INTRODUCED MARINE ORGANISMS IN NEW ZEALAND AND THEIR ...

Tane 36: 197-223 (1997)

INTRODUCED M A R I N E ORGANISMS IN N E W Z E A L A N D AND THEIR IMPACT IN T H E WAITEMATA HARBOUR, A U C K L A N D Bruce W . Hayward Auckland Museum, Private Bag 92018, Auckland

SUMMARY Sixty-one exotic marine organisms are listed that appear to have arrived in New Zealand with human assistance in the last 150 years and have become established. Of these, four were deliberately introduced, 25 probably came in as fouling on vessels, 10 possibly in ships' ballast water, three probably as deck cargo and the remainder as either fouling or in ballast water. The majority have come in from Europe (11), east Asia (10), eastern North America (6), Australia (6) and western North America (5). At least 12 species are known to have been exported from New Zealand and become established in other countries. These numbers are conservative estimates of the real number of introductions. It is not possible to assess the risk posed by any exotic marine organism prior to its arrival and establishment in New Zealand. Two surveys of the fauna of the Waitemata Harbour made sixty years apart, provide an insight into some of the changes that have occurred as a result of the establishment of at least 39 introduced exotic species. Many live in relatively low numbers and seem to have had little significant impact on the original ecosystems. The largest diversity of introduced organisms (especially Bryozoa) are fouling species on hard substrates, but the greatest environmental changes can be attributed to four bivalves introduced in the last 30 years. The Pacific oyster, Crassostrea gigas, is having a major impact on intertidal hard shore communities. Thickets of the small Asian mussel, Musculista senhousia, accumulate mud which temporarily smothers extensive areas of low tidal and shallow subtidal flats in the upper harbour. The small, fragile bivalve Theora lubrica, lives in billions in shallow-water muddy substrates around the harbour edges and is one of the few organisms that thrives in highly disturbed and polluted environments under the wharves and marinas. The file shell, Limaria orientalis, is now one of the dominant molluscs in the muddy shell gravels of the main harbour channels (10-30m deep) and has become a significant component of the diet of bottom-foraging fish, such as snapper. Keywords: Introduced marine organisms; marine invaders; ballast water; fouling organisms; New Zealand; Waitemata Harbour; Orakei Basin.

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INTRODUCTION New Zealanders are aware of the numerous exotic terrestrial plants and animals that have been assisted immigrants to our country since the arrival of humans less than 1000 years ago. Some, such as sheep, cattle, pine trees and pasture grasses, are of great economic benefit to our country. Many others, such as possums, goats, rabbits, Old Man's beard and Kahili ginger, are an economic and environmental disaster. The enormous impact of these introduced pests and weeds on New Zealand's natural terrestrial and freshwater ecosystems is well documented. Many millions of dollars of public funding are spent each year trying to control or eradicate them. New Zealanders are far more aware of these exotic plants and animals on land and in our freshwater lakes and streams than they are about similar introductions in the marine realm. This is quite natural, as on land we can readily observe the arrival of strange organisms and monitor changes, but in the sea it is more difficult to notice new arrivals until they have become well established and have greatly multiplied in numbers. Thus it is particularly difficult to determine which of the widespread cosmopolitan marine species living around New Zealand today came here naturally and which were introduced with the assistance of human activities, such as shipping and have subsequently become well established. HOW FOREIGN MARINE ORGANISMS R E A C H N E W Z E A L A N D Natural transport methods 1. Currents In some years, the natural current patterns around northern New Zealand become favourable to carry juveniles and larval stages of a number of shallow warmer water fish, sea eggs, molluscs and other organisms from Norfolk or the Kermadec Islands to New Zealand (e.g. Powell 1976). These are carried southward along the east coast of northern New Zealand in the East Auckland Current, with new arrivals settling into suitable habitats they encounter. These are mostly around the offshore islands, such as the Poor Knights, Mokohinaus, Aldermen and White islands. Eddies in the current sometimes touch the mainland coast and warm water immigrants are known to have become established in places such as Cape Karikari, Cape Brett and Parengarenga (e.g. Powell 1976). Undoubtedly the vast majority of these warm water migrants do not survive the journey or do not encounter suitable habitats in which to settle. Of those that do find a suitable new homeland, a number, such as the swimming crab Scylla

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(Dell 1964), grow to maturity but find the conditions too cool to breed here and disappear after a few years. Only a few of these natural immigrants appear to find conditions suitable to establish viable breeding populations. The New Zealand fossil record documents thousands of natural immigration events of tropical and subtropical marine species reaching New Zealand and becoming established during warm periods since we split from Gondwana, 80-55 million years ago. It also documents the extinction of many of these warm water taxa during periods of cooler sea climate (Beu 1990). In the ten thousand years since the Last Ice Age, several thousand species may have been added to the modern New Zealand marine fauna by this method of introduction. Most are still restricted in their distribution to the northeast coast of the North Island. These range extensions and contractions occur continually in the marine environment. If climate warming eventuates we can expect many more species to naturally extend their ranges into northern New Zealand waters. Current transport will successfully introduce only those taxa that can survive the journey suspended in oceanic water for perhaps one to several weeks, ie. organisms that have long-lived, planktonic larval stages such as many sea eggs, crustaceans and some molluscs, or organisms that are free-swimming such as reef fish. serrata

2. Attached to logs or organisms Barnacles, tube worms, algae and some nestling molluscs and crustaceans may be attach to free-swimming organisms, such as turtles or whales, or more frequently to floating logs which occasionally cross the oceans. Their chance of survival and successful establishment in New Zealand would be similar to organisms carried in by currents. Fossils document many successful introductions in the distant past and undoubtedly there have been a number since the Last Ice Age that are now part of our native marine biota. Australia is the most likely source of most successful immigrant species introduced attached to logs because of the current and storm patterns, availability of logs and similar climatic factors. Most tropical fouling species would find it too cold to become established in New Zealand. Temperate northern hemisphere fouling organisms are less likely to survive passage through the tropics during their long journey to New Zealand. 3. On feet of migrating seabirds Migrating seabirds are another mode of trans-oceanic transport that has probably been responsible for the natural introduction of a number of terrestrial and tidal flat animals and plants to New Zealand. This is particularly true for many microscopic organisms that live in brackish intertidal mud flats. They could

