7742

• UCREFRP Catalog Number: 7742
• Author: Gilpin, M.
• Title: A Population Viability Analysis of the Colorado Squawfish in the Upper Colorado River Basin
• USFW Year: 1993.
• USFW - Doc Type: A Report to the United States Fish and Wildlife Service, Denver, Colorado.
• Copyright Material: NO

Squawfish Population Viability Analysis --July 1993

Page 37

When a larger male spawns with a larger female, not only the total output
of eggs increases, but also the fraction of the eggs that should be fertilized
also increases. That is, each female egg is now in a solution containing
many more sperm, and thus the chance of fertilization is greater. This
effect could also be nonlinear, perhaps quadratic. Figure 3.6 illustrates the
possibility. Figure 3.7 shows the causal loops that could lead to it.

" '~:. .J.:'.'::"~~'" '" '. _
:' ."'....:.,..} . ~ .
'''''''~_'1''J.~",,, .... .'
"I, ""._ . '. "', ~;,

'{" ~ ~;;~"

\ '-'-

~ i ,- -, l ,,\~. ~ . f'

~'~j")~:~;~;;;:'l;~~~J" '

8

Figure 3.6. A schematic illustration of the effect adult body size has on
spawning output. The larger animals produce more gametes, a larger
fraction of which is fertilized. The fraction fertilized -is indicated as the
intersection of the two circular sets.