Contrast in the importance of arrow squid as prey of male New Zealand sea lions and New Zealand fur seals at The Snares,subantarctic New Zealand

New Zealand sea lions (Phocarctos hookeri) are threatened by incidental bycatch in the trawl fishery for southern arrow squid (Nototodarus sloanii). An overlap between the fishery and foraging sea lions has previously been interpreted as one piece of evidence supporting resource competition for squid. However, there is currently no consensus about the importance of squid in the diet of New Zealand sea lions. Therefore, we investigated this importance independently of spatial and temporal differences in squid availability through a simultaneous study with sympatric New Zealand fur seals (Arctocephalus forsteri), a species known to target arrow squid. Diet sampling at The Snares (48°01′S 166°32′E), subantarctic New Zealand, in February 2012 coincided with peak annual catch in the nearby squid fishery. Diets were deduced by analyses of diagnostic prey remains from scats (faeces) and casts (regurgitations). The contribution of each prey species to the diet was quantified using the per cent index of relative importance (% IRI) that combined frequency of occurrence, mass and number of prey items. Arrow squid was a minor component in sea lion scats (2 % IRI), and none was found in their casts. In contrast, arrow squid was the major component in fur seal scats and casts (93 and 99 % IRI, respectively). This study found that New Zealand sea lions ate minimal squid at a time when squid was clearly available as evidenced by the diet of New Zealand fur seals; hence, there was no indication of resource competition between sea lions and the squid fishery.     

Glucosephosphate isomerase genotype frequencies,homozygous excess and size relationships in the sand flounder Rhombosolea plebeia

Genetic variation was studied at two polymorphic loci for 3 yr (November 1978–February 1982) in juvenile sand flounder (Rhombosolea plebeia) in Wellington Harbour, New Zealand. The Gpi-1 locus showed a heterogeneity in genotype frequencies, but this was not clearly related to season or to fish length. At the Gpi-2 locus, genotype frequencies were dependent upon length and showed a significant excess of homozygotes in juveniles but not in adults. This latter phenomenon has been reported previously in several species of marine molluscs, and so may be common to marine organisms producing large numbers of pelagic larvae. Reasons for the excess of homozygotes are discussed, and it is suggested that assortative mating is the most likely explanation and that this is an area of marine population genetic research which has been over-looked.     

Temporal stability of genetic population structure in the New Zealand snapper, <Emphasis Type="Italic">Pagrus auratus</Emphasis>, and relationship to coastal currents

Genetic diversity and population structure of snapper (Pagrus auratus, Bloch and Schneider), a coastal demersal sparid fish, were determined using six nuclear microsatellite loci and SSCP (single strand conformational polymorphism) analysis of themitochondrial (mt) DNA D-loop in samples collected across the range of the species in New Zealand. Microsatellite data showed similar results to allozyme data collected in the late 1970s that found differentiation between the north-east and southern populations. In addition, an isolated population of snapper in Tasman Bay was identified. The two data sets provide evidence for the temporal stability of the genetic population structure of snapper over 22 years, with differentiation over relatively small spatial scales separated by oceanographic boundaries rather than isolation by distance. In contrast to nuclear markers, mtDNA did not reveal any significant genetic heterogeneity among samples.     

Marine biogeographic disjunction in central New Zealand

We present a phylogeographic analysis of an abundant New Zealand endemic sea-star, Patiriella regularis, to help pinpoint the location of an important biogeographic disjunction in central New Zealand. The analysis incorporates 284 mtDNA control region sequences (approximately 800 bp) of P. regularis from 22 coastal locations around New Zealand. We detected 132 haplotypes, with a mean divergence of 0.96%. AMOVA analysis of New Zealand samples is consistent with a north-south biogeographic disjunction across central New Zealand (among-group genetic variance=6.10%; P=0.0005). Cook Strait, the shallow marine strait separating the main islands, is not correlated with the disjunction: samples from northern South Island are genetically indistinguishable from North Island samples (variance=1.69%; P=0.073). These results are consistent with the hypothesis that upwelling zones south of Cook Strait constitute a significant barrier to larval dispersal.Communicated by M.S. Johnson, Crawley     