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easily be transported in mud attached to the feathers or feet of one of the millions of wading birds that migrate to New Zealand along the east Asia flyway each season. This is the most plausible explanation for the observation that 19 of the 20 brackish species of foraminifera (Protozoa) living in New Zealand have a cosmopolitan temperate-subtropical distribution and also occur along north Atlantic coasts (Hayward & Hollis 1994). Human-assisted transport methods Despite the above-mentioned methods of natural transport and introduction of marine organisms to New Zealand, there are vast numbers of shallow water marine species living in other parts of the world that have not been able to cross the oceanic and climatic barriers. Recognition of introductions of marine species facilitated by some form of human assistance is often difficult. Strong suspicions are raised when coastal species that come from temperate and subtropical seas in the northern hemisphere are recorded suddenly appearing in New Zealand waters or are found living here in limited areas around one or more ports. There are several forms of deliberate and accidental human-assisted transport methods. 1. Deliberate introductions There have been numerous attempts to introduce foreign marine organisms to New Zealand waters especially prior to the 1920s. These have included Atlantic, sockeye and Quinnat salmon, European lobsters, Australian prawns, herrings, turbot and edible crabs. Most have failed, except for the salmon which are commercially farmed (Hine 1995). Three species of the intertidal cord grass, Spartina, were deliberately introduced from the U K and U S A and planted here between 1913 and 1960 (Partridge 1987). They were introduced as a biological aid to reclamation of sheltered tidal flats, which in those days were not valued as ecosystems and important nurseries for marine life as they are today (Chapman & Ronaldson 1958). Spartina is now recognised as an environmental weed and thousands of dollars are spent each year around the country trying to control and eradicate it. 2. Aquarium releases Although freshwater is the preferred medium for aquaria, saltwater is reasonably common especially for colourful, tropical coral reef community imitations. A number of overseas marine organisms are imported live into New Zealand specifically to supply this market. There is every possibility that one or more of these species may be released by accident or on purpose into the New

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Zealand marine environment. A green alga, Caulerpa taxifolia, alleged to have escaped from a Monaco aquarium, is now a rampant marine weed in the western Mediterranean (Nelson 1994). 3. Fouling on vessels Accidental introductions of fouling organisms on commercial ships, fishing and recreational boats and other mobile structures such as towed barges and drilling rigs are believed to be common. Fouling organisms on vessels have been moving across oceans for centuries and are still doing so. Most fouling organisms are tubeworms, barnacles, mussels, oysters, sea-squirts, hydroids, bryozoa, sponges, algae, wood-boring and nestling bivalves and sea slaters (e.g. Chilton 1910, Foster & Willan 1979, Skerman 1960a). Polynesian canoes bringing the first humans to this country, may have introduced fouling organisms but coming from the tropics it is unlikely that any survived to become established. Captain Cook's ship the Endeavour was the first of thousands from the northern hemisphere to have its hull cleaned of fouling organisms on a New Zealand shore. Since then billions of fouling organisms from overseas would have arrived in New Zealand waters and we can not be sure how many species have become established - probably in the hundreds. For every species that arrives and becomes established there must be thousands of introductions that do not survive. For example a survey of the Maui platform when it arrived in New Zealand from Asia in the 1970s showed the presence of 12 species of encrusting barnacle - including 6 not currently living in New Zealand. There were also two exotic algae, an exotic crab, a fish and a hydroid (Foster & Willan 1979). None of these are known to have become established here since then. With the development of metal-hulled ships and antifouling paints the number and diversity of fouling organisms now arriving in New Zealand may be somewhat less than it was in the days of wooden ships. Now however, there are far more vessels (commercial and recreational) coming to New Zealand (Dromgoole & Foster 1983) and the flow of marine organisms arriving by this method certainly has not stopped. Gordon and Matawari (1992) document the fouling bryozoa (moss animals) around New Zealand ports and conclude that a minimum of 18 species are exotic introductions brought in by shipping. They conclude that 42% of the main marine-fouling bryozoa of Europe are now also present in New Zealand ports and harbours. The historical records show a procession of these bryozoa arriving in New Zealand, starting last century and still continuing today. There appears to have been an increase in arrivals of fouling bryozoa in the last 40 years (Gordon

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& Matawari 1992), presumably coinciding with increased shipping and boating movements. 4. In ballast water Ballast water has been used in ships since late last century to lower their centre of gravity in the water when they have little or no cargo in their holds, and to make them safe for travelling (Hayden 1995). Sea water is usually taken into the ship's ballast water tanks as it unloads in the shallows of a foreign port. The ballast water may contain numerous shallow water pelagic organisms or larvae as well as benthic organisms that have been sucked in from the shallow water under the ship (Nelson 1994). Ballast water introductions are a concern, because they are a relatively recent method of human-assisted transport in which larval and non-fouling organisms may be involved. Ballast water provides a mechanism by which organisms previously unable to cross oceanic and climatic barriers may now be introduced to New Zealand. The speed of modern shipping greatly improves the chances of ballast water organisms surviving the trip across the oceans. Studies overseas of the content of ballast water and associated sediment in the bottom of ballast water tanks, have shown that a number of organisms are being transported and surviving trans- oceanic crossings in this medium (Hallegraeff & Bolch 1992, Kelly 1993). It is difficult to prove beyond doubt that any particular organism has definitely been introduced to New Zealand in ballast water. However, the weight of circumstantial evidence suggests that several that are unlikely to have been transported as fouling organisms, have been brought in this way. These organisms include some algae, molluscs, crustaceans and microscopic organisms. These days it is very popular to blame ballast for all new arrivals and marine diseases, but such accusations often do not stand up to scrutiny. For example, ballast water has been ruled out as the vector for introducing or translocating the dinoflagellates that caused the 1993 toxic blooms around New Zealand (Jones & Edwards 1995). Mackenzie (1995) found that the resting cysts of the toxic dinoflagellate Alexandrium ostenfeldii were well distributed all around New Zealand, and not just around the ports, well before the 1993 event. Unusual marine climate conditions are accepted as the main cause of these blooms (J asperse 1993). Although ballast water can be ruled out as causing the 1993 events in New Zealand, it has been shown that live toxic dinoflagellate cysts are present in some ship's ballast water entering Australia (Hallegraeff & Bolch 1992). Thus it is highly probable that toxic dinoflagellates have in the past been introduced to New Zealand in ballast water. Whether they have survived, or whether any of those

