Featured Research

from universities, journals, and other organizations

More Light Makes Redfish Grown Faster

Date:
March 21, 2001
Source:
Texas A&M University
Summary:
Biologists have discovered that longer days make redfish grow faster. This discovery could have far-reaching consequences on fish culture techniques aimed at increasing fish growth and improving their quality.

COLLEGE STATION -- Biologists have discovered that longer days make redfish grow faster. This discovery could have far-reaching consequences on fish culture techniques aimed at increasing fish growth and improving their quality.

Related Articles


Duncan S. MacKenzie, a Texas A&M University professor of biology, and Kevin Leiner, a zoology graduate student, made this discovery while studying the workings of the thyroid gland in redfish and how it affects their behavior and metabolism.

The thyroid gland releases a chemical, thyroxine, which regulates fish growth and metabolism - the way fish receive and use energy.

"Although we still do not know exactly how the thyroid regulates fish growth, the work we have done indicates that animals that are happy and healthy and are growing very actively have very high thyroid hormone levels," says MacKenzie.

Although thyroid activity in mammals is quite high, the first scientists who measured thyroid hormones in fish found very little. So it initially was assumed that thyroid hormones play a minor role in fish metabolism.

"We discovered that, in fact, thyroid hormone is very dynamic in some fish species like the redfish," says MacKenzie. "The hormone is very precisely regulated, its level increasing and decreasing regularly at different times of the day."

Since 1995, MacKenzie has been investigating the mechanisms of thyroid hormone regulation in redfish. He has been mainly interested in the effects of food intake and light exposure on thyroid hormone release.

MacKenzie has conducted experiments involving large fish tanks sampled at different times. In each experiment, lasting between two to eight weeks, the amount of light, food, and the times of day that fish are fed have been precisely controlled.

For each experiment, Leiner measured the daily redfish thyroid hormone levels by taking blood samples every two hours. At the end of each experiment, the fish are examined in order to determine the amount of fat and muscle.

"Different daily feeding times have a minimal effect on the hormone levels of the fish," MacKenzie says. "Instead, dawn appears to activate an increase in the thyroid hormone 5 to 10 times greater than night-time levels. We had not anticipated that light was going to be as important as it was in driving thyroid hormone cycles"

"This has an important implication in aquaculture. If you run a fish farm and keep your fish indoors, how long do you leave the lights on? Keeping them on a long time may cost you more on electricity, but if the fish grow faster, you would be able to get them to the market sooner."

In future studies, MacKenzie would be interested to know if there is also an optimal period of time for light above which fish do not grow faster.

MacKenzie is also interested in the internal mechanisms of the thyroid gland. Leiner's studies on redfish suggest that the biological clock mechanism in the brain may be the primary driver of thyroid hormone production.

"Though we know that thyroid hormone helps animals to stay healthy and grow actively, the question remains: 'How does the thyroid hormone work?'" says MacKenzie. "We think that the two primary controls of the activity of thyroid gland are the day-night cycle of light, which, through a clock in the brain, sets up periodic patterns of the production of the thyroid hormone, and a nutritive control on food intake, which can amplify the production of the hormone."

While MacKenzie needs more research work to better understand how the thyroid gland operates, his research has at least led to the following conclusion: if you want the fish in your fish tank to grow, you should leave the light on longer.


Story Source:

The above story is based on materials provided by Texas A&M University. Note: Materials may be edited for content and length.


Cite This Page:

Texas A&M University. "More Light Makes Redfish Grown Faster." ScienceDaily. ScienceDaily, 21 March 2001. <www.sciencedaily.com/releases/2001/03/010320074309.htm>.
Texas A&M University. (2001, March 21). More Light Makes Redfish Grown Faster. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2001/03/010320074309.htm
Texas A&M University. "More Light Makes Redfish Grown Faster." ScienceDaily. www.sciencedaily.com/releases/2001/03/010320074309.htm (accessed October 24, 2014).

Share This



More Plants & Animals News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins