Reef damage more limited than suspected

A new study from Carl Meyer and Kim Holland of the Hawai’i Institute for Marine Biology encompassing four protected marine sites in Hawai’i reveals that snorkelers and scuba divers only have a low impact on coral reef habitants at these sites and that the impact is limited to comparatively small areas.

The study, funded by NOAA Fisheries and the Department of Land and Natural Resources’ Division of Aquatic Resources, is based on secret observations of snorkelers and scuba divers at four marine life conservation districts: Honolua-Mokule’ia on Maui, Kealakekua Bay on the Big Island, Manele-Hulopo’e on Lana’I, and Pupukea on O’ahu’s North Shore.

“These are areas created with the overarching goal of maintaining an environment in pristine or near pristine condition“, says Meyer. “One of the ironies is that because it’s such a nice area, a lot of people want to come and visit it, and that sets up the potential for the original goal of marine protected areas to be undermined by overuse.“

The researchers used handheld Global Positioning System (GPS) units to map the movements of swimmers in the water and identify “hot spots” where the highest amount of contacts with reefs and other substrate took place. They found that divers and snorkelers use no more than 15 percent of the total reef habitat at each studied site and that the visitors stay within comparatively small areas associated with access points.

“Although Hawai’i marine protected areas were heavily used in comparison to those in other geographic locations, this did not translate into high recreation impact because most fragile corals were located below the maximum depth of impact of the dominant recreational activity (snorkeling),” according to the report.

The Meyer and Holland study provides information on a subject suffering form a severe shortage of reliable data.

“A lot of work on marine protected areas has focused on what the marine life is doing, not people,” saysMeyer, who hopes that information from the study will be used to create designated access points and boat moorings to focus activities away from the most sensitive parts of the reefs. By looking at a dive site’s topographical features, it is possible to predict where snorkelers and scuba divers are most likely to proceed from an access point.

“If you manage those access points somehow, you can determine where people go,” Meyer explains.

Boat access vs. shore access

According to data retrieved from the study, boat access has a lower impact per dive than shore access, for several reasons. People that dive and snorkel from a boat do not access the site from land so there is no wading involved, but information and supervision also seem to play a major role.

Divers and snorkelers on tour boats are instructed on proper reef behaviour before going into the water and they are also monitored by dive tour staff.

“If people are doing things they are not supposed to be doing, I’ve seen them intervene, and that separates boat-based activities from shore-based,” says Meyer.

Shore-based snorkelers and divers may of course receive instructions from shops where they rent their gear, but they will not be as strictly supervised during the actual dive as those who access from tour boats. There is less on-site management at dive spots accessed from shore, Mayer says.

According to the study, most of the substrate contacts between reef and humans occurred at shoreline access points where people waded to enter and exit the ocean. Even in such areas, the reef impact level was low since the contacts mainly involved sand or rocks where no coral grew. (The study does however point out that we “cannot rule out that (coral) colonization is being prevented by continued trampling.”) Only 14 percent of the contacts were between humans and live substrates, such coral, coralline algae, or invertebrates living attached to the substrate, and less than 1 percent of the contacts caused apparent damage, e.g. tissue abrasions or broken branches. Most of the damage was caused by snorkelers accessing from the shore. Scuba divers do however have a greater average impact on coral per dive than snorkelers, chiefly because scuba divers stay down longer each dive, explore a larger area, and venture deeper down.

Impact would be slashed in half if 16% of visitors stopped acting like morons

As in many other parts of the world, a major part of the damage is caused by a comparatively small part of the population.

“One of things we noticed is that about half of the physical impacts that we observed in these areas [shoreline access points] resulted from only 16 percent of the people who are using it,” Meyer says. “There is a subset of people who have a much higher impact. If you can reach that 16 percent, you could literally halve the existing impact.”

Meyer suggests placing educational signs at popular dive sites and letting volunteers provide visitors with information and advice.

Only few places are heavily impacted by tourist, but those places are of high commercial and recreational value

Although coral trampling only damages a very small part of Hawai’i’s total reef resources, the damage naturally tend to take place along beaches and at offshore sites of high recreational value.

The state of Hawai’i’ is heavily dependant on its $800 million ocean recreation industry and managing even heavily visited areas is therefore imperative for the long-term financial stability of this island state and its inhabitants.

According to Ku’ulei Rodgers, another scientist with the Hawai’i Institute for Marine Biology, increased visitor use results in a clear pattern of decreasing coral cover and lower fish populations since popular reefs can’t recover from damages while being continuously trampled.

“It can do really heavy damage to have people standing on the reef, but the good news is there are few places where there is a heavy impact from tourists. It’s mostly concentrated in places like Waikiki and Hanauma,” she said.

During the last fiscal year, the lower beach at the renowned snorkelling site Hanauma Bay was visited by 780,000 people. This can be compared to the areas studied by Meyer and Holland where the most heavily visited site, Kealakekua, was visited by roughly 103,300 snorkelers and 1,440 divers annually. Honolua-Mokule’ia received 84,000 snorkelers and 2,050 divers, Pupukea 47,700 snorkelers and 22,500 divers, and Manele-Hulopo’e a mere 28,200 snorkelers and 1,750 divers.

