Islands discussed in this section include: the Poor Knights, Hen and Chickens, Hauturu (Little Barrier), Mokohinau, and Aotea (Great Barrier) Islands.
Physical Environment
The Poor Knights Islands form a scattered group of islands roughly orientated north-south and lying at latitude 174° 44.2' East and 35° 28.3'south, 18 km from the nearest mainland and 21 km north east of Tutukaka Harbour. There are two large islands, Tawhiti Rahi (129 ha) and Aorangi (66 ha), with numerous smaller islets, stacks and rocks. These are almost entirely bounded by cliffs (up to 240 m above sea level), which drop below the water surface to depths of 50 to 100 m where loose boulders lie on a sandy flat. The Pinnacles (two islets surrounded by five smaller stacks and rocks), found 6 km to the south, and the Sugarloaf, a solitary rock 7.7 km to the south, are also included in the Poor Knights Island group.
The islands have remained separate from the mainland during periods of Pleistocene glaciation as they lie well beyond the 100 m depth contour generated by Northland's coast. This has resulted in a high degree of endemism among the terrestrial fauna and flora.
The islands represent the heavily eroded remains of large larva domes formed during the Pliocene epoch. They are composed of rhyolite weathered into a complex topography that includes archways, caves, tomos and chimneys, as well as the lofty cliffs. There are very steep cliffs and bluffs that contain the best developed marine eroded arches, tunnels and caves in New Zealand. These extend up to 200 m long and 50m wide in size, and are eroded by the sea along joints in silicified rhyolite breccia. There are completely submerged tunnels of depths up to 30 to 40 metres below sea level, and uplifted to 80 metres above the present sea level. They include air bubble caves, many of which have been named. Tawhiti Rahi contains an uplifted sea cave 12 m deep, 8 m wide and 5 m high. The Poor Knights sea arches and sea caves have been classified as being of national geological importance, and are described as extremely well defined landforms of scientific, educational and scenic value (Kenny & Hayward, 1993).
Aorangi has a large valley that dips at its northern end to a boulder beach and a flat with salt pans. The Aorangi Island terraces, from the northern coast to Oneho Hill, Puweto Valley floor, are a well-preserved sequence of eight uplifted marine terraces reaching 170-185 metres, possibly dating from 700,000 years ago. There are locally derived rounded pebbles on the terraces (the most well-rounded occurring on the highest terrace, in contrast with the present day sea-cliffed coast. The terrace surfaces are modified by pre-historic Mäori horticulture. These terraces are classified as being of regional geological importance by Kenny and Hayward (1993), and the stonewall defences around a prehistoric Pa on a rocky knoll above the north end of Shag Bay are classified in the same inventory as being of national significance.
As a result of their geology, the island coastline is strongly convoluted in places, causing extremes of exposure and turbulence over short distances and creating a wide range of marine habitats in close juxtaposition.
The Hen and Chickens Islands are a group of islands only 20 kilometres out to sea from the Whangarei Harbour entrance. The largest island (Taranga) is 475 hectares in size. It is composed of andesitic breccia and flows with very steep cliffs and bluffs rising to 417 metres. The northern shores are constantly buffeted by heavy swells, and rise as steep V-sided valleys to the deeply weathered peaks.
The Hen Island Pinnacles, an area of spectacular rock pinnacles including Balancing Rock on the western end of the crest of Hen Island, have been classified as an extremely well defined landform of regional scientific and educational value (Kenny & Hayward, 1993). Another feature of geological significance is the prehistoric stone works in the area behind Pukanui Bay and Dragon's Mouth Cove. Numerous free-standing walls, stone rows, heaps, platforms and retaining walls have been constructed from andesite scree that was cleared in preparation for gardening. Because this is one of the best preserved areas of stonework associated with prehistoric gardening in New Zealand, this site has been classified as being of national importance (Kenny & Hayward, 1993).
The Chickens group of islands, of which the largest are Lady Alice, Whakupuke and Coppermine, are found about 6.8 km north of Taranga. They have steep sided greywacke and andesitic intrusion cliffs, rising up to 234 metres above sea level. Some small gravel and boulder beaches are found on their southern coastlines.
