Showing papers in "New Zealand Journal of Marine and Freshwater Research in 1989"
TL;DR: Feeding habits of co‐existing populations of the freshwater eels, Anguilla australis Richardson (shortfinned eel), and A. dieffenbachii Gray (long‐finnedEel) were studied in Lake Pounui, Wairarapa, finding that both species probably feed intermittently and are opportunistic feeders, consuming a wide range of food items, although feeding of individual eels was normally selective for a single prey species.
Abstract: Feeding habits of co‐existing populations of the freshwater eels, Anguilla australis Richardson (shortfinned eel), and A. dieffenbachii Gray (long‐finned eel) were studied in Lake Pounui, Wairarapa. A combination of sampling equipment gave a sample of 682 shortfinned eels and 310 longfinned eels ranging in length from 13 to 135 cm. Both species probably feed intermittently and are opportunistic feeders, consuming a wide range of food items, although feeding of individual eels was normally selective for a single prey species. Diet of each species changed with size. Smallest eels of both species ate mainly amphiphods and insect larvae; the snail Potamopyrgus antipodarum was the dominant food organism for shortfinned eels of 30–69 cm but was unimportant to longfinned eels. Longfinned eels > 40 cm were principally piscivorous but fish did not become an important part of shortfinned eel diet until eels were > 70 cm. At similar sizes, the two species had different diets. Eels of the same species but fr...
89 citations
TL;DR: Riparian pasture retirement effects on the chemistry of channellised surface run-off from 2 moderately steep hillslopes was examined in a 22-month study as discussed by the authors. But, it was concluded that pasture retirement is an e...
Abstract: Riparian pasture retirement effects on the chemistry of channellised surface run‐off from 2 moderately steep hillslopes was examined in a 22‐month study. Seventy‐one surface run‐off events occurred. They varied in size by about 2 orders of magnitude. Sediment, phosphorus, particulate‐ and nitrate‐nitrogen concentrations in the run‐off (in each event) at retired riparian pasture sites were significantly (P < 0.001) and substantially lower than concentrations in run‐off at grazed riparian pasture sites. Concentrations also varied less extensively at retired sites (P < 0.001). Riparian pasture retirement impacts on total loads were examined by comparing the average concentrations in run‐off in 22 months at retired and grazed sites. These event‐flow‐weighted total and volatile suspended solids, particulate P and N, dissolved P, and nitrate‐nitrogen means were <87%, <84%, < 80%, < 85%, < 55%, and < 67%, respectively, lower at the retired sites. It was concluded that riparian pasture retirement is an e...
74 citations
TL;DR: The effluent characteristics of 11 dairy shed oxidation ponds designed to national specifications were examined in this paper, where measurements covering a wide range of parameters were made monthly over at least 1 year in ponds from two regions (Manawatu and Southland) and covering two types of farms: town milk supply (non-seasonal) and daily factory (seasonal).
Abstract: The effluent characteristics of 11 dairy shed oxidation ponds designed to national specifications were examined. Measurements covering a wide range of parameters were made monthly over at least 1 year in ponds from two regions (Manawatu and Southland) and covering two types of farms: town milk supply (non‐seasonal) and daily factory (seasonal). There was considerable variation in effluent composition within ponds with time and between different ponds. Biochemical oxygen demand (BOD) concentrations (overall median 98 g m‐3; 3‐fold range of individual pond medians) showed less variation between ponds than suspended solids (SS) concentrations (median 198 g m‐3; 9‐fold range). Available nutrient levels were very high (e.g., an overall median of 12.2 g m‐3 for dissolved reactive phosphorus and 75.0 g m‐3 for ammonium (NH4‐N)). The ammonia represents a 4‐fold higher level of potential oxygen demand than the measured BOD. Faecal coliforms (median 70 000 (100 ml)‐1) showed large variability both within a...
