CONSERVATIONISTS vow to continue the fight against WA's shark kill policy, despite being dealt another blow in a bid to end the so-called cull.

After earlier losing a legal bid to have the baited drumlines off the WA coast removed, the state's Environmental Protection Authority has declined to formally assess the program which has claimed over 100 sharks since the start of the year.

Despite almost 23,000 public submissions during the consultation period, EPA chairman Paul Vogel said the drum line measure would not be formally assessed as the environmental impact was "insignificant".

The number of comments received was at least 10 times more than for any previous issue and Dr Vogel said there was "a lot of public discourse".

But he added: "An impact assessment is not a public-opinion poll. We needed to test this proposal against our environmental objectives and make a judgment about whether there is a significant impact or not."

Dr Vogel said the drum line program was "of a very limited duration and of a very small scale" and the risk to target and non-target species was "negligible".

He said the EPA had received "professional and credible" advice from scientists in the Department of Fisheries who had conducted a risk assessment.

The Department of Fisheries also has responsibility for baiting and patrolling the hooks set off popular Perth beaches.

Greens Senator Rachel Siewert said the ruling that the policy was not impacting the environment was a nonsense.

``This policy is nothing more than a kneejerk, indiscriminate cull that has already harmed over 100 sharks,'' Ms Siewert said.

``Many sharks are being injured or attacked on the lines and we don't know how many are dying after they're released.''

WA Greens MP Lynn McLaren questioned whether the policy would be fully assessed next summer if it was only put in place for three months.

``If the Premier instates the drum lines in brief and frequent stints over a long time frame, does he forever avoid an environmental assessment of this barbaric policy?'' Ms McLaren said.

104 SHARKS CAUGHT, 101 OF THEM TIGERS

Dr Vogel said 101 of the 104 sharks caught so far were tiger sharks.

Forty sharks have been caught dead or were killed and, of those, 30 were bigger than the target three metre size.

A single north-west blowfish was the only non-shark species caught.

"The loss of 30 or 40, or even 100, individuals of sharks localised will have a negligible and immeasurable impact on the population of tiger sharks," Dr Vogel said.

The decision means the drum-lines off Perth and the South-West will stay in place until the end of next month.

Premier Colin Barnett has previously indicated he wants the beach safety measure to continue in future summers.

However, Dr Vogel said there was no "carte-blanche" clearance for the policy next year before he sees a proposal.

Dr Vogel expected a continuation of the program beyond April 30 to be referred by the State Government to the EPA for consideration.

This would restart the public consultation process and likely include an independent assessment of this summer's shark kill.

Late last month, Sea Shepherd failed in its bid to secure a court injunction to force the WA government to suspend its controversial baited drum line policy.