摘要:

A logarithmically increasing relationship was found between fecundity (F) and carapace width in mm (CW) [Ln(F) = 1.81439 + 2.44173 × Ln(CW)] with a slightly better statistical fit being produced with an exponential relation [Ln(F) = 9.79540 + 0.03325 × CW]. The relation between fecundity and drained body weight in g (BWg) was equally well described by both a simple linear relation [F = 25630.76 + 2552.12 × BWg], and a logarithmic relation [Ln(F) = 8.58960 + 0.85978 × Ln(BWg)]. Although all curves were highly statistically significant the precision of prediction was limited as a wide range of fecundities was observed for any given size. Large females (100 mm) would have an expected fecundity per batch of eggs of approximately 500 000. No relation was found between mean egg size and carapace width, nor were there significant relations between development stage and egg size, or between development stage and fecundity. Male paddle crabs carry pre‐moult females for up to eight days prior to the female moulting. Females were carried with their dorsal surface against the males ventral surface, grasped either by the males second or third walking legs. After she moults the pair copulate, generally for between 12 and 36 hours (but up to four days), before the female is released. Guarding during copulation protects females from cannibalism. Females adopted an elevated posture on the tips of their limbs and used vigorous sweeping and flushing motions when releasing larvae.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516622

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Between 1985 and 1992, mortality due to infestation by the protistanBonamiasp. severely reduced the numbers of the oyster,Tiostrea chilensisin Foveaux Strait, New Zealand. In 1990, two dredge surveys gave relative estimates, and a dive survey an absolute estimate, of the size of this oyster population; this allowed us to estimate dredge efficiency precisely. This estimate was used to re‐evaluate the dredge survey of 1975–76 and relate the size of the population in 1990 to that in 1975. By 1990 the population density had declined by 67% while a dredge survey in 1992 showed that the population density had declined by 91% from 1975. A dredge survey in 1993 showed that the population had increased slightly (but not significantly) over the 1992 level. By 1992 the population had probably been reduced below 10% of the virgin level. The fishery was closed in 1993 to allow the population to rebuild. The population surveys have followed stratified random and grid pattern sampling designs and the merits of the designs and methodology are discussed.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516623

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The New Zealand abalone fishery produces about 1200 t annually, mostly from southern New Zealand. The fishery, based onHaliotis iris, is managed over broad management areas within which fishing intensity is spatially dispersed. The size composition of the commercial catch depends on location within a management area but is similar for divers fishing individual populations ofH. irisand reflects the size composition of natural populations. For most populations, length‐frequency distributions of abalone were normally distributed: the mean shell length ofH. iriswas found to vary within populations over small spatial scales (100s m). The relative abundance of juvenileH. iriswas low in relation to adults suggesting, at least for exposed populations, that rates of recruitment to populations ofH. irismay be low. The relative abundance and mean shell length of juveniles and adults ofH. australiswas much less than that ofH. iris. The scarcity ofH. australisand the lack of separate catch quotas for the two species are factors which explain the low to zero catch ofH. australis. The spatial variation in the size composition ofH. irissuggests that management would be more appropriate over spatial scales which reflect local populations rather than the large spatial areas which are used to manage the New Zealand abalone fishery.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516624

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Relationships of shell height, shell width, shell weight, foot weight, dry foot weight, and total weight were examined with shell length forHaliotis irisfrom different localities. Mean length varied among 61 localities explaining more than 70% of the variation in the other parameters which covaried with length. Significant sources of variation in mean length included latitude (sea surface temperature) and relative exposure. Variation in all morphometric parameters occurred among localities but such variation, although significant, was generally not large (< 10 % of mean values). Although the spatial scales examined included 100s of km, the largest morphometric variation shown was between neighboring localities (200 m apart). This and the high residual variation in any morphometric parameter forH. irisfrom any location indicated that morphometric variation occurred over small spatial scales. The suggestion that some localities ofH. iriswere “stunted” with small average lengths and had individuals with relatively peaked shells and greater weights compared with those from other localities, was not supported by our results.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516625

