Observations on the hydrology of bay of Islands,New Zealand

Observations were made on several hydrological features of Bay of Islands during 1970 to 1971. The topography of Bay of Islands allows for a gradual change from estuarine to oceanic conditions within the harbour.

Monthly means of sea surface temperatures ranged between 15°c and 23°c, and some sea stratification was observed during summer. Salinities in the main basin were about 35.5‰; water transparency ranged from 2 m to 6 m by Secchi disc in the estuaries, to more than 15m in outer basin areas. Dissolved oxygen content was high, usually exceeding 100% saturation in surface waters. Water circulation within the bay appears to consist of an anti‐clockwise movement of at least the surface water, induced by a north‐west moving current, possibly derived from the East Auckland Current.

The observations suggest that, except; for the estuarine areas, Bay of Islands is hydrologically a fairly homogeneous, well‐mixed body of water.     

First record of a wild population of the tropical snail Melanoides tuberculata in New Zealand natural waters

The thiarid snail Melanoides tuberculata (Müller, 1774), native to the Middle East and East Africa, is recorded from the wild in New Zealand for the first time from a geothermally influenced stream at Golden Springs, near Taupo. Introduction was most likely the result of one or more releases from tropical aquaria, although the timing of release is uncertain. Specimens were collected at temperatures of 29.0 and 30.4°C, and survival at these sites is likely dependent on the elevated stream temperatures. The possible spread of this species to other habitats, and potential effects on native thermal water communities, are discussed.     

First record of Australian bonito,Sarda Australis,from New Zealand

The range of the Australian bonito, Sarda australis (Macleay, 1880), previously known only from eastern Australia and Norfolk Island, is now extended to include New Zealand. Data on two specimens examined from northern New Zealand are presented.     

First record of manta rays off New Zealand

Three manta rays were seen and photographed in the western Bay of Plenty, New Zealand, in March 1968. Although the species or genus could not be identified, this sighting represents the first substantiated record of the manta ray family (Mobulidae) in New Zealand and confirms the statements of fishermen that, in summer, mantas occasionally appear in offshore game‐fish waters in north‐eastern New Zealand.     

First record of an odontaspidid shark in New Zealand waters

Photographs and a preserved head are identified as Odontaspis herbsti Whitley, 1950, an Australian sand shark growing to about 3 m long and similar to the Mediterranean O. ferox Risso, but differing in having a uniform grey body without black markings on the back or sides. No living odontaspidids have previously been reported from New Zealand. Six specimens were trawled in 119–165 m off Table Cape, Hawke Bay, in October‐November 1972. Californian and. East Atlantic (Madeira) specimens are treated as conspecific with O. herbsti. It is suggested that O. herbsti is normally an inhabitant of the continental slope, and that the present records are of a few individuals that have strayed on to the shelf.     

Further birth records of elephant seals Mirounga leonina in New Zealand (note)

The second and third recorded births of southern elephant seals Mirounga leonina on the mainland of New Zealand occurred at Kaikoura in mid‐October 1976. One female pup died within 14 d of birth and the other (sex unknown) disappeared from the region with its mother on 19 November 1976.     

First record of Lepidocybium flavobrunneum (Pisces: Gempylidae) from New Zealand

Lepidocybium flavobrunneum (Smith, 1849) is widespread in warmer oceanic waters and has recently been recorded in the catches of tuna longline vessels in the New Zealand region. Twenty‐five specimens were caught at 31°46′‐32°03′S, 170°49′‐171°11′ E on 23–27 June 1979, thus extending the known range of the species to northern New Zealand.     

DNA identification of Pacific bluefin tuna (Thunnus orientalis) in the New Zealand fishery

Muscle samples were collected from 69 specimens identified as Pacific bluefin tuna (Thunnus orientalis) (Temminck and Schlegel, 1844) in the New Zealand Exclusive Economic Zone (EEZ) between 1990 and 2000. Identifications before 1996 were based on body size and colour of the caudal keel; later identifications were mostly based on the shape of abdominal cavity. The tissue samples were tested with a diagnostic mitochondrial DNA marker that distinguishes southern bluefin Thunnus maccoyii (Castelnau, 1872) and Pacific bluefin tuna T. orientalis; 59 specimens were confirmed as T. orientalis and 10 as T. maccoyii. Specimens recorded as Pacific bluefin tuna by the shape of the abdominal cavity were correctly identified as T. orientalis, and this character can be used to identify large specimens landed on tuna vessels. Some specimens recorded as Pacific bluefin tuna on the basis of colour and size were T. maccoyii; and early records of T. orientalis in New Zealand waters, based on these characters, are unreliable. Unusual colour patterns were reported in some specimens of T. orientalis but not T. maccoyii. The Pacific bluefin tuna T. orientalis accounted for less than 0.3% of the bluefin tuna catch in the New Zealand EEZ during the 1990s.     

