Hooks and Ladders

a role-playing game where students get the opportunity to experience life as a salmon and some of their major challenges.

Hooks and Ladders

Objectives:
Students will (1) describe how some fish migrate as part of their life
cycles, (2) identify the stages of the life cycle of a trout or salmon,
(3) describe limiting factors that affect Atlantic salmon as they
complete their life cycles, and (4) generalize that limiting factors
affect all populations of animals.

Method:
Students will simulate the Atlantic salmon and the hazards they face in
an activity portraying the life cycle of these aquatic animals.

Materials:
Large playing area (100 feet x 50 feet), about 500 feet of rope or
string or 6 traffic cones for marking boundaries (masking tape may be
used indoors), two cardboard boxes, 100 tokens (index cards, poker
chips, macaroni, etc.), jump rope

Background:
Many fish migrate from one habitat to another during their lives. Both
the Atlantic salmon and the Pacific salmon are examples of fish that
migrate.

The life cycle for the Atlantic salmon begins when the
female deposits her eggs in a redd, or nest. The female will clear away
gravel with a flip of her powerful tail, forming a nest where the eggs
will be deposited. Once she deposits the eggs, the male will fertilize
them. Both the male and the female fish will gently push the gravel back
over the nest, helping to protect the eggs from predators. Eggs may
also be susceptible to oxygen deprivation at this time.

Newly
hatched salmon, called alevins, will stay in the gravel, feeding on the
yolk-sac from their egg. Once all the nutrients from the yolk-sac have
been used, the young fish, fry, begin feeding and move into deeper
water. Atlantic salmon will spend their first few years in small streams
and rivers, where they feed on aquatic insects and other small matter.
These fish are relatively solitary, and will defend their feeding
territory. At this life stage, these young fish are called parr.

After
reaching approximately 4 inches, the smolt stage, these fish are ready
to begin their springtime journey downstream towards the ocean. These
fish will feed in estuaries where fresh and salt water meet as their
body adjusts to a life in the brine. After a few weeks, the fish are
ready to enter the ocean.

In the ocean, the salmon grow quickly,
feeding on other fish, shrimp and crustaceans. They feed as they are
migrating to their major feeding grounds in the North Atlantic near
Iceland and Greenland. These young salmon may encounter limiting
factors, such as seals, larger fish and humans.

Atlantic salmon will spend 1-2 years in the ocean before beginning their
trek home. It is believed that salmon use a magnetic or sun compass to
find their way to the coast of their natal stream and from there use
olfactory clues to find the river and tributary of their birth. These
salmon, unlike the Pacific salmon, may spawn another one or two times
before dying.

Salmon face a number of limiting factors during the
course of their lives. A limiting factor is a reason or cause that
reduces the population of an organism. Some limiting factors are natural
and some result from human intervention into natural systems.

Natural
limiting factors include drought, flood, predators and inadequate food
supply. Throughout their lives salmon rely on a habitat that provides
shady streams and deep pools for spawning and resting. Logging, grazing,
mining, road building and development may destroy streamside
vegetation, erode land and fill streams with sediment.

Dams are
another limiting factor that block or slow migration to and from the
ocean. Salmon become disoriented by the reservoirs formed by dams and
are exposed to high water temperatures and predators. Fish ladders can
be installed to help salmon through the dams. Fish ladders can be
water-filled staircases that allow migrating fish to swim around the
dam.

Another threat to salmon is overfishing. That, along with
habitat destruction, is part of the cause for the decline in salmon
populations.

NOTE: All possible conditions are not covered
by the design of the activity. However, it does serve to illustrate
three important concepts: life cycle, migration and limiting factors.

