Heterotrophic bacteria and their relationship with plankton in a New Zealand freshwater lake

The viable heterotrophic bacteria of Lake Grasmere in inland Canterbury (43° 05 S, 171° 45 E) were studied. Numbers of bacteria in water above a spring were positively correlated with rainfall in the 7 days before sampling, but bacteria in open water and from over the macrophyte Elodea canadensis were not. There was some increase in the bacterial population in the water over E. canadensis in the autumn to winter months. Numbers of bacteria in the open water ranged from 55 to 1020 cells per millilitre, and were outnumbered by algae by a factor of between 4 and 34. The bacterial population tended to increase after blooms of zooplankton, but there was little or no response to changes in phytoplankton populations. Benthic bacteria rarely increased in numbers after the deposition of organic matter.     

Migrating eels in a Canterbury river,New Zealand

A fish trap in the upper reaches of the South Branch stream, Canterbury, New Zealand, caught eels from December 1957 to October 1964. The downstream migrations of immature and adult eels of both New Zealand freshwater species (short‐finned Anguilla australis and long‐finned A. dieffenbachii) were recorded. These migrations showed a seasonal and a lunar periodicity, and the larger runs were also influenced by rainfall, water volume, or the passage of a depression. Seasonal peaks were marked for mature eels of both species, and for immature A. australis, but not for immature A. dieffenbachii.     

Early recoveries of fin‐clipped quinnat Salmon in New Zealand (note)

Early Marine Department records (1930–42) show that of about 100,000 parr, of quinnat salmon Oncorhynchus tshawytscha (Walbaum), fin clipped at the Marine Department's Hakataramea Salmon Hatchery in south Canterbury, only 3 were positively recovered; later independent readings of scales from these fish agreed with the known age. A further 11 scale samples (for 1937 and 1939) of fin clipped fish have been read, but details of their recovery and of their fin‐clip combinations cannot be found. Thus, from approximately 100,000 fin clipped parr, only 14 recoveries can be substantiated.     

The Canterbury mudfish,Galaxias burrowsius Phillipps,a vanishing species

Examination of available samples and of ecological knowledge of Galaxias burrowsius Phillipps (Galaxiidae) suggests that this species is confined to the Canterbury Plains and is now nearly extinct.

Possible reasons for its decline are analysed and it is suggested that this decline may have started nearly 1,000 years ago with the changes in the climate‐vegetation pattern. It has been hastened by the recent drastic transformation of the environment by European settlers. Distribution and habitats of two other New Zealand mudfishes, Neochanna apoda and N. diversus (Galaxiidae) are related to those of G. burrowsius     

Pycnogonida of the snares islands∗

Eight species of Pycnogonida collected by University of Canterbury Expeditions and the New Zealand Oceanographic Institute are recorded from the Snares Islands, which lie at 48° 05’ S, 166° 20’ E, 60 miles SW of South Cape, Stewart Island. The following species are recorded: Pallenopsis obliqua (Thomson, 1884), Cheilopallene trappa n.sp., Ammothea magniceps Thomson, 1884, Achelia dohrni (Thomson, 1884), Tanystylum cavidorsum Stock, 1957, Ascorhynchus insularum n.sp., Austrodecus minutum n.sp. and Austrodecus enzoi n.sp.     

Repeated spawning and survival of male quinnat Salmon in New Zealand (note)

In the Marine Department archives, early records (1930–41) of marked parr of quinnat salmon Oncorhynchus tshawytscha (Walbaum) show that some held in freshwater hatchery ponds in south Canterbury survived development of testes for two consecutive years, and that one fish developed testes for three consecutive years and gave indications that it might survive into the fourth. It is generally believed that all wild adults of this species die after one spawning.     

