Reproduction in Galaxias fasciatus Gray (Salmoniformes : Galaxiidae)

A study of the reproductive cycle was made on Galaxias fasciatus Gray from streams on Banks Peninsula, South Island, New Zealand. There was no spawning migration; adults remained in the usual adult habitat to breed. The course of gonad maturation showed that spawning occurred in the autumn, from the end of April to mid‐June. Most males matured at 2 years of age and most females at 4 years old. Egg numbers in the females varied from 3800 to 23 600. Males were predominant in age groups 1–4, females in the older age groups. Amongst fish of potential breeding age there was an excess of males. Circumstantial evidence suggested that eggs were laid among piles of water‐logged debris lodged in pools and backwaters. The larvae, which are briefly described, probably hatch during floods to be swept quickly downstream to the sea.     

Limnology of Opal Lake

Opal Lake, a cold, acid lake on the central volcanic plateau of the North Island, New Zealand, had an average pH of 4.3 and was highly eutrophic. The biota was less diverse than in neighbouring near‐neutral waters. Macrophytes were rare; phytoplankton were mainly represented by the Chlorophyceae, and there were only 4 zooplankton species. The mean standing crop of macroinvertebrates was 6240 per square metre; this was higher than in other eutrophic lakes in the region and comprised more than 98% chironomid larvae represented by 4 species. Molluscs were absent. The fauna was more diverse than in more acid lakes of the .central volcanic plateau.     

Nursery grounds of Tarakihi (Teleostei: Cheilodactylidae) around New Zealand

Nursery grounds of the tarakihi Cheilodactylus macropterus (Bloch & Schneider) were discovered in 1963–72 mainly off the south‐western coast of the North Island, in Tasman Bay, along the entire eastern coast of the South Island, and around the Chatham Islands. They occurred at depths of 20–100 m, and mostly between 10 km and 30 km from shore. The tarakihi nurseries had a dense and varied invertebrate bemthic epifauna dominated by sponges and small corals. Few signs of nurseries were found in. other New Zealand waters, in spite of the existence of major spawning grounds there. It is not known with which spawning grounds the various nursery grounds are linked.

The Tasman Bay nursery ground is 18–33 km wide and about 75 km long, with a surface area of about 2000 km². There is a rich demersal fish fauna (37 species were recorded) dominated by tarakihi, red gurnard Chelidonichthys kumu (Lesson & Garnot), snapper Chrysophrys auratus (Bloch & Schneider), and leathei'iacket Novodon convexirostris (Guenther). The young tarakihi occur at depths of 20–45 m and concentrate during winter in the warmer deeper water. They first appear in trawl catches in summer, towards the end of their first year (assumed birthdate is 1 March), and stay on the nursery until the age of 3 y. They occur in the deeper water off the nursery during their fourth and fifth year and depart during their sixth year, possibly for the spawning grounds off the west coast of the South Island. The mean lengths at the ages of 15, 27, and 39 months were 12.6, 18.0, and 24.0 cm respectively in 1970. There was some variation in growth rate within the nursery ground, but the age groups could nevertheless be recognised easily from, length frequency modes. Monthly modal lengths showed that growth slows down in winter. Evidence for fluctuations in year class strength was found; year classes 1966 and 1969 were weak and year class 1968 was strong.

The vulnerability of tarakihi less than 4y old to commercial New Zealand trawl gear is low, and the local fishing fleets do no serious damage to the habitat on the nursery grounds. However, a large part of the tarakihi nursery grounds off the east coast of the South Island lies outside the territorial fishing zone. Intensive fishing on these grounds by large foreign vessels using heavy trawl gear could have an adverse effect on the habitat of the young tarakihi in this region.     

Precocious male quinnat salmon oncorhynchus tshawytscha (walbaum) in New Zealand (note)

Samples of yearling parr of quinnat salmon Oncorhynchus tshawytscha (Walbaum) from Lake Heron and the Glenariffe Stream were examined, and precocious ripe males were found. The proportion in the population (29.2%) was higher than is recorded in North America (2.6%).     