Coppermine Island contains several sites of geological significance. The western end of Coppermine Island contains an example of porphyry copper deposit (more specifically pyrrhotite-chalcopyrite hydrothermal mineralisation in pyroxene diorite and dacite breccia) that has been classified as being of national importance. The coastal cliffs on the western end of the island are of regional significance in that they represent the only diorite plutons in the region. These appear as dark coloured, coarse grained, pyroxene diorite, roughly elliptical in shape, with weak foliations parallel to the margins, and date from the Miocene (Kenny & Hayward, 1993). The shore platforms and coastal cliffs around the island also exhibit examples of albite-epidote and hornblende hornfels, which are of regional geological importance (Kenny & Hayward, 1993).
Hauturu (Little Barrier Island) is a roughly circular island of 2,817 hectares at the mouth of the Hauraki Gulf. It is extremely rugged, with 18 km of high sea cliffs, areas of boulder beaches and steep forest-covered ridges that rise to a series of peaks, the highest being Mt. Hauturu at 722 m tall. The island is comprised of the remains of an andesitic volcanic structure formed from intermediate andesite lava, which may have erupted about the same time as the commencement of volcanic activity in the Rotorua and Tongariro areas. During the ice age, the island became connected to the mainland, but became isolated again when the ice sheets melted. The boulder beaches on the southern side of the island extend from hundreds of metres above high tide, down into the sub-tidal zone. The Te Titoki Point Cuspate Foreland is where two boulder barriers have connected to form a triangular-shaped in-filled flat, 25 hectares in size. This site is of regional geological significance. There are two other regionally important geological sites: the large rockfall at Pohutukawa Flat (Hingaia) and the Queens flow banded dacite, both of which are below and above the tide line (Auckland Regional Council, 1995).
The Mokohinau Islands are made up of twelve small, volcanic outcrops lying 23 kilometres north-west of the northern tip of Great Barrier. The islands are rugged, and the group includes a number of steep stacks. Their small size and low elevation result in a very low annual rainfall, and they suffer from severe drought in the summer.
Aotea (Great Barrier) Island lies at 36° South latitude and is situated 80 kilometres north-east of Auckland city at the entrance to the Hauraki Gulf. It is separated by 20 km of water in the Colville Channel from the headlands of the Coromandel Peninsula. It is a hilly island with high standing ranges, numerous deep valleys, ravines and some pockets of coastal lowland. The coastline is rugged and intricately indented by numerous bays and inlets particularly on the western side. At many places small islands also lie close inshore.
The base rock of Aotea is composed of Mesozoic shales and greywackes from the Jurassic-Permian period. It is overlain to a considerable depth on most of the island by roughly stratified Tertiary andesitic breccias, buffs and agglomerates. Extrusions of Pliocene rhyolites in the centre of the island give rise to Hirakimata (Mt. Hobson), Mt. Young, and Maungapika. An overall downward movement of the land on the western side during recent geological times allowed the sea to invade the deep narrow valleys of the earlier land mass, forming a coastline characterised by a series of bays and inlets with a number of islets lying offshore.
On the exposed ocean-facing eastern coast, the coast has been subject to vigorous marine erosion. This, combined with a slight tilting of the island to the west that facilitated the formation of sand-spits and barrier beaches, has resulted in a more regular shoreline. Large indentations in the coastline, such as the harbours of Whangapoua, Awana, Kaitoke and Oruawharo, have been blocked by the accumulation of sand, and the lagoons behind have become in-filled with blown sand and alluvial deposits.
There are several features of regional geological significance on Aotea. A basalt flow within a rhyolitic sequence in the inter-tidal area off Ora Point, Rakitu Island is the only known basalt in the Aotea region. The obsidian breccia on the coast of Rakitu Island is also of regional geological significance (Auckland Regional Council, 1995).