Variability in low tide populations of tuatua,Paphies donacina,in Pegasus Bay,Canterbury, New Zealand

Paphies donacina (Spengler, 1793) populations were surveyed at 11 low tide sites on surf beaches along Pegasus Bay, Canterbury, New Zealand, during summer 1998. Random sampling was not feasible. At the non‐random sites chosen the average number of tuatua per 5 m of shoreline ranged between 0.1 and 62. Total wet weight biomass m^‐2 was highest at the southern sites in the Bay. There were site‐related differences in length frequency distributions of tuatua populations. Northern populations included a wide length range and southern populations were dominated by larger bivalves. Average shell length increased significantly with distance south, being close to 40 mm at Waikuku and 80 mm at Taylors Mistake. The shell length: width and weight relationships were similar for tuatua collected over the whole geographic range. Average dry weight condition index varied significantly between sites (ANOVA F= 23.3, d.f. = 10, 329) depending on the length distribution of the contributing population. Where populations included a wide length range the condition index was positively correlated with shell length but in populations dominated by larger bivalves there was either no relationship or a negative relationship with shell length. Juvenile tuatua were found at average densities between 81 and 1200 m^‐2 at all sites except Taylors Mistake. The mean length of recruits ranged from 2.2 to 3.1 mm and shell length was independent of both juvenile and adult density. These results are discussed in relation to the environmental and other factors thought to influence population structure and recruitment of tuatua in Pegasus Bay.     

Occurrence of gravel in the stomachs of two New Zealand stream‐dwelling fish (note)

Gravel occurred in. the stomachs of 17.8% of 924 Galaxias vulgaris and 2.8% of 430 Philypnodon breviceps taken from the Glentui River, Canterbury, between June 1970 and November 1971. It is suggested that differences in feeding habits and feeding locality are responsible for the difference in occurrence of gravel in the stomachs of the two fish species. Galaxias vulgaris feeds in the water column in riffles and, being a drift feeder, is more likely to ingest inedible material by accident than is P. breviceps, which feeds on the bottom in sheltered or quiet stretches of the river.     

An occurrence of low water temperatures on the north Canterbury coast (note)

A recorded instance of a rapid decrease in sea surface temperature on 10 April 1968 on the north Canterbury coast is found to be caused by increased transport of the Southland Current rather than by wind‐derived upwelling, and shows that gross changes in coastal current characteristics on the north Canterbury coast can occur under particular meteorological conditions.     

Seasonal growth in brown trout in two New Zealand streams

Brown trout Salmo trutta Linn, were marked with individual tags and recaptured throughout a year in two small Canterbury streams. The growth recorded showed a marked seasonal variation which differed in pattern in the two streams. There was a considerable difference in the growth rate between the two populations and fish transferred from the slow‐growth stream to the faster‐growth stream showed an immediate response to the change.     

Pycnogonida of the Antipodes Islands∗

Pycnogonida collected at the Antipodes Islands (49° 45’ S, 178° 45’ E) by the University of Canterbury Antipodes Islands Expedition 1969 and during New Zealand Oceanographic Institute cruises are reported on here, and constitute all material known for this group of animals from these islands. To date eight species are known; two are endemic, (Pallenopsis antipoda n.sp. and Ammothea antipodensis n.sp.); two constitute a circum‐polar element (Tanystylum cayi‐dorsum Stock and Austrodecus breviceps Gordon); the remaining four species are known also from New Zealand mainland waters (Pallenopsis obliqua (Thomson), P. kupei n.sp., Achelia dohrni (Thomson) and Ammothea magniceps Thomson), as is T. cavidorsum. An attempt is made to indicate the range of variation in Achelia dohrni, and Pallenopsis mauii Clark, 1958 is redescribed although not a part of the Antipodes Islands fauna.     

A new species of Zelandobius (Plecoptera: Gripopterygidae: Antarctoperlinae) from the upper Rangitata River,Canterbury, New Zealand

Zelandobius edensis n. sp. is described from a spring‐fed creek in the headwaters of the Rangitata River catchment, South Canterbury, New Zealand. Adult males exhibit varying degrees of brachyptery and the only female collected also had short wings. Larvae are easily identified by their covering of long translucent hairs not found in other members of the Zelandobius confusus‐group. The link between adult and nymph was confirmed by comparing 600‐base‐pair sequences of the mitochondrial gene, cytochrome c oxidase 1. Observations suggest the life cycle may be strongly synchronised by temperature constraints on nymphal growth and development, and/or a short season suitable for feeding and reproduction by the terrestrial adults.     