Allometry and growth of the green-lipped mussel Perna canaliculus in New Zealand

Length is the most precise (and the most practical) linear measurement for predicting total weight (r>0.98 at P=0.001) in the green-lipped mussel Perna canaliculus Gmelin. The allometry varies with the environmental conditions under which the mussels grow, resulting in morphologically distinct forms of raft- and shore-grown mussels. Mussels grown intertidally are wider, less high and heavier than mussels of similar length grown in suspension. Increase in length and total weight of P. canaliculus grown in suspended cultivation was recorded at 8 experimental sites around New Zealand, during 1973–1975. Comparisons are drawn with growth on an intertidal mussel bed, where length increase was less than half that in the same period in suspension. The growth rate of mussels transferred from intertidal to suspended conditions depends on the size at transfer. Close similarity in growth rate occurred at the majority of sites in spite of a direct correlation between water temperature and length increment and substantial, differences in temperature between sites. Reasons for the uniformity are suggested. Average values for growth at sites over the northern half of New Zealand were 73 mm length (32.5 g weight) after 12 months, 113 mm (110 g) after 2 years. Growth continued throughout the year, highest growth rates corresponding to highest water temperatures. Variation due to depth was not significant. Larger mussels grew more slowly. P. canaliculus can be grown in suspended cultivation in New Zealand at a rate comparable to that in other commercial mussel-farming areas.     

Seasonal growth of the giant kelp Macrocystis pyrifera in New Zealand

The seasonal growth pattern of Macrocystis pyrifera (L.) C. Agardh in New Zealand was determined from measurements of blade-elongation rates between March 1986 and December 1987. Growth rates remained relatively constant throughout most of the year, but declined significantly during the summer months. Seawater nitrate levels had a marked seasonal cycle, with concentrations of 0.3 μM detected in summer. The timing of the decline in internal nitrogen concentrations varied for different-aged blades, but occurred ∼1 mo after the decrease in seawater nitrate concentrations. Sufficiently high irradiance levels and seawater nutrient concentrations support active growth for most of the year, but growth is nutrient-limited during summer. No carbon accumulation during summer was observed. Between March and August 1988, growth estimates were also derived from node-initiation rates and stipe-elongation rates to permit comparisons with previous studies from the northern and southern hemispheres. Direct comparisons of the three growth parameters determined for non-terminated canopy and sub-surface fronds were used to assess possible differential resource allocation in the two frond classes. Received: 16 May 1997 / Accepted: 28 May 1997     

Condition cycle of the green-lipped mussel Perna canaliculus in New Zealand

The condition of the green-lipped mussel Perna canaliculus (Gmelin) from 7 sites around the northern half of New Zealand was determined monthly between December 1973 and February 1975. Seven separate estimates of condition were calculated for each sample; 4 condition indices, 2 percentage glycogen analyses and 1 estimate of percentage solids. All showed a similar annual cycle, with minimum values in winter (June/ August) rising to peak levels in spring (October/ December). The 7 sites were divided into 3 groups, (i) a central New Zealand group, characterised by high levels of condition index (CI) throughout most of the year >10 CI_weight for 8 to 11 months, average to high percentage glycogen (annualmeans 25 to 35% dry weight), and high percentage solids (annual means > 20% dry weight); (ii) an intertidal group, having low levels of CI (<10 CI_weight for 10 to 11 months), low percentage glycogen(mean <20%), and low percentage solids (mean <18%); and (iii) a northern group, showing intermediate values for each of the estimates of condition. Difficulties in defining the causes of changes in the condition cycle are discussed. There is an inverse relationship between CI and mussel size, resulting from changes in body proportions. An inverse relationship is also suggested between CI and water temperature. A precise index, $$CI_{weight} = \frac{{100 \times dry meat weight}}{{whole{\text{ weight - shell weight}}}}$$ is recommended for biological studies on mussels and a rapid simple index, $$CI_{commercial} = \frac{{100 \times wet meat weight}}{{whole{\text{ (live) weight}}}}$$ for use in the field and in mussel farming practice.     

