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Errors
Data Errors:
Coastline data are prone to numerous errors. The data was collected between
1994 to 2000 so there is also possibility of errors in physical features.
Further more, expansion of urban and industrial areas could have taken
up more shoreline habitat already. All these error factors have to be
in consideration when modeling for the analysis. The DEM layer of Puget
Sound is in 30m resolution. It means that any physical feature under 30m
is not recorded. It is also prone to being out-dated, although it is less
likely.
System Errors:
The fundamental question one needs to address is: How realistic is this
model? The basic principle behind habitat analysis is fairly simple. Given
the habitat requirements observed in the wild, build a model according
to those requirements and it should succeed. However, it is usually not
this clear cut. The uncertainties of natural world such as ocean conditions
can throw off prediction completely.
Assumption of the models
There are a number of assumptions that applies to this analysis. First
of all, the coastline data must, at least, somewhat accurately reflect
the reality. For physical factors, this is relatively straight forward
since they are not totally dynamic, granted features such as sandbars
can still move. For biological factors, there can be large discrepancy
between model outcome and the reality due to highly fluid nature of biological
distribution. Almost all marine vegetations have seasonal occurrences
that utilizes advantages of different time of the year. Given no change
in condition, it is reasonable to assume that vegetation covered spaces
are highly suitable for growth and they will be in bloom again next year.
This model also assumes no effects from oceanographic conditions such
as temperature and upwelling. It is well documented that rockfish species
(Sebastes spp.) in general receive strong recruitment from ocean upwelling
and temperature regime change. Further more, pollution of Puget Sound
area may play a role in rockfish distribution. There is virtually no baseline
data for the pollution levels and rockfish distribution, so it is relatively
difficult to gauge pollution effects. However, it is no secret that Puget
sound area is under enormous amount of pressure from urban and industrial
pollution. At last, classifications made here are arbitrary but conservative
after reviewing literatures. There is still a chance that they might be
inaccurate in reflecting the true natural history of rockfish species.
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