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involved in the 1993 event were originally ballast water introductions may never be know. One of the best documented candidates for ballast water introduction into New Zealand is the east Asian brown kelp, Undaria pinnatifida. It is believed to have arrived in Wellington Harbour in 1987 in ballast water as the more resilient, microscopic gametophyte stage (Hay & Luckens 1987, Nelson 1994). Since its arrival and establishment here, the more temperature sensitive macroscopic sporophyte stage has been spread as fouling on domestic ships' hulls to many other New Zealand ports (Hay 1990, Nelson 1995). 5. Transfer with aquaculture organisms The introduction of associated species and diseases when importing live organisms to establish aquaculture ventures is well-documented around the world, especially with oysters (Elston 1993, Hine 1995). The importation of adults poses greater risks than the translocation of gametes, larvae or juveniles (Hine 1995). INTRODUCED MARINE ORGANISMS ESTABLISHED IN NEW Z E A L A N D Sixty-one exotic marine immigrants that have successfully established themselves around New Zealand and are currently recognised as having arrived here with human-assistance, are listed in Appendix 1. They include a protist foraminifer, a sea anenome, 2 corals, three tube worms, 2 sea slugs, 2 sea snails, 4 bivalves, a crab, a barnacle, a sea slater, 18 bryozoa, a sea squirt, a fish, 20 seaweeds and 3 sea grasses. There are likely to be many more. Analysis of these organisms' mode of life and life histories suggests that 4 were deliberately introduced, 26 probably came in as fouling, 10 probably came in ballast water, three as deck cargo and the remainder either as fouling or in ballast. These are similar to figures derived several years ago for exotic marine immigrants to Australia (Pollard & Hutchings 1990). The largest number (11 species) of organisms introduced to New Zealand appear to have come from Europe, followed by eastern Asia (e.g. Japan, Korea, etc.), both coasts of North America and Australia (Table 1). Eighteen species have been spread around much of the world and it is impossible to be sure of the source of those that reached New Zealand. IMPACTS OF INTRODUCED MARINE ORGANISMS Human-aided introductions are relatively new phenomena which are bringing in vast numbers of organisms previously unable to get to New Zealand by natural

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Table 1. Zealand

Identified regions of origin for human-assisted exotic marine immigrants to New

Europe East Asia (NW Pacific) eastern Nth America Australia western Nth America Sth America Tropical Pacific not determined

11 10 6 6 5 3 2 18

spp spp spp spp spp spp spp spp

Total

55

spp

processes despite millions of years of opportunity. Around the world these human-assisted migrations are leading towards an homogenised world biota, in which there will be the same marine fauna and flora in similar climate zones. Potentially positive impacts Some introduced marine organisms are currently of economic benefit to New Zealand. For example, Quinnat salmon is the basis for marine ranching operations and the introduced Pacific oyster, Crassostrea gigas, much faster growing than the native New Zealand rock oyster, Saccostrea cucullata, is the basis of the New Zealand oyster farming industry. The small bivalve, Limaria orientalis, that arrived in New Zealand in the 1970s and now lives in billions on the floor of the Waitemata Harbour and inner Hauraki Gulf, could be regarded as beneficial as they are now a significant food source for bottom-foraging fish, such as snapper (Dromgoole & Foster 1983). Potentially negative impacts 1. Ecological Some introduced marine species may become rampant pests or weeds in their adopted home by displacing existing species from the niches they have occupied for millions of years, such as the Pacific oyster has done in New Zealand and worldwide (e.g. Dromgoole & Foster 1983). Introduced species that are voracious predators could have enormous impacts on existing biota, such as the Pacific seastar (Asterias amurensis) has had in Tasmania (Barker 1994). 2. Disease introduction Introduced species, whether new to New Zealand or not, have the potential to introduce new diseases to our marine biota. This is more likely with fouling organisms or aquaculture organisms than ballast water introductions, as they are 204

usually introduced as adults that may carry the diseases. It is less likely with ballast water introductions, many of which are of larval or juvenile stages that are less likely to be diseased (Hine 1995). 3. Environmental alterations Introduced marine species may alter the environment in which they establish, causing major changes to the existing ecosystem. For example, the introduced Asian mussel, Musculista senhousia, settles in large numbers on the sandy sea floor. Within a year they grow into a turf-like mat and their byssal threads accumulate mud (Creese & Hooker 1996) up to 20cm deep (Fig. 1). The mud kills off the original sand-dwelling organisms and provides a completely new environment for a different biota (e.g. Theora lubrica, pers. obs.). Fortunately, the Asian mussels usually die after two years and the mud thickets break down and are washed away (Creese & Hooker 1996), allowing the original sanddwelling organisms to return. 4. Human health risks The introduction of cholera or further toxic phytoplankton species that we currently do not have could pose a serious threat to consumers of fish and

Fig. 1. A thick layer of mud accumulates around the beds of Asian mussels {Musculista senhousia) and smothers the pre-existing sandy shore ecosystem. Heme Bay, Waitemata Harbour, 1996.

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shellfish in this country (Jones 1991). 5. Economic Introduced marine organisms may impact on the economics of marine aquaculture, or commercial fisheries, through the introduction of diseases, toxic phytoplankton or of voracious predators of the farmed species (Jones & Edwards 1995). New arrivals of fouling organisms could have major economic impacts. For example, the introduced tube worm, Ficopomatus enigmaticus (Fig. 2), first noticed in the Whangarei and Waitemata Harbours in 1967, grows profusely in estuaries on submerged artificial structures such as piles, pontoons and pleasure craft (Read & Gordon 1991). In 1980 massive growths of F. enigmaticus fouled cooling water intake pipes for the Otara power station in the Tamaki Estuary, Auckland (Fig. 3). Its regular and luxuriant growth in the pipes was a major contributing factor towards the station's switch to the use of freshwater (Read & Gordon 1991). 6. Tourism and recreation Exotic marine immigrants may also impact on the recreational and aesthetic values of the coast and sea. For example, the rocky shores and pebbly beaches

Fig. 2. The introduced tube worm, Ficopomatus enigmaticus, growing in profusion on the sides of rocks near the Otara power station, Tamaki Estuary, Auckland.

