invasive animals — Maui Invasive Species Committee (MISC)

Invasive jellyfish removed from Kaunakakai harbor

Posted on November 23, 2020 by Lissa Strohecker

Crews from the Molokai/Maui Invasive Species Committee and the Division of Aquatic Resources remove invasive upside-down jellyfish from the swimming area at Kaunakakai Harbor. They visit several times a year to keep the community swimming area free of these stinging pests. — Molokai/Maui Invasive Species Committee photo.

Back in 2009, a father and his two kids, still wet from the beach, walked into the office of the Molokai/Maui Invasive Species Committee. The kids were covered in welts. Dad carried a bucket containing a flat brownish thing. “This is stinging my kids,” he said.

He had captured an upside-down jellyfish, a relatively new creature in Hawaiʻi. The species anchors itself to the ocean floor upside-down, tentacles waving in the shallow water. “They look like big pancakes,” says Lori Buchanan, manager of the Molokai/Maui Invasive Species Committee (MoMISC).

For the jellyfish, this wrong-side-up strategy works: they use their bell as a foot to anchor themselves in place then, like coral, they partner with symbiotic algae that feed the jelly through photosynthesis. But these gelatinous blobs can pose problems for people in their midst: like many of their upright relatives, these jellyfish sting shooting harpoon-like nematocysts into the water when touched. When a single upside-down jelly stings, it can trigger the same reaction in his neighbors, leaving a stinging nematocyst floating in the water—a nightmare for snorkelers and swimmers.

The jellyfish delivered to Buchanan’s MoMISC office came from Kaunakakai Harbor–specifically, the roped-off swimming area that teemed with kids that summer. This was an urgent problem and Buchanan and her crew sprang into action to solve it.

Upside-down jellyfish arrived in Hawaiʻi hitchhiking on the bottoms of boats or in ballast water. They rest on the ocean floor, favoring shallow calm areas like lagoons and fishponds. Without predators, they can completely cover an area. — Molokai/Maui Invasive Species Committee photo.

With nets and buckets, the crew went to work, scooping jellies from the wharf. That first year, MoMISC crews removed 200 stinging jellies. They’ve kept at it, sometimes partnering with the crews from the Department of Natural Resources’ Division of Aquatic Resources. Visiting two to four times per year keeps the population down. Since their initial trip, they’ve removed 400 more of the squishy stingers.

These invasive jellyfish probably hitched a ride to Kaunakakai on the bottom of a boat – but that was not the first time they were seen in Hawaiʻi. First reported from Pearl Harbor in 1914, then in Kāneʻohe Bay, they likely arrived on the hull of a visiting ship, or as larvae in ballast water. They’ve invaded several places throughout the state, favoring shallow lagoons and fishponds where the water is calm.

Scientists believe the various populations resulted from at least two different introductions from far-flung places. Looking at the genetics of the different colonies, they traced one to Papua New Guinea and another to the Atlantic.

These spineless invaders are sometimes called mangrove jellyfish, for good reason. The two species are often found together. Here in Hawaiʻi, mangrove trees are invasive, and their presence can influence the population of upside-down jellyfish. As mangrove leaves break down in the water, they release chemicals that trigger larval jellyfish to settle down. The alien invertebrates then flip themselves over and rest in the shallow, clear water around mangroves. During MoMISC’s drive to remove the upside-down jellyfish, the crew noticed mangroves lining the wharf and removed them as well.

Without natural predators, these aquatic aliens can quickly cover an area. Buchanan says a fishpond on Molokai’s east end is so infested you can’t see its bottom.

Upside-down jellyfish have migrated from Pearl Harbor to Coconut Island in Hilo. So while Buchanan’s team won’t be able to remove them completely, it’s worth the effort to keep them suppressed in swimming areas. “The wharf is the most popular place on Molokai,” says Buchanan. “Especially in the summer, it’s like the mall.”

Aquatic invaders are no fun. You can help prevent them from spreading by keeping your boat free of hitchhikers. If you are interested in the role of hull-fouling and ballast water contamination in the spread of invasive species, check out this web page: http://dlnr.hawaii.gov/ais/ballastwaterbiofouling/ballastwaterdetails/

Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy, and quality of life.

