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DATA
WHAT TYPE OF DATA IS IMPORTANT
TO TRACKING AND STUDYING CETACEANS?
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1. Geographical location -- GPS coordinates
sent from transmitters on tagged animals
a. Radio telemmetry -- more difficult and
labor intensive; less expensive tag; lasts longer; more accurate
b. Satellite telemmetry -- transmits automatically
and received without further field work; expensive; can be inaccurate and
unpredictable
c. Additional factors learned from telemmetry:
surfacing frequency, local water temperature, depth, date, time
WHY: Researchers must begin
their study by knowing where and when the cetaceans they have tagged are.
They use GPS coordinates, upload them into a GIS, and geocode the points onto
a map of the study area. GIS can display the movement patterns of all dolphins
in the study relative to each other to determine trends in the data.
2. Water temperature, water current patterns,
weather fluctuations
WHY: Some research indicates
that certains dolphins and whales migrate along the gulfstream, seasonally
or to avoid weather systems. Scientists are trying to correlate movement patterns
with these hypotheses. Additionally, certain types of fish move with changes
in current and temperature. Researchers can download satellite data from NOAA
and other weather monitoring agencies into a GIS and compare the weather/temperature/current
data with cetacean movement to determine associations.
3. Fish movement
a. Advanced doppler readings can determine
locations of large schools of fish
b. Large-scale monitoring projects usually
require data from other researchers that study fish
WHY: If researchers can obtain
fish movement data and compare it to cetacean movement data within a GIS,
they can more clearly distinguish between "migration" patterns and
"following the fish" patterns. This type of information is ultimately
important in policy-making decisions that limit fisheries.
4. Fishery interactions (also called human interactions)
a. presence of fishing/shrimping boats --
determined by aerial surveys and with assistance from fishery management;
taken by GPS
b. presence of nets, traps and fishing debris
-- determined by aerial survey; taken by GPS
WHY: Historically, fisheries
are the biggest threat to pelagic cetacean populations. Their impact is two-fold:
they deplete food resources and cause drowning (via entanglement) in nets
that are not "dolphin-safe". The accumulation of GPS points within
a fishing season give researchers information regarding frequency and duration
of fishing activity. If ranges of cetacean movement and fisheries are consistently
in close proximity, and subsequently mortality rates increase, then scientists
have causal evidence of the negative impacts of fishery interactions.