Flora & Fauna
It has frequently been observed that the off-shore islands of northern New Zealand have a comparatively high diversity and abundance of fish. This has been the subject of several scientific studies. Ward and Roberts (1986) investigated the distribution and abundance of the black angelfish and eight species of the wrasse family at ten coastal (mainland) and eight offshore island sites along the north-eastern coast of New Zealand. They found that more species were present at island sites than at coastal sites of the same latitude, and that species number decreased with latitude and increased with distance from the coast. A similar study was undertaken by Kingsford (1989), in which the distribution patterns of planktivorous reef fish were examined. This study compared the abundance of thirteen fish species both with respect to latitude and distance from the mainland (i.e. inner shelf, mid-shelf, and outer shelf). Contrasting patterns of abundance were found for the 13 species both along the coast and across the shelf. The total abundance of fish at each location was compared with the average depth of the water column in which the counts were made. A positive relationship existed between average depth and number of fish i.e. the greatest numbers of fish per unit volume of seawater were found at the outer edge of the shelf. The authors of both studies suggested that hydrology (for example, the influence of the East Auckland Current) may influence these patterns of abundance, either directly or indirectly.
Rocky shores are the predominant marine habitat across all the offshore islands in the study area. Many ecosystems contain an abundance and variety of species not found on the mainland coast. Most contain some tropical or subtropical species, presumably due to the influence of the East Auckland Current. A typical underwater cliff face at the Poor Knights Islands was described by Ritchie et al., (1979):
“The high water splash zone is dominated by surf barnacles and large shore crabs, while towards mean high water mark a crust forming red alga, small barnacle and red anemone are common. These are separated from the deeper brown kelp forest by a clearly defined dense curtain of the brown strap weed, (Xiphophora chondrophylla var. minor), which gives way below to a 5-7 m wide belt of algal wrack (mainly species of Carpophyllum) with associated red, brown and green seaweed…. In the most exposed areas where light penetration is greatly reduced these large seaweed curtains are replaced by floating straps of bull kelp. Within caves and arches, the light is constantly subdued, so that all the algae except for a few shade–dwelling species are absent. Brilliant encrusting sponges, tunicates, ascidians and anemones are dominant.
The tidal and shallow sub-tidal belt of algal wrack merges into the main, and deeper extending, sub-tidal forest of the brown kelp Ecklonia radiata, which forms a dense canopy to 30 m and thins at around 45 m…It directly supports a huge fauna on its laminae or “leaves”; notably cantharid and maurea topshells, shrimps and isopods, silvery-white sheets of bryozoans; tubeworms, and hydroids. The holdfasts contain numerous worms – both tube-dwellers and free-living types.
While Ecklonia is the dominant sub-tidal brown kelp, Lessonia variegata also contributes to the underwater forest, particluarly in the more exposed localities…The overall picture is one of an extremely rich and dense underwater forest, particularly when compared to the Northland coast.
Many fish dwell in this forest. Sheltering among the fronds are juvenile butterfish, leatherjackets and blennies. Clouds of demoiselles and blue maomao move over and through the canopy. Lurkers such as the grandfather hapuku, and Moray eels (three species) hold crevice territories on the forest floor. The large labrids, including the green, orange and banded parrotfishes and the red pigfish, wander and search over their larger forest territories. Others such as Sandager's parrotfish, combfish, and the yellow labrid, usually occupy holes in the canopy such as patches of sand.
The forest floor is thickly covered with bryozoans, including the green and pink bushy types, small red algae… and encrusting sponges of yellow and orange. Coelenterates include soft corals, brilliant orange zooanthids, and pockets of multi- coloured anemones. Delicate and often gaudy nudibranchs (sea slugs) are common.
Caves among the forest have a dense encrusting fauna which includes colonial ascidians (sea squirts) and the staghorn bryozoan; lace “coral” (actually a bryozoan); cup corals, and feather stars which would be found in the open only in much deeper water. There are also numerous, more active cave dwellers, such as the red rock lobster, pack-horse lobster and Spanish lobster, and the exquisitely-coloured and patterned coral shrimp. Forest caves have a large and diverse fish fauna, including three subtropical gropers- the yellow-banded perch, spotted black groper and the toadstool groper. Other common species include the Lord Howe Island coral fish (almost invariably seen in pairs), tribes of red moki; marble fish; bigeye and slender roughy.
Where the forest thins below 30 m, the large sponges become dominant – for example, the thin finger sponge, yellow finger sponge, and organ pipe sponge. Fan corals and several gorgonian species carpet the cliff face…. Other spectacular animals of this zone include the red urchin, the solitary-living mosaic moray, long-fin boarfish, and schools of pink maomao, golden snapper and fluorescent splendid perch occur. Eerily pale and magnificent in the twilight of 50 m and deeper water, giant tube sponges and black coral trees sprout from boulders littering the foot of the cliff.”
