Hauraki Gulf Research Articles

Kyphosus vaigiensis (Kyphosidae), a new fish record from northeastern New Zealand

A drummer (Family Kyphosidae) collected at Little Barrier Island, Hauraki Gulf (36°10’ S, 175°06’ E), is a new record for New Zealand. The herbivorous Kyphosus vaigiensis (Quoy & Gaimard, 1825) is widespread in the tropical Indo‐Pacific, and is the third species of its genus to be recorded from New Zealand waters.

Introduced versus native subspecies of Codium fragile: how distinctive is the invasive subspecies tomentosoides?

After its introduction, the green alga Codium fragile (Sur.) Hariot ssp. tomentosoides (van Goor) Silva has spread widely on several temperate-zone, rocky shores where non-weedy conspecific subspecies occur (N.E. Atlantic, N.E. Pacific, S. Pacific). To determine how phenologically and morphologically distinctive the invasive alga was relative to native subspecies, I compared marine intertidal populations of C. fragile ssp. tomentosoides and the native C. fragile ssp. novaezelandiae (J. Ag.) Silva (hereafter referred to as ssp. tomentosoides and ssp. novae-zelandiae respectively on New Zealand shores in 1992, 1993 and 1995. On the North Island, the invasive ssp. tomentosoides is sparsely distributed on low intertidal benches on wave-protected shores in the Hauraki Gulf (east coast) in spring and summer, and thalli die back to the perennial holdfast in autumn. In contrast, the native ssp. novaezelandiae forms dense beds within the low intertidal mussel zone on wave-swept shores of Maori Bay (west coast), and fronds are perennial. Whereas ssp. tomentosoides has only a few fronds arising from the spongy basal hold-fast, ssp. novae-zelandiae thalli are composed of many fronds. The ssp. tomentosoides from the Hauraki Gulf is significantly more branched than comparably sized native conspecifics from Maori Bay. These phenological and morphological differences were used to predict the subspecific identity of C. fragile from three other locations on the North Island, two locations on the South Island, and four locations on S.E. Australian shores; microscopic examination of utricles was used to check the predictions. Seasonality and number of fronds per thallus are the most reliable characters for field identification of native vs invasive subspecies: perennial intertidal thalli with large numbers of fronds are indicative of native subspecies for different geographic regions.

Spatial and seasonal variation in the abundance of juvenile snapper (Pagrus auratus) in the north‐western Hauraki Gulf

Abstract Spatial and seasonal variability in the abundance of juvenile Pagrus auratus were investigated in the north‐western Hauraki Gulf using trawl tows over soft‐bottom habitats. Small‐scale (1 km) spatial variability was high and consistent over a period of 2.5 years. This variability was attributed to differences in micro‐habitat type, with snapper preferring a mud substrate over one comprising muddy sand with a significant percentage of shell. The two micro‐habitats probably result from differing current regimes, but reasons for the snapper preferences are unknown. Snapper catch rates in the Kawau Island region peaked in spring, near the time of maximum day length, and declined to low levels in autumn‐winter. This seasonal cycle is thought to reflect real changes in abundance rather than variations in snapper catchability. However, no seasonal abundance cycle was found in the adjacent Whangaparaoa region, where abundance was consistently low. There was no consistent depth‐related trend in abundance ...

Metazoan parasites of the snapper,Pagrus auratus(Bloch & Schneider, 1801), in New Zealand. 1. Prevalence and abundance

