WAILUKU, Maui — Two of the biggest environmental concerns facing the Hawaii Superferry — whales and invasive species — are expected to dominate testimony today in a Maui Circuit Court hearing on whether the company should be allowed to resume interisland service.

Greg Kaufman, head of the Pacific Whale Foundation and a Superferry opponent, had just begun his testimony yesterday afternoon when the hearing was recessed for the day. He said the North Pacific population of humpback whales that winters in Hawaiian waters has been growing at a rate of 7 percent a year, increasing the risk of boat collisions.

Experts have estimated that 5,000 to 10,000 of the endangered whales visit Hawai'i annually to mate, calve and nurse their young.

Kaufman said 70 percent are found in shallower waters of 100 fathoms (600 feet) or less, with the highest concentrations found off Penguin Bank west of Moloka'i and around the four islands of Maui County.

The ocean off O'ahu from Kalaeloa to Makapu'u is another popular breeding ground, he said, noting the ferry's initial leg out of Honolulu Harbor to Maui cuts through the sensitive area.

Kaufman was called as a witness by attorney Isaac Hall, representing the Sierra Club, Maui Tomorrow and the Kahului Harbor Coalition, which obtained a Hawai'i Supreme Court ruling ordering the state to conduct an environmental assessment of ferry-related projects at Kahului Harbor.

Maui Judge Joseph Cardoza has banned the company from using the Maui port until he can decide whether the ferry should resume service during the review process.

In a February appearance before two state Senate committees, Kaufman said the high-speed ferry poses a substantial risk of collision with whales. He noted the marine mammals in Hawai'i are particularly vulnerable to vessel strikes because they spend more time on the surface nursing, calving and socializing.

The risk of collision and serious injury to whales also is much greater at vessel speeds above 13 knots, he said during his Senate appearance. The Hawaii Superferry's 350-foot catamaran the Alakai will be cruising at 37 knots.

The Maui-based Pacific Whale Foundation is a nonprofit organization involved in education and research activities, as well as whale-watch and other boat tours.

Hawaii Superferry's whale-avoidance policy includes avoiding waters of 100 fathoms or less during whale season; posting two dedicated whale observers on board; and using special binoculars and other spotting gear.

Also scheduled to testify when the hearing reconvenes at 9 a.m. today is Carol Okada of the state Department of Agriculture, who will talk about the ferry's procedures for preventing the spread of invasive species.

In a court declaration filed by the Hawaii Superferry, Okada stated that officials with the state's Plant Quarantine Branch met on numerous occasions with company representatives to develop a vehicle inspection policy and provide training for ferry employees.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.