guilds of species have been recognised (Russell 1971a). Hence, there are 12 guilds altogether, comprising bottom grubbers, bottom cleaners, bottom

Transcription

1 guilds of species have been recognised (Russell 1971a). Hence, there are 12 guilds altogether, comprising bottom grubbers, bottom cleaners, bottom fossickers, invertebrate grazers, plant grazers, plant browsers, bottom stalkers, invertebrate browsers, general predators/scavengers, parasite cleaners, plankton pickers and midwater hunters. Virtually every phylum of animals and the four major groups of macroscopic algae are utilised as food items. Using a relatively simple index of utilisation, based upon the intensity of consumption of food items and the dispersion of that food among the predators, Russell (1971a) determined that the 10 highest values were scored, in decreasing order, by amphipods, brachyurans, fishes, gastropods, copepods, errant polychaetes, anomurans, bivalves, rhodophytes and ecninoids. Additional information on food and feeding is provided by Ayling (1968b), Cassie (1956a), Coleman (1972), Doak (1972), Godfriaux (1969, 1970a,b) and Russell (1971b, 1975). D. Behaviour Apart from a partial study of the behaviour of blennies (Anderson 1973), the cleaning behaviour of wrasses (Ayling & Grace 1971), and the feeding behaviour of leatherjackets (Ayling 1976a), most information is scattered in ecological works. Ayling (1968) and Russell (1971a), for example, provide a considerable amount of data on the way fish behave when seeking out and ingesting food, meanwhile commenting on whether they are schooling (see earlier) or solitary, and whether or not territoriality is exhibited. Some fish have definite homes (hiwihiwi, blue cod, red cod) while others have limited ranges (banded sea perch, red moki, black angelfish, scarlet parrotfish and possibly the banded parrotfish and twister). Even school-forming koheru, when juvenile, appear to have a limited home range. A school of occurred over an artificial reef off Goat Island for several months. Territoriality is marked in three species of Tripterygion (T. bucknilli, T. varium, T. capito), especially during the breeding season. Hiwihiwi and red mullet appear to form family groupings while the crested blenny has a definite social hierarchy. Several species are nocturnal in their habits (grandfather hapuka, yellow moray eel, conger eel, red cod, bastard red cod, roughie and big-eye) while a few (drummer, parore) are largely crepuscular. The giant boarfish, Sandager's parrotfish and Pseudolabrus miles are sexually dimorphic and the butterfish exhibits cryptic behaviour and colouration. P. miles and Sandager's parrotfish are facultative cleaners (Ayling & Grace 1971). Dellichthys morelandi lives in a commensal relationship with Evechinus. INVERTEBRATE BIOLOGY The invertebrate life of the Marine Reserve appears visually fairly diverse, although, at the time of this writing, only 942 species have been definitely recorded within the Reserve boundaries. Much of the research carried out at the Leigh Laboratory has been on aspects on invertebrate biology, with some emphasis on the Mollusca, partially reflecting the numerical preponderance of the molluscs (299 species) and no doubt also of the malacologists. Much 34

2 information is found in general works on community biology. The literature is mentioned below under each major invertebrate group. Where an authority is not quoted for a record it is to be assumed that the source is the Faunal Index of the Leigh Laboratory. A. Protozoa. The protozoa are underrepresented in faunal lists (51 species total). About 40 foraminiferans (Eade 1967; Thompson 1975) and some conspicuous ciliates (folliculinids and Zoothamnion) are reported. Most of the foraminifera were recorded from a sample of terrigenous sand, taken at 24m off Goat Island. The total population was estimated at 10 individuals per gram of sediment, one fifth of which were "living" (i.e. responding to staining techniques, the results of which tend to be equivocal). Of the 38 species from the one sample, 18% were porcellanous, 52% were hyaline-calcareous and 29% arenaceous. The ratio of planktonic to benthonic forms was 0.09 (Thompson 1975). These 38 species probably represent about half of the forams that may be expected in the sediments of the Reserve (pers. comm. Dr M.R. Gregory, Geology Department, University of Auckland, 