Morphology and growth of the giant kelp Macrocystis pyrifera in New Zealand and California

At three sites (Papanui Inlet, Aquarium Point and Seacliff) on the Otago coast of New Zealand and at one site (Point Loma) off southern California, morphometric and shortterm growth measurements were made of single fronds of plants of Macrocystis pyrifera (L.) C. Ag. near the time of the autumn equinox, in 1977. Near the apex, internodes and laminae were shorter in wave-exposed Seacliff and California populations than in those of Papanui Inlet and Aquarium Point in strong currents, although lamina thickness was similar. In the immature region near the apex, linear relationships were apparent from double logarithmic plots of stipe distance from apex vs node number, internode fresh weight vs length (different in the two areas), lamina width vs length, fresh weight vs lamina area and immature lamina, pneumatocyst and internode fresh weight vs node number. Morphologically, Seacliff plants resembled those in California more closely than those in the other New Zealand populations. The relative growth rate in length of stipe internodes decreased linearly with the logarithm of the distance from the apex, but was less closely related to node number. Extrapolation gave zero growth at 1.6 m at Aquarium Point and 2.9 m in California, where the internode lengths coincided with a change in their weight/length relationship. Slow relative growth proximal to these points indicated a different type (mainly elongation). It is suggested that the first, apical, type of growth, being apparently unrelated to frond length, would be a useful measure of activity over short time-periods. The relative growth rate in lamina area (and probably volume), while also related to distance from the apex, showed a very different pattern, increasing slightly to a peak at 100 to 200 mm and declining to nil by 1 m at Aquarium Point and 2 m in California. Maximal lamina size was maintained for only 10 to 15 nodes at Aquarium Point. Calculated node initiation frequencies were 2.7 d at Papanui Inlet, 2 d at Aquarium Point, and 1 d in California. At the latter sites it took about 2 mo for laminae and 2^1/2 mo for stipe internodes to mature. Deduced relative growth rates in stipe tissue and pneumatocyst fresh weight decreased from 0.24 (log_e units per day) at the apex to 0.11 at 200 mm, where basal lamina tissue had a rate of 0.29, a doubling in just over 2 d. The production of tissue per frond was estimated as 25 and 36 g fresh wt d^-1 at Aquarium Point and in California, respectively.     

Flower color influences insect visitation in alpine New Zealand

Despite a long-standing belief that insect pollinators can select for certain flower colors, there are few experimental demonstrations that free-flying insects choose between natural flowers based on color. We investigated responses of insect visitors to experimental manipulations of flower color in the New Zealand alpine. Native syrphid flies (Allograpta and Platycheirus) and solitary bees (Hylaeus and Leioproctus) showed distinct preferences for visiting certain flower species. These responses were determined, in part, by flower color, as insects also responded to experimental manipulations of visible petal color in 7 out of 11 tests with different combinations of flower species and insect type. When preferences were detected, syrphid flies chose yellow over white petals regardless of flower species, whereas Hylaeus chose white over yellow Ourisia glandulosa. In some cases, the strength and direction of color preference depended on the context of other floral traits, in which case the response usually favored the familiar, normal combination of traits. Syrphid flies also visited in response to floral morphological traits but did not show preference based on UV reflectance. The unusually high preponderance of white flowers in the New Zealand alpine is not explained by complete generalization of flower color choice. Instead, the insect visitors show preferences based on color, including colors other than white, along with other floral traits. Furthermore, they can respond in complex ways to combinations of floral cues, suggesting that traits may act in nonadditive ways in determining pollinator visitation.     

