Chapter 36
The Grass Carp
The Carp is the Queen of Rivers: a stately, a good,
and a very subtle fish.
(Walton Angler, 1653)
36.1 Grass Carp Model
The Grass Carp model is a large one. It combines insight from the herbivore-algae
model discussed in the previous chapter with the need for human management of
the predator–prey relationship. A management practice known as “biomanipulation” has sprung from the idea of manipulating predator–prey relationships
and is gaining popularity among lake management organizations. The model was
motivated by the need of controlling the growth of grass in ponds and lakes.
Nutrient rich waters flow into these bodies producing prodigious growth rates of
a variety of plants. Plant growth is so luxuriant that sport fish cannot find food. To
control the grass, carp are introduced to eat the plants. To prevent the waterway
from being overrun by the carp, they are bred to be sterile. Such sterile carp are
called “triploid” in this model. The carp can overdo it as well—if they eat all of the
plants, they will starve and the young sport fish become easy prey for the large fish.
When the carp reduce the grass biomass to about 35–45 % of the unregulated
biomass, on the average, the optimum level of control is reached. The problem
becomes one of finding the appropriate number, size, and time of introduction of the
carp into the waterway. If such a way can be found, then biological control can
successfully displace chemical vegetation control.
Nursery-raised carp are commonly sold at 200 g, the minimum size for safe
transfer to a new waterway. The time horizon for most waterways is assumed to be
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_36,
© Springer International Publishing Switzerland 2014
311
The Grass Carp
The Carp is the Queen of Rivers: a stately, a good,
and a very subtle fish.
(Walton Angler, 1653)
36.1 Grass Carp Model
The Grass Carp model is a large one. It combines insight from the herbivore-algae
model discussed in the previous chapter with the need for human management of
the predator–prey relationship. A management practice known as “biomanipulation” has sprung from the idea of manipulating predator–prey relationships
and is gaining popularity among lake management organizations. The model was
motivated by the need of controlling the growth of grass in ponds and lakes.
Nutrient rich waters flow into these bodies producing prodigious growth rates of
a variety of plants. Plant growth is so luxuriant that sport fish cannot find food. To
control the grass, carp are introduced to eat the plants. To prevent the waterway
from being overrun by the carp, they are bred to be sterile. Such sterile carp are
called “triploid” in this model. The carp can overdo it as well—if they eat all of the
plants, they will starve and the young sport fish become easy prey for the large fish.
When the carp reduce the grass biomass to about 35–45 % of the unregulated
biomass, on the average, the optimum level of control is reached. The problem
becomes one of finding the appropriate number, size, and time of introduction of the
carp into the waterway. If such a way can be found, then biological control can
successfully displace chemical vegetation control.
Nursery-raised carp are commonly sold at 200 g, the minimum size for safe
transfer to a new waterway. The time horizon for most waterways is assumed to be
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_36,
© Springer International Publishing Switzerland 2014
311