Chapter 6- Conservation and Aquatic Life Studies
Conservation and Aquatic Life Studies
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significant things you saw. The more you ponder your
experience, the more you will learn and retain, and the
more effective you will be on your next dive. Finally,
transfer your observations and circumstances from your
slate and record them in your logbook. Writing reinforces
your memory.
Much aquatic life is not out in the open where it
can be easily viewed. You must either discover the hiding
place of the animal or attract it. Dive lights are very
useful for peering into holes and crevices and beneath
overhangs.
Baiting animals with food is a common practice as a
means to observe them. The desire for food is often greater
than the fear an animal may have for your presence.
Your goal is to observe the animal within its environment
without harming the creature. The use of lights and bait
can help you to achieve this goal.
During biological studies, searches for plants and
animals are usually controlled. Depending on the underwater
terrain, the density of the objects being surveyed,
and other factors, more or less methodical forms of
quantitative studies can be used. For high-density situations,
such as a sand dollar bed, a square formed from
plastic pipe may be used. The square is placed over a
representative section of the animals being studied and
the number of animals inside the square is recorded. By
measuring or estimating the total area covered by the
animal population and multiplying it times the number
of animals per area covered by the square, the total population
can be estimated.
To survey animals on a larger scale, such as starfish
on a sandy bottom, a different method is used. A transect
line of a specific length–say 20 meters (6 feet)–is
stretched and anchored along a selected heading on the
bottom. The divers making the count swim up one side
of the line and down the other using a measured pole to
delineate the survey area. One end of the pole is kept next
to the line, and all animals passing beneath the pole are
counted. In this way, multiplying the density per known
area times the estimated total area can approximate
the total population. For increased accuracy, the search
line can be moved parallel by two pole lengths one or
more times and the survey repeated to determine a more
accurate density average.
Another method of surveying using the transect
method is for divers to follow an assigned heading
through an area and count all of a certain species
encountered on that course. The area viewed needs to
be determined, and will depend on the distance covered,
the animal being studied, the visibility, and other factors.
FIGURE 6-5. Surveys should always be conducted in buddy pairs.