Biomass
The possible effects of intensive human
predation can be investigated through studies of changes to the biomass of
particular fish species. An important concept in these studies is the Maximum
Constant Yield (MCY). This is defined as "the maximum constant catch that is
estimated to be sustainable, with an acceptable level of risk, at all probable future levels of biomass"
(Annala 1994: 10). It is a complex problem to work
out what the MCY is for a particular species, but one important variable used
by fisheries scientists is the Virgin Biomass. In New Zealand, this is assumed
to be the biomass at some time between the end of the prehistoric period and
the beginning of significant European impact on the fishery. In other words,
when trying to set limits to fish catches it is currently assumed that the
pre-European Maori had no significant impact on any commercial species. This
has yet to be demonstrated in an accepatable manner, and is one of the
focuses of archaeological research.
Of particular interest in this area is any archaeological evidence of human
impact on resources over long periods. This is useful in helping to refine
virgin biomass estimates and can reveal subtle effects of human harvesting
of resources from the sea which are only manifest over hundreds or thousands
of years. Accordingly, we should consider which species of fish might be
particularly susceptible to human exploitation, and which are less likely to
be so.
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