Navigation Links
River flow and temperature limit trout numbers
Date:9/9/2009

Over a 23-year study, Javier Lobn-Cervi 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 Lobn-Cervi, 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, Lobn-Cervi 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 Lobn-Cervi.

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. Lobn-Cervi 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.


'/>"/>

Contact: SINC
info@plataformasinc.es
34-914-251-820
FECYT - Spanish Foundation for Science and Technology
Source:Eurekalert  

Related biology news :

1. UC Riverside research on barley genome gets boost from $1 million USDA grant
2. Pesticides -- easier detection of pollution and impact in rivers
3. 2009 Charles River Laboratories Excellence in Refinement Award
4. Shifting baselines confound river restoration
5. UC Riverside student is 1 of only 5 persons selected for challenging Arctic expedition
6. Carnegie Mellons Jean VanBriesen leads research team on Monongahela River
7. Scientists discover Amazon river is 11 million years old
8. Troubled waters: Low Apalachicola River flow may hurt gulf fisheries
9. Public lecture at UC Riverside to discuss origin and fate of universe
10. UC Riverside geneticist receives highest honor from Botanical Society of America
11. River delta areas can provide clue to environmental changes, Texas A&M prof says
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
River flow and temperature limit trout numbers
(Date:5/16/2017)... , May 16, 2017   Bridge ... health organizations, and MD EMR Systems , ... development partner for GE, have established a partnership ... Portal product and the GE Centricity™ products, including ... EMR. These new integrations will ...
(Date:4/18/2017)... April 18, 2017  Socionext Inc., a global expert in SoC-based ... edge server, the M820, which features the company,s hybrid codec technology. ... by Tera Probe, Inc., will be showcased during the upcoming Medtec ... show at the Las Vegas Convention Center ... Click here ...
(Date:4/11/2017)... , April 11, 2017 Crossmatch®, a ... authentication solutions, today announced that it has been ... Research Projects Activity (IARPA) to develop next-generation Presentation ... "Innovation has been a driving force ... program will allow us to innovate and develop ...
Breaking Biology News(10 mins):
(Date:6/22/2017)... ... June 21, 2017 , ... RMC Pharmaceutical Solutions, Inc. ... Timothy Reinhardt to manage the new site. , Tim has 25 years of ... most recent role as the Director of Manufacturing and Supplier Quality Assessment. ...
(Date:6/22/2017)... ... June 22, 2017 , ... ... clients throughout the biopharma and life sciences industries, continue to be in demand ... Tunnell’s Kip Wolf will be speaking on “The State of Information Governance in ...
(Date:6/20/2017)... ... ... Biologist Dawn Maslar MS has found a biomarker that she claims verifies ... The Neuroscience of Meeting, Dating, Losing Your Mind, and Finding True Love, Maslar found ... step, in my estimation, was to scientifically track the evidence of commitment in men,” ...
(Date:6/20/2017)... ... June 20, 2017 , ... ... therapeutics from millions-diverse immune repertoires, announces launch of its new Surge(TM) Discovery ... Johnson, PhD, CEO of GigaGen, will present on Surge at the conference. , ...
Breaking Biology Technology: