PERCH simulates the population dynamics of Perch in Lake IJssel.
With the simulation program PERCH students can study the effects
of several management measures (increasing or decreasing the fishing
effort, changing efficiency and mesh size of the nets, adjusting the
close season) on the distribution of the catch and on the structure
of the population of a single fish species under conditions of gill
net fishery. It is hard to understand the mutual dependency on the
effects of these measures when the concepts are taught in a purely
PERCH allows the students to build a conceptual model of the
relations in the Lake IJssel system and to adjust this model to
concrete experience gained by active experimentation. By means of
induction students will generalize from the specific case of Lake
IJssel to more general concepts of fishery management. The
conceptualization of these general concepts may help students
specializing in fishery management to solve other fishery problems
which they may meet in their future careers.
During simulation 30 screens with dynamic graphic output are
available. Four examples are shown in the figure above. (a.
length-frequency distribution of the standing stock; b.
length-frequency distribution in the standing stock and in the catch
in each age class; c. time registrations of biomass; d. time
registrations of mean length and deviation of the mean in 7 year old
Apart from courses of fishery management PERCH can
also be used in more general university biology courses like courses
of population dynamics or courses of nature management. In these
courses PERCH may be used as an example for the way modelling
techniques are applied in fishery management and in nature
management in general.