Variations in the spores of Myxidium zealandicum Hine, 1975 (Protozoa: Myxosporidea)

Myxidium zealandicum Hine, 1975 was recorded from several tissues in New Zealand freshwater eels. The gills were the most frequent site of infection, but spores also matured on the gill arch, in the skin, and occasionally in the urinary and swim bladders. Thus M. zealandicum is a histozoic species that may have evolved from a coelozoic form.

Variation in spore size (8.0–11.5 jam) was found in relation to site of infection; variation in the number and arrangement of valve striations was also observed. Deposition of fibro‐blasts occurred at all sites of sporogony, except among the goblet cells of the epidermis.

The small size (6.0–10.5μm) of unstriated spores occurring with normal spores in the gills of eels from Lake Otomangakau appeared to be related to the size of the cysts in which they occurred, and to the host Anguilla dieffenbachii.     

Spatial and temporal distribution of landlocked Galaxias maculatus and Galaxias platei (Pisces: Galaxiidae) in a lake in the South American Andes

Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their temporal and spatial distribution, intralacustrine movements (horizontal and vertical), and spawning periods were analysed using several sampling techniques (ichthyoplankton net, seine net, gill net, and baited benthic taps). We identified the early life stages of both species based on their morphology and otolith shape. The free embryos of both species migrate to the limnetic zone, where they coexist as larvae, facing the same food availability and probably the same predation risk. Each species then moves on to its own juvenile and adult habitat: the littoral and benthic zone for G. maculatus and only the deeper benthic zone for G. platei. Their adult habitats and part of their spawning periods partly overlap.     

Tsunami travel times to New Zealand

A table is given for the intervals between the time that a tsunami propagating radially from a distant source first reaches a position 600 nautical miles from Wellington and the times when the tsunami first reaches any of 11 selected places in New Zealand.     

Variation and taxonomic changes in the family Retropinnidae (Salmonoidea)

The family Retropinnidae contains one monotypic genus, Stokellia, in New Zealand, and nine nominal species of Retropinna: five in New Zealand, three in Australia, and one on Chatham Island. Four Chatham Island populations contain much of the recorded range of variation for the family for head length in standard length ratios, numbers of dorsal and anal rays, and numbers of scale rows. These characters are analysed for 29 populations incorporating five nominal species from New Zealand and Chatham Island. When interrelated these characters are shown to be linked (loosely) and high values are typical of coastal populations. When related to latitude their values increase to the south. The reverse trend is found with increase in altitude. Decrease in salinity depresses the values. Area of the lake habitat has little effect.

Observations suggest that size of fish and numbers of teeth vary predictably. Thus all observed variation is related to environmental conditions. The four nominal lake species are submerged in Retropinna retropinna (Richardson), the type species of the genus, which is considered to be highly adaptable rather than highly variable. R. osmeroides Hector is recognised as distinct from R. retropinna on one character and on sympatric distribution. Records of Australian and Tasmanian species suggest that R. victoriae Stokell differs fundamentally from all other species but that R. semoni Weber and jR. tasmanica McCulloch do not differ greatly from R. retropinna Similar environmentally correlated variation is suggested to relate some diadromous species of Galaxias and their lacustrine isolates.     

Spontaneous locomotory activity of Galaxias vulgaris Stokell (Pisces: Salmoniformes)

Feeding of captive Galaxias vulgaris was found to be dependent on open‐water activity. It did not occur when fish remained beneath boulders. Pat'erns of spontaneous locornotory activity of individual fish were recorded to determine potential feeding times. The apparatus used to measure spontaneous locomotory activity is described. Fish were found to be active mainly at night for most of the year, but became predominantly diurnal during the spawning period.     