Genetic and meristic variation in black and smooth oreos in the New Zealand exclusive economic zone

Meristic and genetic methods were used to determine the stock relationships of black Allocytus niger (James, Inada & Nakamura, 1988) and smooth oreo Pseudocyttus maculatus (Gilchrist, 1906) in the New Zealand Exclusive Economic Zone (EEZ). Samples were collected from four management areas—OEO 1 (south‐west), OEO 3A (Chatham Rise west), OEO 4 (Chatham Rise east), and OEO 6 (subantarctic) during the 1998 October‐December spawning period. Lateral line scale counts and pyloric caeca counts revealed differences between black oreo samples from OEO 6 and the other three OEO management areas. Lateral line scale counts in smooth oreo showed no significant differences between areas. Genetic analyses of four non‐coding regions of nuclear DNA and mitochondrial (mt) DNA haplotypes in black oreo showed no significant differentiation among the four management areas. Likewise for smooth oreo, genetic analyses of five non‐coding regions of nuclear DNA and mtDNA haplotypes showed no overall regional differentiation, although there was weak evidence at one locus for a difference between OEO 3A and OEO 6. The data do not reject the null hypothesis of a single genetic stock in New Zealand waters, and are typical of marine species with long pelagic juvenile stages.     

Biotic consequences of a shift in invertebrate ecosystem engineers: Invasion of New Zealand rocky shores by a zone‐forming ascidian

The pervasive effects of invasive ecosystem engineers, that is those species that modify their environment, are well documented, but rarely have the broader impacts of one foundation invertebrate species being replaced by another been examined. In New Zealand, green‐lipped mussels, Perna canaliculus, commonly dominate wave‐exposed rocky shores. The recent appearance of an invasive ecosystem engineer, the ascidian Pyura doppelgangera, at the very northern tip of New Zealand now threatens to exclude these bivalves from this habitat. Here, we report major shifts in assemblages associated with the invader and chronicle its continued spread. We examined epibiota associated with clumps of mussels and clumps of Pyura from two rocky shore habitats—pools and emergent substrata at two locations. We detected some differences in species richness in biota associated with the two foundation species, but faunal abundance only differed between the locations. These minor changes were dwarfed by the shift in species composition within clumps of each foundation species. Molluscs, particularly gastropods, and crustaceans dominated the assemblage within mussels. In contrast, tubicolous polychaetes dominated the fauna associated with the ascidian. Sessile epifauna, notably barnacles and calcareous tube‐dwelling polychaetes, were common on mussels, but never encountered on the ascidian. Multivariate analysis revealed marked dissimilarity (>80%) between the characteristic mussel and ascidian faunas with virtually no overlap. This biotic shift overshadowed any differences between habitats and locations. The broader implications of these faunal shifts for local and regional patterns of biodiversity, as well as ecosystem function, remain unclear, but deserve further attention.     

First record of the crocodile shark,Pseudocarcharias kamoharai (Chondrichthyes: Lamniformes), from New Zealand waters

Commercial tuna longline fishing targeting bigeye tuna, Thunnus obesus (Lowe 1839), on the Three Kings Rise, northern New Zealand, resulted in the bycatch of a single specimen of a mature male crocodile shark, Pseudocarcharias kamoharai (Matsubara 1936). This is the first record for the New Zealand Exclusive Economic Zone, and a major southern range extension of the species in the Indo‐Pacific.     

Genetic variation and population structure in the New Zealand snapper

Fifteen proteins encoded by 23 gene loci were electrophoretically surveyed in two samples of snapper Chrysophrys auratus (Forster) from Wellington Harbour and the Hauraki Gulf. Between 17% and 26% of the loci examined were found to be polymorphic and the proportion of heterozygous loci per individual was 7.9% to 8.4%. Using Rogers’ genetic distance coefficient an overall similarity of 0.98 was calculated between the two samples.

Three polymorphic loci Est‐4, Gpi‐1, and Idh were examined in an additional 10 samples from around New Zealand. Two genetically distinct stocks were apparent: one along the west coast, the other along the east coast of the North Island. There was an indication of stock mixing at Ninety Mile Beach and in the Bay of Plenty and East Cape. The distribution of alleles at the Est‐4 locus revealed a third stock in Hawke Bay that is genetically more similar to the west coast than the east coast stock. Hydrological conditions in Hawke Bay are more similar to those of the west coast than to those of the north east coast of the North Island. Thus it is possible that Est‐4 alleles are selectively maintained in response to an environmental factor.     

Antarctic Intermediate Water variability in the northern New Zealand region

In the region between 30°S and northern New Zealand, vertical salinity profiles through the core of the Antarctic Intermediate Water (AAIW) show a high degree of spatial and temporal variability, and this variability is much larger than that found in nearby ocean areas. Characteristic features are interleaving of salinity layers and large changes in the salinity minimum between adjacent stations. Quantifying the changes through the calculation of an intrusion index highlights the degree of variability and the importance of boundary mixing along the New Zealand slope. However, the main cause of the variability is the meeting and mixing of higher salinity AAIW, arriving from the north‐west (having travelled around the subtropical gyre) with lower salinity AAIW arriving by more direct entry from the north‐east. These waters meet in the region through the action of the meso‐scale eddy field. Present data indicate that where strong salinity interleaving occurs, the length scales are of the order of 10 km and the time scales are of the order of a few days. Resolution of the processes at work will require studies on finer scales than presently available.     