69 citations
TL;DR: In an intensive survey of tributaries of the Mokau River, nine native diadrornous and two exotic fish species were recorded in this article, and sites were grouped on the basis of their species composition using the classification procedure 2-way indicator species analysis.
Abstract: Nine native diadrornous and 2 exotic fish species were recorded in an intensive survey of tributaries of the Mokau River. At the site level, species diversity was low and much of the fauna had a very restricted distribution. Sites were grouped on the basis of their species composition using the classification procedure 2‐way indicator species analysis. Four groups of sites were identified, characterised by: (1) a longfinned eel‐elver assemblage; (2) a longfinned eel‐adult redfinned bully assemblage; (3) an inanga‐adult redfinned bully assemblage; and (4) a torrentfish‐bluegilled bully‐redfinned bully‐elver assemblage. Relationships between fish assemblage distribution patterns and environmental factors were examined with multiple discriminant analysis. The overriding feature influencing patterns of fish distribution was the prevalence of diadromy in the fauna with species varying in their ability to penetrate upstream. Distance from the sea and gradient from the river mouth were the environmental...
67 citations
TL;DR: In this article, preliminary oxygen and carbon isotopic analyses were made on otoliths of the common smelt retropinna (Richardson) and compared with the isotopic composition of their habitat waters in Lake Taupo and 5 lower Waikato lakes.
Abstract: Preliminary oxygen and carbon isotopic analyses were made on otoliths of the common smelt Retropinna retropinna (Richardson) and compared with the isotopic composition of their habitat waters in Lake Taupo and 5 lower Waikato lakes. The results, though limited in sample size, suggest that the calcium carbonate forming the otoliths may be precipitated close to isotopic equilibrium with the waters in which the fish live. Furthermore, because the isotopic composition of waters in each of the estuarine, river, and lowland and upland lake environments appears to lie within a specific range, the potential exists for using 18O and 13C abundance in the otoliths to reveal interpopulation variations resulting from differences in migratory behaviour of the smelt between these diverse habitats.
65 citations
TL;DR: C. dubia was more sensitive than D. magna in acute tests with 5 reference toxicants and 2 effluent samples and was recommended as a routine test organism because of its good laboratory growth and higher sensitivity.
Abstract: Four New Zealand cladoceran species (Daphnia carinata, Simocephalus vetulus, Ceriodaphnia dubia, and Ceriodaphnia cf. pulchella) were compared with Daphnia magna for their acute (short‐term) and chronic (long‐term) sensitivity to toxicants. In acute tests with 5 reference toxicants and 2 effluent samples (chromium (Cr6+), pentachlorophenol, boron, fluoride, biocide (Alfloc 324), kraft bleach effluent pond, and a geothermai discharge), C. dubia was more sensitive than D. magna by up to a factor of 4. In chronic tests on 4 toxicants no differences in sensitivity were observed within 1 order of magnitude. Acute: chronic ratios ranged from 1.3 to 13.5. C. dubia is recommended as a routine test organism because of its good laboratory growth and higher sensitivity than D. magna. D. carinata would also be suitable, but both S.vetulus and C. cf. pulchella showed poor laboratory performance.
64 citations
TL;DR: The percentages of trout remaining in the surveyed reaches after the flood were highly correlated with river gradient and instream cover, and largera in bow trout increased substantially whereas that of small fish decreased by 94%.
Abstract: The effects of a major flood on instream habitat and trout numbers in 7 rivers in the South Island, New Zealand, were determined by drift diving (snorkeling) sections of each of the rivers before and after the event. A general coarsening of the substrate was noted in runs and pools but not in riffles. In most of the rivers there was significant scouring of pools but little change of run and riffle habitats. In 6 of the 7 rivers, brown trout (Salmo trutta) abundance decreased significantly, with small fish (10–20 cm fork length) being reduced by 90–100%, medium fish (20–40 cm FL) by 62–87%, and large fish (> 40 cm FL) by 26–57 %. Rainbow trout (Salmo gairdneri) occurred in 3 of the rivers but were not present in 2 of these after the flood. In the third river the abundance of largera in bow trout increased substantially whereas that of small fish decreased by 94%. The percentages of trout remaining in the surveyed reaches after the flood were highly correlated with river gradient and instream cover...
