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What do scientists
already know about Striped Bass?
Striped bass move north in ocean water as the water warms, and
retreat south as the ocean cools. As they move they choose rivers
up which they move to spawn in fresh water. Many stay in the ocean
off North Carolina in winter. Some “groups” of striped
bass may stay in rivers (“group hypothesis”).
Notable Observations about Striped Bass:
- Striped bass are found from Florida to Nova Scotia.
- Striped bass are found in salt water, fresh water, and estuaries.
- Striped bass must spawn in fresh water.
- Striped bass are most plentiful in near shore ocean waters in
spring and fall.
· Striped bass can live locked in freshwater (behind dams)
so we know they don’t have to have salt water access.
- Striped bass tagged in winter or fall are usually caught north
of their tagging sites in spring and summer
- Striped bass tagged in late spring or summer are usually recaptured
to the south in fall or winter
- Some striped bass are caught where they were tagged years later.
- The amount of certain chemicals in the bones of different striped
bass suggest that some stay in fresh water even though they could
leave, while others spend most time in salt water.
Questions Scientists still have about Striped Bass:
Do some striped bass choose to stay in rivers even when they have
access to the ocean? Do the stripers that migrate north and south
return to the same river? Are the striped bass found in the rivers
the same fish throughout a season (also known as resident fish),
or is there a constant exchange of striped bass in and out of the
river?
In order to answer these questions, scientists follow the scientific
method and develop hypothesis which they then try to prove or disprove.
The scientific method consists of the following steps:
- Observe events or characteristics
- Present an hypothesis, to explain what you have observed
- Use the hypothesis to make predictions.
- Test those predictions by experiments or further observations
The scientific method works through the steps of observation,
hypothesis generation, hypothesis testing, and communication of
findings as further observations. Below are some observations
and questions still to answer about striped bass.
Developing your Hypothesis
(click
here to print out a PDF of this worksheet)
 The
scientists at Rutgers have set up “Striper Tracker”
in the Mullica River – Great Bay estuary to test their
ideas about striped bass. Scientists are using the Striper
Tracker research to test two parts of the “group hypothesis”
described above.
Hypothesis 1: Striped bass enter and exit
in well defined groups.
If this hypothesis is true, then we can expect that the
striped bass are separated into groups….one group
is in the Mullica River briefly and the other group is in
the river the whole season. Some of the striped bass that
stay in one river for a long time are there for SO LONG
that they very rarely move into any other rivers.
Hypothesis 2: Striped bass are grouped by either
using fresh water habitats OR using salt water habitats.
If this hypothesis is true, then we can expect that a group
or groups of striped bass stay in the river and another
group stays in the mouth of the estuary (closer to Great
Bay).
How is the striper tracker system set up to test
either of the two hypotheses?
Why do striped bass movements in an out of an estuary
matter to fisheries managers?
To test these ideas, you will “virtually” tag
and trap a Striped Bass using the Striper Tracker site http://www.stripertracker.org
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