Limnology of Lake Rerewhakaaitu

The limnology of Lake Rerewhakaaitu (36°18'S, 176° 30'E) was studied at various intervals between 1971 and 1974; comparisons were made between the main lake (area 6.32 km², mean depth 7 m, maximum depth 15 m), and the smaller (0.15 km²) and deeper (mean depth 15 m, maximum 31 m) crater which are connected by a narrow, 1 m deep channel. The main lake was usually homothermal, although temporary stratification periodically occurred, and the oxygen content of the deeper water could be as low as 2 g.m^‐3. The crater showed strong thermal and chemical stratification persisting well into the winter. Its heat budget and other factors related to lake stability are compared with those of some other New Zealand lakes. The failure of the crater to become fully re‐oxygenated during its brief period of homothermy is believed to be related to its morphometry, since the amount of phytoplankton did not appear to be great enough to explain the low levels of dissolved oxygen in the hypolimnion. The hypolimnetic oxygen deficit in 1973–74 was 0.038 mg. cm^‐2.day^‐1. Qualitatively the phytoplankton, usually dominated by desmids, was characteristic of oligotrophic waters, but quantitatively the main lake could be rated as mesotrophic. Differences were also found in the abundance of zooplankton between the crater and the main lake: there were usually more Bosmina but considerably fewer Ceriodaphnia in the main lake which had greater numbers of Piona. Adult Calamoecia were generally more abundant in the crater.     

Distribution and ecology of Nectocarcinus antarcticus and N. bennetti (Brachyura: Portunidae) in the New Zealand region

The distributions of two swimming crabs endemic to the New Zealand region are described, mostly from material obtained at 118 of 2544 New Zealand Oceanographic Institute benthic stations sampled.

Nectocarcinus antarcticus (Jacquinot) was found within the geographic limits 34°S‐51°S and 166° E‐176° W, with concentrations around Cook Strait, the Chatham Rise, Foveaux Strait, and the Auckland Is. N. bennetti (Takeda & Miyake) occurred between 44° S and 53° S, and 165° E and 180°, most frequently in the south and west, on the ‘highs’ of the Campbell Plateau. Although the distributions overlap between 44° S and 51° S, and this overlap zone produced most of the available material, only one joint occurrence of the two species was noted. This apparent separation was not satisfactorily explained by any of the ecological factors recorded. The depth ranges of both species were broadly similar (0–550 m for TV. antarcticus, 20–474 m for JV. bennetti); both were most frequently obtained at depths less than 200 m. Both occurred primarily on the coarser sediment grades, though N. antarcticus occupied a broader range of grades than N. bennetti.

The size ranges of the two species were similar; carapace lengths were 8.0–62.0 mm for N. antarcticus and 5.8–68.0 mm for N. bennetti. The larger specimens of both species were found towards the southern limits of distribution. Larger specimens of N. antarcticus were absent from depths greater than 120 m; smaller N. antarcticus and all N. bennetti occurred throughout their respective depth ranges. Ovigerous N. antarcticus (smallest, 8.8 mm carapace length) were obtained at depths of 17–263 m from May to October; ovigerous N. bennetti (smallest 36.1 mm) were from depths of 150–183 m in May only.     

Biogenic structure and foraging by five species of shorebirds (Charadrii)

Observations were made of the location and duration of foraging by five species of shorebirds in relation to the tubes of Diopatra cuprea (Polychaeta). Infaunal abundances in sites with D. cuprea tubes exceeded those in surrounding tubefree areas (120 individuals vs 29 individuals per 0·01 m², respectively). Of 112 shorebird foraging episodes observed only 4 were in the vicinity of D. cuprea tubes. Despite a greater abundance of prey items around worm tubes, shorebirds avoided feeding in such areas. D. cuprea tubes appear to provide an effective refuge for macrofauna from shorebird predation.     

Hydrozoa (Cnidaria) symbiotic with Porifera: a review

Many hydroids are symbiotic with other organisms. Sponges, because of their complex canal system and their filter‐feeding activity inducing a continuous water flow, are used by numerous species as either exclusive or facultative substrata. The associated hydroid fauna thriving on or inside sponges shows a wide range of relationships with their hosts. Hydroids may be simply epibiotic on sponges, their stolons running on the host surface. Alternatively, the stolons may grow inside the sponge body, the polyps emerging from the sponge surface, having also the possibility of retraction inside the sponge tissue. Finally, stolons and branches may develop deeply inside the sponge body, producing a skeletal network for sponge growth. This paper reviews the described relationships of hydrozoans symbiotic with sponges and reports new observations.     