Procedure:
1.    Ask students what they know about the life
cycles of fish that live in their area. Do any local fish migrate to
spawn? If yes, which ones (shad, lake trout, striped bass, suckers, carp
and salmon are examples).
2.    Set up a playing field as shown in Diagram 1,
including spawning grounds, reservoir, downstream, upstream and the
ocean. The area must be at least 100 feet by 50 feet. Assign roles to
each of the students. Some will be salmon; some will be potential
limiting factors to the salmon. Assign the student roles as follows:
•  
 Choose two students to be the turbine team. They will operate the jump
rope, which represents the turbines in hydroelectric dams. Later in the
simulation, when all the salmon have passed the turbine going
downstream, those students move to the upstream side to become the
waterfall-broad jump monitors (see diagram)
•  
 Choose two students to be predatory wildlife. At the start of the
simulation, the predators will be stationed in the reservoir above the
turbines to catch the salmon fry as they move downstream. Then they will
move below the turbines where they catch salmon heading downstream.
Later in the activity, when all the salmon are in the sea, these same
two predators will patrol the area above the “broad jump” waterfalls.
There they will feed on salmon just before they enter the spawning
ground (see diagram).
•  
 Choose two students to be humans in fishing boats catching salmon in
the open sea. The students in the fishing boats must keep one foot in a
cardboard box to reduce their speed and maneuverability.
•    All the remaining students are salmon.
NOTE: These figures are based on a class of 20-30, adjust the number of limiting factors accordingly.
3.  
 Begin with all the salmon in the spawning ground. The salmon first
move into the reservoir above the dam. They must stay in the reservoir
until they count to 30. This pause simulates the disorientation that
salmon face because of a lack of current in the lake to direct them on
their journey. During this time the predators may catch the salmon and
escort them one at a time, to become part of the fish ladder. The salmon
then start their journey downstream. The first major limiting factor
that the salmon encounter is the turbines at the dam. At most dams,
escape weirs guide migrating salmon past the turbines. The student
salmon cannot go around the jump-rope swingers, but they can slip under
the jump-rope swingers’ arms if they do not get touched while doing so. A
salmon dies if the turbine (jump-rope) hits it. The turbine operators
may change the speed at which they swing the jump rope. Any salmon that
“dies” at any time in this activity must immediately become part of the
fish ladder. The student is no longer a fish, but becomes part of the
physical structure of the human-made fish ladders now used by migrating
salmon to get past barriers such as dams. The students who are the fish
ladders kneel on the ground as shown in Diagram 2, with one body space between them.
4.  
 Once past the turbines, the salmon must pass some predatory wildlife.
The predators, who have moved from the reservoir area to the area below
the turbine, must catch the salmon with both hands – tagging isn’t
enough. Dead salmon are escorted by the predator to become part of the
fish ladder. Later, the salmon that survive life in the open ocean will
pass through the fish ladder to return to the spawning ground. NOTE:
Both the predatory wildlife in the downstream area and the people
fishing in the open ocean must take the dead salmon to the fish ladder
site. This action moves predators and fishing boats off the field
regularly, helping to provide a more realistic survival ratio.
5.  
 Once in the open ocean, the salmon can be caught by fishing boats. The
salmon must move back and forth across the ocean area in order to gather
four tokens. Each token represents ½ year of growth (2 years), that
fish can begin migration upstream. The year tokens can be picked up only
one at a time on each crossing. Remember that the salmon must cross the
entire open ocean area to get a token. The “two years” that these trips
take, make the salmon more vulnerable; thus they are more readily
caught by the fishing boats. For this simulation, the impact of this
limiting factor creates a more realistic survival ratio on the
population before the salmon begin the return migration upstream.
6.  
 When four tokens are collected, the salmon can start upstream. The
salmon must walk through the entire pattern of the fish ladder. This
enforced trip through the fish ladder gives the students a hint of how
restricting and tedious the upstream journey can be. In the fish ladder,
predators may not harm the salmon.
7.    Once through the ladder,
the salmon face the broad-jump waterfall. The waterfall represents one
of the natural barriers salmon face going upstream. Be sure the jumping
distance is challenging but realistic. The two former turbine students
will monitor the jump. The salmon must jump the entire breadth of the
waterfall to be able to continue. If the salmon fails to make the jump,
then it must return to the bottom of the fish ladder and come through
again. NOTE: When playing indoors, the broad-jump waterfall can
be changed to a stepping-stone jump defined by masking tape squares on
hard floors.
8.    Above the falls, the two predators who started the
simulation, as the predators below the turbines have now become the
last set of limiting factors faced by the salmon. They represent bears,
one example of predatory wildlife. Again, remember that the predators
must catch salmon with both hands. If they catch a salmon, they must
then take the student they caught to become part of the structure of the
fish ladder.
9.    Since Atlantic salmon can spawn more than once,
have the salmon complete as many full migratory trips as possible, then
at the end of the activity, report how many times they completed the
migration. Graph the data. Have the students explain how age influence
mortality rates and susceptibility to limiting factors.
10.    The
activity is done when all the salmon are gone before the spawning ground
is reached – or when all surviving salmon reach the spawning ground.
11.    Next engage the students in a discussion. Explore such topics as
•    The apparent survival or mortality ratio of the salmon,
•    The role of barriers
•    The role of predatory wildlife and the people fishing,
•    Where the losses were the greatest
•    Where the losses were the least,
•    What the consequences would be if all the eggs deposited made the journey successfully, and
•    What seemed realistic about this simulation and what did not?
12.  
 Ask the students to summarize what they have learned about the life
cycle of salmon, the salmon’s migration, and limiting factors that
affect salmon. Make sure the students have a clear working definition of
limiting factors. Encourage students to make the generalization that
all animals – not just Atlantic salmon – are affected by limiting
factors. Ask the students to give examples of limiting factors. They
might mention the availability of suitable food, water, shelter and
space, disease, weather, predation and changes in land use and other
human activities.

