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Water exchange and the holding capacity of sites for fish farming in fjords and other inshore areas

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Benthic model to compute the oxygen transport to the sea bed and ... allows a fauna of benthic animals. Fish cage model to compute oxygen and ammonium concentrations ... – PowerPoint PPT presentation

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Title: Water exchange and the holding capacity of sites for fish farming in fjords and other inshore areas


1
Water exchange and the holding capacity of sites
for fish farming in fjords and other inshore areas
  • SPEAR-Training March 16, 2006
  • Anders Stigebrandt, Univ. of Gothenburg, Sweden

2
Aim of the course
The aim of the course is to teach elements of
physical oceanography and fish metabolism
needed to estimate the holding capacity of
sites for fish farming, in particular sites in
fjords and other inshore areas and to compute
the holding capacity of a few sites The
holding capacity is determined by environmental
effects caused by the turnover of organic matter
in fish farms, in particular effects on the
bottom beneath the farm in the fish cages on
the surrounding inshore environment
3
Water quality sub-model
4
Models needed to estimate holding capacity Fish
model to compute the turnover of matter by
fish Dispersion model to compute dispersion of
particulate matter emitted by a farm. Benthic
model to compute the oxygen transport to the sea
bed and from that the maximum loading with
organic matter that allows a fauna of benthic
animals Fish cage model to compute oxygen and
ammonium concentrations in the cages Water
quality (Secchi depth) model of surface waters in
inshore water Water quality (oxygen
concentration) model of basin waters in
fjords Model of the natural flow of organic
matter into basin waters of fjords The models
presented during the course are based on first
order processes and kept as simple as possible
5
  • Two computer programs have been developed
  • FjordEnv - computes water exchange of different
    strata in fjords and
  • other inshore areas and how this is influenced
    by changes of
  • e.g. the topography of the mouth. It also
    computes how outlets
  • of particulate organic matter and nutrients,
    e.g. from fish farming,
  • influence Secchi Depth and deepwater oxygen
    conditions in the
  • whole system.
  • MOM computes the holding capacity of sites for
    fish farming based
  • on acceptable changes of the state of the local
    environment (the
  • sea bed) and on expected extreme states with
    respect to oxygen
  • and ammonium concentrations in the fish cages.
  • The holding capacity is given by the lowest of
    the estimates from the
  • local and the regional aspects, i.e. the lowest
    of the estimates given by
  • MOM and FjordEnv, respectively.

6
Literature Aure, J., and A. Stigebrandt, 1989
On the influence of topographic factors upon
the oxygen consumption rate in sill basins of
fjords. Est., Coastal and Shelf Science, 28,
59-69. Aure, J., and A. Stigebrandt, 1990
Quantitative estimates of the eutrophication
effects of fish farming on fjords. Aquaculture,
90, 135-156. (Regional effects) Stigebrandt,
A., 1999 Turnover of energy and matter by fish
a general model with application to Salmon.
Fisken og Havet, No 5, 1999. Stigebrandt, A., J.
Aure, A. Ervik, P.K. Hansen, 2004 Regulating the
local environmental impact of intensive marine
fish farming. III A model for estimation of
the holding capacity in the MOM system
(Modelling Ongrowing fish farm Monitoring).
Aquaculture, 234, 239-261. (Local effects)
7
The underlying physics are presented
in Stigebrandt, A., 2001 Fjordenv a water
quality model for fjords and other inshore
waters. Rep. C40, Earth Sciences Centre.
Gothen- burg University. 41pp. This builds
heavily on the following papers Stigebrandt,
A., 1981 A mechanism governing the estuarine
circulation in deep, strongly stratified fjords.
Estuarine, Coastal and Shelf Science, 13,
197-211. Stigebrandt, A., and J. Aure, 1989
Vertical mixing in basin waters of fjords. J.
Phys. Oceanogr., 19, 917-926. Stigebrandt, A.,
1990 On the response of the horizontal mean
vertical density distribution in a fjord to
low-frequency density fluctuations in the
coastal water. Tellus, 42A, 605-614. Aure, J., J.
Molvaer and A. Stigebrandt, 1996 Observations of
inshore water exchange forced by a fluctuating
offshore density field. Marine Pollution
Bulletin, 33, 112-119. Stigebrandt, A., 1999
Resistance to barotropic tidal flow in straits by
baroclinic wave drag. J. Phys. Oceanogr., 29,
191-197.
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