63 citations
TL;DR: Field observations of Mugil cephalus corresponded with limited flume data, suggesting this species is a less vigorous swimmer: water velocities below 0.15 m s‐1 would allow its passage over obstacles less than 5 m in length whereas longer obstacles, without resting areas of static water, may requ...
Abstract: Observations were made of the response to water velocity for upstream migrating juveniles of 5 diadromous native fishes (Anguilla auslralis, Galaxiasmaculatus,Galaxiasfasciatus,Retropinna relropinna, Gobiomorphus colidianus). Swimming performance within a hydraulic flume was measured and observations made of the behavioural adaptions of some species to swim through high water velocities. Timed swimming at known water velocities allowed estimation of critical velocities for fish passage. For juvenile fishes (30–80 mm total length), velocities below 0.3 m s‐1 should allow unrestricted passage over obstacles less than 15 m in length. Water velocities below 0.25 m s‐1 may be necessary for obstacles over 15m. Field observations of Mugil cephalus corresponded with limited flume data, suggesting this species is a less vigorous swimmer: water velocities below 0.15 m s‐1 would allow its passage over obstacles less than 5 m in length whereas longer obstacles, without resting areas of static water, may requ...
60 citations
TL;DR: The use of periphyton to monitor the effects of organic pollution in shallow, swift New Zealand rivers was tested using a slaughterhouse effluent discharge to the South Branch, Canterbury.
Abstract: The use of periphyton to monitor the effects of organic pollution in shallow, swift New Zealand rivers was tested using a slaughterhouse effluent discharge to the South Branch, Canterbury. Eight 1 ‐week long artificial substrate accrual periods were used. A range of taxonomic and biomass determinands were analysed for during the first 2 periods. However, only chlorophyll a, ash‐free dry weight (AFDW) and their derivative the Autotrophic Index (AI), were used for subsequent monitoring as they provided the most efficient means of discriminating the effluent impacts. Intensive chemical monitoring during these first 2 sampling periods identified a highly concentrated organic waste with high daily variability (x total Kjeldahl nitrogen = 5.04 and 1.90 mg 1‐1, %CV = 74 and 79). Effluent volumes were slowly reduced over a 4‐month period. This resulted in reductions in the AI (maximum of 4377 down to 191) of downstream communities and demonstrated the benefit of effluent diversion. The community also res...
54 citations
TL;DR: Galaxias maculatus has considerable potential as a laboratory animal and laboratory techniques used to maintain, artificially spawn, hatch, and rear this New Zealand native freshwater fish are described.
Abstract: Galaxias maculatus has considerable potential as a laboratory animal. Laboratory techniques used to maintain, artificially spawn, hatch, and rear this New Zealand native freshwater fish are described. Potential research applications for the fish, the eggs, and the larvae are outlined. The development of the larvae is described.
54 citations
TL;DR: The study showed that the selected indicators could be detected in groundwater used for domestic purposes, and could be used for assessing whether septic tanks were implicated in contaminated domestic wells.
Abstract: Two indicators of septic tank effluent were measured in a groundwater quality survey of an unsewered, semi‐rural community. The selected indicators were fluorescent whitening agents and sodium tripolyphosphate (STP). Other water quality determinands indicated that the groundwater was of good chemical quality for drinking purposes but, in about half of the wells, levels of total coliform bacteria exceeded New Zealand Board of Health recommended guidelines for drinking water. Fluorescent whitening agents and/or STP were detected in 17% of the samples and concentrations of STP correlated significantly (P<0.001) with levels of faecal coliform bacteria. The study showed that the selected indicators could be detected in groundwater used for domestic purposes, and could be used for assessing whether septic tanks were implicated in contaminated domestic wells.
