Points of view
A framework for multispecies modelling of
LAFUR K. PA
Marine Research Institute, Reykjavõ
Keywords: multispecies modelling, ®sheries, Arcto-boreal ecosystem
The marine ecosystems off Labrador and Newfoundland, east and west Greenland,
Iceland and that of the Barents Sea will be termed Arcto-boreal systems in the following.
In terms of environmental conditions, these ecosystems are characterized by large annual
and seasonal ¯uctuations, in physical parameters such as temperature and nutrients, as
well as in biological conditions such as primary and secondary production. Such
¯uctuations may give rise to biological variability in higher trophic levels in recruitment,
growth rates, stock sizes and yields. Typically, such an Arcto-boreal system includes
Atlantic cod (Gadus morhua, Gadidae) as a major ®sh predator with capelin (Mallotus
villosus, Osmeridae) and shrimp (Pandalus borealis) as its main prey. Also typically,
several components of the ecosystems are harvested, including both prey and predator
species. Apex predators include several whale and seal species as well as seabirds, and in
some cases it may be important to take these into account. When considering the
economics of a harvesting strategy, it is important to consider the ecosystem components
which clearly affect the relevant stocks, and thus factors such as the capelin and the
shrimp, and eventually marine mammals, clearly need to be considered when the ®shery
for cod is under consideration.
In the following, a conceptual model of the dynamics of an Arcto-boreal system will
be described. Because some important multispecies interactions are clearly inherent in
the system, this will be a multispecies model.
Several multispecies models have been suggested in the past few decades. The most
famous one, MSVPA, as developed for the North Sea, has yielded important results in
terms of stock sizes and species interactions, including predation mortality (Gislason
and Helgason, 1985). This model, however, does not incorporate the effect of prey
abundance on predator growth. This effect seems to be very important in Arcto-boreal
systems and needs to be incorporated in any model which is to be used as a description
of the ecosystem.
The ®rst true multispecies ecological model of an Arcto-boreal system must be
MULTSPEC (Bogstad et al., 1992, 1997). This model incorporates many species and
can potentially allow for varying growth owing to diet constraints, annual variability in
migration and thus spatial overlap. Thus, MULTSPEC includes many of the essential
building blocks of a model of an Arcto-boreal system, but there is a conspicuous lack
0960±3166 # 1998 Chapman & Hall
Author to whom correspondence should be addressed (e-mail: email@example.com).
Reviews in Fish Biology and Fisheries 8, 101±104 (1998)