Abstract The prevalence and abundance of nine species of ectoparasites and seven species of endoparasites found on the snapper, Pagrus auratus, collected from the Hauraki Gulf, New Zealand, is reported. The metazoan fauna of Pagrus auratus in this study was dominated by a single highly prevalent and abundant species, Diphthero‐stomum sp., which accounted for 84% of all the parasites collected during this study and occurred in all snapper older than 2 years. Several other moderately abundant species were highly prevalent, occurring in 50–60% of the snapper sampled. These included Lamellodiscus pagrosomi, Bivagina pagrosomi, Cucullanus sp., and Unicolax chryso‐phryenus. The remainder of the parasite fauna comprised rare species of limited prevalence and low abundance, accounting for 7.7% of the individuals collected. These included Choricotyle australiensis, phyllobothriid and dasyrhynchid plerocercoids, Proctoeces sp., Philometra lateo‐labracis, and Anisakis sp. Correspondence analysis indicated that different age classes of the host snapper had distinctive parasitic faunas, with 0+ snapper characterised by low abundance and prevalence of all species except C. australiensis and the phyllobothriid plerocercoid. A progressive increase in many of the species of parasites constituted the major faunistic differences between 1+, 2+, and 3+ snapper. The implications for fisheries and aquaculture of the composition of the metazoan parasitic fauna of P. auratus are discussed.

Metazoan parasites of the snapper,Pagrus auratus(Bloch & Schneider, 1801), in New Zealand. 2. Site‐specificity

Abstract The metazoan parasites of the snapper, Pagrus auratus, collected in the Hauraki Gulf of New Zealand were surveyed and their distribution mapped and examined in relation to the age of the host. Nine species of ectoparasites and seven species of endoparasites were recorded and all were found to exhibit some degree of site‐specificity. The gill monogeneans Lamellodiscus pagrosomi and Bivagina pagrosomi were found in well‐defined microhabitats on the gills. L. pagrosomi was abundant on the middle section of the second gill arch and was found in greater numbers on the distal zone of the gill filaments of the external hemibranch. In contrast, B. pagrosomi was particularly abundant on the first gill arch and on the basal zone of gill filaments of the external hemibranch. A third gill monogenean, Choricotyle australiensis, was found attached to the gill filaments in snapper of 3 years and older but was largely restricted to the buccal cavity in younger host fish. This suggests that site‐specificity may n...

Salp grazing:effects on phytoplankton abundance, vertical distribution and taxonomic composition in a coastal habitat

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 126:267-283 (1995) - doi:10.3354/meps126267 Salp grazing: effects on phytoplankton abundance, vertical distribution and taxonomic composition in a coastal habitat Zeldis JR, Davis CS, James MR, Ballara SL, Booth WE, Chang FH This paper comes from a 3 yr study of environmental effects on egg and larval mortality of snapper Pagrus auratus (Sparidae), during their spring-summer spawning season in the Hauraki Gulf. In the first 2 yr, the salps Thalia democratica and Salpa fusiformis dominated mesozooplankton biomass in November and December, average chl a concentrations in the mixed layer were reduced and chl a maxima were well below the mixed layer. In the third year, salps were very rare, and the mixed layer was richer in chl a and the chl a maxima were at the bottom of the mixed layer. Diatoms dominated the phytoplankton community in the first 2 yr, especially below the mixed layer, but a more even mix of diatoms, dinoflagellates and flagellates was present in the third year. Averaged mixed layer depth and stratification intensity varied little across the 3 yr, suggesting that variation in vertical mixing rates did not drive the phytoplankton contrasts. Salp population grazing rates were high enough to overtake phytoplankton population growth at many sites. However, most sites had lower salp biomass than this, yet the reduction of chl a concentration and deepening of chl a maxima were widespread and temporally persistent. The vertical distributions of chl a were simulated in a nutrient-phytoplankton-zooplankton model which contrasted a salp-dominated community that had high sedimentation of organic wastes with a microzooplankton community within which wastes were recycled in situ. This model, and calculated rates of grazing, sedimentation, and water column mixing, showed that rates of nutrient incorporation into salp mass and sedimentation of waste material from salp grazing would be much greater than mixing of remineralized nutrient back up through the pycnocline. This causes formation of deep chl a maxima which can persist well after significant grazing pressure has dissipated. The variation in phytoplankton taxonomic composition is explained in terms of growth rates of the taxa under different grazing, nutrient and light regimes. The major effects of salp grazing in the coastal environment appear to be to deepen phytoplankton distributions and reduce biomass, rather than to remove phytoplankton biomass from the euphotic zone completely, as can occur in slope and oceanic waters. Salps . Phytoplankton biomass . Vertical distribution . Grazing . Zooplankton . Larval fish . Hauraki Gulf Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 126. Publication date: October 05, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Life at the edge: population dynamics and salinity tolerance of a high intertidal, pool-dwelling ascoglossan opisthobranch on New Zealand rocky shores