1976). Future records may include species of particular interest to specialists. For example, a common foraminiferan at Goat Island Bay, which settles readily on objects in aquaria, is Dendronina arborescens. This species, originally described as a new genus and species from m off North Cape and Three Kings in 1922, was not again recorded until its rediscovery at Goat Island Bay in 1967 (Mr J.V. Eade, N.Z.O.I., in litt., 1968). Apart from foraminifera, free-swimming protozoans are numerically abundant, interstitially in sediments and in the seawater system of the Leigh Laboratory, but none of these has been identified. B. Porifera. The sponges have been fairly well characterised taxonomically (81 species) (Hogg 1967, Bergquist 1961, 1968, 1970) and Goat Island Bay is the type locality of one species (Timea aurantiaca). Hogg gave ecological data for 33 species with notes on the breeding seasons of 9 species. Sponges are significant components of subtidal communities (Ayling 1968, 1974d). On the northeast point of Goat Island Ayling (1968) has estimated the standing crop of sponges at varying depths on different slopes (table 6). Studies on the aggregation of dissociated sponge cells were carried out by Reid (1969). It was found that monospecific aggregates differentiated rapidly into a form resembling an adult sponge, whereas even forced bispecific aggregates (viz. Halichondria spp.) did not. C. Mesozoa. Mesozoans have not been recorded from the Reserve, but Octopus and Robsonella, which occur locally, are known hosts of five species of dicyemid mesozoans at Kaikoura (Short 1969; Short & Hochberg 1971), and it is possible that, if they were examined, they may be found to contain these parasites. D. Cnidaria. Cnidarians are abundant numerically, especially during seasonal peaks of hydroids and jellyfish, but are not diverse taxonomically. Hydroids have not been well characterised and only 24 species of Hydrozoa are known within the Reserve. Ayling (1968b) has noted the zonation with depth of 8 species of hydroid off the northeast point of Goat Island. 35

3 Jellyfish (Aurelia aurita, Phyllorhiza punctata, Cyanea capillata) occur seasonally, and Aurelia washes ashore at times in great numbers. The Anthozoa (17 species) are represented by the orders Alcyonaria, Stolonifera, Actiniaria, Corallimorpharia and Madreporaria. Two species of coral are found commonly (Flabellum rubrum, Culicia rubeola) and Russell (197la:64) records discovering Paracyathus conceptus on his artificial reef off the north-east point of Goat Island. Squires (1963) formally recorded F. rubrum from Cape Rodney. The anemone Actinothoe albocincta is common subtidally, attaining 36.5 g/m dry weight (representing 12.41% of the biomass)at 13m depth on flat rocky 2 areas of Goat Island, where it may occur in numbers >1000/m (Ayling 1968b, 1974b). Light intensity and water movement affect the distribution 2 of Actinothoe, which occurs on vertical surfaces at 6m and on flat surfaces at 13-16m (ibid). Depth m Slope % community dry weight grams/m J L Table 6: Percentage contribution of sponges to the standing crop of the biota of the north-east point of Goat Island. (From data of Ayling 1968.) Depth m Carnivores Deposit feeders Filter feeders Table 7: Standing crop, in grams per m 2, of polychaete worms on the north-east point of Goat Island. Each figure is the total for that depth over all slopes. (From data of Ayling 1968.) 36

4 E. Ctenophora. Pleurobrachia pileus and a species of Bolinopsis occur in the plankton while a creeping species, Coeloplana willeyi, is a benthic form. First recorded from Pakiri (Gordon 1969), this species has since been discovered on Pecten shells 19m off Goat Island. These are the only known New Zealand localities of this wide-spread Indo-Pacific species. An unidentified cestid ('Welamen sp.) occurs in outer Gulf waters which might possibly be found in the Reserve. F. Platyhelminthes. Parasitic flatworms (trematodes and cestodes) occur in fishes, birds, cetaceans and some invertebrates in Reserve waters, but none has been formally recorded. Of the larger poly clad Turbellaria, 12 species have been found (by Prof. J.J. Holleman, Merritt College, California) but not all have been described. The biology of none of the local species is known. Many small acoels and rhabdocoels occur in algal or invertebrate biotopes but these have not been studied by any