FISH Over 90 species of fish have been recorded from the Marine Reserve (Russell 1971a; Anderson 1973, Russell & Ayling 1976, Ayling pers comm.

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1 FISH Over 90 species of fish have been recorded from the Marine Reserve (Russell 1971a; Anderson 1973, Russell & Ayling 1976, Ayling pers comm. 1976). About fifty per cent of these are New Zealand endemics, while most of the rest (36%) are shared with SE Australia. The fish populations are typically coastal and contain few of the elements typical of offshore islands. As Russell pointed out, relatively little biological information exists for the vast majority of species in New Zealand waters, but recent work in the area of the Marine Reserve (and elsewhere in north-eastern North Island) (Ayling 1968b; Ayling & Grace 1971; Doak 1972; Doak & Ballantine 1966; N.Z. Underwater Association 1971; Russell 1969, 1971a,b,c, 1975) has made substantial inroads into our ignorance. The biology of the local fishes will be considered under the following subheadings: A. ecology; B. breeding biology; C. food and feeding; D. behaviour. A. Ecology Distribution of many fishes is related to bottom topography, and on this basis Russell (1969, 1971a) defined a zonation of habitats relative to the bottom, i.e. hyperfundal, epifundal and infundal. (i) In the hyperfundal zone (above lm from the bottom to the surface) fishes are independent of the bottom for food and/or shelter e.g. surface-living piper, grey mullet, barracouta, kahawai (11 species total) and mid-water dwelling shoalforming blue mao mao and demoiselle, the bronze whaler shark and kingfish (16 species). (ii) In the epifundal zone, which is a narrow belt to lm above the bottom, fishes are more or less dependent on the bottom for food and/or shelter e.g. the algal associates parore, kelpfish, butterfish (14 species), the open rocky bottom associates moki, porae, snapper (13 species), the broken rocky bottom associates black angelfish, drummer, leatherjacket (Fig. 10) (21 species), and sandy bottom associates goatfish, rays and gurnard (16 species). (iii) Infundal fishes live within the interstices of bottom material in crevices or caves or beneath overhangs or under an algal canopy e.g. crevice-dwelling blennies, banded sea perch, eels (27 species); pipefish, seahorses and blennies amongst algae (5 species), and cave-hiding roughy, bigeye and grandfather hapuka (9 species). Detailed information on population dynamics is lacking for most species. The commercially important snapper (Chrysophrys auratus) in Hauraki Gulf waters grows 30cm over 3-5 years and apparently reaches 26 years of age (Cassie 1956b). Age is partly determined from counting of scale annuli, using the number of completed annuli with the addition of fraction relevant to the quarter of the year in which the fish was taken. Thus a 3+ fish taken in March is assumed to have completed 3.25 years of growth (Longhurst 1958). Longhurst did not specify from which part of the body the scales were taken ana Paul (1968a) cautions that the 'generally best' area for snapper is the pectoral area (based on Gulf populations). A comparison of length-frequency distribution of Gulf fish by Longhurst (I.e.) with data of Hefford (1929) indicated no significant change over 30 years of exploitation by fishermen. The demoiselle (ichromis dispilus) starts life as larvae 1.1mm long attaining 1.5cm in one month (January) and 15cm in 4 months (April). As adults in shallow water, demoiselles 30

2 Photograph by M.F. Larcombe, Photograph by M.F. Larcombe, Fig. 10: Hand-feeding friendly leather-jackets in water off Goat Island. Fig. 11: School of juvenile koheru (Decapterus koheru) at Goat Island. 31

3 occur in schools of individuals (Russell 1971c). Shoal populations of other fish in shallow water are as follows: piper, to 300; butterfly perch, ; juvenile koheru (Fig. 11), ; kingfish, 3-15 or >100; kahawai, to 30; red mullet, in 'family' groups of 2-3 presumed males, 5-6 presumed females and sub-adults; juvenile snapper, to 30; drummer, 3-5; parore, "aggregations" of various sizes; blue mao mao, 20-30; porae, 1-5; hiwihiwi, 'family' groups of 5-8; black angelfish, solitary or groups of 2-5; scarlet parrotfish, 1-2; barracouta, 2-4; leatherjacket,.solitary or (Russell 1971a). Estimates of standing crop (Russell 1971a, 1975) indicate that local stands of fish are greater than for other temperate areas and are more comparable with some coral reef fish populations. Furthermore, an experimental reef off the north-east point of Goat Island at 20m depth supported 300 individuals in an area of only 50m 2, representing times the standing crop of adjacent rocky areas, though less than half the diversity i.e. the artificial reef supported to 1.458kg of fish per m 2 compared to on adjacent rocky areas. Ayling (1976a) has calculated the impact on the sessile biota of the dietary habits of the leatherjacket {Navodon scaber) (Fig. 12), one of the commonest reef fishes at Goat Island. Navodon individuals ingest virtually any organism which they are able to bite, whether soft jellyfish or hard sponges, bryozoans or sea urchins. On the bottom slopes of Goat Island leatherjackets collectively take around 36,500 bites per m 2 per year and are directly responsible for recycling 20% of the rock surface in this area every year, providing settling space for algal spores and invertebrate larvae. B. Breeding biology Few studies have been carried out on the reproductive characteristics of species occurring within the Reserve. Only the snapper and demoiselle have been subject to detailed study and much other information tends to be anecdotal. Mature snapper in Gulf waters appear to spawn when a surface temperature of 18 C is reached. When spawning both the male and female usually drift lethargically near the surface discharging clouds of eggs and milt (Cassie 1956a). Eggs hatch 45 hours after fertilisation and the yolk sac is completely absorbed in about 3 days (Cassie 1956c). The occurrence in the Gulf in early summer of spawning shoals of school fish notable for their uniformity of size, silvery coloration and relatively unworn teeth (compared to normal Gulf snapper which include many molluscs in their diet) has caused speculation that the school fish may not be an aggregation of a relatively few year-classes from the Gulf area itself, but may represent an inshore migration of deep-water stock (Longhurst 1958). The demoiselle deposits eggs in a nest, usually about 350,000 at a time, which are then guarded by the male (Russell 1971c). The breeding activities of the eagle ray are not clear, but it is known that during spring and summer males are outnumbered by females 2:1 in the outer Gulf (3:1 in the inner Gulf). In winter there is a preponderance of females also but the significance of the varying proportions is not known (McKenzie 1960). C. Food and feeding Rocky reef fishes show a diversity of feeding habits and utilise a wide variety of food organisms. According to their foraging relationships, several 32

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5 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