The population dynamics of the pool-dwelling ascoglossan (= sacoglossan) opisthobranch Stiliger felinus were examined from September 1992 to August 1993 on the North Island of New Zealand. The small (≤13 mm long), stenophagous herbivore associates with and feeds on the filamentous green alga Chaetomorpha aerea (Dillw.) Kuetz. in high intertidal rocky pools. The ascoglossan's phenology and demography differs between N.E. and N.W. New Zealand shores. In the Hauraki Gulf (N.E. shore), S. felinus inhabits pools all year, occurring in 26% of the small, shallow Chaetomorpha pools surveyed. Recruitment peaks in summer, and mean slug length peaks in winter. At Piha (N.W. shore), S. felinus is common and large during winter and spring; the species' absence during summer is not attributable to food availability or physical conditions of tidepools. Slugs are tolerant of a wide range of salinities (9 to 60 ppt). Egg mass production and tenacity of adults and developmental rate of encapsulated embryos decline at extreme salinities. Thus, suboptimal tidepool conditions delay ascoglossan embryonic development and larval hatching until pools are flushed with fresh seawater and planktonic larvae can emigrate. This strategy differs markedly from the accelerated development of larval chironomids and amphibians inhabiting transient rain pools.

Effects of gonadotropin releasing hormone analogue, human chorionic gonadotropin and gonadal steroids on milt volume in the New Zealand snapper, Pagrus auratus (Sparidae)

Sexually mature male snapper ( Pagrus auratus) were captured from the Hauraki Gulf in northeastern New Zealand by long-lining, and treated with exogenous hormones within 2 days of return to the laboratory. Plasma and milt samples were taken up to 24 h post-injection (p.i.) and plasma concentrations of 17 α-hydroxyprogesterone (17P), 17 α,20 β-dihydroxy-4-pregnen-3-one (17,20 βP), testosterone (T) and 11-ketotestosterone (11KT), and milt volume were determined. Gonadotropin releasing hormone analogue (100 μg·kg −1) stimulated increases in milt volume at 4 and 24 h p.i., accompanied by significant increases in plasma T and 11 KT at 24 h p.i. Injection of human chorionic gonadotropin (1000 U·kg −1) also resulted in an increase in milt volume, and plasma levels of T only. Treatment with 17P and 17,20 βP (0.5 mg kg −1) both stimulated increases in milt volume by 24 h p.i., whereas treatment with 17 α,20 α-dihydroxy-4-pregnen-3-one, T and 11 KT did not. Injection of 17P resulted in only a small elevation in plasma 17P (2 h p.i.), but an increase in plasma 17,20 βP that was larger than that resulting from injection with 17,20 βP. Taken together, the results indicate that the increase in milt volume is at least partially gonadotropin (GtH)-dependent, and possibly mediated by 17,20 βP. The failure to detect increases in plasma 17,20 βP in response to treatments designed to increase GtH may be explained by the rapid metabolism and clearance of 17,20 βP from the plasma.

Calcification rates of rapidly colonising bryozoans in Hauraki Gulf, northern New Zealand

Abstract Very little is known about calcification rates of bryozoans, despite their importance in modern temperate‐latitude shelf carbonate sediments and in temperate limestones. Here we report the carbonate production rates for 19 species of bryozoans over 3, 9, and 12‐month periods from a settling experiment in 14 m water depth at Cape Rodney, Hauraki Gulf. Based on the larger bryozoan colonies, estimates of calcification rate range from 25 to 740 mg CaCO3 y‐1. Extrapolation of calcification rate to overall bryozoan sediment production is not straightforward, but a value of 24–240 g CaCO3 m‐2 y‐1 for the sample site has been determined, equivalent to a sediment accumulation rate of 4–40 cm per 1000 years (ky). In reality, over a large shelf region both dilution by other organisms and a patchy areal distribution of living bryozoans would reduce these values to only a few cm ky‐1. The relatively low rates of accumulation deduced here are mainly consistent with the few other studies of bryozoan sedimentati...