TL;DR: Shell thickening was found to occur in C. gigas where its incidence was correlated with the TBT body burden, and evidence for the toxic influence of TBT on non‐target organisms in New Zealand is provided.
Abstract: Water and sediment samples were collected from the Waitemata Harbour, Opua Inlet, and Tutukaka Harbour, and analysed for tributyl tin (TBT) using a hydride generation atomic absorption method. Specimens of oysters (Crassostrea gigas, Saccostrea glomerata, Ostrea heffordi) and oyster borer, Lepsiella scobina, were collected from the Tamaki Estuary and surrounding areas. These specimens were analysed for TBT using graphite furnace atomic absorption, and the oyster shell valves were examined for thickening. Concentrations of TBT in the water column were as high as 0.32 μg TBT‐Sn H. Marina sediments contained up to 0.240 μg TBT‐Sn g‐1. Shell thickening was found to occur in C. gigas where its incidence was correlated with the TBT body burden. Concentrations up to 2.24 μg TBT‐Sn gr‐1 (on a dry weight basis) were observed for C. gigas. This survey provides evidence for the toxic influence of TBT on non‐target organisms in New Zealand.
TL;DR: In this paper, the relationship between some physical and chemical parameters of streams, the degree of catchment development, and benthic invertebrate distributions were investigated on two dates at 26 running water sites in North Westland, New Zealand.
Abstract: Inter‐relationships between some physical and chemical parameters of streams, the degree of catchment development, and benthic invertebrate distributions were investigated on two dates at 26 running‐water sites in North Westland, New Zealand. Streams draining catchments recently developed for forestry had higher summer water temperatures, greater total reactive aluminium concentrations (up to 31°C and 911 mg m‐3, respectively), and lower pH (down to 4.1) than most streams draining undeveloped wetland or native‐forested catchments. Apparent differences in water chemistry were attributed to the most recent development being at the heads of wetland catchments where leaching of organic acids into drainage waters was probably highest, rather than to any effects of development per se. Overall, streams that were very acidic (pH mostly 4.5 and drained native‐forested catchme...
TL;DR: The 3 Otago coastal water masses (Neritic water, subtropical Southland Current water, and Subantarctic Surface Water) defined in the literature were identified on 1 cruise in early summer and 1 in mid winter as mentioned in this paper.
Abstract: The 3 Otago coastal water masses (Neritic water, subtropical Southland Current water, and Subantarctic Surface Water) defined in the literature were identified on 1 cruise in early summer and 1 in mid winter. Winter results showed that Neritic water is derived from the Clutha River. During winter the Southland Current was characterised by temperatures between 9.0 and 10.6°C and a salinity range of 34.4 to 34.9 × 10‐3. During summer a thermocline and pycnocline were observed at 30–50 m depth sloping down toward the coast. Low‐salinity Neritic water was less apparent than in winter. Summer nutrient levels were depleted over all of the continental shelf, relative to winter. This is probably caused by the enclosure of coastal surface waters inshore of the pycnocline. Reactive Si was conservative in winter regardless of water mass. Reactive P was approximately constant in Neritic water and Southland Current water. In summer, neither nutrient was conservative.
TL;DR: Foraging by Galaxias vulgaris on drift and benthos may provide fish with suitable prey to feed on, and prey selection was indicated by the over‐representation of Austrosimulium spp.
Abstract: To determine the extent of prey selection by the nocturnally active fish Galaxias vulgaris, samples of fish, drift, and benthos were collected over a 24‐h period in summer in a stream draining the foothills of the Southern Alps in New Zealand. Feeding started after sunset, peaked by midnight, and virtually ceased by midday. Both drifting and benthic foods were consumed, and timing of peak feeding was synchronous with the period of greatest abundance of aquatic drift. Larvae of Austrosimulium spp., Deleatidium spp., and Aoteapsyche colonica comprised the major proportion of the prey eaten. Prey selection was indicated by the over‐representation of Austrosimulium spp. and under‐representation of both the smaller size classes of Deleatidium spp. and other aquatic invertebrates in the diet of fish. With the exception of the coleopteran Costelytra zelandica, terrestrial organisms were not eaten by fish, but several aquatic taxa were. Foraging by Galaxias vulgaris on drift and benthos may provide fish ...