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Pacific oyster

Crassostrea gigas

widespread abundant

' 1

Theora lubrica

m

^

POLLEN• ISLAND

Asian mussel Musculista I | senhousia LTH

Barnacle Balanus amphitrite

OTARA

Pyromaia tuberculata

widespread few

Bryozoa Watersipora subtorquata

INTRODUCED ORGANISMS IN THE WAITEMATA HARBOUR Fig. 3. Examples of the variety of introduced marine organisms that are now established in Auckland's Waitemata Harbour and their 1990s distribution within the harbour.

of parts of the Waitemata and particularly the Manukau Harbour have been transformed by the prolific growth of the introduced Pacific oyster in the last two decades. The beaches used to be pleasant, sheltered recreational areas where locals could walk and swim in bare feet. Now they are rather unpleasant muddy 207

and shelly areas spiked with a multitude of dangerously sharp oyster shells (Fig. 4). It is virtually impossible to predict prior to their arrival and establishment here, what impact, if any, each introduced exotic marine organism might have. The majority may have little perceptible impact, but there will always be a few that relish the conditions in their new home, possibly even more than in their native country and may become a pest or weed along New Zealand's coast. INTRODUCED M A R I N E ORGANISMS IN T H E W A I T E M A T A H A R B O U R (Fig. 3) There is limited information on the present status and particularly the past condition of our coastal marine ecosystems. This makes it very difficult to determine what impact any introduced exotic marine organism may be having. Auckland's Waitemata Harbour provides an excellent opportunity to document new arrivals and their impact on the biota and environment. The Waitemata Harbour has been New Zealand's busiest international port for at least the last 100 years and has warmer water than most of our other major ports. It is thus the prime candidate to show the most impact from human-assisted immigrants. It is also fortunate that in the 1930s the Waitemata Harbour was the site of the first major study of seafloor communities in New Zealand (Powell 1937). This provides a useful baseline against which results of a repeat survey of the seafloor biota in the 1990s have been assessed (Hayward et al. in press). Since the 1930s, there have been a number of environmental changes that have potentially impacted on the sea floor biota (Dromgoole & Foster 1983). For example most of the sewerage discharges have stopped, subdivision has increased siltation in the upper harbour, and T B T (tributyl tin in antifouling paint) poisoning has devastated some of our common harbour neogastropods - such as the oyster borer, Lepsiella scobina, and the olive shells (Stewart et al. 1992). The most dramatic changes to the harbour's biota in the past 60 years however, can be attributed to human-assisted exotic marine immigrants. Of the 61 marine species that are believed to be human-assisted introductions to New Zealand (Appendix 1), 39 species (70%) are currently living in the Waitemata Harbour. Fourteen of these have not spread beyond the Waitemata and

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Fig. 4. Large, erect shells of the introduced Pacific oyster, Crassostrea gigas, stick up from the muddy floor of Orakei Basin, Waitemata Harbour, 1996.

inner Hauraki Gulf. Many of the 39 introduced organisms appear to play only minor roles in the ecology of the Waitemata Harbour but several bivalves have had a major impact. Some examples are: Foraminifera One unicellular foraminifer, Siphogenerina raphanus, which is common in other parts of the world, was probably introduced in ballast water. It is now common throughout the subtidal sediments of the Waitemata Harbour (Hayward et al. in press), but not common elsewhere in New Zealand. Sea anenome The anenome, Sagartia luciae, which occurs intertidally in muddy, slightly brackish parts of the harbour, is believed to have arrived as fouling on ships from its native home in the North-west Pacific and has not spread beyond the Waitemata (Dromgoole & Foster 1983). Bryozoa The bryozoa are our best studied and documented fouling organisms with at least 15 introduced exotic species occurring around the wharf areas (Fig. 5) in 209

Fig. 5. Auckland's commercial wharf area in the Waitemata Harbour is inhabited by a number of introduced fouling organisms.

the Waitemata Harbour (Gordon & Matawari 1992). The prominent dark bryozoan, Watersipora arcuata, appears to have been introduced in 1957 (Skerman 1960b). It had an initial period of luxuriant growth around low tidal rocky areas in the 1970s, but appears to be nowhere near as common today (J.E. Morton, pers. comm.). Sea slater The cosmopolitan, wood-inhabiting, intertidal isopod, Limnoria tripunctata, is known only in New Zealand around the Waitemata Harbour. It was probably introduced in wooden cargo many years ago (Cookson 1991, A . B . Stephenson pers. comm.). Barnacle The widely-distributed barnacle, Balanus amphitrite, well-known for fouling ships' hulls (Foster 1978), is presumed to have been introduced to New Zealand last century on a hull. Its introduction is supported by its lack of a fossil record in New Zealand (Buckeridge 1983). Balanus amphitrite is found here only in several intertidal locations around the Waitemata Harbour (Foster 1978).

