Author: Conservation

Montane Mist Region

                                                                                         

Photo by Matt Wall

Ascension Island’s cloud forest zone, or mist region, is confined to the summit slopes of Green Mountain. The area is frequently enveloped by cloud banks, resulting in perpetually damp conditions. Although the ecosystem shares many of the features of a true cloud forest, the original vegetation of this zone was treeless and dominated by ferns and bryophytes, including several endemic species.

Most of these native habitats have been replaced by a novel ecosystem of introduced species like yellow boy, guava, ginger and bambooHowever,  isolated pockets of native vegetation still survive on the most exposed slopes and outcrops. The mist region remains the centre of botanical diversity within the Territory, supporting populations of 15 out of the 18 known endemic plant species , such as purple fern (Ptisana purpurascens), hedgehog grass (Sporobolus caespitosus) and moss fern, (Stenogrammatis ascensionensis). The native fauna is  composed of a limited number of invertebrate species, vastly outnumbered by introduced counterparts. One unique resident of this ecosystem is the endemic moth, Gray’s fungus moth (Erechthias grayi),  This moth has evolved smaller wings so that it does not get blown away off Green Mountain and has evolved to hop instead of fly.

 Photo by Adam Sharp

The montane mist region is Ascension Island’s most restricted bioclimatic zone, confined to an area of less than 1 square kilometre.  This region encompasses the summit ridge and uppermost slopes of Green Mountain. Due to the lack of detailed habitat mapping and climatic data, an elevation range between 660 and  870 meters is generally used to describe the mist-affected area. However, it’s important to note that the prevailing south-easterly trade winds likely create some variations in conditions between the windward and leeward slopes.

Invasive species posethe most immediate threat to the ecological integrity of the mist zone; these introduced species have already smothered large tracts of prime native habitat. The impact extends to Green Mountain National Park, where invasive growth obstructs footpaths and hinders panoramic views of the Island.

 

Photo by Vicky Knight

Climate change presents  a potentially significant, but unpredictable, long-term threat. Global trends suggest rising temperatures and reduced low-level cloud cover could displacemany high-altitude cloud forests. In the case of Ascension Island, even a minor increase in the altitude where clouds form could mean that Green Mountain would lack its characteristic mist region for a significant part of the year. This would fundamentally alter both the hydrology and ecology of this unique montane ecosystem.

Preserving this rare and delicate bioclimatic zone remains a high-priority conservation goal for Ascension Island, especially in the face of immediate invasive threats and the longer-term uncertainties posed by climate change.

Conservation and Fisheries Directorate

11 September 2023

Author: Conservation

Nature Notes: Barracuda (Sphyraena barracuda)

Barracudas are muscular fish with streamlined, torpedo-shaped bodies. The largest species, the great barracuda, can grow up to 3 m (10 ft) in length. Females are typically larger than males.

They have fang-like, razor-sharp teeth. Some of the teeth are pointed backwards to prevent slippery fish from escaping once they are seized.

Hanging near temperate and tropical waters, this species preys on much smaller fish, such as mullets, anchovies, and grunts. They are esteemed as sport fishes. However, the smaller forms are also valued as food.

Ingesting barracuda is considerably more harmful to humans than eating any other fish species. People often become ill from ciguatera fish poisoning after ingesting barracudas, perhaps because the reef fish that barracudas eat themselves consume algae that may contain high levels of the toxin produced by marine microalgae called Gambierdiscus toxicus. Symptoms of Ciguatera poisoning involve vomiting, diarrhoea, stomach pains and nausea.

Great barracudas can be spotted around Ascension’s coast. They are territorial fish so the same individuals can be spotted again and again, patrolling their environment.  Attacks on humans are very rare, but they have been known to follow divers and snorkelers and may charge if you get too close. They are also reportedly attracted to shiny reflective items, such as earrings and necklaces so wearing jewellery should be avoided in their habitat.

Barracuda – Lorna West

Author: Conservation

Parsley Fern (Anogramma Ascensionis)

The curly leaf of a Parsley Fern. Photo taken by Matt Stritch.

The Anogramma ascensionis, more commonly known as the parsley fern is an endemic to the steep slopes of Green Mountain.  The tiny fern, reaching no more than 4cm in length, has delicate lime green fronds which appear similar to small sprigs of parsley.

The fern was first recorded in 1842 by an amateur botanist, and then officially described and named by Joseph Dalton Hooker. Another specimen was recorded in 1889, with few to no reports of specimens again until 1958, when a British scientist collected one on the north slope of the mountain.

Further searches were conducted throughout the years but were unsuccessful, and in 2003 it was officially declared extinct. Until 2009, when during an annual plant census it was rediscovered by local and visiting botanists. It is now classified as Critically Endangered.

The main threat to the Anogramma is competition with invasive plant species; over 200 non-native plant species have destroyed much of the original habitat and flora on the mountain. Its presence is now limited to a single location on the mountain but we continue to cultivate these plants in the lab and in our shade houses with the hope to restore this native population.