Reproductive biology and endocrinology of female red gurnard, Chelidonichthys kumu (Lesson and Garnot) (family Triglidae), from the Hauraki Gulf, New Zealand

Red gurnard, Chelidonichthys kumu, were sampled by long-lining and from a fish processing factory to investigate the seasonal cycle of reproduction in a population from north-eastern New Zealand. Female red gurnard showed changes in gonadosomatic index (GSI) and frequencies of stages of ovarian development consistent with spawning from spring (September) until autumn (May). Peak GSI (approximately 6%) occurred in late spring or early summer, and minimum GSI (approximately 1%) occurred in winter (June). Blood samples were taken from live fish caught on long-lines, and seasonal changes in plasma concentrations of oestradiol-17� (E2) and testosterone (T) were measured by radioimmunoassay. Plasma E2 and T reached maximum concentrations of 1.99 ng mL-1 and 2.06 ng mL-1, respectively, as GSI levels peaked, and then declined as GSI decreased over summer. Plasma E2 and T increased again as GSI began to increase prior to the next spawning season. Maximum hepatosomatic index (HSI) occurred in association with gonadal recrudescence. HSI decreased significantly as the spawning season progressed and showed a significant but irregular increase as recrudescence occurred prior to the following spawning season.

Plasma levels of sex steroids during sexual maturation of snapper, Pagrus auratus (Sparidae), caught from the wild

Snapper, Pagrus auratus, were caught by baited hook from the Hauraki Gulf, northeast New Zealand, from April (autumn) 1990 to January (summer) 1991. Fish were blood-sampled immediately upon being taken aboard the vessel. From April to August, all female fish caught were sexually immature, the first ovulated fish was caught in late September and, thereafter, they occurred through to December. Male fish caught from April to July were sexually immature, the first spermiating fish was caught in October and they occurred through to January. In females, plasma estradiol (E 2) increased from low levels in sexually immature fish, to peak (0.93 ng ml −1) in fish undergoing ovarian recrudescence and ovulation. Plasma testosterone (T) levels followed a similar pattern to E 2, with a maximum mean of 0.63 ng ml −1. There was evidence that levels of both of these steroids changed according to time of day during the spawning season. Levels of 17 α,20 β-dihydroxy-4-pregnen-3-one (17,20 β-P) were low (mean level 0.3 ng ml −1) and did not change significantly with either month or time of day. In males, plasma T level increased from a minimum in sexually immature fish, to peak at 1.1 ng ml −1 in fish undergoing spermiation. Plasma 11-ketotestosterone levels followed a very similar pattern to T levels, but the range of values was greater (max. 2.8 ng ml −1). Levels of both androgens varied according to time of day in spermiating fish. Plasma levels of 17,20 β-P changed significantly with month, and were highest (0.63 ng ml −1) during the period of spermiation, but no change with time of day was apparent. Plasma levels of 17,20 β-P sulphate were determined in selected fish, and were low ( < 1 ng ml −1) at all times. The absence of changes in plasma 17,20 β-P level during sexual maturation in females is at variance with its suggested role in final oocyte maturation in snapper.

Calloria variegata, a new Recent species of brachiopod (Articulata: Terebratulida) from northern New Zealand

A new species of terebratellid brachiopod, Calloria variegata, is described from rocky, subtidal habitats in the Hauraki Gulf, northern New Zealand. The distribution and ecology of C. variegata are compared with the closely related C. inconspicua, and a detailed description of the new species, including loop development, is provided.

An evaluation of two possum trap types for catch-efficiency and humaneness

A padded leg-hold trap (Victor 1½ Soft Catch™) and a kill-trap (Timms™) were compared for their catch-efficiency and humaneness during work on an eradication plan. Forty five Timms and forty Soft Catch traps were set alternately for three nights on two islands in the Hauraki Gulf. The Soft Catch traps were found to be at least three times as efficient as the Timms. No animals escaped from the Timms trap whereas at least 15 possums managed to free themselves from the Soft Catch traps, and these may be trap shy in the future. None of the possums or non-target animals caught in Soft Catch traps sustained significant physical injuries while being held. The majority of animals caught in the Timms trap appeared to have been killed quickly, but there were signs to indicate that several possums may not have died immediately. Both traps caught non-target animals. It appears that the Soft Catch trap is a more suitable trap than the Timms for undertaking a possum eradication programme.