Life history of Cornularia cornucopiae (Anthozoa: Octocorallia) on the Conero Promontory (North Adriatic Sea)

The life cycle of the stoloniferan Cornularia cornucopiae (Pallas, 1766) (Anthozoa: Octocorallia) was studied from March 2009 to October 2010 on the rocky cliff of the Conero Promontory (North Adriatic Sea, 43°34.865′ N, 13°34.320′ E). In this area the species showed unusual high densities never recorded in other sites of the Mediterranean Sea. The density trend of the species showed a marked seasonal cycle, with a winter minimum of about 1000 polyps m^?2 and a summer maximum of about 30,000 polyps m^?2. In accordance with other Mediterranean literature data, polyps were fertile during spring–summer, from March to August, but the number of eggs per polyp continuously decreased during this span of time. Variations of polyp density were strongly correlated to water temperature, which can be considered the main environmental factor triggering this seasonal behaviour. The possibility, for C. cornucopiae, to face adverse winter conditions is probably related to the presence of a characteristic perisarcal envelope covering the stolon and the calyx of each polyp, which isolates the living tissues from the exterior. During winter, polyps degenerate but the stolons remain dormant inside their envelopes. The perisarc covering represents a morphological convergence of C. cornucopiae with benthic hydrozoans. As the latter, the studied stoloniferans are able to live in habitats characterized by periodic favourable conditions thanks to a seasonal life strategy. A similar trend is shared also by other important components (cnidarians and some sponges) of the filter‐feeding community of the North Adriatic Sea. Differently to the Western Mediterranean basin, this area is characterized by high food availability all year around, so benthic organisms are strongly constrained by the very low winter temperatures.     

Life history of white stumpnose Rhabdosargus globiceps (Pisces: Sparidae) off South Africa

Fishery-dependent and fishery-independent distribution analyses together reveal four discrete areas of white stumpnose Rhabdosargus globiceps abundance between Port Nolloth and the Kei River off the Cape Province of South Africa: the Western Cape (Saldanha Bay), the South-Western Cape, the Southern Cape and the South-Eastern Cape. On the basis of migratory patterns determined from tagging and catch data, and on differences in growth rate and size-at-maturity, it is concluded that these areas of abundance represent four separate stocks. Each stock apparently disperses offshore in winter (to c. 130 m depth) and concentrates inshore (<60 m depth) in response to ocean ographic patterns during summer. Growth rate and size-at-50% maturity (L ₅₀) increased clinally from the South-Eastern Cape through to the South-Western Cape, and in all three regions males matured at larger size than females. Sizes at maturity for male and female R. globiceps were respectively 18.6 and 15.3 cm (fork length, FL) in the South-Eastern Cape, 22.1 and 18.1 cm in the Southern Cape and 24.3 and 23.6 cm in the South-Western Cape. The fitted Von Bertalanffy growth equations for the three regions were: L_t = 349 (1?e^{?0.114(t+3.60)}) mm for the South-Eastern Cape; L_t = 337 (1?e^{?0.207(t+1.05)}) mm for the Southern Cape; and L_t = 379 (1?e^{?0.290(t+0.16)}) mm for the South-Western Cape. Maximum ages recorded in each region were 21 years for the South-Western Cape, 20 years for the Southern Cape and 10 years for the South-Eastern Cape. Lack of older fish in the South-Eastern Cape sample, attributed to inadequate sample size, has probably resulted in overestimates of both L _∞ and K in this region. Spawning is from August to February, with a peak in spring (September–November). Early juvenile R. globiceps recruit into estuarine and surf-zone marine nursery areas at around 2–5cm (±3 months), but move progressively farther offshore with growth; those trawled deeper than 50 m east of Cape Agulhas were predominantly adults (20–35 cm FL). Because of cooler water temperatures west of Cape Agulhas, adults there are found from the surf zone to depths of only 20 m in summer.     