Conservation status of New Zealand freshwater fish, 2009

The threat status of 74 freshwater and estuarine fish present in New Zealand was determined. Fifty-one native taxa were ranked of which 67% were considered Threatened or At Risk. A single species was classified as Extinct, the New Zealand grayling, which has not been observed since the 1920s. Four taxa were classified in the highest threat category, Nationally Critical, and a further 10 taxa as Threatened (Nationally Endangered or Nationally Vulnerable). Twenty taxa were ranked in the At Risk group with the majority ranked as Declining. Endemic galaxiids (Galaxiidae) dominated the Threatened and At Risk taxa. The majority (68%) belonged to the Galaxias genus, comprising 81% of recognised taxa in this genus and all five species in the genus Neochanna were also ranked as Threatened or At Risk. In addition to 51 native taxa, a further three fish species were considered colonists and 20 introduced species were classified as naturalised, although two of these are considered rare. The majority of the Threatened species occur in the Canterbury and Otago regions where a suite of rare non-migratory galaxiids exist. Threat mechanisms that were identified as causal in the decline of freshwater fish species were the impact of introduced fish species, declining water quality, effects of water abstraction, loss of habitat via land-use change and land-use activities, and river modifications.     

Spatio-temporal variation in species composition of New Zealand's whitebait fishery

ABSTRACT

Whitebait comprise a culturally, commercially and recreationally important fishery in New Zealand, where post-larvae are netted while returning from their marine phase. In this study, we expanded an historical (1964) sampling programme to gain a contemporary understanding of the species composition of the whitebait fishery; 87 rivers were sampled over six months in 2015. Over the entire country, >12 species were found in samples and 87.6% of these were īnanga (Galaxias maculatus). Kōaro (G. brevipinnis) and banded kōkopu (G. fasciatus) were abundant in some rivers and regions at particular times of the year. Buller was the most variable region, spatially and temporally, for species composition; Canterbury was the least variable. Banded kōkopu whitebait migrated one month earlier north of Cook Strait than in the south. There was a positive association between the abundance of kōaro and banded kōkopu in samples and the level of indigenous forest cover in catchments. Compared to samples from 50 years ago, there was a greater proportion of kōaro and banded kōkopu whitebait throughout the country. This spatio-temporal variability requires fishery regulations to be more tailored and flexible if they are to conserve the diversity of life-histories present in the catch and sustain the whitebait fishery.     

Recovery of benthic macroinvertebrate and epilithic communities following a large flood,in an unstable,braided, New Zealand river

Benthic macroinvertebrates and small stones were collected from a riffle in the Ashley River, North Canterbury, New Zealand, on 12 occasions within a 132‐day period following a particularly large flood in 1986. Despite the occurrence of smaller floods during this period, benthic macroinvertebrate communities and stone surface organic layers recovered rapidly. Mean concentration of stone surface organic carbon increased from 0.23 g/m² to 1.01 g/m² stone surface in the first 23 days after the flood and chlorophyll a concentration increased from 0.13 mg/m² (day 3) to 9.2 mg/m² by day 132. Minor floods during the recovery period had little effect on organic layer biomass. Mean faunal density increased from 230/m² to 7920/m² during this time and taxon richness from 7 to 21 per 5 benthic samples. Immediately after the flood and throughout the study period the fauna was dominated by larvae of Deleatidium (Ephemeroptera: Leptophlebiidae), Hydora (Coleoptera: Elmidae), and Chironomidae. Re‐establishment of Deleatidium populations in previously denuded brands was effected by oviposition, egg‐hatching, and larval immigration. Minor braids are likely to represent important epicentres from which recolonisation proceeds.     

Census survey approach to quantifying īnanga spawning habitat for conservation and management

Here, we describe a methodology for quantifying the spawning habitat of īnanga (Galaxias maculatus), a protected native fish species. Our approach is demonstrated with a survey of the Heathcote/ōpāwaho following the Canterbury earthquakes that produced unexpected findings. Spawning habitat was detected over a 2.5?km reach and the area occupied by spawning sites (75m²) was much larger than in previous records (ca.?21m²). Sites dominated by the invasive Phalaris arundinaceae were found to support high egg numbers. Spawning has not previously been recorded on this species and it is identified in the literature as a threat to spawning habitat. Considerable spatio-temporal variation was also detected in the location of spawning sites and pattern of egg production. Together, these aspects illustrate the need for a comprehensive survey methodology to reliably quantify spawning habitat. The Heathcote/ōpāwaho example shows the utility of our census approach for achieving this, and supporting habitat conservation objectives.     