This rather graphic description, which continues to discuss the fish found at these depths (hapuku, large blue moki, kingfish, and occasionally, bronze whaler sharks) illustrates the abundance and variety of marine life found at the Poor Knight Islands. The same report also listed 10 species of uncommon fish, 21 rare fish species, and two endangered fish species recorded at the Poor Knights Islands. Nineteen rare molluscan species were also recorded, along with five other organisms regarded as being endangered (Ritchie et al., 1979).
The Poor Knights Islands are also noted for their large numbers of petrels. Ten species of petrel are known to breed on the Poor Knights Islands, and petrel population numbers are high. The most abundant of these species is the Bullers shearwater. The Poor Knights Islands are the only breeding place for this species. The other common resident sea birds are gannets, which nest on the Sugar Loaf and the Pinnacles. Fairy prions also nest on the islands. Although beyond the scope of this report, it is pertinent to note that there is a high degree of endemism in the terrestrial biota on the Poor Knights, due to the islands' separation from the mainland during the last period of glaciation. These include numerous endemic insects, including weta species. Some of the plant species exhibit features not found elsewhere in the same species, such as particularly large leaves or unusual growth forms. The Poor Knights Islands have been identified as an area of significant conservation value.
Unlike the Poor Knights Islands, the Hen and Chickens Island were connected to the mainland during the last glacial period. However, these islands are also important because of their terrestrial fauna, specifically their bird populations, which include forest species that are rare or endangered elsewhere. There are also significant reptile populations, including tuatara, and ten species of lizard (DoC, 1995). The Hen and Chickens Islands have been identified as an area of significant conservation value.
Hauturu (Little Barrier Island) is a nature reserve of international significance, as it is the habitat of several endangered bird species endemic to New Zealand, the most notable being the kakapo. It is surrounded predominantly by boulder beaches, which support a variety of marine biota.
Considering that the boulders are comparatively smooth and spherical, and constantly moved by wave action, the boulder beaches support a surprising variety of marine life. High in the inter-tidal area, small gastropods ( Littorina unifasciata ) are found, with the gastropod Nerita atramentosa forming a distinct band within the mid-tide level. The gastropod Melagraphia aethiops , limpet Cellana radians , and barnacles, Chamaesipho brunnea and C. columna, clamp tightly to the smooth rock surfaces. Apophloea , a dull red, tough encrusting alga, occurs as patches on the sides of boulders. A variety of crabs also occur (for example, Cyclograpsus lavauxi , Leptograpsus variegatus , Ozius truncatus , Heterozius rotundifrons and Petrolisthes elongatus ).
Below low tide, the boulders are often encrusted on their upper surfaces with bright pink algae called Lithothamnium , and on the lower sides tightly coiled white tubeworms ( Spirorbis ) occur. This is also an environment in which black-footed paua Haliotis iris are found. Clamped onto the boulders, the seaweed Xiphophora chondrophylla , followed with increasing depth by Carpophyllum maschalocarpum and Ecklonia radiata form distinct zones. Beyond the boulders in the sub-tidal area are large areas of white sand with significant beds of scallops ( Pecten novaezelandiae) .
Moving up the shore, the marine ecosystem grades into a high value terrestrial ecosystem. Hauturu supports some 370 plant species including 90 fern varieties – it is the largest remaining native forest area in New Zealand unmodified by browsing animals and man (Hauraki Gulf Maritime Park Board, 1983). As a predator-free nature reserve, Hauturu plays an important role in the conservation of rare and endangered bird species, which nest and breed on the island. While the island is most significant in its conservation of terrestrial bird species, and number of marine birds also occur on the island. These include northern blue penguins, flesh footed shearwaters, white-fronted terns, gannets, Bullers shearwater, diving petrels, grey-faced petrels, fairy prions, fluttering shearwaters and little shearwaters. Less frequently observed birds include the wandering albatross, black browed mollyhawk, shy (Salvin's) mollyhawk, giant petrel, Cape pigeon, black-winged petrel, Arctic skua, common diving petrel, and white-faced storm petrel. A small population of the endangered brown teal is found on the Hauturu. Ten reptile species and two species of bats also occur on the island, as does a species of giant weta, found only there.