worker. G. Gnathostomulida. These inhabitants of anoxic marine sediments have not been discovered in New Zealand. H. Nemertea. Several nemerteans occur intertidally (Morton & Chapman 1968; Morton & Miller 1968) but none has been identified to species level. I. Acanthocephala. None of these parasites has been formally recorded from Reserve waters, but it is likely that some fish and sea birds may harbour them. J. Entoprocta. Pedicellina hispida and Barentsia gracilis are frequently found in association with bushy bryozoans or at the bases of some small low-tidal algae. An unidentified loxosomatid occurs at times on walls of aquaria at the Leigh Laboratory. K. Aschelminthes. Free-living nematodes are abundant in algal and invertebrate biotopes and in sediments but little information exists on nematodes in local waters (Ditlevsen 1929). Parasites have been found in snapper and other fish (by students at the Leigh Laboratory) but not identified. Much basic taxonomic work is needed on both parasitic and free-living forms. A rotifer, attached to the body wall of a holothurian (possibly Kolostoneura novaezelandiae) from the Echinoderm Platform has been recorded. Gastrotrichs, kinorhynchs and nematomorphs are not known from Reserve waters. L. Annelida. The polychaetes of the Reserve have been well characterised (Whitley 1966). Of the Errantia 26 species are known, with 30 species of Sedentaria. Excluded from this number is the Spirorbidae, of which there are several species in the Reserve (Vine, in press). While the habits and feeding behaviour of many species is partially known (King 1964, Whitley 1966, Morton & Chapman 1968, Morton & Miller 1968, Wells 1968), the biology of most remains unknown. Ayling (1968) estimated the amount of biomass contributed by carnivorous, deposit-feeding and filterfeeding polychaetes at various depths at the northeast point of Goat Island (table 7). Marine leeches and oligochaetes are not known from the Reserve, 37

5 while an interstitial protodrilid is the only known local archiannelid. M. Pogonophora. Only one pogonophoran is known from New Zealand coastal waters (Batham 1973) but the minimum recorded depth of occurrence is 230m and none are likely to be found in the relatively shallow waters and coarser sediments of the Reserve. N. Priapulida. No priapulid is known from local waters. 0. Sipunculida. One species (Dendrostomum aeneurri) occurs abundantly in silt-filled cracks and crannies in sandstone and Corallina turf at Goat Island Bay (Morton & Chapman 1968). Little is known of its biology. P. Echiurida. No echiuroid is known from local waters, though an unidentified species (possibly Urechis novaezelandiae) has been recorded from stomachs of snapper caught by Northwest Reef near Little Barrier Island (Colman 1972). Q. Mollusca. The molluscs are the best studied group of marine invertebrates in the Marine Reserve and exhibit the greatest diversity. Even when figures for protozoans become established it is unlikely that they will exceed those of the mollusca, with 298 species, dead or alive, found within Reserve boundaries. These comprise gastropods (233), bivalves (48), chitons (14) and cephalopods 4)). Following the methodology of Prof. J.E. Morton, in teaching, in the field and in publications (Morton & Miller 1968, Morton & Chapman 1968, Morton 1975), many have contributed to a knowledge of the systematics, ecology and physiology of local molluscs. The gastropoda, which are highly represented numerically and in species diversity (prosobranchs (183), opisthobranchs (47), pulmonates (5)), are important in intertidal communities. The limpets Cellana ornata and Patelloida corticata are abundant in exposed areas at lower levels of the shore, where they adhere firmly. P. corticata may occur in numbers up to 2000 per m, although the average standing crop is usually less than 30 g/m (Smith 1969). 