Test results due back today may point scientists towards the cause of the mystery illness or illnesses affecting dogs and wildlife in the Hauraki Gulf.

Many fishermen defied advice to avoid fishing until the results were received, but other water sports were cancelled at the weekend.

Organs of the second of two dogs to die on Narrow Neck beach on the North Shore in the past month are being examined for clues about what further tests could be done to reveal the toxin.

Along with the organ tests:

* Preliminary results of tests on pilchards that washed up near Whangaparaoa Peninsula and Martins Bay in recent weeks are expected early this week. The fish are being tested for a virus that killed large numbers of pilchards twice in the 1990s and again five years ago.

* At the same time, tests on potentially toxic algae found on North Shore beaches on Friday by scientists at the Cawthron Institute are expected back today or tomorrow.

In case the professionals do not find the cause, a group of amateur scientists including Milford man Rob Bowden have taken it upon themselves to test the water along North Shore beaches.

Mr Bowden and his friends used a Eureka multiprobe water quality testing device to take samples from nine spots on the Hauraki Gulf.

They were on the hunt for a laboratory to test the water last night, but said initial results appeared to show higher-than-usual levels of dinoflagellates - a type of algae that in large numbers can form toxic algal blooms.

Cawthron Institute scientists believe brown-black mat algae, which live on rocks and seaweed, are a more likely culprit.

Meanwhile, many people ignored warnings to avoid fishing and water contact until test results were received and enjoyed a sunny weekend out on the water.

Recreational fishermen and charter companies spoken to by the Herald said they were happy to eat fish from the Hauraki Gulf.

Auckland Fish Market manager Tom Searle said fish sales had not suffered, though most of the fish he sold was from outside the inner Hauraki Gulf anyway.

A manager at high-end restaurant Kermadec said locally caught snapper was still on the menu.

Likewise fisherman Leo Sorrenti, spotted by our photographer fishing near the Auckland Harbour Bridge, said he had no qualms about eating the "beautiful" snapper he landed for dinner.

The Ministry of Agriculture and Forestry hopes tests on the dog's internal organs will help it to decide which other toxins may be worth testing for.

Seaweed, jellyfish, water and other samples have been taken for testing from near where the dogs became ill.

Marine biologist Karen Stockin said last week scientists were having to do wide, sweeping tests because they did not yet know that they were looking for.

Five dolphins were being tested for damage to internal organs, including toxins in their blubber, liver and kidneys, as well as any evidence of toxic algae, said Dr Stockin.

MAF has been speaking to the vets who treated sick dogs and gathering information from councils about the areas in which the dogs became ill. Spokeswoman Naya Brangenberg has said MAF would not be testing for any exotic diseases or pests.

Shellfish beds in different parts of the country have been closed several times in the past decade because of algal blooms, which collect in shellfish and can make them toxic to humans.

Vomit from the two dead dogs showed no sign of toxic algae but Ms Brangenberg said that did not rule it out.