The Mokohinau Islands contain a variety of marine habitats, including broken rock, boulder beaches, sandy sediments, and kelp forests. These contain a large diversity of marine species. The islands are particularly noted for their high diversity of encrusting invertebrates and fish. The islands are the closest to Auckland to contain a subtropical element in their marine biota (Auckland Regional Council, 1995). The coastal waters around the islands are renowned for their larger marine life particularly marlin, shark, kingfish and hapuku.
Fanal Island (75 hectares) is the least modified of the Mokohinau Islands with respect to its terrestrial environment, and is surrounded by cliffs up to 150 m high. Half of the island is covered in mountain flax but the remainder mainly consists of houpara and young kohe kohe. Fanal, Flax, Trig and Groper Islands are all wildlife sanctuaries. Burgess Island (52 hectares) is the site of a lighthouse station. All of the islands have suffered from naturally occurring bush fires and the resulting vegetation is fairly stunted. The cliff vegetation within the coastal environment is the habitat of several threatened plant species. A number of species of coastal and sea birds breed on most of the islands and stacks in the group (Auckland Regional Council, 1995). In addition to a range of native terrestrial birds, eight species of reptiles occur, including a small endangered skink. Rare beetles have also been identified on the islands (Hauraki Gulf Maritime Parks Board, 1983). The area has been selected by the Department of Conservation as an Area of Significant Conservation Value.
Simpson Rock, located to the south of the Mokohinau Islands, is an isolated rocky outcrop surrounded by deep water. Although closer to the Mokohinau Islands, the rich encrusting fauna present is more similar to that of the northern tip of Aotea. A number of new species of sponges and other encrusting organisms have been recorded here (Auckland Regional Council, 1995).
Aotea has a variety of coastal habitats, encompassing: rocky outer shores and enclosed bays and harbours on the western side of the island; rocky offshore islands; broad ocean beaches and dunes at Medlands, Kaitoke and Whangapoua; and estuarine and marsh areas at Whangapoua and Kaitoke. Water depths along the coast of Aotea vary, with relatively shallow water (10-30 m deep) lying off most shores except on the eastern coast, providing habitat characteristics similar to those found in the islands in the inner Hauraki Gulf. Deeper oceanic water is found close inshore on the eastern coast. The rocky marine habitats of the western and southern shores of the island are less exposed to wave swells than the northern and eastern coasts.
The subtropical East Auckland Current reaches the north-eastern coast of Aotea at times, and appears to influence the coastal ecology of the island by bringing rare subtropical species in its warmer water.
The north-eastern coast of Aotea is the marine environment on the island that has been studied most closely (e.g. Hayward et al., 1986; Francis & Grace, 1986; Roberts et al., 1986). The rocky intertidal shores appear to contain biota characteristic of both ‘mainland' North Island, and other north-eastern offshore islands. The presence of shore turfing seaweeds, the black shore snails Nerita atramentosa and the vermetid snail Novostoa lamellosa on many shores is typical of north-east offshore islands. However, some other species, such as rock oysters and zone-forming seaweeds, are typical of mainland shores within the Hauraki Gulf. The variety of sub-tidal rocky habitat structure means biological communities are diverse. Five broad sub-tidal habitat ‘types', similar to those found in other northern locations, have been identified, including: shallow mixed weed habitat; kina and corallines habitat; Ecklonia forest habitat; mixed red and green seaweed habitat; and sponge habitat (Francis & Grace, 1986). Sixty-six species of seaweed are found on this coast, most of which are common to north-eastern New Zealand (Francis & Grace, 1986). This coast is also unusual in that it is one of few locations in north-eastern New Zealand where the southern bull kelp Durvillaea antarctica (normally a cold-water species) is found. Four species of warm water sea urchins are also found here, reflecting the influence of the East Auckland Current.
A study of the soft sediment seafloor in shallow water along the north-eastern coast of Aotea indicated that at least five different groupings of benthic species and one sub-association are present in the sediments of the area. These include: polychaete/crustacean communities; communities in which the bivalves Myadora and Scalpomactra predominate; communities dominated by the bryozoan Otionella , (and a sub association in areas where both Otionella and the turret shell Zeacolpus are dominant); a starfish/bivalve association comprising Amphiura , Cuspidaria and Notocallista ; and a bivalve community in which Gari stangeri and Felaniella zelandica predominate. It appears that a complex interplay of factors, some of them not easily identifiable, determines the distribution of shallow water, soft-bottom benthic organisms. Among the more significant factors are the degree of exposure to wave and current energy, water clarity, sediment grain size, and factors strongly associated with increasing water depth (Hayward et al., 1986).
