Fish and Ponds in West Hawai`i: Highlights of the Conservation Conference

 

 

The 23^rd annual Hawai`i Conservation Conference, held last month, brought some 1,300 scientists, natural resource managers, and students to the University of Hawai`i-Hilo.

For four days, participants criss-crossed the lush, sprawling campus as they walked from one symposium to the next. When lecture halls proved inadequate to hold the crowds, nearby classrooms, linked by video to the power-point screen and by audio to the speaker, accommodated the spillover.

In the past, the Hawai`i Conservation Alliance, which sponsors the conference, has posted on its website videos of selected speakers. To learn more, go to the HCA site: http://www.hawaiiconservation.org.

In this and coming issues, Environment Hawai`i reports on some of the highlights of the conference.

 

* * *

The Aquarium Fishery

In West Hawai`i:

Myth and Reality

“The aquarium fishery hasn’t got a lot of aloha over the years,” said William Walsh, master of the understatement.

Walsh, an aquatic biologist with the state Department of Land and Natural Resources’ Division of Aquatic Resources in Kona, noted that more than a decade ago, critics of the aquarium fishery in West Hawai`i engaged in “lots of hyperbole.”

”Nowadays,” he added, “there’s pretty much the same kind of rhetoric,” but it is limited to “a group of environmental zealots on Maui. It’s not broadscale anymore.”

It’s easy to see why the capture and export of colorful reef fish could the subject of heated disputes. But is the aquarium trade depleting wild stock of the very fish that draw tourists to snorkel and dive in waters off the coast of some of the state’s ritziest resorts? Or is it a sustainable, well-regulated industry?

Partly in response to the outcry, at the end of 1999, the state put in place a system of Fish Replenishment Areas (FRAs), zones along about a third of the West Hawai`i coast where no aquarium fishing is allowed.

“Part of the rationale for establishing network was focused on aquarium management,” he said, “but it was also to serve as a model for the application of a Marine Protected Area network in Hawai`i more generally.”

The aquarium industry, Walsh continued, is, the most economically valuable inshore fishery in the state, even though, “like all inshore fisheries in Hawai`i, it’s small-scale in dollar value.”

The fishery expanded greatly from the mid-1980s to the present day, although in recent years, the number of permits to fishery participants has declined. Now, said Walsh, there are around 15 permit holders who fish full-time, with around 40 total permits issued in West Hawaii.

In addition to setting aside the FRAs, two years ago the state developed a “white list” of 40 species of fish that may be taken by aquarium collectors. Most of those make up only a tiny fraction of the overall haul. Yellow tang represent more than 84 percent of the total take, Walsh said, with kole making up about 8 percent.

To monitor the effectiveness of the FRAs, the state set up 25 monitoring sites, which are visited four times a year.

Not surprisingly, the FRAs “have more fish than areas where fishing occurs,” Walsh said. However, “even in the open areas, the number of yellow tang has increased by 10 percent.”

Walsh attributes much of the increase to the enhanced protection of the FRAs in association with several years of high recruitment that occur naturally. “Last year, 2014, was the highest recruitment year we’ve had since we began surveys” in 1999, he said.

He provided estimates of overall numbers of fish in both protected and unprotected areas of West Hawai`i.

From over 2.3 million yellow tangs in 1999-2000, the number has risen to 4.8 million today, Walsh reported. Kole abundance has also increased – from 4.4 million to 7.7 million, he said.

Data from the National Oceanic and Atmospheric Administration and the Division of Aquatic Resources also indicated that these two species are also more numerous in most size classes in West Hawai`i than in any other place in the state. Even when compared with fish in the Northwestern Hawaiian Islands, he added, “we see the same sort of pattern – more kole in West Hawai`i than anywhere else.”

Kole, he noted, “is an endemic species. So it’s fair to say there are more kole in West Hawai`i than anyplace else in the world.”

Yellow tang, on the other hand, is a “super-endemic” species – a species that first evolved in Hawai`i and then radiated outward to other Pacific islands. Nonetheless, Walsh said, “its densities are highest here in West Hawai`i.”

For some other species, the news is less encouraging. “Achilles tang, which is a valuable food fish and also the third-most popular fish taken by aquarium collectors, has been going down in most areas over time,” Walsh said, although there has been a small spike recently in protected areas.

The saddle wrasse is “going down in all areas, protected or not. It is experiencing low levels of recruitment.” Aquarium collectors cannot be blamed for this, he noted, since they take less than one tenth of one percent of the estimated population out on the reef. Rather, said Walsh, it’s just a “natural fluctuation” in recruitment patterns.

* * *

The Need for Refugia

From Rising Seas: The Case

Of Anchialine Pools

Lisa Marrack recited the familiar and ever more depressing litany of impacts associated with a changing climate.

Sea levels have risen about 8 inches globally in the last century and are predicted to increase up to half a meter by the year 2050, she noted. By the end of the century, the increase will stand at nearly two meters, though perhaps somewhat less in Hawai`i – from 1 to 1.5 meters.

“And it won’t stop there, though,” added Marrack, a Ph.D. candidate in the Department of Environmental Science, Policy, and Management at the University of California-Berkeley.

While there has been a lot of concern over the effects of sea-level rise on humans, including erosion and flooding, Marrack is concerned about its impacts on coastal ecosystems – in particular, Hawai`i’s anchialine pools.

Among those impacts are “changes in wave dynamics, the increased salinity of aquifers, changes in species,” Marrack noted. And these sea-level-rise impacts will be in addition to other stressors that are already affecting anchialine ponds, she said, including non-point-source pollution, overharvesting, and invasive species.

Anchialine pools have no surface connection to the ocean, but they are connected through porous bedrock. Although they are found worldwide, one of the highest concentrations of anchialine pools in the world exists in West Hawai`i, along the Ala Kahakai National Historic Trail.

Of the 400 or so pools Marrack has surveyed in the area, there’s a variety of sizes, vegetation, and animals. A few species – including some yet to be described – are found only in Hawai`i.

But what will happen to those ecosystems as sea levels rise, Marrack asked.

Some pools will be inundated, and, if adequate habitat exists, new pools will be created inland.

“The exciting thing for me,” Marrack said, “is that hypogeal fauna” – the animals living below the ground – “will disperse into new habitat further upslope.” For that to happen, though, “we need to think about protecting these areas.”

And to do that, “we need to step away from the idea of protecting only the area right around that habitat, since the habitat will be moving.”

“We often try to focus on the best habitat in our protection efforts,” she continued. “But we need to look at marginal sites as well – for example, pools that go dry every day at low tide but where, when water comes up, shrimp flood in. These marginal pools are important refugia for shrimp. They’ll become more flooded as sea-level rise occurs.”

Rising ocean water might actually help the native species in one significant way. Marrack noted that tilapia, an introduced fish, were in four percent of the pools surveyed, while poeciliids, such as mosquito fish, were in 24 percent. “These prey on the endemic grazers,” including the native shrimp, she said.

With sea level rise, the shrimp can move into the new habitats where the invasive species cannot, she continued, and this “can help focus efforts for the removal of introduced fish.”

None of this can happen, however, if measures aren’t taken now to protect the lands where the anchialine pools can migrate.

Eons ago, Marrack noted, sea level change happened and the anchialine pools survived. But back then, “the coastal zone didn’t have the impediments to movement that now exist.”

 

— Patricia Tummons