Conservation and Fisheries Directorate

Author: Conservation

Nature Notes – Bluntnose sixgill shark (Hexanchus griseus)

During the Discovery expedition on the 19th of November at 3:45 am, 250 metres deep at Grattan seamount, we noticed something glinting in the darkness…a pair of eyes. These eyes belonged to the bluntnose sixgill shark. A primitive-looking shark that lives in the deep ocean.

 

Image 1: The glinting eyes of the sixgill sharks.

 

These sharks  live in the tropical and temperate waters worldwide such as the Atlantic, Indian, and Pacific oceans. It’s the largest of the hexanchiform sharks, growing to a maximum length of 8 metres. The largest ever caught was in Ascension and weighed 588 kg.

As the name suggests, this shark’s snout is blunt and wide and its eyes are small but a beautiful fluorescent blue-green. There are 6 rows of saw-like teeth on the shark’s lower jaw and smaller teeth on their upper jaw. While juveniles have short and flexible jaws, mature male sixgills have rigid, calcified longer ones. Their skin colour ranges from tan, through brown, to black with darker spots staining their fins that get darker as they mature. Male sharks sexual maturity is determined by the length of their claspers.

Weighing over 500 kilograms (1102 lbs), the Bluntnose sixgill shark feeds on a wide variety of prey. This includes a diverse selection of fish, rays, chimaeras, squid, crabs, shrimps, seals and other smaller sharks.

Due to their diet, the bluntnose sixgill shark is classified as a generalist species and is less likely to be affected by scarcity in any one of its food sources .Although, the sixgill is classed as “near threatened”. Its longevity and popularity as a sport fish makes it vulnerable to exploitation and unable to sustain targeted fishing for very long, it is also found in only deep waters ranging from 180m – 2500m (590 ft. – 8202 ft.).

 

Image 2: A close encounter with a sixgill shark during a deep sea camera survey while onboard the Discovery.

Author: Conservation

Nature Notes – Mole crab (Emerita Hippo sp.)

What is a mole crab?

A mole crab is a small decapod (ten-footed) crustacean that burrows in sandy shorelines.

What does a mole crab look like?

  • They have short stumpy legs that are adapted to digging into the sand.
  • They are approximately 1-2 inches in length.
  • Females are generally larger than males.
  • Their eyes are positioned on the top of their head on moveable stalks.
  • They use counter shading for camouflage which means they are sand coloured on their backs and white underneath.

How does a mole crab feed?Mole crabs burrow themselves into the sand on the shoreline, either facing the sea or the beach.
They hold their antennae above the surface of the sand, and as the waves pass over the antennae,
they use their feeding appendages to filter food particles (algae and plankton). In Ascension, they
also consume small zooplankton such as land crab eggs, and mass gatherings of mole crabs can be
seen at North East Bay during land crab spawning.

Mole crabs on Ascension Island
Little is known about how mole crabs got to Ascension, but it was likely they travelled here as zooplankton in ocean currents. For spawning they favour areas of high swell activity making Ascension’s coastline the perfect habitat for them. It is thought the strong currents may give the mole crab larvae a head start because they are quickly removed from the adult habitat which is full of predators. Like the island’s land crabs, they rely on currents to take them out to sea where they can develop properly before returning to the sandy shoreline.

Author: Conservation

Nature Notes – Shark Parasites

A tale of two sharks and their many parasites (Alebion carchariae)

During a 2021 research trip, with the help of Shaun Scipio, Alex Knipe and Adriene Levknecht, visiting researcher Dr. Danielle Orrell from the Hussey Lab at the University of Windsor collected the first record of the fish parasite, Alebion carchariae, in Ascension’s waters. Through a collaboration with Alaska Fairbanks University, these samples now provide the first DNA barcode of this parasite species and the first record of its attachment to Galapagos sharks.

While fishing, two juvenile sharks were accidentally captured from ashore at Comfortless Cove and English Bay. In total, six parasites were plucked from the snout and face of these two sharks during hook removal, and the sharks were quickly returned to the water. Collected parasites were identified as copepods, a type of tiny crustacean distantly related to land crabs and lobster. This type of parasite is known to feed on tissue, mucus, or blood of marine fishes, ranging from small bait fish to large sharks.

To date, this parasite species has been recorded on at least 15 shark species and one fish species. The closest records of this species to Ascension were documented off the eastern U.S., São Paulo and the coast of West Africa. Its life cycle and reproduction are unknown. However, its distant parasite relative, the sea louse, has been relatively well studied owing to its impact on aquaculture (seafood farming). Studies of sea louse suggest that these parasites will gather near the water’s surface to increase their chances of finding a host. The infective stage lasts 1-9 days, and only once attached to a host can it fully develop and reproduce, with a > 210-day life span recorded. It is not yet known how this parasite species made it to Ascension Island. However, its long lifespan may allow it to hitchhike onto migratory species which travel across oceans, or it may incidentally arrive via ocean currents.

