Eavesdropping on trout building their nests
Seismic sensors can record signals produced by fish building spawning
pits

Date:
July 28, 2020
Source:
GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Summary:
Steelhead trout stirring up the sediment of the river bed were
detected by seismic sensors. Researchers have used geophones to
analyze the trout's nest-building process in detail.



FULL STORY ========================================================================== Steelhead trout (Oncorhynchus mykiss) stir up the sediment of the river
bed when building their spawning pits, thus influencing the composition
of the river bed and the transport of sediment. Until now, this process
could only be studied visually, irregularly and with great effort in the natural environment of the fish. Now, researchers led by Michael Dietze
of the GFZ German Research Centre for Geosciences in Potsdam have used
seismic sensors (geophones) to analyze the trout's nest-building process
in detail. The study was published in the journal Earth Surface Processes
and Landforms.


==========================================================================
To lay their eggs, trout use their caudal fins to dig pits up to three
metres long on each side and ten centimetres deep into the river bed. The
aim of the researchers was to locate these spawning pits and to analyze
the chronological sequence of the construction process. To this end, the researchers set up a network of seismic stations on a 150-meter section
of the Mashel River in the US state of Washington. The geophones embedded
in the earth are highly sensitive and detect the slightest vibrations
in the ground. Small stones moved by the fish caused short frequency
pulses in the range of 20 to 100 hertz and could be distinguished from background frequencies of flowing water, raindrops and even the pulses
of passing airplanes. "The same signal arrives at each of the stations
slightly delayed. This enabled us to determine where the seismic wave
was generated," says Dietze, first author of the study.

The researchers listened to the construction of four spawning pits for
almost four weeks from the end of April to the end of May. The geophones revealed that the trout were mostly busy building their nests within
eleven days of the measurement period. The fish preferably started at
sunrise and were active until early noon, followed by another period
in the early evening. The trout dug in the sediment for between one and
twenty minutes, typically at two- to three-minute intervals with 50 to
100 tail strokes. This was followed by a break of about the same length.

"Normally, the nest-building behaviour of the trout was recorded
only very irregularly, at most weekly. We can now resolve this to
the millisecond. In the future, we want to extend the method to the
behaviour of other species, for example animals that dig along the
banks and destabilize them," explains Dietze. The new measurement method
might support fish and behavioural biology and provide a more accurate
picture of the biotic and abiotic contribution of sediment transport in
rivers. "Fish can move as much sediment as a normal spring flood. The biological component can therefore play a very important role," said
Dietze.


========================================================================== Story Source: Materials provided by GFZ_GeoForschungsZentrum_Potsdam,_Helmholtz_Centre. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Michael Dietze, James Losee, Lina Polvi, Daniel Palm. A seismic
monitoring approach to detect and quantify river sediment
mobilization by steelhead redd‐building activity. Earth
Surface Processes and Landforms, 2020; DOI: 10.1002/esp.4933 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200728113627.htm

--- up 1 week, 6 days, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)