Activity Extensions
1.    Write a report on the life cycle of the Atlantic salmon. Create a mural showing the life cycle of the salmon.
2.    Research and illustrate the life cycle of any local fish. If possible, look for one that migrates.
3.  
 Compare how the life cycle of an Atlantic salmon is similar to and
different from the life cycle of one or more local fish.
4.  
 Investigate similarities and differences in the migration and life
cycles of the Atlantic and Pacific salmon. Investigate the life cycle of
the salmon in the Great Lakes region of the United States.
5.    Visit fish hatcheries that work with migratory species and investigate how they function.
6.    Explore ways that dams can be modified to let fish safely pass downstream and upstream. Design the “perfect” fish ladder.
7.  
 Investigate and discuss commercial fishing for salmon. Investigate and
discuss personal, including recreational, fishing for salmon.
8.    Find out about laws protecting migratory species, including fish.
9.    Consider this approach, and try the activity again:
In
the past 100 years, salmon have experienced many new, human-caused
limiting factors. Dams, commercial fishing, timber harvest, and road
construction have had a tremendous impact on salmon populations. In
1991, the Snake River sockeye salmon was placed on the federal
endangered species list. In the past, tens of thousands of sockeyes
would make the 900-mile return trip from the sea to Idaho’s mountain
streams and lakes. There they spawned and died. Their offspring hatched
and began their early development in fresh water. The actual migration
to the Pacific Ocean could be completed in as few as 9 days. Today that
trip takes more than 60 days. In 1991, only four Snake River sockeye
returned to their spawning grounds.

To simulate these increases
in salmon limiting factors, play several rounds of the Salmon Survival
Game. Allow each round to represent the passage of 25 years. Start in
1850. In that year, do not include dams or commercial fishing operations
in the scenario. As time passes, add the human commercial fishing
operations. Build dams (jump ropes) as the scenario progresses into the
21st century.

Describe some of the possible effects on salmon
from increased limiting factors as a result of human activities and
interventions. Discuss possible positive and negative effects on both
people and salmon from these increases in limiting factors affecting
salmon. When the activity reaches the “present,” predict what might
happen to salmon in the future. Recognizing the complexity of the
dilemma, discuss possible actions, if any, that might be taken to
benefit both people and salmon.
10.    Find out if salmon exist in your state. If so, are they native or were they introduced?

Evaluation
1.    List, describe and illustrate the major stages in an Atlantic salmon’s life cycle.
2.    Identify and describe some limiting factors that affect salmon as they complete their life cycles.
3.    Identify and describe some limiting factors that might affect other animal populations.


Adapted from Project WILD Aquatic K-12 Curriculum and Activity Guide published by Council for Environmental Education

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