This article was originally published in the Maui News on September 10th, 2017, as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.

A hidden world in Maui’s streams

Posted on October 12, 2012 by Lissa Strohecker 1 Comment

After 27 years of working with the Department of Land and Natural Resources, aquatic biologist Skippy Hau has become pretty familiar with Maui’s streams and the creatures dwelling in them. But there are always surprises. Several years ago, Hau discovered hīhīwai, one of two species of native Hawaiian freshwater snails, crawling single file up the cement bottom of a channeled stream next to a West Maui grocery store. The stream is typically dry, with few rocks to shelter the hīhīwai, but there they were.

This hīhīwai, a native Hawaiian snail, clings to a rock in a Maui stream. The presence of slow-movnig hīhīwai can indicate the frequency and quantity of water needed for a healthy stream.

It’s amazing that Hawaii has any native freshwater species to begin with. Streams in Hawai‘i are 2,400 salty miles away from the nearest continental sources of freshwater. Yet fish, crustaceans and mollusks colonized island waterways well before the first Polynesians arrived, most evolving into species found no where else in the world. These animals have evolved to cope with intermittent stream flow and climb waterfalls. ‘Ōpae kala‘ole, an endemic crustacean, is the best climber of all, known to scale 100-foot cascades. But like other native Hawaiian plants and animals, these riparian creatures now face threats from introduced species.

Invasive armored catfish have added the eggs of the native ‘o‘opu (goby) to their diet. Guppies and mosquito fish devour Hawaiian stream dwellers’ larvae and contribute to the decline of native damselflies at low elevations. Swordtails and other non-native aquatics spread new diseases to native fish. Tilapia compete with native water birds for food and released pet turtles dine on ‘o‘opu.

‘O‘opu nōpili. Photo by Skippy Hau

‘O‘opu nākea in ‘Iao stream. Photo by Skippy Hau

‘O‘opu ‘alamo‘o. Photo by Skippy Hau

Most of these invasive species were intentionally introduced – starting with Asian immigrants bringing in Chinese catfish, rice-paddy eels and other species for food in the 1800s. Mosquito fish, or topminnows, were released into streams from the 1900s through 1960s to control mosquitoes. This was an era when state officials frequently introduced game species, such as trout, bass and tucunare, or peacock bass, into streams. During the 1970s, managing resources for native species became more important; game fish are no longer introduced.

In the 1980s and ’90s, aquarium fish and mollusks began appearing in Hawaiian streams. In addition to guppies and swordtails, a variety of cichlids and ramshorn snails now snack on larvae of native stream animals returning to the ocean. Aquarium owners who dump unwanted pets are the most likely source of this problem, which is ongoing.

Hīhīwai, like all Hawaiian stream dwellers, are only part-time residents. They spend the first year of life in the ocean, then ascend single file into a freshwater stream. Not all make it as they colonize the stream’s upper reaches, instead becoming a source of food for other riparian species. In addition to the hīhīwai, another native mollusk, five species of fish and two crustaceans spend a part of their lives in the ocean. During rare flood events, these freshwater animals move quickly upstream for the less salty part of their lives, finding shelter in upper elevation pools.

Hau regularly monitors the slender tributary of ‘Iao where he first witnessed the climbing snails. When it exceeds a trickle, he dons a snorkel mask and peers under rocks for slow-moving hīhīwai. By carefully studying Maui’s streams, Hau has documented the frequency and volume of water necessary for our native freshwater animals need to move between ocean and stream.

These remarkable aquatic animals need our help. Don’t release unwanted pets into streams. If your fish is too large for your aquarium, contact a local pet store. They often take back fish and snails. Consider selling or gifting your unwanted fish or turtle online or to a friend.

Learn more about the fascinating animals in Hawaii’s streams and how to help protect them at hawaii.gov/dlnr/dar/streams.html.