2 Smith recognised three communities of mollusca in the intertidal 2 region and gave data on the numbers, standing crop and median size by weight of 12 species (table 8). Beckett (1969:275) gave abundance data for 8 additional species of gastropod (table 9) at Goat Island Bay. The highest values were obtained for Notoacmea parviconoidea (71.25/m ), Cellana ornata (56.44) and C. radians (49.20). Beckett's studies included 2 information on the homing behaviour and four other types of movement exhibited by 20 species of grazing mollusc in relation to their abundance and food preferences. Most individuals of Notoacmea pileopsis, N. parviconoidea, Cellana omata, Patelloida corticata, Siphonaria zelandica and Sypharochiton pelliserpentis show homing behaviour (Beckett 1968, 1969). Certain species are often found aggregated (Nerita atramentosa, Lepsiella scobina. At EHWS tide, 78%, and at mean tide level, 81% of Nerita individuals are in aggregations, but the aggregations do not comprise the same individuals for long periods (Beckett 1969). Diet and feeding behaviour has been documented for many species of intertidal and subtidal mollusc, viz. of Alloiodoris lanuginosa, Aphelcioris luctuosa, Archidoris wellingtonensis, Chromodoris amoena, Rostanga rubicunda 38

6 (Ayling 1967, 1968a), Calliostoma (Maurea) punctulata, C. tigris, Ranella (Mayena) australasia (Ayling 1968b), Cellana radians (Murray 1965), C. omata, Lunella smaragda, Sypharochiton pelliserpentis (Beckett 1969), Siphonaria zelandica (Bedford 1967), herbivorous gastropods (Luckens 1974), Lepsiella scobina, Haustrum haustorium, Thais orbita (=Neothais scalaris) (Luckens 1975b) Caldukia rubignosa (Miller 1970), Cryptoconchus porosus, Guildingia obtecta (Nass-Thomassen 1967), Gadinia conica (=Gadinalea nivea) (Walsby et Item ^Spp. C.or C.ra C.st Leps Lune Mela Neri N.pa N.pi Pate Siph Syph T PR A <1 <1 0 <1 34 < Wet wt. T in Wl gms A XT W2 PR T A T A < <1 per T m Wl A W2 T A % by wt PR total grazing Wl molluscs W Table 8: Numbers, weight and importance of twelve molluscs at three stations in the Marine Reserve i.e. pump reef (PR), waterfall reef west (Wl) and east (W2). For wet weight and niynbers, the figures are given as totals (T) for all levels at that station, and average (A) per m, of the total. (Total numbers of m quadrats are 11 each at PR and Wl and 14 at W2). Mollusc species from left to right in the table are Cellana ornata, C. radians, C. stellifera, Lepsiella scobina, Lunella smaragda, Melagraphia aethiops, Nerita atramentosa, Notoacmea parviconoidea, N. pileopsis, Patelloida corticata, Siphonaria zelandica, Sypharochiton pelliserpentis. (From data of Smith 1969.) 39

7 al. 1973), and Berthella ornata,berthellina citrina and Pleurobranchaea maculata (Willan 1975). Many rare, new or interesting molluscs have been recorded from the Marine Reserve. Among the prosobranchs are a cowrie, Lyncina vitellus (Powell 1974), Buccinulum linea (Ponder 1971a and Paratrophon quoyi quoyi (Ponder 1971b). There are 35 species of small rissoaceans and littorinaceans (Ponder 1965a,b,c, 1966, 1967, 1968) and for five of these (Eatoniella (Dardaniopsis) notolabra, E. (Dardanula) minutocrassa, Notoscrobs (Microfossa) falsestea, Rissoella (Rissoella) elongatospira, and Awanuia porcellana) Goat Island Bay is the type locality. The opisthobranchs include the tiny coralline turf dwelling Runnica katapoides (Miller & Rudman 1968), which is fairly widespread north of 37 S, and two nudibranchs, Caldukia rubignosa (Miller 1970) and Babakina caprinsulensis (Miller 1974) for which Goat Island Bay is both the type and only known locality. The thecosomatous pteropods Creseis virgula and Limacina inflata are components of the zooplankton of the Jellicoe Channel (Jillet 1966, 1971) and Creseis, at least, has been encountered in plankton tows in the Goat Island channel. Bivalves include tiny Pachykellia minima (Ponder 1969), slug-like Scintilla stevensoni (Ponder 1967b) and an apparently self-introduced Japanese species, Limaria orientalis, first recorded in New Zealand from Goat Island Bay in January 1972 (Grange 1974). Other molluscs from the Reserve have been recorded by Hipkins (1949, 1951, 1958), Warren (1949a,b, 1951, 1955, 1956, 1957) and Rudman (1971). Species Numbers per square metre Average Range Cominella maculosa Thais orbita Diloma zelandica Haustrum haustorium Iittorina cincta 0 0 Iittorina unifasciata Onchidella nigricans Risselopsis varia Table 9: Abundance of eight gastropod species of the mid-littoral zone at Goat Island Bay. (From data of Beckett 1969.) Reproductive behaviour and spawning seasons have been recorded for several cymatiids (Laxton 1968, 1969) and in the broad squid Sepioteuthis bilineata (Larcombe & Russell 1971, Russell 1971b,c, 1974). O'Keefe (1973) investigated the ecology and sexuality of the New Zealand slipper limpet 40