The fish fauna of north-eastern Aotea is also diverse (Roberts et al, 1986). Seventy-three species have been recorded. This fish fauna is considered typical of the north-eastern coast of New Zealand with species such as red moki and leatherjacket being abundant. However, the fish fauna also reflect the subtropical influence, with the black spotted goatfish and notch-head marblefish both recorded in the area in small numbers. (Both these species are very common around the subtropical Kermadec Islands). Other subtropical species found around this coast are the toadstool grouper and clown toado.
Species more normally associated with offshore islands isolated from significant fishing pressure, such as two-spot demoiselles and black angelfish, are found in high numbers at several locations on the north-eastern coast of Aotea. Blennies and triplefins are generally more abundant on the north-eastern coast of Aotea than at mainland locations.
In the north of Aotea, the rocky shores grade into a naturally forested ecosystem along most parts of the coast. The cliffs of the coastal environment offer a habitat for a variety of threatened plants, as do the small areas of saltmarsh in the mouths of some of the streams entering Rangiwhakaea Bay. This terrestrial environment is an important wilderness area. The area has been ranked as having outstanding wildlife value and provides a natural habitat for the Great Barrier Skink, Hochstetters frog, Rhytida snail, parakeet, kokako, coastal skinks, and other lizards and birds of the coast and forest (Dept. of Lands & Survey, 1983).
Terrestrial environments on both Aotea and Hauturu provide an important habitat for the black petrel. This is an endangered New Zealand endemic bird species, which currently breeds only on Aotea and Hauturu, having been exterminated from the mainland. Black petrels live in burrows, located only in unmodified forest at altitudes above 300 m. A study on Aotea in 1989 estimated the black petrel population to be approximately 4,100, including 3,100 pairs, and 1,500 non-breeding birds. The feeding range for some birds was found to be restricted to within 160km of Aotea, and concentrated on the Continental Shelf (Schofield, 1989).
On the north-eastern side of the island lies the Whangapoua Harbour, bounded by a significant sandspit to the north. The sandspit is an important area with respect to rare and endangered birds: It is considered to be one of the least disturbed breeding sites for the New Zealand dotterel in northern New Zealand. Other migratory wading birds use the sandspit as a high tide roosting area, and fernbird and marsh rail inhabit the vegetated regions of the spit. Due to the absence of marram, the sandspit is also an important area of mobile sand vegetation, being one of the few places in which the three native sand-binding plants, spinifex, pingao, and sand tussock, grow together (Auckland Regional Council, 1995).
Inside the sandspit are unmodified areas of mangroves and saltmarsh, grading landwards into freshwater wetland and native forest. This area of mangrove and salt marsh is regarded as one of the least modified in New Zealand for its size. Of any area on Aotea, this presents the greatest diversity of bird species, and it is considered one of the most valuable for its wildlife. It is most important for Brown teal, and endangered species that are particularly numerous in the upper estuary, but are also found at Harataonga Stream, and in substantial numbers at Mabey's Farm Stream. The harbour also provides an over-wintering area for birds such as Wrybill and New Zealand Dotterel. Other species of importance include the fernbird, banded rail, spotless crake, bittern, pied stilt, variable oystercatcher, white-faced heron, banded dotterel and various gulls, terns ducks and shags. The Whangapoua estuary has been identified as an area of national significance because of its large size, lack of modification, and unbroken vegetation sequences from deep sub-tidal marine habitats to terrestrial forest (DoC, 1994).