Reproduction in the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

This study investigates the reproductive periodicity and reproductive output of the seagrass Zostera novazelandica on two intertidal reefs. Peak numbers of flowering shoots occurred during March (late summer) of two years at both sites and no flowering shoots occurred during the winter months of July to September. There were greater numbers of flowering shoots in seagrass patches in the low intertidal zone (up to an average of 55 per 0.1 m²) compared to the middle (up to 20 per 0.1 m²) and upper (up to 9 per 0.1 m²) zones, and about three times greater reproductive output in patches associated with tidepools compared to those not bordering tidepools. The average number of inflorescences per shoot was 3.1 (±0.25) at one site vs 1.2 (±0.08) at the other, and showed a progressive decrease from the lower shore to the upper shore. Patches associated with tidepools had twice the number of inflorescences per shoot (2.8 ± 0.24) than patches not bordering tidepools (1.5 ± 0.16). The number of flowering shoots was highly correlated with leaf width, leaf length, and ramet density, while the leaf-area index decreased from the lower shore to the upper shore. The reproductive effort of plants, as measured by the percent biomass invested in flowering shoots during peak reproduction, was significantly different between sites, tidepool associations, and shore level. For all the variables measured, there was considerable spatial variation, with significant interaction terms between most factors investigated. In laboratory experiments, more inflorescences were produced at light intensities of 30 and 300 μE m⁻² s⁻¹ than at 100 μE m⁻² s⁻¹. At a salinity of 17‰, 1.5 × the number of flowers was produced than at 33‰, while none was formed at 70‰. Plants cultured at 5 °C had about three times the number of inflorescences than those at 15 °C, while none was formed at 25 °C. Received: 25 June 1997 / Accepted: 24 September 1997     

Effects of nutrition and temperature on metabolic enzyme activities in larval and juvenile red drum,Sciaenops ocellatus,and lane snapper,Lutjanus synagris

The metabolic enzyme activities were determined in larvae of red drum, Sciaenops ocellatus, and lane snapper, Lutjanus synagris, to determine the effect of temperature and nutrition on metabolic enzyme activities and to evaluate if metabolic enzyme activities are useful in assessing the feeding condition of larval fish. During experiments conducted during the spring of 1990, lactate dehydrogenase (LDH) activities in both red drum and lane snapper were approximately an order of magnitude lower than values typical for adult fish; LDH and citrate synthase (CS) activities increased during early developmental stages, but nutritional effects were apparent. Clear differences (up to 4-fold) between well-fed and starving fish were evident in both LDH and CS activity in red drum. Differences between well-fed and poorly fed larvae were evident until 9 d after hatching. Lane snapper larvae reared at a 25°C had significantly lower LDH activities than larvae reared at 28°C.     

Aboveground and belowground effects of single-tree removals in New Zealand rain forest

There has been considerable recent interest in how human-induced species loss affects community and ecosystem properties. These effects are particularly apparent when a commercially valuable species is harvested from an ecosystem, such as occurs through single-tree harvesting or selective logging of desired timber species in natural forests. In New Zealand mixed-species rain forests, single-tree harvesting of the emergent gymnosperm Dacrydium cupressinum, or rimu, has been widespread. This harvesting has been contentious in part because of possible ecological impacts of Dacrydium removal on the remainder of the forest, but many of these effects remain unexplored. We identified an area where an unintended 40-year "removal experiment" had been set up that involved selective extraction of individual Dacrydium trees. We measured aboveground and belowground variables at set distances from both individual live trees and stumps of trees harvested 40 years ago. Live trees had effects both above and below ground by affecting diversity and cover of several components of the vegetation (usually negatively), promoting soil C sequestration, enhancing ratios of soil C:P and N:P, and affecting community structure of soil microflora. These effects extended to 8 m from the tree base and were likely caused by poor-quality litter and humus produced by the trees. Measurements for the stumps revealed strong legacy effects of prior presence of trees on some properties (e.g., cover by understory herbs and ferns, soil C sequestration, soil C:P and N:P ratios), but not others (e.g., soil fungal biomass, soil N concentration). These results suggest that the legacy of prior presence of Dacrydium may remain for several decades or centuries, and certainly well over 40 years. They also demonstrate that, while large Dacrydium individuals (and their removal) may have important effects in their immediate proximity, within a forest, these effects should only be important in localized patches containing high densities of large trees. Finally, this study emphasizes that deliberate extraction of a particular tree species from a forest can exert influences both above and below ground if the removed species has a different functional role than that of the other plant species present.     

