Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

River flow and temperature limit trout numbers

11.09.2009
Over a 23-year study, Javier Lobón-Cerviá has found the mechanism that controls the number of salmonids found each year in Cantabrian rivers.

His method has been to monitor population numbers in relation to river flow in March, when the juvenile fish emerge. He concludes that environmental conditions change each year and modify river flow, positively or negatively affecting survival rates. This information throws light on a long debate within ecological theory about the mechanisms that regulate the size of animal populations.

In 2000, populations of trout (Salmo trutta) in the rivers of north East Spain suffered an alarming decline, but fishing was never banned, and fish numbers fell still further. However, these populations recovered "naturally" within a very short time period. Javier Lobón-Cerviá, lead author of the research study and a researcher at the National Museum of Natural Sciences (CSIC) has the answer, and has published it in the journal Freshwater Biology.

"If we use a small measurement and calculate the amount of water that was flowing in March (when the fish eggs emerge), we can predict how many trout there will be now, how many there will be in two years, how many should be fished, how many females are going to reproduce – in other words, we can monitor the entire population perfectly", the researcher tells SINC.

It has taken him 23 years of study to arrive at this conclusion. Contrary to conventional theories, which hold that populations have endogenous mechanisms to respond to variations, and that these depend upon the density of individuals, Lobón-Cerviá says populations "simply respond to the environmental conditions that exist at the time".

Since 1986, the scientist has been studying the Chaballos river in the basin of the Esva river in Asturias, where environmental conditions have varied widely year-on-year up to 2007. "Information as simple as river flow in the month of March is enough to enable us to predict everything that will happen in the river", stresses Lobón-Cerviá.

Rain and temperature are natural factors that create the ideal conditions for young trout. The number of juveniles is highest when river flow is average, because there is an ideal amount of useable river area for the larvae. "If the amount of water flowing rises, this space is reduced, because water velocity increases too much, which is harmful to the larvae", says the scientist. However, drought is the worst condition for this species, because "river sections dry up".

The river is a vital space for larvae

Rain determines river flow, and creates useable area in rivers for a particular size of trout. "Small larvae live in a certain river area, but when they grow they move to deeper waters. The river's flow determines how much useable area is available for each size group of trout", explains the researcher.

Temperature regulates the so-called "embryonic stream", in other words the two months that fertilised salmonid eggs remain in the river. For this reason, an increase in temperature affects embryonic development. "Temperature also plays a role in the strength of recruitment, the number of juveniles, but there is an inverse relationship between river flow and temperature – when flow is very low, the water heats up more, and in years with much more water the river heats up less", adds the scientist. However, the great changes in temperature each year make it difficult to work out the direct relationship between this aspect and the number of juveniles born.

This research could also be applied to salmon (Salmo). Although they occupy different parts of the river, they have the same population dynamics processes as trout. Lobón-Cerviá is now looking at the possibility of a link between reproduction and reproductive success among populations swimming out into the Cantabrian Sea and those that swim into the Duero. "If this can be demonstrated, this study could be widely applied", the researcher concludes.

References:

Lobón-Cerviá, Javier. "Why, when and how do fish populations decline, collapse and recover? The example of brown trout (Salmo trutta) in Rio Chaballos (northwestern Spain)" Freshwater Biology 54(6): 1149-1162 junio de 2009.

SINC | EurekAlert!
Further information:
http://www.plataformasinc.es

More articles from Life Sciences:

nachricht Light-driven reaction converts carbon dioxide into fuel
23.02.2017 | Duke University

nachricht Oil and gas wastewater spills alter microbes in West Virginia waters
23.02.2017 | Rutgers University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Organ-on-a-chip mimics heart's biomechanical properties

23.02.2017 | Health and Medicine

Light-driven reaction converts carbon dioxide into fuel

23.02.2017 | Life Sciences

Oil and gas wastewater spills alter microbes in West Virginia waters

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>