Closure, permit only or mandatory guides

In some situations, education and information simply isn’t enough. Last year, people straying onto unmarked coastal trails and trampling reefs at two popular snorkelling coves (the Aquarium and the Fish Bowl) forced managers of the ‘Ahihi-Kina’u Natural Reserve Area in South Maui to close much of the reserve’s 2,045 acres.

“It was a big step for us,” says Bill Evanson, Maui District natural area manager for the Department of Land and Natural Resources (DLNR).

The closure took place in October and will be in effect for two years to give damaged areas a chance to recover. An advisory board is currently considering whether to allow future access by permit only or through guided hikes. Before the closure, the ‘Ahihi-Kina’u Natural Reserve received 700 to 1,000 visitors a day.

The ‘Ahihi-Kina’u reserve was created for conservational reasons and is home to some of Hawai’i’s oldest reefs. Within the reserve, you can find rare anchialine ponds as well as numerous extraordinary geological and archaeological features.

Even though the reserve has only been closed since October last year, there are already noticeable signs of recovery.

“We’re seeing that many of the tide pools and coves where there used to be people are inhabited by fish in numbers and variety we haven’t seen,“ says Evanson. “Fish aren’t being scared away by the presence of people. Now they are able to feed, hide from larger predatory fish and breed.“

Since the first specimens were spotted in the year 2000, the number of lionfish living off the coast of North Carolina is now so high that scientists fear it is too late to eliminate them. Instead, marine researchers are joining forces with sport divers and cooks to keep the fish population in check the old fashion way – with rice, spicy sauce and a slice of lemon.

The lionfish has a sweet meat that tastes similar to that of the appreciated food fishes like the snapper and the grouper. If you want to help save the native North Carolinian fauna by putting lionfish on as many dinner plates as possible, there are several things you can do.

For all you scuba divers, Discovery Diving Co. in Beaufort and Olympus Dive Center in Morehead City are recruiting sport divers for a series of “lionfish rodeos” that will take place during the summer dive season. The first event is planned to May 18 and 19, and new events will then be held regularly throughout the summer.

During the first lionfish rodeo, participating divers will be thought how to collect lionfish in a safe way using protective gloves. In addition to getting some lionfish off the reefs and provide all participants with a tasty meal, the rodeo will also give marine researchers a chance to study how rapidly lionfish repopulate an area after being vanquished.

In addition to divers and marine researchers, representatives of the Carteret Community College culinary school will be involved in the rodeo project. One of their main goals is to persuade restaurants in the area to start serving lionfish, so those of you that don’t dive can still help out by asking for lionfish when dining out.

“They taste good, and if we can create a food market for them maybe that will not only help keep them in control but maybe take the pressure off some other species,” sais Debby Boyce, owner of Discovery Dive Shop.

The lionfish is not a welcomed guest in North Carolina since it competes with native species for space and food and puts even more stress on already threatened fish like snappers and groupers. The lionfish seem to lack natural predators in western Atlantic waters because the lionfish population has increased at a pace unlike anything scientists have ever seen from an invasive fish species in this part of the world.

“In places off North Carolina the population density appears to be several times the norm in their native waters”, said NOAA researcher James Morris.

North Carolina is not the only state with an exploding lionfish problem on their hands; the species can now be found in large quantities all the way down into the Caribbean.

“They’re eating everything,” said Lisa A. Mitchell, executive director of Reef Environmental Education Foundation, a Florida non-profit group that is helping several Caribbean governments deal with invasive lionfish. “They could wipe out entire reefs.

The lionfish is not only a problem for native flora and fauna; it is also disliked among snorkelers and scuba divers since it is equipped with long spines capable of delivering a painful venomous sting. The venom itself it usually not lethal, but it can cause paralysis and excruciating pain – two things you definitely don’t want to suffer from while trying to get up from the deep.

In North Carolina ordinary swimmers and snorkelers rarely have to worry about lionfish since this tropical species prefer to stay in the warm waters of the Gulf Stream, i.e. miles offshore and mostly at depths of at least 100 feet. In the warmer places like the Caribbean you can on the other hand encounter lionfish in the shallows right next to the beach.

In North Carolina it is usually the scuba divers who see this fish and they are alarmed by the situation. Divers off the North Carolina coast now routinely find up to 100 lionfish during a single wreck dive.

“If you go deeper than 100 feet, they’re ubiquitous now,” said Paula Whitfield, a researcher with the National Oceanic and Atmospheric Administration (NOAA) in Beaufort. “They’re absolutely everywhere.”

Catching lionfish is labour intensive but not very difficult; all you need is a net or a spear and some protective clothing to keep yourself from being stung. The divers organized by Discovery Diving Co. in Beaufort and Olympus Dive Center in Morehead City will be fitted with the kind of puncture-proof gloves worn by workers who handle used hypodermic needles and other medical waste. Before the lionfish is cleaned and cooked it will be held down using pliers and have its venomous spines snipped off by a wire cutter.

Lionfish is not very hard to net or spear-fish since they are virtually fearless and will hold their ground even when approached by divers. Since they have so few enemies in the wild, they probably don’t see any point in fleeing. However, if we are to really eat our way out of the lionfish problem a less labour intensive method than sending down divers armed with spears and nets must naturally be developed and NOAA researchers are therefore currently working on a trap system that uses live bait.

Hopefully, we will soon see the invasive lionfish on dinner tables all the way along the western Atlantic.