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Crab Shallow subtidal sediments in the Waitemata and inner Hauraki Gulf are the home to low numbers of a small Californian masking crab, Pyromaia tuberculata, which first appeared here in 1978. It possibly came in ballast water from Japan, where it had previously been introduced (Webber & Wear 1981). Sea-squirt The elongate sea-squirt, Ciona intestinalis, lives around the Auckland wharves and other rocky low tidal Waitemata Harbour shores. It appears to have arrived here in the 1950s (Morton & Miller 1968, Dromgoole and Foster 1983). Algae A common sight around the sheltered shallows of the Waitemata harbour is the Japanese green alga, Codium fragile ssp. tomentosoides. It was first discovered on the eastern wall of the container terminal in 1973 (Dromgoole 1975). Today it lives attached to cockle shells and pebbles on the muddy and sandy harbour floor and is often washed up on harbour beaches as drift (pers. obs.). It has been introduced to many northern hemisphere areas and has caused major devastation to the oyster fishery in Chesapeake Bay (Nelson 1994). Fortunately it has not become such a worrisome weed in New Zealand. A n attractive perforated brown alga, Hydroclathrus clathratus, occurs infrequently on rocks around sheltered low tidal parts of the harbour (Dromgoole & Foster 1983). It was first recorded from northern New Zealand in the 1970s and was possibly introduced from warmer regions by shipping. Sea grasses Two small patches of deliberately introduced cord grass are known along the shore of the Waitemata Harbour - one on the end of Te Atatu Peninsula (Spartina x townsendii) and the other beside the boat launching ramp at Orakei Basin {Spartina alterniflora, Fig. 6). Because they have not spread their impact in the Waitemata is very minimal compared with some other New Zealand harbours. Gastropods The colourful nudibranch, Thecacera pennigera, was first noticed in New Zealand in the early 1970s. In New Zealand it has been recorded only on fouling bryozoan and sponges in the Waitemata Harbour (Willan 1976). The introduced lilac and reddish-brown spotted nudibranch, Okenia plana, also occurs in the Waitemata Harbour where it feeds on bryozoa on wharf piles (Morton & Miller 1968, Willan & Morton 1984). A small ellobiid snail, Microtralia occidentalis, lives among the high tidal

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Fig. 6. A patch of the introduced cord grass, Spartina x townsendi, grows near the boat ramp, Orakei Basin, Waitemata Harbour, 1996.

rocks of Rangitoto Island. Formerly thought to be an endemic species restricted to the island (called Rangitotoa insularis), it is now believed to have been introduced from the West Indies, probably as eggs attached to wooden deck cargo on ships last century (Climo 1982). Bivalves Numerically and ecologically the largest changes in the seafloor biota of the Waitemata Harbour that have occurred between Powell's 1930s surveys and our repeat surveys in the 1990s, are those brought about by four exotic immigrant bivalves (Hayward et al. in press). Profuse growths of the introduced Pacific oysters, (Dinamani 1971, Dromgoole & Foster 1983), are taking over many of the intertidal rocky shores around New Zealand's northern harbours, including the Waitemata. Additionally it is beginning to form intertidal banks of live Pacific oysters by colonising cockle shell accumulations in the upper part of the Waitemata Harbour off Te Atatu and in Pollen Island Marine Reserve. Dead oyster shells are beginning to accumulate in intertidal drifts and their sharp shells are converting high tide beaches into unpleasant substrates. Wherever the oysters Crassostrea

Crassostrea

gigas:

gigas

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grow in profusion around the more sheltered shores of the Waitemata Harbour they are accumulating mud around them and are thus contributing to further environmental changes. Musculista senhousia: The introduced small Asian mussel, Musculista senhousia (Willan 1985) lives in patches (5m - lOha) which accumulate thick mud drifts over the shallow subtidal and low tidal seafloor in many parts of the Waitemata Harbour. These thickets continually die off, with new patches being established each year (Creese & Hooker 1996). Subtidal and intertidal surveys of the Waitemata Harbour in the 1990s (Hayward et al. in press) show that the largest area of infestation is between mean low water and 2m depth in the extensive low tide and shallow subtidal flats above the harbour bridge (Fig. 3), which is where the mussel was first discovered about 1978 (J.E. Morton pers. comm.). Within a decade it had spread north to Parengarenga and south to East Cape but does not appear to have extended its range since then (Willan 1985, 1987, Morley 1988). 2

Limaria orientalis: Another bivalve immigrant that is now a prominent member of the Waitemata Harbour seafloor communities is Limaria orientalis. It was first noticed around the Waitemata Harbour and Hauraki Gulf in 1972, when it appeared in large numbers in coarse sediment around low tide mark (Grange 1974, Dromgoole & Foster 1983). After a few years it disappeared almost entirely from intertidal areas but is now one of the three dominant molluscs living in the muddy shell gravels of the Rangitoto and Waitemata Harbour channels (Fig. 7). It lives in densities of between 5 and 100 per square metre (Hayward et al. in press). Theora lubrica: A small, thin-shelled, infaunal bivalve, Theora lubrica, has in recent decades become the dominant mollusc living in mud and muddy sand in the extensive low tidal and shallow subtidal flats throughout most of the Waitemata Harbour (Fig. 8). Theora lubrica arrived in the northern harbours about 1972, probably in ballast water from its home in Japan (Climo 1976, Dromgoole & Foster 1983). It has since spread to most other ports in the country and has recently been reported for the first time in harbours on the west coast (Morley 1995, Morley et al. this issue). It is a short-lived species that can rapidly colonise disturbed and muddy habitats and is perhaps the most pollution-tolerant mollusc in the harbour, living in the contaminated sediments of the Westhaven marina, beneath the Auckland wharves and in the Tamaki Estuary ( M . Morley pers. comm.).

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recreational amenities. The railway embankment and a set of control gates created a permanent salt water lagoon that currently is flushed on average once a month during spring tides. Since it was enclosed run-off from the surrounding suburbs and accumulation of rotting algae have deposited a 10 to 30cm deep layer of mud over the floor of most of the basin. One of the two most abundant algae in the Basin that seasonally cover the extensive shallow muddy floor is an unidentified, exotic, red, filamentous alga, known from nowhere else in New Zealand and thought to have been recently introduced from South-east Asia (Nelson 1994). Growing in thick patches among and beneath these algae are millions of the introduced Asian mussels. The mussels are present throughout the mud on the floor of the basin in densities ranging between 5 and 2000 per m . A 2 to 20m wide band around the margin of the basin is studded with the sharp, erect shells of Pacific oysters which stick up from the soft muddy substrate (Fig. 4). Many of these oysters have grown to unusually large sizes with 20-cm-long shells not uncommon. Basalt rocks around the edge of the Basin support the introduced seaanenome, Sagartia luciae, and the highest densities of the introduced barnacle, Balanus amphitrite, to be found in the harbour. 2

