Agriculture
Flush-Free Fertilizer
Chicken Eggs as Drug Factories
Cleaning Up Fish Farms
Amphibians
Tree Frogs
Frogs and Toads
Salamanders
Animals
From Chimps to People
Not Slippery When Wet
Firefly Delight
Behavior
Puberty gone wild
Math Naturals
Longer lives for wild elephants
Birds
Owls
Doves
Vultures
Chemistry and Materials
Smelly Traps for Lampreys
Bang, Sparkle, Burst, and Boom
Undercover Detectives
Computers
The hungry blob at the edge of the universe
Getting in Touch with Touch
Toxic Dirt + Avian Flu = Science Fair Success
Dinosaurs and Fossils
Message in a dinosaur's teeth
Winged Insects May Go Way Back
Fossil Fly from Antarctica
E Learning Jamaica
2014 GSAT Results for Jamaican Kids
E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
Results of GSAT are in schools this week
Earth
Earth Rocks On
Polar Ice Feels the Heat
Coral Islands Survive a Tsunami
Environment
Forests as a Tsunami Shield
Toxic Cleanups Get a Microbe Boost
Whale Watch
Finding the Past
Decoding a Beverage Jar
A Volcano's Deadly Ash
Ancient Cave Behavior
Fish
Whale Sharks
Sharks
Freshwater Fish
Food and Nutrition
Food for Life
A Pepper Part that Burns Fat
How Super Are Superfruits?
GSAT English Rules
Finding Subjects and Verbs
Subject and Verb Agreement
Who vs. Whom
GSAT Exam Preparation Jamaica
GSAT stars reap scholarship glory
GSAT Practice Papers | GSAT Mathematics | Maths
The Annual GSAT Scholarships
GSAT Exams Jamaica Scholarships
GSAT Scholarship
GSAT Practice Papers | GSAT Mathematics | Maths
Access denied - Disabled boy aces GSAT
GSAT Mathematics
Detecting True Art
Prime Time for Cicadas
GSAT Mathematics Quiz, Teaching Math, teaching anxiety
Human Body
What the appendix is good for
A Sour Taste in Your Mouth
Don't Eat That Sandwich!
Invertebrates
Corals
Leeches
Ticks
Mammals
Hoofed Mammals
Lynxes
Narwhals
Parents
Raise a Lifelong Reader by Reading Aloud
Expert report highlights the importance to parents of reading to children!
Children and Media
Physics
Hold on to your stars, ladies and gentlemen
Electric Backpack
Invisibility Ring
Plants
Seeds of the Future
Plants Travel Wind Highways
Making the most of a meal
Reptiles
Black Mamba
Garter Snakes
Snakes
Space and Astronomy
A Dusty Birthplace
Pluto's New Moons
A Star's Belt of Dust and Rocks
Technology and Engineering
Beyond Bar Codes
Bionic Bacteria
Young Scientists Take Flight
The Parts of Speech
Adjectives and Adverbs
What is a Noun
Pronouns
Transportation
Morphing a Wing to Save Fuel
Flying the Hyper Skies
Charged cars that would charge
Weather
Either Martians or Mars has gas
Earth's Poles in Peril
The Best Defense Is a Good Snow Fence
Add your Article

Bringing fish back up to size

 

Anyone who has ever gone fishing probably knows this general rule: Keep the big ones, throw the smaller ones back. The idea behind the rule is simple — the larger fish are assumed to be older. If you were to keep the smaller ones, they would not be able to reproduce, and the fish population would be in jeopardy. That rule may have done as much harm as good. Fishing out the largest fish from a population can have an unwanted consequence: Over time, fewer adult fish get really big. If only the smaller fish can reproduce, then future generations of the fish will tend to be smaller. This is an example of evolution in action.

Evolution is the process by which species adapt and change over time. The survival of the smallest fish is an example of an evolutionary process called natural selection. For years, scientists have wondered if the fish would stop shrinking if such catch-big fishing practices were stopped. Now, David Conover, a fish scientist at Stony Brook University in New York, has an answer — at least for the silverside, one particular kind of fish. “The good news is, it’s reversible,” he says. “The bad news is, it’s slow.” Conover should know — he spent five years studying if fish would shrink and then another five years studying if fish could regain their former size.. To set up the experiment, Conover and his team caught hundreds of silversides, small fish usually used as bait, in Great South Bay, New York.
The tiny fish were divided up into six groups. For two groups, Conover followed the “keep the large ones” rule and took out the biggest fish. In fact, he fished out all but the smallest 10 percent. For two other groups, he removed only the small fish. For the last two groups, he removed fish at random.

After five years, he measured the fish in each population. In the two groups where he had regularly removed the largest fish, the average fish size was smaller than the average size in the other groups. Here was evolution in action: If only small fish survive to reproduce, then future generations of fish will also tend to be small. For the second five years of his experiment, Conover changed the rules. Instead of removing fish based on size, he took fish randomly from each group. At the end of the experiment, he found that the fish that were in the “keep the large ones” group for the first five years had started to get larger again. These fish were on the road to recovery.
Those fish didn’t return to their original size, however. Conover calculates that it would take at least 12 years for the average size of a silverside to return to the original length. In other words, it takes less time to shrink than it does to recover. For other fish that don’t reproduce as often as silversides, it may take many times longer.

Conover’s study shows that organizations in charge of fisheries need to keep evolution in mind. Something like this could be going on with fish in the wild, though it’s much harder to test. For example, it may be time to get rid of the “keep the large ones” rule, since lab experiments show it causes the fish to shrink. Instead, fisheries managers might allow people to keep fish that are neither small nor large — which ought to help fish stay their original size.

Power words:
(adapted from materials from the Yale-New Haven Teachers Institute: http://www.yale.edu/ynhti/curriculum/units/1979/6/79.06.01.x.html)
 

biological evolution: the slow process by which life changes from one form into another (adapted from the Yahoo!

Kids Dictionary: http://kids.yahoo.com/reference/dictionary/english/entry/natural%20selection) natural selection: the evolutionary process by which organisms best adapted to their environment tend to survive and pass on their genetic characteristics to future generations, while those less adapted to their environment tend to be eliminated.

 Bringing fish back up to size
Bringing fish back up to size








Designed and Powered by HBJamaica.com™