Feeding habits of two fish species in relation to invertebrate drift in a New Zealand river

The relationship between the composition of the invertebrate drift fauna and the feeding habits of the common river galaxias Galaxias vulgaris and the upland bully Phily pnodon breviceps was examined in the Glentui River, Canterbury, New Zealand, between 1500 h on 12 November and 1500 h on 13 November 1971. The drift consisted of both night‐active and day‐active components. Galaxias vulgaris fed mainly at night, with peaks of feeding at dusk and dawn. Philypnodon breviceps had two peaks of feeding, at midday and midnight, between the peak feeding times of G. vulgaris. Feeding of G. vulgaris on its major food items coincided with the presence of the food items in the drift, whereas feeding of P. breviceps did not coincide with the occurrence of the food items in the drift. It is concluded that G. vulgaris is primarily an open‐water feeder and that P. breviceps searches for food on the river bed.     

Diel feeding periodicity of torrentfish (Cheimarrichthys fosteri) in two braided rivers of Canterbury,New Zealand

Torrentfish Cheimarrichthys fosteri Haast were collected at 4‐hour intervals over a full day in winter and summer, 1984–85, from the Ashley and Rakaia Rivers in Canterbury, New Zealand, to determine their diel feeding periodicity. Both populations fed, almost exclusively, from dusk to dawn in both seasons, with the quantity of food in their stomachs accumulating to peak levels by early morning. However, Ashley females had significantly less food in their stomachs than did males in summer, the season with a high incidence (91%) of females in spawning condition. Aquatic stages of Deleatidium spp. (Ephemeroptera: Leptophle‐biidae) and Chironomidae constituted from 85 to 98% by number and 63 to 80% by dry weight of all foods eaten. Chironomids (small prey) comprised up to 85% of the total foods eaten by number but only 17% by dry weight, while Deleatidium (large prey) comprised up to 69% of the prey by number and 63% by dry weight. Numerically, chironomids were an important component in the torrentfish diet in both seasons in the Rakaia (71 to 75%), but only so in winter in the Ashley (85%). The reported daily feeding cycle is consistent with observations in a simulated stream, that torrentfish largely remain inactive during the day and come out to feed at night.     

Growth of red gurnard (Teleostei: Triglidae) from Pegasus bay,Canterbury, New Zealand

Growth of the red gurnard, Chelidonichthys kumu (Lesson and Garnot), from Pegasus Bay, Canterbury, was measured during 1966–67. Otoliths were used as an indicator of fish growth; mean length‐at‐age data were obtained from back‐calculated fish lengths at the time of formation of successive annual rings in the otoliths. Growth in length was found to be adequately expressed by the von Bertalanffy growth equation :

l_t = 52.0 [1 ‐ e‐^{0.406 (t‐o.291)}]

(where l_t is the fork length in cm at age t). The length: weight relationship was:

w = 78.56 × 10^‐4 l ^3.072

(where w is the weight in grams). From this relationship, growth in weight was described by the equation:

w_t = 1469 [1 ‐ e‐0.406 (t‐0.291)]³.     

Population connectivity of an overexploited coastal fish,Argyrosomus coronus (Sciaenidae), in an ocean-warming hotspot

The West Coast dusky kob Argyrosomus coronus is a commercially exploited fish with a distribution confined to the Angola–Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean. A previous study revealed that during a recent period of local warming the species extended its distribution into Namibian waters, where it hybridised with the resident and congeneric Argyrosomus inodorus. Environmental changes are a major threat to marine biodiversity and when combined with overfishing have the potential to accelerate the decline of species. However, little is known regarding the evolutionary history and population structure of A. coronus across the ABFZ. We investigated genetic diversity, population structure and historical demographic changes using mtDNA control region sequences and genotypes at six nuclear microsatellite loci, from 180 individuals. A single, genetically homogeneous population was indicated across the distributional range of A. coronus (φ_ST = 0.041, F_ST = 0.000, D = 0.000; p > 0.05). These findings imply that the oceanographic features within the ABFZ do not appear to significantly influence population connectivity in A. coronus, which simplifies management of the species. However, reconstruction of the demographic history points to a close link between the evolutionary history of A. coronus and the environmental characteristics of the ABFZ. This outcome suggests the species’ vulnerability to the rapid environmental changes being observed across this region, and highlights a pressing need for transboundary management to mitigate the impacts of climate change in this global hotspot of seawater temperature changes.