Changes in biomass structure and trophic status of the plankton communities in a highly dynamic ecosystem (Gulf of Venice,Northern Adriatic Sea)

The changes in the plankton biomass structure in relation to nutrient inputs were studied in the Gulf of Venice (Northern Adriatic Sea), an area characterized by a very marked trophic state variability. The investigation was carried out at two stations, in March, May and July 2005 and 2006, considering the whole water column. The size structure (from picoplankton to mesozooplankton) of both autotrophs and heterotrophs was analysed. Signals of diluted waters and nutrient inputs were more marked in 2005 than in 2006. In 2005, the total plankton biomass was almost double (87 ± 37 μg·C·l^?1) that in 2006 (44 ± 26 μg·C·l^?1). The variations were determined mainly by phytoplankton, with a 70% decrease, and a shift from a community dominated by microphytoplankton (49 ± 12%) in 2005 to one dominated by bacteria (43 ± 11%) in 2006 was observed. The relationship between the heterotrophic (H) and autotrophic (A) biomass indicated a rapid decline of the H/A ratio with increasing phytoplankton biomass. This study, although temporally limited, is consistent with the results reported for other marine environments and it seems to confirm the importance of nutrient inputs in structuring the biomass of plankton community.     

Life history and productivity of Pectinaria koreni Malmgren (polychaeta)

Growth, survivorship, reproduction and productivity of a Pectinaria (Lagis) koreni population was studied in Colwyn Bay, from July 1975 to August 1976. The cephalic disc diameter of the worms was chosen as an index of size, after the relations between linear and weight measurements of the body were established. Settlement of Pectinaria was estimated to have occured at the beginning of June, and the whole population had disappeared by April. Growth was initially fast but it ceased completely during the winter, probably due to low temperatures and disturbance by storms. Bundles of gametes first appeared in the coelomic fluid in November, but maturation was not completed before May. Mature ova, 60–65 μ in diameter, were released individually: sperms, a few microns in diameter, were released in bundles. The highest standing crop, 47·5 g m^?2 was present in September and the total production of the cohort during its lifetime was 138·8 g m^?2. The ratio between total production and mean biomass was given by P/B: 7·3.     

Life history and seasonal breeding of the deep-sea annelid Ophryotrocha sp. (Polychaeta: Dorvelleidae)

Shallow-water annelids of the genus Ophryotrocha have become a popular biological system for exploring ecological, behavioral, developmental, and toxicological questions. Here we report on the successful maintenance in holding tanks, complete life cycle, and reproductive phenology of a first deep-water representative that could be used as a model species. This Ophryotrocha, which has yet to be formally described, is large (12–16 mm long) and exhibits simultaneous hermaphroditism. Specimens collected off northeast Newfoundland (eastern Canada) between 500 and 1500 m depth were monitored under flow-through laboratory conditions for over three years. They consistently exhibited seasonal feeding from April to February, followed by a reproductive season between February and May. Gametogenesis was initiated in early January and completed in early to mid-February, followed by courtship, which mainly involved pairs of individuals attached head to tail for hours to days. Transparent gelatinous masses containing 80–110 eggs were laid from mid-February to late-March. Propagules developed in the mass to the 1-chaetiger stage and, at an ambient temperature of ~1–4 °C, offspring emerged 30–45 days post-laying. Only ~40–45% of the eggs laid developed to the 1-chaetiger stage, with evidence of adelphophagy. After emerging from the gelatinous mass, 1-chaetiger stages remained aggregated and were guarded by adults for a few days before dispersing. All parents died following the dispersal of their offspring. The new generation reached sexual maturity in 8–9 months and was ready to reproduce the following January–February. A few cases of segmenting adult worms were also observed. Three complete generations developed successively to sexual maturity over the course of this study.     

Population variations in the grazing turbinid Lunella smaragda (Mollusca: Gastropoda)

The grazing turbinid gastropod Lunella smaragda was sampled regularly over 3.5 y from precise sites of different microtopography and height on the platform shore at Goat Island Beach near Leigh, Northland, New Zealand. Growth is linear for over 3 y, and the year‐classes distinct. The position of the different size‐classes is related to both the shelter afforded by the microtopography, and to the height on the shore. The populations in the mid‐eulittoral turf flats, low eulittoral bare rock areas, and the sublittoral fringe are distinct, and there is a general movement down the shore with age and size. Wave action apparently dislodges the animals from higher areas when they grow to a critical size and transports them to sites lower on the shore, where wave disturbance is less. Field experiments with marked animals and laboratory studies with a wave tank confirm that the wave‐effected distribution is size related. However measurements showed that the ratio of foot attachment area to the shell area presented to the wave does not vary with animal size. The possible benefits of wave dislodgment and wave‐effected distribution are considered.