新西兰保护区管理及其对中国的启示

在分析了新西兰保护区的管理体系、管理模式、法律政策和资金来源基础上,从建立完善的保护区管理体系、完善法律政策、有节度的开放式管理、公众参与、加大保护区科研投入以及资金筹集与国际合作6方面探讨了新西兰保护区管理的成功经验对中国的启示。     

Habitat-specific variation and performance trade-offs in shell armature of New Zealand mudsnails

Studies documenting phenotypic variation among populations show that ecological performance in one activity is sometimes traded off against another. Identifying environment-specific costs and benefits associated with performance trade-offs is fundamental to knowing how conflicting selection pressures shape phenotype-environment matching in populations. We studied phenotypic variation in shell armature (spininess) of the New Zealand mudsnail, Potamopyrgus antipodarum (Gray), and explored how this variability relates to performance trade-offs between flow resistance and predator deterrence. Smooth- and spiny-shell morphotypes exist in populations in New Zealand streams and lakes, but the patterns and correlates of spatial variation of these phenotypes, and the possible hydrodynamical constraints and antipredatory benefits associated with spiny shell armature, are unknown. Samples from 11 rivers and nine lakes on the South Island showed that, on average, nearly 70% of snails in streams were smooth-shelled, whereas >80% of snails in lakes were spiny, suggesting dissimilar selective pressures between habitats. A laboratory flume experiment revealed that spines collected seston (i.e., suspended algae) at current speeds <40 cm/s, making spiny morphs more prone to flow-induced dislodgment than smooth morphs. However, a fish feeding experiment showed that one benefit of spines on shells was a decrease in predation risk from the common bully (Gobiomorphus cotidianus), a widespread predator of mudsnails in both streams and lakes. All snails egested by bullies were dead, further suggesting that these fishes may exert strong lethal effects on mudsnail populations in nature. Spine expression in lakes also appeared to be temperature related. We conclude that functional trade-offs between risk of flow-induced dislodgment and risk of fish predation affect shell armature frequencies of Potamopyrgus in freshwater habitats.     

Survival and Recruitment of Captive-Reared and Wild-Reared Takahe in Fiordland, New Zealand

Captive rearing for release back into the wild is considered a useful management tool for endangered species because it can potentially increase the rate of recruitment by bypassing the early, high-risk stages in an individual's life history. In evaluating the benefits of captive rearing to conservation, it is important to monitor the survival rate of animals after release, to be sure that they have the skills necessary for survival in the wild. Using radio telemetry, we compared the movement and survival of captive-reared Takahe (  Porphyrio mantelli), a large flightless rail endemic to New Zealand, to wild-reared Takahe in the rugged mountains of Fiordland over a 5–year period. The results indicated that captive-reared birds survived at least as well as wild-reared birds. Survival of wild-reared Takahe up to 1 year of age, which is prior to the release of captive-reared birds, was poor over two winters marked by particularly cold temperatures, which made the benefits of captive rearing more pronounced. Differences in post-release movements and habitat selection of the two groups did not have a detrimental effect on survival rate of captive-reared birds. Although there was no difference in the survival rate of captive-reared females versus males, eight out of nine (89%) surviving females have formed pairs since their release compared with only two of eight (25%) males. This unexpected result suggests there may be a shortage of females in the wild population. We conclude that captive rearing for release back into the wild increases the adult Takahe population in Fiordland.     

Habitat modification affects recruitment of abalone in central New Zealand

The habitat experienced during early life-history stages can determine the number and quality of individuals that recruit to adult populations. In a field experiment, biogenic habitat complexity was manipulated (presence or absence of foliose macroalgae) at two depths (2–3 m and 5–6 m) and the habitat-dependent effects on recruitment of the black foot abalone (Haliotis iris) were examined at three field sites along the south coast of Wellington, New Zealand (41°20′S, 174°47′E), between July and November 2005. Recruit density (<5 weeks post-settlement) was measured on cobbles covered with crustose coralline algae. Habitats of low complexity (barrens treatments) had consistently greater densities of recruits than habitats of high complexity (algae treatments). However, recruits in algae habitats were larger, and for deep habitats, there was greater survival in algae habitats compared with barrens habitats. While depth had no significant effect on early recruit (<2 weeks post-settlement) density, late recruit (<5 weeks post-settlement) density was greater in shallow habitats, and so it seems recruit survival was greater in shallow habitats. In this experiment, algal habitat complexity had strong effects on early recruit abundance, but habitat-dependent variations in recruit growth and survival may modify initial patterns of abundance and determine recruitment to adult abalone populations.     