TL;DR: The fauna on artificial substrates was similar to that of natural benthic samples, but with a greater macroinvertebrate density and total taxa number, and dominated by Austrosimuliwn australense and Chironomidae larvae.
Abstract: Perspex multiplate artificial substrates were deployed in the Ohinemuri River on two occasions from May to November 1987. A pilot study was conducted to compare the fauna on substrates with that occurring naturally in the benthos, and a second study to investigate the colonisation dynamics. In general, the fauna on artificial substrates was similar to that of natural benthic samples, but with a greater macroinvertebrate density and total taxa number, and dominated by Austrosimuliwn australense and Chironomidae larvae. Colonisation stabilised after 28 days, after which there was little change in diversity. In contrast, equitability decreased, reflecting the greater contribution from A. australense and Chironomidae. There was a steady build‐up of fine particulate organic matter (FPOM) on the perspex surface. The relatively low exposure time necessary for equilibrium levels to be reached was attributed to the distinctive characteristics of the New Zealand aquatic fauna. The artificial substrates wer...
TL;DR: A combination of trap net and gill net caught the widest range of species and sizes for individual or pairwise combinations of gear types, and is recommended as being the best combination for sampling shallow‐lake fish communities in New Zealand.
Abstract: This paper describes the first tests of a fine mesh trap net suitable for sampling shallow‐lake fish communities in New Zealand. The catch from 2 shallow lower Waikato lakes of this and 5 other gear types frequently used in freshwater fisheries research in New Zealand are compared. The trap net caught the widest range of fish species and sizes, and was the least selective for species composition and relative abundance of any individual gear type. A combination of trap net and gill net caught the widest range of species and sizes for individual or pairwise combinations of gear types, and is recommended as being the best combination for sampling shallow‐lake fish communities in New Zealand.
TL;DR: Size is inversely related to abundance in 3+ females but not in the other cohorts, suggesting density‐dependent growth between ages 2 and 3, which appears to be important in determining recruitment strength in this species.
Abstract: Settlement of puerulus‐stage New Zealand red rock lobsters (Jasus edwardsii) and abundance of the first three juvenile cohorts were measured from 1981 to 1989 near Halfmoon Bay, Stewart Island. Puerulus settlement on subtidal collectors shows great annual variation. Juvenile abundance, estimated from the number caught in annual diver collections, shows less variation. One‐year‐olds appear less vulnerable to diver sampling than older juveniles. Abundance of 2‐ and 3‐year‐olds is highly correlated with puerulus settlement 2 and 3 years previously. Survival between puerulus and 1+ stages appears to be density‐dependent, but survival of older juveniles does not. Size is inversely related to abundance in 3+ females but not in the other cohorts, suggesting density‐dependent growth between ages 2 and 3. Puerulus settlement rates and processes on shallow inshore reefs appear to be important in determining recruitment strength in this species.
TL;DR: In this article, four polymorphic enzyme loci were tested in 13 samples of tuatua, Paphies subtriangulata, from around New Zealand, and the distribution of electromorphs indicate three geographical groups: north, central, and Chatham Islands.
Abstract: Four polymorphic enzyme loci were tested in 13 samples of tuatua, Paphies subtriangulata, from around New Zealand. Statistical analyses of the distribution of electromorphs indicate 3 geographical groups: north, central, and Chatham Islands. One sample from Stewart Island may represent a fourth southern group owing to its geographical isolation and genetic differences with the central group. It is suggested that the genetic differentiation is maintained by current movements which restrict gene flow between regions. Samples from the Chatham Islands showed lower hetero‐zygosities than mainland samples. This offshore island group is beyond the normal limits of larval dispersal from mainland populations.