NEW Z E A L A N D MARINE ORGANISMS INTRODUCED T O OTHER COUNTRIES There are documented cases of at least 12 New Zealand marine organisms having been assisted to emigrate by humans and successfully established in overseas countries. One is our small marine acorn barnacle, Elminius modestus, which was introduced to South Africa and Europe on ships in the 1940s and is now widespread there (Buckeridge 1982). The export of live Bluff oysters to Tasmania a few decades ago, resulted in the largest number of recorded introductions to any foreign land. Accidentally introduced to Tasmanian waters when the shells were discarded were one chiton, two snails, three bivalves, two crabs, a lamp shell and a star fish (Appendix I, Hine 1995) - some of which are now major members of the Tasmanian marine fauna (e.g. Maoricolpus roseus). DISCUSSION There is now documented evidence of the establishment of 61 exotic marine species in New Zealand that have probably arrived with human assistance in the last 150 years. We know of at least 12 that have been exported to other

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countries. These numbers are conservative minimums. This paper provides a glimpse of the changes brought about by these marine invaders to the ecosystems in the Waitemata Harbour. It may be the most impacted area of New Zealand coast, but similar changes are likely to be occurring throughout the country. It is not possible to accurately assess the risk posed by any introduced exotic organism prior to its arrival and establishment in New Zealand. The only way to remove the risk is to eventually eliminate any possibility of human-assisted introductions of exotic marine organisms arriving in New Zealand, whether deliberate, in ballast water or as fouling. ACKNOWLEDGMENTS This paper was prepared as a talk for a public forum on Marine Invaders organised by the Auckland Conservation Board in 1996. The talk and paper draw heavily on material gathered together by speakers for a National Symposium on Ballast Water held in Wellington in 1995 and organised and published by the Royal Society of New Zealand. I am grateful to Margaret Morley, Jenny Riley, Brett Stephenson and Hugh Grenfell for their advice and assistance with the Waitemata Harbour data summarised here from our 1990s resurvey of the harbour's biota. Jenny Riley is thanked for her drafting of Figures 3, 7, 8. The manuscript has benefitted from the critical reading and suggestions of Margaret Morley, Brett Stephenson and Barbara Hayden. REFERENCES Adams, N . M . 1983: Checklist of marine algae possibly naturalised in New Zealand. New Zealand Journal of Botany 21: 1-2. Adams, N . M . 1991: The New Zealand species of Polysiphonia. New Zealand Journal of Botany 29: 411-427. Barker, M . 1994: Unwelcome visitors! Japanese starfish invades Tasmania. Could it happen in New Zealand. Seafood NZ, May 1994: 6-9. Beu, A . G . 1990: Molluscan generic diversity of New Zealand Neogene stages: extinction and biostratigraphic events. Paleogeography, Paleoclimatology, Paleoecology 77: 279-288. Buckeridge, J.S. 1982: The barnacle subfamily Elminiinae - two new subgenera and a new Miocene species from Victoria. Journal of the Royal Society of New Zealand 12(4): 353-357. Buckeridge, J.S. 1983: Fossil barnacles (Cirripedia: Thoracica) of New Zealand and Australia. New Zealand Geological Survey Paleontological Bulletin 50. 151pp. Cairns, S.D. 1995: The marine fauna of New Zealand: Scleractinia (Cnidaria: Anthozoa). New Zealand Oceanographic Institute Memoir 103. 210pp. Chapman, V.J. & Ronaldson, J.W. 1958: Mangroves and salt marsh flats of the Auckland Isthmus. New Zealand DSIR Bulletin 125. 79pp. Chilton, C. 1910: Note on the dispersal of marine Crustacea by means of ships. Transactions of the New Zealand Institute 43: 131-133. Climo, F . M . 1976: The occurrence oi Theora (Endopleura) lubrica Gould, 1861 (Mollusca: Bivalvia: Semelidae) in New Zealand. Auckland Museum Conchology Section Bulletin 1: 11-16. Climo, F . M . 1982: The systematic status of Auricula (Alexia) meridionalis Brazier, 1877 and Rangitotoa insularis Powell, 1933 (Molluscs: Pulmonata: Ellobiidae) in Australasia. National Museum of New Zealand Records 2(6): 43-48. Cookson, L . J . 1991: Australasian species of Limnoriidae (Crustacea: Isopoda). Memoirs of the

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Jones, M . M . 1991: Marine organisms transported in ballast water: a review of the Australian scientific position. Bureau of Rural Resources Bulletin 11, Canberra. 48pp. Kelly, J.M. 1993: Ballast water and sediments as mechanisms for unwanted species introductions into Washington State. Journal of Shellfish Research 12(2): 405-410. Mackenzie, L . 1995: Importance of taxonomic data of marine flora and fauna. In Ballast Water a marine cocktail on the move. Royal Society of New Zealand Miscellaneous Series 30: 91-94. Morley, M . 1988: Report on the continuing study of Musculista senhousia (Benson, 1842). Poirieria 5(15): 4-8. Morley, M . S. 1995: Extension of Range in New Zealand for Theora (Endopleura) lubrica Gould, 1861: Selemidae. Poirieria 4: 21. Morley, M . , Hayward, B.W., Stephenson, A.B., Smith, N. & Riley, J. 1997: Molluscs, crustaceans and echinoderms from Kawhia, west coast, North Island. Tane 36: 157-180. Morton, J. & Miller, M . C . 1968: "The New Zealand Sea Shore". Collins. 638pp. Nelson, W.A. 1994: Marine invaders of New Zealand coasts. Journal of the Auckland Botanical Society 49: 4-14. Nelson, W.A. 1995: Nature and magnitude of the ballast water problem in New Zealand. In: Ballast Water a marine cocktail on the move. Royal Society of New Zealand Miscellaneous Series 30:1319. Nelson, W.A. & Duffy, C.A.J. 1991: Chnoospora minima (Phaeophyta) in Port Underwood, Marlborough - a curious new algal record for New Zealand. New Zealand Journal of Botany 29: 341-344. Nelson, W.A. & Knight, G.A. 1995: Asperococcus bullosus - a new record for northern New Zealand of an adventive marine brown alga. Tane 35: 121-125. Nelson, W.A. & Maggs, C . A . 1996: Records of adventive marine algae in New Zealand: Antithamnionella ternifolia, Polysiphonia senticulosa (Ceramiales, Rhodophyta), and Striaria attenuata (Dictyosiphonales, Phaeophyta). New Zealand Journal of Marine & Freshwater Research 30: 449-453. Parsons, M . 1982: The genus Colpomenia (Phaeophyta) in New Zealand. New Zealand Journal of Botany 20: 289-301. Partridge, T.R. 1987: Spartina in New Zealand. New Zealand Journal of Botany 25: 567-575. Pollard, D.A. & Hutchings, P.A. 1990: A review of exotic marine organisms introduced to the Australian region. II. Invertebrates and algae. Asian Fisheries Science 3: 223-250. Powell, A.W.B. 1937: Animal communities of the sea-bottom in Auckland and Manukau Harbours. Transactions of the Royal Society of New Zealand 66: 354-401. Powell, A.W.B. 1976: On the considerable influx of warm water mollusca that have invaded northern New Zealand waters within recent years. Records of the Auckland Institute and Museum 13:141166. Read, G.B. & Gordon, D.P. 1991: Adventive occurrence of the fouling serpulid Ficopomatus enigmaticus (Polychaeta) in New Zealand. New Zealand Journal of Marine and Freshwater Research 25: 269-273. Skerman, T . M . 1960a: Ship-fouling in new Zealand waters: a survey of marine fouling organisms from vessels of the coastal and overseas trades. New Zealand Journal of Science 3: 620-648. Skerman, T . M . 1960b: The recent establishment of the polyzoan Watersipora cucullata (Busk) in Auckland Harbour, New Zealand. New Zealand Journal of Science 3: 615-619. Stewart, C , de Mora, S.J., Jones, M . R . L . & Miller, M . C . 1992: Imposex in New Zealand neogastropods. Marine Pollution Bulletin 24: 204-209. Walne, P.R. 1974: "Culture of bivalve Molluscs, 50 years' experience at Conwy". Fishing News Books Ltd, Farnham, Surrey. 189pp. Webber, W.R. & Wear, R.G. 1968: Life history studies on New Zealand Brachyura, 5. Larvae of