8 Maoricrypta monoxyla, determining that this species is irregularly protandric while breeding year-round. It appears that sexual development is controlled both by heredity and environment. Isolated individuals seem to be primarily under genetic control, becoming males or females according to the preponderance of maleness or femaleness in their genotype. On the other hand, individuals can be affected by the presence of adults, developing sexuality opposite to that of the adult neighbour(s). R. Arthropoda. Zone-forming barnacles have been the most studied arthropods in the Marine Reserve. The adaptations and responses of barnacles to the rigours of periodic emersion and immersion and to heat stress have been recorded by Foster (1965, 1969) and Ritz & Foster (1968). Body tissue temperatures of Epopella plicata and Chamaesipho brunnea approximate that of the rock surface and may thus be higher than air temperatures. The highest recorded tissue temperatures in the field were 38.5 Cfor C. brunnea and 37.0 C fori?, plicata. Differential tolerance to high temperatures reflects the vertical distribution on the shore of the zone-forming species, as does competition and predation (Luckens 1966, 1970, 1975a,b), while water movement dictates orientation and distribution of the short lived Balanus trigonus (Ayling 1976b). The production of ova and the appearance of the early stages in the plankton has been recorded by Foster (1965, 1967), Luckens (1966, 1970, 1975a) and Barker (1971, 1976). Chamaesipho brunnea breeds from November to April while C. columna and E. plicata breed year-round with intermittent peaks. C. columna settles from the top of the C. brunnea zone to the top of the brown algal belt. While Lepsiella scobina can prey upon C. columna, its preference is for the two larger species; hence the lower limits of C. brunnea and E. plicata are determined largely by predation, as well as competition between C. brunnea and C. columna. The range of C. columna is set, at its upper limits by physical stresses (e.g. desiccation), and at its lower limits by competition with algae, Xenostrobus pulex and rock oysters (Luckens 1975a,b). While barnacles are conspicuous and have been well-studied, their diversity (Foster 1967) is small (14 recorded species) relative to other crustacean groups. The Malacostraca are clearly the most important group numerically, with more than 60 known species, and yet not all the orders of Malacostraca represented in the Reserve have been well studied taxonomically. Decapods (crabs, shrimps, crayfish) number about 27 species. Four tanaids occur, two of them commonly but are not yet identified, while cumaceans and nebaliaceans have not yet been noted in Reserve sediments. Of the Amphipoda, over 30 species of algal-living Gammaridea have been recorded (Barnard 1972), for one species of which (Microdeutopus apopo) Goat Island Bay is the type locality. There are many non-gammaridean amphipods, however, which remain to be characterised, in addition to the many isopods, both parasitic and free-living. Branchiopods are probably represented in the plankton by 4 species of cladocerans, which are known from the Jellicoe Channel (Jillet 1966, 1971); 35 species of Copepoda are likewise to be expected. In addition, Anderson (1973) recorded the presence of parasitic caligoid copepods on blennioid fishes. Ostracods are abundant in sediments or in algal or cryptic invertebrate biotopes, but not a single species has been formally recorded. The biology of relatively few of the local crustaceans has been studied. 41

9 Bacon (1971a,b,c) has investigated the ecology of several grapsid crabs; their zonation, responses to physical stress and niche separation in two sympatric species of Cyclograpsus (see section on boulder beaches under 'Coastal features and habitats'). Ayling (1968b) estimated the standing crop of crabs in mixed communities on subtidal rock faces. This ranged from 0.37 g/m on a flat surface at 6m to 3.90 g/m on a 60 slope at 18m. Records of other crabs 2 in the area include those of Dell (1968), 2 Griffin (1973) and Melrose (1975). Intertidal insects are not uncommon. These comprise Philanisus plebejus, a caddis-fly commonly found in coralline turf, but which is also known from 12m depth (Ayling 1975e); Opifex fuscus, a mosquito which breeds in littoral fringe and maritime pools; Anisolabis littorea, an earwig found commonly under rubble on boulder beaches, a small blue unidentified