TL;DR: In this paper, a depth-averaged 2-dimensional numerical model was used to study the Hauraki Gulf's residual circulation arising from the tides, steady winds, and oceanic inflows.
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.
TL;DR: There was a decline in the mean length of most age classes of shortfinned eels samples taken in July and October, probably a result of shrinkage during winter, compounded by the annual formation of new hyaline rings in otoliths during September‐October, which lowered mean length‐at‐age.
Abstract: Growth rates of both species of New Zealand freshwater eel, Anguilla australis (shortfinned eel) and A. dieffenbachii (longfinned eel), in backwaters of the lower Waikato River were determined from otolith examination. Condition factors (CF) were calculated for isometric growth on a restricted length range (350–500 mm). Annual length increments for eels less than 500 mm were 13 mm and 15 mm for shortfinned and longfinned eels, respectively. Shortfinned eels grew at rates of between 2 and 6 mm per month in summer (December 1984‐March 1985), and older eels (10–15 years) grew faster than younger eels in autumn (March‐June) (5.0–6.5 mm per month). There was a decline in the mean length of most age classes of shortfinned eel samples taken in July and October. This was probably a result of shrinkage during winter, compounded by the annual formation of new hyaline rings in otoliths during September‐October, which lowered mean length‐at‐age. Backwater shortfinned eels younger than 20 years were smaller t...
TL;DR: The total production of larvae as well as the total numbers of planktonic larvae released by oysters in the central and southern areas of New Zealand, the data point to a greater proportion of plankTONic larvae being released in thecentral area.
Abstract: Planktonic larvae of the flat oyster, Tiostrea chilensis (Philippi, 1843), were discovered in Tasman Bay and Golden Bay (central New Zealand) and Foveaux Strait (southern New Zealand). This oyster was previously thought not to have planktonic larvae. The central New Zealand larvae ranged from 394 to 533 μm in length, significantly smaller than those from southern New Zealand which ranged from 448 to 541 μm. By comparison the prodissoconch length of spat indicated these larvae settled between 429 and 537 μm in length in Tasman Bay and Golden Bay, and between 470 and 556 μm in Foveaux Strait. We estimated the total production of larvae as well as the total numbers of planktonic larvae released by oysters in the central and southern areas of New Zealand, the data point to a greater proportion of planktonic larvae being released in the central area. The great majority of T. chilensis larvae appear to be incubated until ready to settle. The ability to release some planktonic larvae should play a consi...
TL;DR: Dietsofthealpinegalaxias and the longjawed galaxias, small, slender fish with entirely freshwater life cycles, were studied in Deep Creek, a high‐country stream in the central South Island of New Zealand.
Abstract: Thedietsofthealpinegalaxias(Galaxias paucispondylus Stokell, 1938) and the longjawed galaxias (G. prognathus Stokell, 1940) were studied in Deep Creek, a high‐country stream in the central South Island of New Zealand. Both species are small, slender fish with entirely freshwater life cycles. Their diets were very similar and consisted of aquatic invertebrates, dominated by the larvae of Deleatidium spp. (Ephemeroptera), Hydrobiosis spp. (Trichoptera), and Chironomidae (Diptera). Although diets partly reflected what was available in the stream, both fish selected soft‐bodied prey in preference to cased or harder shelled prey. Both species are probably nocturnal feeders.
TL;DR: Four species of mysids are resident in the Avon-Heathcote Estuary, Christchurch and, for all 3 Tenagomysis species, males were mature at a smaller size than females, whereas the opposite was true for G. australis.