Hagfish in the New Zealand fjords are supported by chemoautotrophy of forest carbon

Forest litter is often considered to be a minor energy source to marine communities due to its refractory nature. Large volumes of forest litter are deposited in the New Zealand fjords, and likely recycled into available energy by microbial activity. In this study we used evidence from stable isotope analyses to test whether recycled carbon from chemoautotrophs was an important contributor to the diet of hagfish (Eptatretus cirrhatus). We then analyzed fatty acid biomarkers from the chemoautotrophic clam Solemya parkinsoni and E. cirrhatus to further discriminate the contribution of marine, terrestrial, and chemoautotrophic sources. Bulk isotopic signatures of E. cirrhatus varied considerably (delta13C, from -29.2 per thousand to -16.7 per thousand; delta15N, from -2.8 per thousand to +15.5 per thousand; delta34S, from -21.7 per thousand to +16.7 per thousand) and indicated that a significant percentage of organic matter (38-51%) originated from chemoautotrophs (delta13C, -31.3 per thousand +/- 0.1 per thousand [mean +/- SE]; delta15N, -5.7 per thousand +/- 0.2 per thousand; delta34S, -32.per thousand +/- 3.8 per thousand). Fatty acid biomarkers were depleted in 13C, particularly cis-vaccenic acid (18:1omega7: delta13C, -39.0 per thousand) indicating specific microbial origins of carbon. A high proportion of forest litter in sediments, coupled with isotopic and fatty acid biomarker results, indicates that terrestrial organic matter is a dominant contributor to this marine benthic system. This study demonstrates a clear linkage between terrestrial and marine ecological processes.     

Reproductive periodicity in the euryalinid snake star Astrobrachion constrictum in a New Zealand fiord

The euryalinid snake star Astrobrachion constrictum (Farquhar), a normally deep-water species, exists within SCUBA diving range in New Zealand flords, and thus presents a unique opportunity for study. A population of A. constrictum in Doubtful Sound was investigated from February 1990 to July 1994 to determine the reproductive cycle. Unlike most ophiuroids, the gonads of A. constrictum are positioned along the aboral coelom in the proximal portion of the arms. The proximal 2 to 3 cm of the arms of individuals were thus removed on an approximately monthly basis for histological examination of the gonads. Image analysis was used to determine oocyte size-frequency distributions. A gonad index was calculated for each individual based on the ratio of cross-sectional area of the gonads to cross-sectional area of the arm. Maturity indices were calculated based on stage of development of the gonads of each individual. A. constrictum has a period of enhanced breeding activity in April–June, after which both the gonad and maturity indices decline. The increase in gametogenic activity during these months was correlated with rising sea temperature within the fiord. Although the females showed an annual pattern of gonad development, oogenesis was continuous throughout the year, with oocytes at different stages of development present in the gonads. Males also showed continuous spermatogenesis and, although the same annual pattern of gonad development was evident as seen in the females, it was less marked. The presence of females with large oocytes and ripe males throughout the study indicates that breeding in the Doubtful Sound population is prolonged, and possibly continuous, as found in many deep-sea ophiuroids.     

Population genetic variation in the New Zealand greenshell mussel: locus-dependent conflicting signals of weak structure and high gene flow balanced against pronounced structure and high self-recruitment

A pronounced north–south multitaxon genetic discontinuity occurs in central New Zealand (NZ). Polymorphic microsatellite markers have been used to test the location and structure of this discontinuity in the endemic greenshell mussel, Perna canaliculus. Nine neutral loci revealed limited evidence of genetic structure, but one outlier locus (Pcan1-27) which may be under selection provided evidence of the discontinuity in central NZ. Whilst the limited multilocus evidence of structure is assumed to result from high levels of gene flow among populations of this continuously distributed species, assignment tests indicated high to very high mean levels of self-recruitment within the 14 populations and the north and south regions. The nine neutral loci were unable to provide further clarification as to the geographic location of the discontinuity, whereas the Pcan1-27 locus was particularly informative. These results highlight a tension between limited evidence of genetic structure and presumptive high gene flow among populations versus high levels of self-recruitment and pronounced structure depending on microsatellite loci and analyses in question. Evidence from all 10 loci indicates that the genetic discontinuity is maintained by high levels of self-recruitment, and evidence from Pcan1-27 suggests that selection may also be important in explaining the existence of the discontinuity.