collembolan (Lipura sp.) (Morton & Chapman 1968); Hyphalus wisei, a tiny (2mm) brown beetle from an intertidal rock platform near the Laboratory (the type locality) (Britton 1973); a tiny unidentified black beetle from the same habitat (Dr W. Kuschel, D.S.I.R. pers. comm., 1976), a larval dipteran (unidentified) from Carpophyllum holdfasts; and three new species of midges viz. Smittia spp. and Telmatogeton mortoni (Leader 1975) for which Goat Island Bay is the type locality. Chilopods are represented by Scolioplanes sp. (Morton & Chapman 1968). Arachnids of three orders are found intertidally, mostly in crevices or cryptic habitats, although mites scuttle about in the open. Desis marina is a crevice spider, while a pseudoscorpion, Maorichthonius mortenseni shelters in cracks among Chamaesipho columna (Beier 1969). Opsochernes carbophilus (as Obisium sp. in Morton & Chapman 1968) occupies crevices (pers. comm. Dr W. Kuschel, D.S.I.R., 1976). Several species of mite occur on intertidal rocks, including Tangaroellus porosus in the Chamaesipho columna zone (Luxton 1968), while Hydrogamasus kensleri and Fortuynia elamellata, first described from the Takatu Peninsula (Luxton 1967), may be expected locally. Unidentified halacarid mites are common intertidally and subtidally in algal and invertebrate biotopes. Two species of sea spider (Pyconogonida) are known in the Reserve (viz. Achelia assimilis,?anoropallene sp.) (Dr W.C. Clark, in litt., 1968). A. assimilis is common under rocks on the Echinoderm Platform. Anoropallene is rarer in the same situation. Achelia males with egg bundles occur in February and protonymphon larvae were observed hatching in June, S. Tardigrada. Tardigrades have not yet been found in local waters. T. Phoronida. Phoronis ovalis is a small (c. 6mm) species that bores into dead or live shells. It is not uncommon in shell debris on the Echinoderm Platform and is also found in Glycymeris off Cape Rodney. U. Brachiopoda. Only Terebratella inconspicua is known live from the Marine Reserve where it occurs from the sublittoral fringe under slabs and boulders, to 20m subtidally at Goat Island. Under overhangs at 12m it is especially abundant, occurring in stands of 1200/m 2, representing 127g/m 2 dry weight (Ayling 1968, 1974c). The biology of adults and larvae, including feeding efficiency and population dynamics has been studied by Doherty (1976). Only one dead shell of Crania huttoni has been found in the Reserve. 42

10 V. Bryozoa. With 115 recorded species from the Reserve, the Bryozoa rank second after molluscs in diversity. In some invertebrate biotopes they may attain spatial and numerical dominance, as under rock slabs and boulders on Echinoderm Platform (Gordon 1968a, 1972; Ryland 1975), and in localised areas subtidally (Ayling 1968b). In trying to relate the diversity of the species of the shore platform to parameters of their feeding apparatus, Ryland determined that is the commonest tentacle number (of a potential range of 840) and that the majority of colonies in this habitat are probably exploiting a common food resource. While there are three types of breeding season among the bryozoa of the Reserve, the majority of species have summer maxima in embryo production. Availability of food appears to influence growth and reproduction more directly than sea water temperature (Gordon 1970). Hippothoa trigemma from Goat Island Bay is one of only two members of the order Cheilostomata known to possess a gizzard (Ryland & Gordon, in press). Colony formation has been studied in detail in Fenestrulina thyreophora (Gordon 1971a,b), which is common on Echinoderm Platform in summer. Hippopodinella adpressa, which occurs on shells, exhibits an unusual sexual dimorphism of polypides (Gordon 1968b). W. Echinodermata. While echinoderms are locally abundant, their species diversity is low. There are 7 species of brittle-stars, 8 asteroids, 4 species of sea cucumber and 3 echinoids. A comprehensive study of the diet and feeding methods, reproduction and ecology of ophiuroids on Echinoderm Platform was carried out by Pentreath (1968). Ophionereis fasciata, Ophiactis resiliens, and Ophiopteris antipodum are microphagous omnivores, found under rock slabs, feeding on mucous-trapped particles. Axiognathus squamata occurs mostly in coralline turf or amongst coarse sand and shell on the platform, feeding on small algae, gastropods and