Occurrence of Hydroclathrus clathratus in northern New Zealand waters

Hydroclathrus clathratus (C. Agardh) Howe (Phacophyta: Punctariales) is recorded from two harbours on the Northland east coast, North Island, New Zealand. The possibility of its being a recently introduced species is discussed.     

First record of Bonnemaisonia hamifera (Bonnemaisoniales,Rhodophyta) in the South Pacific,from the South Island of New Zealand

ABSTRACT

The tetrasporophytic ‘Trailliella’ stage of the red algal genus Bonnemaisonia is reported for the first time from the Southern Hemisphere. Here we describe a bloom of the tetrasporophyte of B. hamifera from the mouth of the Waikouaiti River, Karitāne, South Island, where it occurred as thousands of free-floating tufts up to 1?cm wide in shallow water, accumulated in windrows on sand banks and beaches, and in the water column at depths of 10–12?m on the adjacent open coast. Gametophytic stages have not yet been found in New Zealand. The material collected to date is strictly vegetative, and reproduction occurs via fragmentation. The identity of the New Zealand samples as B. hamifera was confirmed by both morphology and rbcL sequencing. The abundance and floating dispersal of B. hamifera suggests that it is invasive and will become widely distributed in New Zealand.     

冠瘤海鞘幼体附着和变态的离子控制

研究了人工海水中三种金属离子K+,Mg2+和Ca2+分别在不同浓度下对冠瘤海鞘(Styelaca nopusSavigny)幼体附着和变态的影响,同时采用K+通道阻滞剂TEA检验其可兴奋细胞膜上的K+通道特性,对冠瘤海鞘幼体附着和变态的离子控制机制进行初步探讨,结果表明:K+的浓度为20~40mmol/dm3时诱导幼体附着和变态的效果最佳,低于45 mmol/dm3和高于80mmol/dm3的K+浓度都表现出抑制效果;Mg2+浓度在0~32 mmol/dm3时显著促进幼体附着和变态,达88mmol/dm3时起抑制作用;在人工海水中无论添加或减少Ca2+,均有效抑制幼体变态.TEA不能阻抑增加K+的诱导作用,这表明冠瘤海鞘幼体可兴奋细胞膜上的K+通道对外部TEA不敏感.另外,人工海水中缺乏K+或Ca2+或K+浓度达80mmol/dm3都会对冠瘤海鞘幼体产生毒害作用.     

Second New Zealand record of the Holothurian giant larva Auricularia Nudibranchiata Chun

Seventy‐nine specimens of the holothurian larva Auricularia nudibranchiata from north of New Zealand are described, and relationships with previously described specimens of the same or related species are discussed.     

Occurrence and recruitment of fish larvae in a northern New Zealand estuary

The occurrence of fish larvae and the effect of diel and tidal variation on catches was studied at about biweekly intervals for a year in Whangateau Harbour, a small well mixed northern New Zealand estuary. Larvae from 31 taxa were identified. The annual pattern of larval occurrence was typical for fish in temperate waters, with a major peak of abundance in early summer. For six taxa, larval densities were significantly greater in night-time than in daytime catches, and analysis of length-frequency distributions suggested that for two species this was due to daytime net avoidance.No significant differences were found between the densities of larvae caught on flood and ebb tides, but changes in length-frequency distributions were significant for two species. Recently hatched larvae of an unidentified goby were found leaving the harbour, where they were probably spawned, while older larvae of this species appeared to be recruiting back in. Larvae of the flounder Rhobosolea plebeia were also apparently recruiting into the harbour. In the absence of a two-layered circulation pattern larvae relied upon tidal transport for recruitment, and probaby ensured their retention by rapidly settling to the bottom.     

Algal interactions on shallow subtidal reefs in northern New Zealand: A review

In north‐eastern New Zealand, nearshore subtidal reefs are dominated by large brown algae of the orders Fucales and Laminariales. Species of the genera Carpophyllum, Sargasswn, and Landsburgia are the most conspicuous fucaleans, whereas Ecklonia radiata is the only common laminarian. Three categories of events affect the composition of stands of these algae: first, the competitive effects of adult canopies on recruitment to the substratum below; second, the seasonality of spore release and availability of free space; and third, the demographic characteristics of species and their influence on recruitment. Adult canopies suppress recruitment of all species. Both repro‐duction and recruitment are seasonal in occurrence and most recruits appear within a few metres of adults of their own species. A comparison of representative Fucales and Laminariales shows important differences in how these taxa colonise substrata. Propagules of fucaleans are larger at settlement and fewer in number than those of laminarians. Compared to laminarians, however, higher numbers of fucalean adults are generally required to form a closed canopy. The number of recruits and the survival of each life history stage are affected by the population structure of algal stands. The importance of the demographic characteristics of individual species in assessing these processes is highlighted.