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15. Fish Population Responses to Sea Floor Habitat Alteration
15.6. Questions and Tasks
1. Change the value for Zj in each of the functional response curves. Run a
sensitivity analysis with a range of values of Zj and plot the results. Interpret your results.
2. Quantify juvenile cod survivorship in areas surrounding MPAs and plot
as a response surface in a spreadsheet program . How does it vary relative to survivorship inside MPAs?
3. Change the model to include juvenile fish movement diagonally among
adjoining cells. How does this change patterns in survivorship?
4. Make settlement of juvenile cod among cells a random function. How
does this influence overall survivorship?
MPA MODELl
FISH[SEAFLOOR] (t) = FISH [SEAFLOOR] (t - dt) +
(SETTLE[SEAFLOOR] + MOVE_IN [SEAFLOOR] - DIE [SEAFLOOR] -
MOVE_OUT[SEAFLOOR]) * dt
INIT FISH [SEAFLOOR] = ° {FISH}
INFLOWS:
SETTLE [SEAFLOOR] = PULSE(NO_FISH,O, 50) {NEW FISH}
MOVE_IN [HAB_l_l]
MOVE_OUT [HAB_l_2] *0 .4+MOVE_OUT[HAB_2_1] *.3
MOVE_IN[HAB_l_2] =
MOVE_OUT[HAB_l_l]*.5+MOVE_OUT[HAB_l_3]*.4+MOVE_OUT[HAB_
2_2]* .2
MOVE_IN [HAB_l_3] =
MOVE_OUT [HAB_l_4] *0.5+MOVE_OUT[HAB_l_2] *4+MOVE_OUT[HAB_
2_3]*.2
MOVE_IN [HAB_l_4] =
MOVE_OUT [HAB_l_3] *.4+MOVE_OUT[HAB_2_4] *.3
OUTFLOWS:
DIE [SEAFLOOR] = FISH[SEAFLOOR]*M[SEAFLOOR]
MOVE_OUT [HAB_l_l]
MOVE_OUT [HAB_l_2]
MOVE_OUT [HAB_l_3]
MOVE_OUT [HAB_l_4]
FISH[HAB_l_l]*MOVE[HAB_l_l]
FISH [HAB_l_2] *MOVE [HAB_l_2]
FISH [HAB_l_3] *MOVE [HAB_l_3]
FISH [HAB_l_4] *MOVE [HAB_l_4]
The main components associated with only four of the "cells" of the model, and the
key parameters and their values of the entire model are shown here . The equations
for the remaining cells are analogous to those above . The full set of all equations is
available on the CD ROM accompanying the book.