other organisms. O. fasciata is the most abundant intertidal species, but there are seasonal changes in abundance, such that in 12 pools on the platform numbers varied from 91 individuals in July (1967) to 225 in March (Pentreath 1968). The function, histochemistry and fine structure of podia and stomachs, the rate of growth of arms and respiratory function of bursae was also investigated by Pentreath (1970). The asteroid Patiriella regularis occurs in large numbers intertidally, sometimes in association with the more active Coscinasterias calamaria. The latter species preys upon Evechinus subtidally and may have been responsible for the depletion of Modiolus areolatus in the Goat Island channel. Crump (1969) gives data on wet weight and gonad indices for Coscinasterias from Goat Island Bay, and the diet of both species. Further information on feeding biology is given by Martin (1970). Holothurians Stichopus mollis, Trochodota sp., Kolostoneura novaezelandiae and Ocnus sp. occur in the Reserve, but their ecology is not well known. Evechinus chloroticus, Centrostephanus rodgersii and the small pink Holopneustes inflatus occupy similar niches on rocky bottoms. Aspects of the behaviour of the two larger species have been studied by Russell (1970), and Castle (1974), who determined that Evechinus produces a noise at dusk from the scraping of its teeth across rock surfaces. The numerically abundant Evechinus is 43

11 in important in the economy of subtidal communities, greatly influencing the distribution of seaweeds, including Ecklonia radiata (Ayling 1974a; Dromgoole 1964), and making available bare space for the settlement of invertebrate larvae (Ayling 1974b). X. Chaetognatha. Sagitta serratodentata and Pterosagitta draco are known from the Jellicoe Channel (Jillet 1966, 1971). Unidentified arrow-worms from plankton tows in the Goat Island channel probably belong to these species. Y. Hemichordata. No hemichordate is known from the Reserve, but Saccoglossus otagoensis might be expected to occur in Glycymeris shell gravel. It occurs in this habitat at Whangarei Heads. Z. Chordata. Three species each of larvaceans and thaliaceans are components of the plankton in the Jellicoe Channel (Jillet 1966, 1971) and probably occur in the Marine Reserve. Ascidiaceans are represented by 40 species (Croxall 1972), and Dr R.A. Cloney (pers. comm. 1976). Aspects of the feeding, growth rates, settlement seasons of and predation pressure upon several species have been studied by Croxall (1971). Ascidians generally occur in the same biotopes as bryozoans and sponges where they may vie for space and food. Compound species (e.g. Sigillinaria arenosa) may attain 43.2g/m 2 on flat surfaces at 6m with solitary Cenmidocarpa bicornuata producing 348g/m 2 dry weight in the same locality (Ayling 1968b). Biomass of both solitary and compound species appears greater on flat surfaces than on slopes although this is variable. The New Zealand lancelet Epigonichthys hectori occurs in sand off Goat Island. ZOOPLANKTON The Zooplankton of the Hauraki Gulf and northern New Zealand has a strong subtropical affinity, with decreasing numbers of species in common with south-east Australia, South Africa, Great Barrier Reef, equatorial Pacific and southern New Zealand. The Gulf zooplankton has been characterised by Jillet (1966, 1971), who added considerably to the small amount of information that previously existed (Kramer 1894, Fuller 1950, 1953), while Grace (1968) further considered vertical distribution and diurnal migration of Gulf species. The northern boundary of the outer Gulf is regarded as a line from Cape Rodney to Cape Colville, with waters beyond this line as the Hauraki Gulf Approaches (Taylor 1973) (q.v. section on Hydrology). Jillet's sampling station, about 14km from Cape Rodney, was in the Approaches near the outer Gulf boundary (in the Jellicoe Channel). His findings probably apply to the waters of the Marine Reserve, since the species composition of the Jellicoe Channel is strikingly similar to that of the Bay of Islands and open ocean. Only three studies in the Reserve have contributed information on local zooplankton, viz. those of Luckens (1966, 1970, 1975a), Foster (1965, 1967) and Barker (1971, 1976) with data on the identification, seasonal abundance and distribution of barnacle nauplii. Copepods represent the commonest holoplanktonic group (63% of the 44