Further sampling of the parasitic assemblage around Ascension through water sampling or opportunistic collection during future tagging work could provide insight into the life cycle and ecology of this poorly studied group of parasites. They could also help identify the movements and genetic connectivity of their host, the Galapagos shark. In light of this discovery, the Marine science team welcome any photos of sharks with unusual “clingers on”. These tiny animals could help unravel many mysteries surrounding Ascension’s Galapagos sharks and the microscopic communities that Ascension hosts.

For more information, please contact the Conservation office or read the full paper which is now available online https://doi.org/10.1017/S0025315422001060.

 

Dr. Danielle Orrell, University of Windsor

 

Conservation and Fisheries Directorate 2023

Author: Conservation

Consultation on inshore fisheries launched

Fishing is at the heart of the Ascension community.  The opportunity to fish is so important and precious that AIG are proposing a new system that will ensure fish stocks stay healthy and that future generations of people living on Ascension can enjoy the same great fishing we have today. We are launching a public consultation on the strategy to get the views of people living on Ascension and ensure the system works for the community and will have wide support.

The proposed management system would be light-touch.  It is based on the principle that ‘if it ain’t broke, don’t fix it,’ and won’t restrict people’s ability to fish unless a fish stock is in trouble and it is absolutely necessary.  However, just as you take your car in for an MOT to check if there are any problems before the engine fails completely, so we need to keep checking how healthy our fish stocks are so we can spot issues early on and take sensible measures to keep things running smoothly.

The aim is to create a responsibly and sustainably managed fishery that benefits everyone on Ascension and has the people who fish at the heart of decision making.

The proposed strategy has five important parts:

  1. Registration and licencing

Everyone over 18 will need to register or have a licence to fish on Ascension. People who live on Ascension (those with a contract of more than 6 months and their dependents) would only need to register each year to be able to fish from a boat or the rocks.  This will be FREE.  Visitors and businesses will need a licence to fish on Ascension.    Businesses would include both those selling fish on the island and sports fishing companies.  Boat owners taking friends out fishing and receiving a contribution towards the running costs of the boat would not be classed as a business.

 

Proposed licence costs are shown in the table below.

 

Category Registration or licence Time period Cost
Under 18s None required Free
People living on Ascension Registration Annual Free
Visitors/short term contractors Licence Annual £15
Visiting sports fishing vessel Licence Up to 30 days £2,500
Sports fishing business licenced on Ascension Licence Annual £2,000
Sports fishing client Licence Weekly £50
Retail fish businesses Licence Annual £100
Scientific research fishing Licence Annual £100

 

  1. Data collection

We need good data so that any problems with a fish stock are identified early and the right management measures put in place.  AIG Conservation can collect some data, but the fishing community is in the best position to collect information about the health of fish stocks.  Everyone registering to fish will be asked to do this by filling in a log book about what they catch.  Licence conditions will mean all businesses and visitors will need to provide data on the fish they catch.

 

  1. Assessment of the health of fish stocks

The data collection described above will be the starting point for assessing how well Ascension’s inshore fish stocks are doing. For example, if we see a very rapid decline in the number of eels caught or a reduction in the size of grouper recorded in surveys, then we may be concerned about these stocks and consider recommending management measures. If the data do show a decline in a fish species, it does not necessarily mean overfishing is to blame.  However, adjusting the fishing pressure may still be necessary to maintain good fish stocks in the face of factors such as climate change.

AIG Conservation scientists will compile and analyse the data, but it is the fishing community that will be most affected so they should be at the heart of decision making.  The Inshore Fisheries Advisory Committee (IFAC), made up of members of the fishing community, and AIG Conservation will work together to provide recommendations to the Ascension Island Council about whether any stocks are in trouble and need management measures.  The Council in turn will advise the Administrator about whether any measures should be introduced.

 

  1. Management measures

To meet our international obligations, minimum landing sizes of 251cm for blue marlin, 168cm for white marlin and 125cm for swordfish will be introduced. Other management measures will only be introduced if it is felt necessary to protect the stock based on an analysis of the data collected. The same process for deciding whether management measures are needed will also recommend what types of measures should be introduced. As a minimum, all management measures will be reviewed by AIGCFD and the IFAC every six months to ensure they are still relevant and necessary.  The types of management measures that could be introduced if they are needed include:

  • Closed areas
  • Closed seasons
  • Size limits
  • Bag limits
  • Restrictions on gear type
  • Prohibition on catching species
  1. Prohibited fishing methods

There are some types of fishing that are never sustainable and would be prohibited under the new system.  These are not commonly practiced by Ascension fishermen and are:

 

  • Bottom and mid-water trawling
  • Tangle/gill netting
  • Drift netting
  • Longlining
  • Purse seine netting
  • Unconventional fishing methods (dynamite, poison, electricity)

 

We know fishing is important to many people living on Ascension and that people care passionately about it.  We would, therefore, encourage everyone interested to give us their thoughts on the proposed new system.  There will be public meetings at Saints Club at 19:00 on 27 April and Two Boats Club at 19:00 on 28 April as well as questionnaires distributed around the island.  We really do want to hear your views.

 

  AIG Conservation and Fisheries Directorate