After using and abusing the Earth all year long, people around the world took the time yesterday to give back to the environment and heal some of the harm done.

On O'ahu, dozens of groups combed beaches, cleaned streams, stocked the ocean with new life and removed invasive species for Earth Day.

The Army Corps of Engineers hosted an interactive exhibit focusing on environmental concerns and safeguarding the ecosystem. City, state and federal agencies participated, including the Natural Resources Conservation Service, Board of Water Supply and the Coordinating Group on Alien Species.

Some 200 people visited the displays in the first hour it was opened, including Cub, Boy and Girl Scouts, who also volunteered to clean the park next to the Army Corps office at Fort DeRussy in Waikiki.

Jan Surface, with Natural Resources Conservation Service, said the exhibit wanted to spread the message of responsibility to visitors.

"If every single person took responsibility for conservation and cared for the Earth, there wouldn't be any problems," Surface said. "It's a cumulative impact. It's not the one piece of trash that one person throws, it's the 70,000 people who throw one piece."

Boy Scouts Kevin Duong, 15, and Carson Chun, 17, said they were especially interested in learning about a flood-control project in Kane'ohe, and disaster prevention.

The information will be useful Duong said. "Knowledge is power," said Duong, an Iolani School student. "The more you know the more you can help. The more you help, you make the world a better place."

After touring the exhibit, the boys took a bus to the Waikiki Aquarium where they were to help tag and release moi fishes into the ocean.

At the same time some 40 volunteers were removing armored catfish from Manoa Stream.

The Honolulu Aquarium Society and the state Division of Aquatic Resources coordinated the fish eradication netting 640 pounds of the dark gray fish. The organization had conducted a similar roundup two years ago, said Alan Teraoka, with the aquarium society.

The alien species is especially destructive because it contributes to the erosion of the stream bank, Teraoka said. The fish burrow into the stream banks to make their nest and that erodes the soil, he said.

"We're not picking on them just because they're ugly," Teraoka joked, adding that the fish were once aquarium pets but were dumped in the stream when they were no longer wanted.

Teraoka and about 10 men, women and children were stationed on the Lowry Street bridge over Manoa Stream, responsible for hauling in the fish and counting them. About 30 others were in the stream herding the fish into a net that spanned the width of the channelized concrete stream.

Bucket after bucket was lifted out of the water. Following Hawaiian Humane Society procedure, the fish were anesthetized in one barrel and placed in ice to kill them. The fish were to be dropped off at the Humane Society for disposal.

Alika Sarne, of Big Brothers and Big Sisters, said he read about the fish roundup in the paper and decided to help. The project piqued his interest and when he got there he was welcomed.

"We're glad we did come because they needed the help," Sarne said as he and Nick Francis hauled a 40-pound bucket of fish up from the stream about 20 feet below him.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.