Oocyte maturation and changes in plasma steroid levels in snapper Pagrus (=Chrysophrys) auratus (Sparidae) following treatment with human chorionic gonadotropin

Snapper Pagrus (= Chrysophrys) auratus were captured by long-lining from the Hauraki Gulf, NE New Zealand, and returned to the laboratory. Eighteen female fish were injected with either saline or 1000 U kg −1 human chorionic gonadotropin (hCG). Blood samples were taken at the time of injection and subsequently at 1, 6 and 24 h post-injection (pi). Plasma levels of 17β-estradiol (E 2), 17,20β-dihydroxy-4-pregnen-3-one (17, 20βP), and testosterone (T) were measured by RIA. Seven out of the eleven hCG-injected fish ovulated within 24 h, whereas no control fish ovulated. In fish injected with hCG, plasma E 2 levels were elevated at 24 h pi, 17,20βP levels at 6 h pi, and T at 6 and 24 h pi, relative to controls. In a second experiment, twelve fish were injected with 1000 U kg −1 hCG as before and bled at 0, 4, 7, 13, 17 and 26 h pi. At each sample time a small piece of ovarian tissue was taken from each fish using a 12 G syringe needle introduced through the body wall. Aspirated follicles were measured and then cleared to determine the position of the germinal vesicle. Follicles from six of the fish underwent a significant increase in diameter, accompanied by germinal vesicle breakdown (GVBD) and oocyte hydration. Plasma E 2 and T levels were elevated in fish with maturing oocytes from 13 h pi. 17,20βP showed a peak at 4 h pi, but only in the group of fish in which oocyte maturation did not occur. There was no difference in plasma cortisol levels between fish that showed oocyte maturation and those that did not, suggesting that proximate stress factors were not responsible for the differential response to hCG treatment observed in this experiment.

Growth rate estimates for New Zealand Rig (Mustelus lenticulatus)

Growth rate estimates were obtained for New Zealand rig (Mustelus lenticulatus) by analysing length frequency and tag-recapture data. Rig (0+) sampled by set-net in Porirua and Pauatahanui Inlets grew from about 25-30 cm total length at birth to 46-49 cm at age of about 6 months. Samples of juvenile and adult rig trawled in Pegasus Bay and Hauraki Gulf suffered from under-representation of large adults, probably because of escapement. Growth curves derived from length-frequency analysis indicated that Pegasus Bay males matured at 5.0 years and had a minimum longevity of 12 years. Hauraki Gulf males and females matured at 3.7 and 4.7 years, respectively. Growth rates and ages at maturity fell within the ranges reported for other Mustelus species. Tagging data for South Island rig suggested that females grew faster than males. However, growth rate estimates from length-frequency analysis were 2.7-3.3 times greater than estimates from tagging data, probably because the latter were biased by the combined effects of tagging on growth and set-net mesh selectivity.

Circulation in the Hauraki Gulf, New Zealand

Abstract Results from five current meters moored in Hauraki Gulf are analysed. Tidal flows and the tidal constituents M2, S2, and N2 are deduced. Time series techniques are used to examine the effects of wind stress and the spatial coherence in the flow. It is found that currents of oceanic water, set up under south‐west to southerly directed winds, flow into the Gulf through Jellicoe and Cradock Channels, with those through Cradock Channel probably passing more or less directly out through Colville Channel. A net anti‐clockwise circulation is suggested to occur in the inner Gulf, south of the latitude of Kawau Island. A lack of any particular spectral features and limited spatial coherence suggests that in the Hauraki Gulf, variations in circulation in the 2‐ to 15‐day time band considered are not well defined but that the Gulf responds to external forcing events with transient currents which last typically from 2 to 5 days.

