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ผู้เขียน หัวข้อ: El Nino and Shrimp Farming  (อ่าน 4672 ครั้ง)
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« เมื่อ: พฤศจิกายน 19, 2006, 12:45:03 PM »

Introduction

Every three to five years, driven by a reversal in the trade winds, an El Nino, a huge bulge of warm water under a blanket of tropical storms, hits the western most extension of South America, burying the cool Humboldt Current and dropping heavy rains on Peru and Ecuador, often around Christmas--hence the name El Nino (the boy), in honor of the Christ Child. Over the past three decades, shrimp farms around the Gulf of Guayaquil (just a few degrees south of the equator, on the Peru/Ecuador border), have learned to deal with El Nino's various moods--and relatives, like his cool weather cousin, La Nina.


After seasonal changes, El Nino is the planet's most important source of climatic change, causing devastating droughts and storms around the world. In 1982-83, a huge El Nino caused droughts and storms blamed for 1,500 deaths and up to $8 billion in damage worldwide. Scientists at Mississippi's Stennis Space Center think big El Ninos like that one influence world weather patterns for over a decade, as they bounce from continent to continent, slowly dissipating their energy.

The 1991-1993 El Nino (of average intensity, but unusually long) triggered major weather changes and disrupted shrimp farming on a global basis. It caused drier than normal conditions in the Philippines, Indonesia, Thailand, northern Australia, northeastern Brazil and Central America. It brought record drought to southeastern Africa and dropped heavier than normal rains on southern Brazil, Uruguay, central Argentina, California, Texas, Ecuador and Peru. Coastal China experienced unusually heavy rains in 1993.

The granddaddy of all El Ninos hit Peru, Colombia and Ecuador in April 1997 and lasted until May 1998. Skip ahead to "The Monster El Nino of 1997-98" for all the details. Stay right here for a little background information.

Production of farm-raised shrimp usually increases along the Pacific coast of South America during El Nino years. Shrimp like the warm El Nino waters and grow rapidly in the brackish-water environment created by the heavy rains, which also flush out the ponds and estuaries. Wild shrimp reproduce in great numbers during El Ninos, supplying farmers with endless quantities of the highly prized wild postlarvae. Shrimp hatcheries have a tough time competing with the abundant wild seedstock and most temporarily close their doors.

Although Ecuador's production of farm-raised shrimp increases during El Ninos, big El Ninos, like the ones in 1981-82 and 1997-98, result in a net loss to the industry. Roads and bridges get washed out so harvests have to be barged or flown to processing plants. Low-lying ponds get flooded. Big hatcheries, which are usually closed during El Ninos, suffer damage that may not be revealed until the middle of the next production run. Some of Ecuador's current political/economical problems can be blamed on the monster El Nino of 1997-98.

In Central America and Mexico, El Nino spawns tropical storms and hurricanes during its early phases, followed by hot, dry weather during its later phases. Shrimp like the warm temperatures, but the absence of rain eventually leads to lower water quality and slower growth, so El Nino is a mixed blessing in this part of the world.

El Ninos suppress hurricane formation in the Atlantic Ocean and encourage it along the Pacific Coast of Central America and Mexico. In September 1997 Hurricane Nora, spawned by the 1997-98 El Nino, spun through the Mexican shrimp farming industry and reached as far north as Dr. Donald Lightner's Shrimp Disease Laboratory at the University of Arizona in Tucson.

In the eastern hemisphere, El Nino usually has a negative effect on shrimp production. During the 1991-93 El Nino, major droughts in Thailand, the Philippines and Indonesia took a heavy toll on shrimp farming. Wild broodstock and seedstock were in short supply and disease and water quality problems popped up all over Southeast Asia.


read more article
http://www.shrimpnews.com/ElNino.html

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« ตอบ #1 เมื่อ: ธันวาคม 04, 2006, 11:34:08 AM »



Thursday, 30/11/2006

El Nino weather systems may have a bad name for bringing drought to Australia but they might bring benefits for fishing and aquaculture.

The interaction between weather systems and the ocean will soon be tracked more closely, with the installation of high-tech monitoring equipment along the Australian coast.

South Australian based oceanographer Dr John Middleton says the equipment will give a more accurate picture of the impact of El Nino systems on marine life.

"The research I've done to date suggests they can actually lead to more nutrients available to the food web and thus more productivity," he said.

"So it's not all necessarily bad news about El Nino. It may be that in our oceans they may in fact be beneficial, while on the terrestrial side of course we know that they can be pretty miserable in terms of rainfall."
http://www.abc.net.au/rural/news/content/2006/s1801127.htm
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