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the family Majidae. New Zealand Journal of Marine and Freshwater Research 15: 331-383. Willan, R . C . 1976: The opisthobranch Thecacera pennigera (Montagu) in New Zealand with a discussion of the genus. Veliger 18: 347-352. Willan, R.C. 1985: Successful establishment of the Asian mussel Musculista senhousia (Benson in Cantor, 1842) in New Zealand. Records of Auckland Institute and Museum 22: 85-96. Willan, R . C . 1987: The mussel Musculista senhousia in Australasia; another aggressive alien highlights the need for quarantine at ports. The Bulletin of Marine Science 41(2): 475-489. Willan, R . C . & Morton, J.E. 1984: Marine Molluscs, Part 2. Opisthobranchia. University of Auckland, Leigh Marine Laboratory. 106pp.

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APPENDIX I. Preliminary list of exotic marine species that appear to have been introduced into New Zealand with human assistance and have become established here. Also listed are New Zealand species that appear to have been exported to other countries by the same means.

Date of intro.

How introduced

Present NZ distribution'

Native to 2

introduced also to 2

Wait Hbr

References

INTRODUCED MARINE TAXA Kingdom Protista: Phylum Sarcodina: Foraminifera

Siphogenerina raphanus

pre 1960 ?ballast

Hayward et al in press

Wait

Kingdom Animalia: Phylum Coelenterata: Order Actinaria (sea-anenomes) 1977 ?fouling Wait

Sagartia luciae

NW Pac

NAm,SAm,Eur

Dromgoole & Foster 1983

Order Scleractinia (corals)

(J O

?ballast/fouling ?ballast/fouling

Tethocyathus cylindraceus Hoplangia durotrix

Cairns 1995 Cairns 1995

W Atl NE Atl

Phylum Annelida (worms)

Ficopomatus enigmaticus Hydroides norvegicus Polydora cornuta

1967 fouling pre 1950 fouling 1967 fouling

Wait,Whang,HkBay NI.SI

?N Pac Aust

Wait, Whang

Eur,Aust World-wide

Read & Gordon 1991 Dromgoole & Foster 1983 Read & Gordon 1991

Phylum Mollusca: Class Gastropoda (snails and slugs)

Microtralia occidentalis Okenia plana

19th C

?cargo ?ballast

Wait neNI

WIndies Jap

Pac Is Aust

Phytia myosotis Thecacera pennigera

19th C 1973

?cargo ?fouling

Otag Wait

e Atl ?SAm

Aust,NAm Aust,Eur,Jap

1964 1972 1978 1972

?deliberate ?ballast ?ballast ?ballast

NI,SI neNI neNI NI,SI

N Pac Jap E Asia E Asia

World-wide

Climo 1982 Willan & Morton 1984, Hine 1995 Climo 1982 Willan 1976, Dromgoole & Foster 1983

Class Bivalvia (bivalves)

Crassostrea gigas Limaria orientalis Musculista senhousia Theora lubrica

WAust,wNAm wNAm

Dinamani 1971 Dromgoole & Foster 1983 Willan 1985 Dromgoole & Foster 1983

Phylum Crustacea: Subclass Decapoda (crabs)

Pyromaia tuberculata Subclass Cirripedia (barnacles) Balanus amphitrite Order Isopoda (sea slaters) Limnoria tripunctata

1978

?ballast

Wait.HGulf

fouling

Wait

cargo

Wait

Wait,Nels Wait

Phylum Bryozoa ?fouling Anguinella palmata 1950s Aeverrillia armata pre 1960s ?fouling (=Buskia, Morton & Miller 1978) pre 1960s ?fouling Amathia distans Bowerbankia gracilis pre 1960s ?fouling Bowerbankia imbricata prel967 ?fouling ?fouling Bugula flabellata 1949 1949 Bugula neritina ?fouling Bugula simplex 1988 ?fouling Bugula stolonifera 1962 ?fouling Buskia socialis 1977 ?fouling 1963 ?fouling Conopeum seurati 1890s ?fouling Cryptosula pallasiana 1977 plastic drift Electra tenella Schizoporella errata pre 1960s ?fouling Tricellaria occidentalis ?fouling 1950s ?fouling 1957 Watersipora arcuata Watersipora subtorquata 1982 ?fouling Zoobotryon verticillatum pre 1960s ?fouling Phylum Chordata: Order Ascidiacea (sea squirts) ?fouling Ciona intestinalis 1950s Teleostei (fish) deliberate Oncorhynchus tshawytscha 1870s