Extracellular organic carbon (EOC) in the genusCarpophyllum (Phaeophyceae): Diel release patterns and EOC lability

Release of extracellular organic carbon (EOC) by the four species of the brown alga genusCarpophyllum was investigated in light : dark incubations of 30 to 40 h duration using a14C-method. Plants were collected during 1986 in the Hauraki Gulf area, Auckland, New Zealand. InC. maschalocarpum (Turn.) Grev. andC. plumosum (A. Richard) J. Ag. rather low release rates in light (2 to 5% of the photosynthetic rates) were followed by high release rates after 4 to 5 h in darkness (10 to 15% of previous photosynthetic rates). The opposite pattern, with high release in light and low in darkness, was found in experiments withC. angustifolium J. Ag. andC. flexuosum (Esper) Grev. The pattern with substantially higher release in dark than in light is observed for the first time. EOC products were dominated by small molecules (<1000 daltons) in all four species and both in light and darkness. Decomposition experiments exhibited a preferential bacterial utilization of low molecular weight products. Thus, a relative enrichment with larger molecules took place. Bacterial conversion efficiencies of EOC in 5-d experiments averaged 0.24 and 0.09 for products released in light and dark, respectively. The rate constants for decomposition of products released in light were lower than for those released in darkness.

A numerical model investigation of the residual circulation in Hauraki Gulf, New Zealand

Abstract The homogeneous residual circulation in Hauraki Gulf arising from the tides, steady winds, and oceanic inflows is considered by use of a depth‐averaged 2‐dimensional numerical model. Vertical current structure of the wind‐driven circulation is derived by using the computed wind‐induced sea surface slopes, the wind stress, and a prescribed vertical eddy viscosity. Tidal residual circulation is weak, less than 0.01 ms‐1 over most of the Gulf. The response of the Gulf to wind‐forcing indicates a preference for north‐west/south‐east directed winds, the flow through the Gulf being more than 3 times as strong as for winds from other directions. Surface currents are mainly in the wind direction, but subsurface currents reveal closed circulation cells in near‐coastal areas. Simple oceanic inflows give rise to water movements which penetrate to the inner part of the Gulf.

Energy Requirements of Australasian Gannets Morus serrator (Gray) at a Breeding Colony

A model and empirical data (based on regurgitation weights from adult gannets and chicks) are used to estimate the energy requirements of the Australasian Gannet during the 1980-81 breeding season at Motukaramarama gannetry in the Hauraki Gulf, New Zealand. The model calculates the daily energy requirements of males, females, non-breeders and chicks using information from a study over three seasons (1978-80) at this gannetry. Output precision of the model is largely determined by a few parameters: the Kendeigh equation for daily existence energy requirements and the proportion of foraging time spent in flapping and gliding flight. The model suggests that two feeds are required per foraging trip to cover the costs of metabolism and rearing a chick. It is estimated that gannets take about 7% of fish production in the Hauraki Gulf within the 61 km² feeding range from Motukaramarama gannetry. This represents approximately a quarter to a third of total predation by seabirds on fish production.

Picophytoplankton in the Hauraki Gulf, New Zealand

Abstract Qualitative and quantitative data for picophytoplankton from the Hauraki Gulf, northeast New Zealand, were gathered from May 1986 to February 1987. Records for both whole and size‐fractionated samples (net‐, nano‐, and picophytoplankton) allowed the relative contribution by the picophytoplankton to total biomass and overall rates of carbon fixation to be estimated. Picophytoplankton represented a mean value of over 30% of the total chlorophyll a in winter and c. 20% in other seasons. In terms of total carbon fixation, values of 23% and 13% contribution were obtained. The picophytoplankton were composed of chroococcoid cyanobacterial cells, 0.7–1.2 μm in diameter, at densities between 103 and 104 ml‐1 together with larger (1–2 μm) eukaryote cells at densities up to 103 ml‐1. Winter counts were lower than those for summer. Cyanobacteria displayed subsurface peak densities higher in the water column than the eukaryotes. The cyanobacterial cells at depth tended to be larger and more brightly fluorescing than those in the surface waters.