most
susceptible fish are captured, with later CPUE values becoming
underestimates;
2 failure of CPUE to fall as stocks decline because fishers focus on the
remaining centers of distribution;
3 intentional misreporting of both catches and effort to avoid reaching
quotas, to make stocks look strong, to make fishers appear successful (low
Y, high Y, low X, and high X are all possible biases to reports under different
circumstances);
4 continuous or stepped improvements in the power of a given level of
fishing effort, X (at least as measured) to catch fish (also outlined above);
5 shifts in the accessibility of the stock to prevalent fishing methods because
of climate or weather variations, prey redistributions or other environmental
changes.
(^) To overcome at least (2), (3), and (4), some fisheries are regulated on the basis of
management agency research surveys on standard station grids with fixed methods, in
recent decades coupling effective sonar biomass assessments with trawling or species-
appropriate capture methods. There is a reasonably good track record for such agency
surveys as predictors of subsequent catch relative to industry effort. Fishers often
view agency surveys as wrong because, in their view, no attention is paid to where the
fish are; that is, fishers know where to fish and they do not tell the agencies. That, of
course, is the cause of error source (2) above. The struggle to get reliable data, to