Wait Wait,Oneh,Nap,Nels Wait,Nels NI.SI ports NI.SI ports Lytl NI.SI ports HGulf Nl.nSI NI.SI HGulf Wait,Opua Nl.nSI ports NI,Nels ports NI.SI ports Wait,Oneh

Calif

wNAm

y

Dromgoole & Foster 1983

World-wide

y

Foster 1978

World-wide

World-wide

y

Cookson 1991

World-wide eNAm,eSAm

NSW

y y

Gordon & Matawari 1992 Gordon & Matawari 1992

World-wide World-wide World-wide World-wide World-wide SAust World-wide SAm eNAm World-wide Jap World-wide Aust,Eur Aust Aust

y y y y y y y y y y y y y y y

Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Gordon & Matawari Skerman 1960b Gordon & Matawari Gordon & Matawari

y

Dromgoole & Foster 1983

Eur,eNAm Eur Eur eNAm,eSAm N Pac wUSA wNAm,wSAm tropics

Wait,Lytl SI

wUSA

1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1983 1992

Hine 1995

Kingdom Plantae: Algae: Chlorophyceae (green seaweeds)

Codium fragile tomentosoides

1973

?fouling/ballast

Wait,HGulf

Jap

eNAm,Eur

y

Dromgoole & Foster 1983

Phaeophyceae (brown seaweeds) Asperococcus bullosus

1950s

?fouling/ballast

StI,Marlb,Rangaunu

Eur

SAust

Jap,wNAm

Chnoospora minima Colpomenia durvilleae (=C. bullosa) Cutleria multifida Hydroclathrus clathratus Punctaria latifolia Sargassum verruculosum Striaria attenuata Undaria pinnatifida

:4830s 1980

'.'fouling ^ballast

Port Underwood NI

tropics SAm

c.1870 1970s 1940s 1840s 1950s 1987

'.'fouling/ballast ?ballast ''ballast fouling ?fouling/ballast ballast

Wait,Wgtn,SI neNI Wgtn,SI,StI SI,StI Wgtn-StI sNZ ports

World-wide World-wide Eur Aust Eur eAsia

World-wide trop/subtrop SAust

Rhodophyceae (red seaweeds) Antithamnionella ternifolia Champia affinis Chondria harveyana Griffithsia crassiuscula Polysiphonia brodiae Polysiphonia constricta Polysiphonia sertularioides Polysiphonia subtilissima Polysiphonia senticulosa

1900s 19th C 19th C 1950s 1930s 1970 1930s 1970s 1980s

Fouling/ballast fouling/ballast ?fouling ?fouling/ballast ?fouling^allast ?fouling/ballast ?fouling/ballast ?fouling/ballast ?fouling/ballast

Wgtn .Tim aru Otag.SI Porirua Marlb.Otag.StI Wgtn.SI Otago Hbr neNI.SI neNI,Wgtn,Marlb Wgtn,Marl b

SAm SAust Tasm SAust Eur SAust Eur SAm NAm

Aust

Solieriaceae indet.

1980s

?fouling/ballast

Wait

1953 1924 1913

deliberate deliberate deliberate

neNI NLSI Auck,BoP,Sthd

9

Adams 1983, Nelson & Knight 1995 Nelson & Duffy 1991 Parsons 1982, Nelson 1994 y y

Aust,SAm,Jap Tasm,Eur

NAmJap.Aust

Aust,NPac y

Adams 1983 Johnson & Dromgoole 1977 Adams 1983 Adams 1983 Nelson 1994 Hay&Luckes 1987, Nelson 1995 Nelson & Maggs 1996 Adams 1983 Adams 1983, Nelson 1994 Adams 1983 Adams 1991 Adams 1991 Adams 1991 Adams 1991 Nelson 1994, Nelson & Maggs 1996 Nelson 1994

Angiospermae

Spartina alterniflora Spartina anglica Spartina x townsendii

eUSA UK UK

y y

Partridge 1987 Partridge 1987 Partridge 1987

EXPORTED MARINE TAXA Phyllum Mollusca: Class Polyplacophora (chitons)

Chiton glaucus

oyster exports

NZ

Tasm

Hine 1995

Class Gastropoda (snails)

Maoricolpus roseus Zeacumantus subcarinatus

oyster exports

NZ

Tasm NSW

Hine 1995 Powell 1975

oyster oyster oyster oyster

exports exports exports exports

NZ NZ NZ NZ

Tasm Tasm Tasm Wales

Hine 1995 Hine 1995 Hine 1995 Walne 1974

oyster exports oyster exports

NZ NZ

Tasm Tasm

Hine 1995 Hine 1995

Elminius modestus

fouling

NZ

Eur,SAfr

Foster 1978, Buckeridge 1982

Phylum Brachiopoda (lamp shells) Calloria inconspicua

oyster exports

NZ

Tasm

Hine 1995

NZ

Tasm

Hine 1995

Class Bivalvia (bivalves)

Neilo australis Perna canaliculus Ruditapes largillierti Tiostrea chilensis

1960s

Phylum Crustacea: Order Decapoda (crabs)

Cancer novaezealandiae Halicarcinus innominatus Order Cirripedia (barnacles)

Phylum Echinodermata: Class Asteroidea (starfish)

Patiriella regularis

oyster exports

Akar = Akaroa Harbour; BoP = Bay of Plenty; Fiord = Fiordland; HGulf = Hauraki Gulf; HkBay = Hawkes Bay; Lytl = Lyttleton Harbour; Marlb = Marlborough; Nap = Port Napier; Nels = Nelson; NI = North Island; Oneh = Onehunga; Otag = Otago Harbour; SI = South Island; Sthd = Southland; StI = Stewart Island; Wait = Waitemata Harbour; Wgtn = Wellington Harbour; Whang = Whangaroa Harbour. Aust = Australia; Calif = California; Eur = Europe; Jap = Japan; NAm = North America; NSW = New South Wales; Pac = Pacific; SAfr = South Africa; SAm = South America; Tasm = Tasmania Living in the Waitemata Harbour or not. 1

2

3