Further south, Kaitoke Beach is an important habitat for mobile sand vegetation, being one of the only two places in the region in which the sand-binding plants pingao, spinifex and sand tussock grow together. The Kaitoke Stream is a tidal stream that crosses the beach, draining from a significant freshwater swamp area. Kaitoke Swamp is a large low lying wetland complex that is impounded between the vast accumulations of sand deposits lying for a distance of almost 2 kilometres behind Kaitoke Beach and an encircling enclosure of steep sided hills which rise to the summit of Hirakimata on the southwest. The swamp is considered to be an area of national significance because of its large size and its natural condition, which has remained virtually unmodified. Vegetation ranges from a dense cover of raupo, sedges and manuka with scattered cabbage trees and Kaihikatea in the upper portions of the freshwater swamp, to mangroves, and sedges, rushes characteristic of saltmarsh in the lower reaches. During the winter months, a combination of easterly gales, torrential rain together with blockages and tidal effects at the outlet to Kaitoke Stream, causes the swamp to become severely flooded. Kaitoke Stream, in conjunction with the associated freshwater swamp, scrub areas and roosting sites in the coastal environment above mean high water springs, is an internationally significant habitat for brown teal, an endangered species.
Several other important habitats for brown teal are also present on the eastern coast of the island including the tidal streams and freshwater marshes of Sugarloaf Creek (Medlands Beach) and Saltwater Creek (Oruawharo Bay).
The rocky habitats on the southern coast of Aotea are more sheltered than those on the eastern side of the island. The fish species are more similar to those on the mainland coast, and include fewer subtropical species than the more exposed coasts.
Several streams, and their associated wetlands, flowing into Tryphena Harbour, including the Tryphena Stream, Shoal Bay Stream, and the streams crossing Par Beach, provide significant habitat for the endangered brown teal. The Whangaparapara Stream, which flows into the Whangaparapara Harbour, forms the basis of a wetland area used by brown teal and banded rail. Off the coast to the north of this harbour, lie a series of rocky islands and stacks, known as Broken or Pig Islands. The habitats on these islands grade from rocky shores into coastal scrub, mainly consisting of taupata. The eastern tip of Mahuki Island is the site of one of the major breeding colonies of Australasian gannets in the region. One of the stacks in this island group is rat-free. Large numbers of geckos have been recorded on this island, along with petrels and fluttering shearwaters, which breed in the scrub (Auckland Regional Council, 1995). Tuatara were once common in this type of environment (W. McGregor, pers. comm .).
Tidal stream mouths, with associated saltmarsh and freshwater wetlands, form important habitat for brown teal and banded rail in Port Fitzroy. Port Fitzroy is also an important fish feeding and shellfish habitat (Auckland Regional Council, 1995).
The endangered brown teal area also found in tidal stream mouths and associated wetlands in Karaka Bay, and Motairehe Bay and Swamp (Auckland Regional Council, 1995).
References:
Auckland Regional Council. 1995. Proposed Auckland Regional Plan: Coastal. Environmental Division, Auckland Regional Council.
Department of Conservation (DoC). 1994. Draft Application Rakitu Marine Reserve. Department of Conservation, Auckland.
Department of Conservation (DoC). 1995. Draft conservation management strategy for Taitokerau Northland - Volume 2. Northland Conservancy Management Planning Series No. 1, Department of Conservation, Wellington.
Department of Lands and Survey. 1983. Great Barrier Island County: Coastal reserves investigation. Department of Lands & Survey, Auckland.
Francis, M. P. & Grace, R. V. 1986. Marine algal survey of northeastern Great Barrier Island, New Zealand. Journal of the Royal Society of New Zealand. 16 (4):335-346.
Hauraki Gulf Maritime Parks Board. 1983 . The Story of Hauraki Gulf Maritime Park. Hauraki Gulf Maritime Parks Board.
Hayward, B. W., Grace, R. V. & Francis, M. P. 1986. Sediments and benthos of northeastern Great Barrier Island, New Zealand. Journal of the Royal Society of New Zealand. 16 (4):347-355.
Kenny, J. A. & Hayward, B.W. 1993. Inventory of important geological sites and landforms in the Northland region. Geological Society of New Zealand Miscellaneous Publication No. 67 (2 nd Edition).
Kingsford, M. J. 1989. Distribution patterns of planktivorous reef fish along the coast of northeastern New Zealand. Marine Ecology Progress Series. 54 :13-24.
Ritche, L., Mason, R., Saul, P., & Bradstock, M. 1979. Environmental impact report: Poor Knights Islands Marine Reserve. Ministry of Agriculture and Fisheries, Fisheries Management Division.
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