Abstract: Four species of mysids are resident in the Avon-Heathcote Estuary, Christchurch. Tenagomysis macropsis is by far the most abundant daytime species and has a wide distribution, not linearly correlated with salinity. Tenagomysis novae-zealandiae and T. chiltoni are much less abundant, increase in numbertoward the upper estuarineregion, and (especially T. chiltoni) have distributions significantly correlated with salinity (P < 0.05–0.001). T. chiltoni has a spring/summer population maximum. Gastrosaccus australis appears to be an obligate nocturnal plankter and its; distribution in the system is unresolved. The largest mysid was T. chiltoni and the smallest T. novae-zealandiae, although there was considerable intraspecific size variation. For all 3 Tenagomysis species, males were mature at a smaller size than females, whereas the opposite was true for G. australis. For each species, ovigerous females generally achieved the maximum size recorded. Embryo numbers carried in the marsupium ranged from 4 to 25 for T. macropsis, from 6 to 19 for T. novae-zealandiae, and from 22 to 39 for T. chiltoni. Embryo sizes for the New Zealand species are in accord with the range found generally for coastal mysids.
TL;DR: The involvement of an endogenous timing system in this species is indicated, although its control is not rigid and in the majority of animals studied it appears to be completely overridden.
Abstract: Laboratory studies of the locomotor activity of individual rock lobsters (Jasus edwardsii) were made in a 24 h light/dark cycle (LD) and in constant dim red light. The majority of animals studied in a normal LD cycle exhibited nocturnal activity patterns. Levels of illumination as low as c. 0.03 μE nrV1 were usually sufficient to suppress activity during the light phase. If the duration of the dark phase was normal for the time of year, the majority of animals became active at the beginning of the dark period and remained active until its end. Thus in winter, animals were active for 13–14 h each day whereas in summer theaetive period was curtailed to 8–9 h. In summer, animals held in a LD cycle with 13–14 h of darkness did not increase the length of their active periods to match the dark phase. The involvement of an endogenous timing system in this species is indicated, although its control is not rigid and in the majority of animals studied it appears to be completely overridden. The weak intern...
TL;DR: Two‐thousand‐and‐ten rig were tagged around southern New Zealand during the 1982/83 and 1983/84 fishing seasons to estimate exploitation rates, suggesting increasing exploitation by the predominantly set‐net commercial fishery.
Abstract: Two‐thousand‐and‐ten rig were tagged around southern New Zealand during the 1982/83 and 1983/84 fishing seasons to estimate exploitation rates 520 were double‐tagged to estimate tag shedding rates Tags placed in front of the first dorsal fin were shed more often than those placed between the 2 dorsal fins, possibly because of entanglement in the meshes of set nets during recapture The estimated front tag shedding rate was used to correct recapture numbers Reported recapture rates increased with total length, reflecting increasing exploitation by the predominantly set‐net commercial fishery Reported recapture rates of trawl‐tagged rig were less than those of set‐net tagged rig, suggesting that initial mortality was significant for the former method Annual exploitation rates probably exceeded 10% year‐1 for 75–89 cm rig off both east and west coasts of southern New Zealand Exploitation rates of rig > 90 cm probably exceeded 20% year‐1 for males and may have exceeded 30% year‐1 for females T
TL;DR: Invertebrate numbers were greatest at polluted sites where Chironomidae and tubificid oligochaetes predominated and taxonomic richness and species diversity of invertebrates were highest at unpolluted sites where Gastropoda (6 species), and Chironmidae were numerically dominant.
Abstract: Effects of bleached kraft mill effluent on macroinvertebrate and fish communities in weedbeds were investigated in Lake Maraetai in December 1987 and February and March 1988. Water from polluted sites was highly coloured (absorbance at 270 nm: 0.25–1.80), had relatively high concentrations of suspended solids (5.2–25.0 g m‐3), high biochemical oxygen demand (2.1–12.3 g m‐3), but low dissolved oxygen concentrations (4.5–8.5 g m‐3) and Secchi disc visibility (< 0.8 m). In contrast, unpolluted lake water was relatively clear (Secchi disc visibility 1.2–1.5 m, absorbance at 270 nm: 0.09), biochemical oxygen demand was 1.5–2.1 g m‐3 and concentrations of dissolved oxygen exceeded 10.0 g m‐3. Invertebrate numbers were greatest at polluted sites where Chironomidae and tubificid oligochaetes predominated. Taxonomic richness and species diversity of invertebrates were highest at unpolluted sites where Gastropoda (6 species), and Chironomidae were numerically dominant. Overall catch of fishes was 1.5–2.8 t...
