|
VHF Telemetry |
This method uses
VHF transmitters in the frequency range 173-174 MHz with 1mW output. The
system is used to monitor the postion of tagged animals. Transmitter can
be detected from up to 6000m away, depending on the amount of intervening
vegetation and the orientation of the transmitter. Receiving stations are
placed in the capony level of the rainforest. The VHF telemetry method has been used in the Amazon to monitor botos (Amazon River dolphins). Over a four year period, the researchers were able to study the movement of the dolphins in yearly bases as well as reproduction cycle, social behaviors, and other activities of the dophins. Although this is a very effective method for monitoring the location of aquatic life, this is a very labor intensive and expensive method. In addition, becuase of the high density of the rainforest, signals are often blocked, reducing their effective range. This means that animals will often move out of range of the receiving stations. Another problem with this is that the receiving stations may become nests for bees and other insects. |
| Robotic Boat |
This method was developed as a less costly alternative to VHF telemetry.
This tracking system is contained in a 10' low-cost kayak hull. It includes
subsystems that allow for its autonomous operation. GPS is used to monitor
the position of the boat and acoustic transducers are used to locate aquatic
life. The entire system has an edurance of 24hrs, meaning it operates on
a one-day cycle. Because this is currently an experimental system, no data
is available yet. |
Fish Data
Every year, on average, 35 species of fish are discovered in the Amazon basin using a variety of methods. Frequently species are even found unitentionally as a consequence of studies on currently studied species.
The diverse fish population
of the Amazon River basin is due to three factors:
Affects on fish populations by water management
Fish reproductive success for both native and non-native fish is related to water flow of the previous year. Manipulations of water flows are therefore a powerful tool for managing fish populations. Such manipulation can be made with the use of dams, diversion, and channelization. Conversely, the implementation of artificial flow control means may have an averse effect on fish populations.
Damned rivers can
be divided into four main segments: 1) an upstream segement, 2) the segment
immediately behind the damn, 3) the segment immediately downstream of the
damn, and 4) the segment downstream of the darm. The upstream segment of
the river is largely unaffected by the dam. The segment of the river most
affected by the dam is the portion directly downstream of the dam. In this
section native fish population are the most severely affected, to the point
that the population may be dominated by non-native species. With increasing
distance from the dam, and with the influx of other rivers and streams, the
affect of the dam becomes less severe. Correspondingly, native fish populations
are more successful with this increasing distance
.
Sources
A Robotic Boat for Autonomous Fish Tracking
Authors:
Clifford A. Goudey et al
Source: MTS Journal Vol 32, No. 1 p. 47-53
Date:
Freshwater Riches
of tha Amazon
Author: Lundberg, John
Source: Natural History
Date: September 20, 2001
Tracking Aqautic Vertebrates in Dense Tropical Forest Using VHF Telemetry
Authors: Anthony R. Martin et al
Source: MTS journal Vol 32, No. 1 p. 82-87
Date:
Effects of flow
on the fish communities of a regulated California river: implications for
managing native fishes
Authors: Brown, Larry R. and Ford, Tim
Source: River Research and Applications
Date: May 15, 2002