By Lissa Fox Strohecker. Originally published in the Maui News, June 10th, 2012 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.
You can find all the articles in the Kia‘i Moku series http://www.hear.org/misc/mauinews/

A most unwanted neighbor–coqui frogs

Posted on October 27, 2011 by Lissa Strohecker Leave a Comment

A coqui frog hiding on a landscape plant

A recent trip to Hilo highlighted the impact coqui frogs can have on our quality of life. It was not just the chorus heard throughout town and in my hotel room, but the fact that they could be heard while having dinner, enjoying a beach park and hiking through native forests. They’re everywhere. Recent estimates indicate that coqui have infested more than 60,000 acres of East Hawaii, from the ocean to 4,000 feet in elevation. With Hawaii County now planning to liquidate its coqui-control equipment, this noisy neighbor seems to have become a permanent resident on the island of Hawaii.

My work creates many opportunities to talk about coqui, and I am often asked why they are perceived as a nuisance in Hawaii when they are beloved in their native home of Puerto Rico.

One consideration is that they have no natural enemies here and can reach population densities more than twice that of their native range. This may cause significant problems for native insects (which they eat), change soil composition to the benefit of non-native plant species and compete with Hawaii’s native birds for food. Possible economic impacts in infested areas include diminished property values and sales, a change in the quality of visitor experiences due to their persistent nocturnal calls and decreased sales in the floriculture and nursery industry.

During my short visit to Hilo, I learned that a colleague with deep ties to Hawaii agriculture was facing the prospect of moving and foregoing personal professional opportunities, primarily because of the coqui. These experiences strengthened my motivation to keep coqui from becoming widely established on Maui.

Signage indicating the coqui-free status of a local business.

Coqui are believed to have been introduced to Hawaii by hitchhiking on plants or associated products in the late 1980s. Since then, coqui have shown up on most of the main Hawaiian Islands, in California, and Guam on plant shipments. This is still the primary avenue for dispersal, particularly from heavily infested areas. To help minimize the risk of introducing coqui to your neighborhood, the Maui Invasive Species Committee started a coqui-free certification program. The voluntary program encourages plant industry participants to adopt specific practices to reduce movement via the nursery trade. If you see a business designated as “coqui-free,” you can feel confident that you will not be purchasing coqui along with your plants or plant products.

Like the Big Island, Maui has coqui. Unlike the Big Island, Maui has only six infested areas, which cover an estimated 227 acres. Eleven population centers (areas with five or more calling males) have been removed since 2004. Five others have very low numbers of coqui. Really, only one substantial population remains. Maui has kept populations from becoming established by quickly responding to reports of new coqui locations. Although new introductions from infested areas are a constant concern for Maui residents, quickly identifying and capturing a few rogue males typically prevents a couple of coqui from becoming thousands. Left unchecked or unreported, coqui populations on Maui would be sure to rival East Hawaii at some point.

The author preparing a large-volume sprinkler for citric acid delivery.

In Haiku, for example, an area that once had low numbers of coqui has now spilled over into a steep-sided gulch. Efforts have begun to remove coqui from the 225-acre area by applying a 12 to 16 percent solution of citric acid (a food additive). But challenging terrain and trying to work at night (when coqui are most active) have demanded the development of creative citric application tools. These include fixed-line sprinklers, high-volume sprayers and even limited use of a helicopter in inaccessible areas. Although daunting, successful control efforts over the last four years have shown that the key to preventing coqui from permanently establishing is early detection of new locations, repeated systematic treatment of known populations and removal of frog-friendly habitat.

Unfortunately, even the combined resources of state and county agencies on Hawaii, as well as regular outings by community-based coqui control groups, have been no match for the coqui.

On Maui, we only have one large population left. We still have a strong chance to become and remain coqui-free. Please help by calling the Maui Invasive Species Committee at 573-MISC (6472) if you happen to hear a coqui frog.

More information about the coqui-free program can be found at www.coquifreemaui.org.

Adam Radford is the operations manager for the Maui Invasive Species Committee. He manages MISC’s efforts to control invasive plants, animals, and banana bunchy top virus.

Originally published in the Maui News, March 14, 2010 as part of the Kia‘i Moku Column.
You can find all the articles in the Kia‘i Moku series http://www.hear.org/misc/mauinews/

Invasive jellyfish removed from Kaunakakai harbor

A hidden world in Maui’s streams

A most unwanted neighbor–coqui frogs

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