TL;DR: More than 4000 specimens of the puerulus stage of the rock lobster, Jasus edwardsii, were collected in the sea water intake of the New Plymouth Power Station during 1977-84 as mentioned in this paper.
Abstract: More than 4000 specimens of the puerulus stage of the rock lobster, Jasus edwardsii, were collected in the sea water intake of the New Plymouth Power Station during 1977–84. Most specimens were caught between July and September. Sizes of pueruli were similar within years, but there were significant differences in size and number of pueruli between years. Puerulus occurrence was correlated with the late winter and spring increase in frequency of onshore winds, but the seasonality in settlement was probably not caused by this factor alone. Most pueruli at the power station were 9–13 months old, and occurred at any part of the lunar cycle. Oceanic flow patterns in the region suggested that most specimens originated from hatchings along the west coast of New Zealand, north of Hokitika. As the high numbers of pueruli at the power station were inconsistent with the zero catch of pueruli on adjacent collectors, and with the relatively low numbers of juveniles and adults nearby, the power station may att...
TL;DR: Changes in the sediments indicated that the effluents contained inorganic paniculate material in the mud/very fine sand size range, and Peaks in concentrations of oil and grease, ROC, TKN, and volatile solids occurred at the diffusers.
Abstract: The benthic ecological impacts of 2 New Zealand ocean outfalls were studied. They are the country's largest (discharging 0.8 m3 s‐1) at Hastings, and longest‐established (operating since 1965 and with a present discharge of 0.28 m3 s‐1) at Gisbome. Both discharge essentially biodegradable domestic and food‐processing‐industry wastes. Samples were collected about each outfall and analysed for particle size, oil and grease, readily oxidisable carbon (ROC), total Kjeldahl nitrogen (TKN), volatile solids, and macrofauna. Changes in the sediments indicated that the effluents contained inorganic paniculate material in the mud/very fine sand size range. Peaks in concentrations of oil and grease, ROC, TKN, and volatile solids occurred at the diffusers. Numbers of taxa were low near the outfalls, but increased with distance away. Numbers of individuals were also low at the outfalls, increasing within 100 m, before dropping to normal levels. No grossly polluted zone, devoid of macrofauna, was found; howeve...
TL;DR: In this paper, an acoustic survey was carried out on the Chatham Rise to the east of New Zealand in mid winter 1986 on a spawning population of orange roughy (Hoplostethus atlanticus) by using a narrowbeam transducer mounted in a very stable tow body, towed at a depth of 200 m.
Abstract: Orange roughy (Hoplostethus atlanticus) are found in depths from 700 to 1300 m around New Zealand and support an important fishery. An acoustic survey was carried out on the Chatham Rise to the east of New Zealand in mid winter 1986 on a spawning population of orange roughy. The great depth and poor weather conditions created a number of problems, particularly with respect to signal‐to‐noise ratio. These were tackled principally by use of a narrow‐beam transducer mounted in a very stable tow body, towed at a depth of 200 m. A scientific echo sounder operating at 38 kHz was used and echo data were recorded digitally on magnetic tape. A total of 1700 km2 was surveyed covering a bottom depth range from 750 to 1250m. The orange roughy were located near the bottom, 77% lying between 5 and 10 m. Highest density was found where the bottom depth exceeded 950 m. The overall areal density was 0.16 kg m‐2. One small area with very high fish densities extending up to 65 m was encountered during the survey. T...