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Wind data from the ERS‐1 scatterometer have been processed for New Zealand waters. These show spatial features of marine wind fields which have previously been difficult to resolve using conventional surface‐based measurements. Winds across the western access to Cook Strait, delineated by a corridor between Farewell Spit and western Taranaki, were analysed and profiles of wind stress extracted. These show characteristic structures for south‐easterly events in which the stress steadily increases from Farewell Spit towards the Taranaki Coast. In westerly or north‐westerly events the structure is more uniform. The mean stress across this corridor has been compared to that calculated from surface‐based measurements at Farewell Spit and the Maui‐A oil and gas production platform off Cape Egmont. The Farewell spit data lead to underestimates of the stress, which partially reconciles previous attempts to model wind‐driven currents off the west coast of the South Island from these data. In these the currents were underestimated. The Maui‐A data are unbiased in westerly events but give overestimates in southeasterly winds. An improved estimate of the mean stress can be derived from using a combination of wind data from these two stations.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516626

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A bloom of the green microalgaTetraselmissp. in a small lagoon in Wellington Harbour, New Zealand, is considered to have caused a fish kill of pilchards (Sardinops sagax). The fish deaths are attributed to anoxia brought about by a combination of reduced dissolved oxygen levels and the microalgae sticking to and clogging the secondary gill lamellae of the fish.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516627

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Juvenile torrentfish (Cheimarrichthys fosteri), which enter New Zealand rivers from the sea during spring through summer and into autumn, differ from post‐migratory juveniles and subadults in being tadpole‐like, with relatively longer but narrower heads and larger eyes, a highly compressed caudal region, and a spinous postero‐ventral preopercular margin; the fins appear larger. Migratory juveniles mostly lack the colour pattern of larger fish, and have extensive unpigmented areas on the margins of the dorsal and anal fins, most of the tail, and much of the pectoral fins. The condition found in post‐migratory juveniles and later growth stages develops soon after migration.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516628

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The upper thermal tolerances of 12 New Zealand freshwater invertebrate taxa were compared using a laboratory lethality testing protocol. Temperatures that were lethal to 50% of the test organisms (LT50S), following acclimation to 15°C, generally declined over the 4 day period of the tests. LT50values after 48 and 96 h exposure ranged from 24.5 to > 34°C and 22.6 to 32.6°C, respectively, indicating that temperatures that occur in summer in many NZ streams and rivers may limit the distribution and abundance of some of these invertebrate species. Larval insects included both the most sensitive species (a plecopteran and two Ephemeroptera) and the most tolerant (the larvae of the elmid beetleHydorasp.) in this study. The two molluscs studied (Potamopyrgus antipodarum(Prosobranchia: Hydrobiidae) andSphaerium novaezelandiae(Bivalvia: Sphaeriidae)) showed high thermal tolerance, whilst two crustaceans (Paratya curvirostris(Atyidae) andParacalliope fluviatilis(Eusiridae)) were moderately tolerant. The effect of a higher acclimation temperature (20°C) on thermal tolerance was also investigated for the three most sensitive species. This appeared to increase the thermal tolerance of the two Ephemeroptera{Deleatidiumspp. andZephlebia dentata(both Leptophlebiidae)) but to reduce the tolerance of the plecopteranZelandobius furcillatus(Gripopterygidae).

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516629

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Upper lethal and preferred temperatures were determined experimentally for eight common species of New Zealand freshwater fish. Upper lethal temperatures ranged between 28.3 and 39.7°C and preferred temperatures between 16.1 and 26.9°C.Anguilla australiswas the most tolerant of high temperatures, whereasRetropinna retropinnaand two species ofGalaxiaspreferred cooler water. The relationship between lethal and preferred temperatures for New Zealand species was similar to that calculated from data for 38 other species of freshwater fish, meaning that either lethal or preferred temperatures could be used accurately to predict lethal, preferred, and growth optima, and to recommend temperature regimes for waterways. However, New Zealand field records show that significant relationships between fish density and water temperature exist for only two species,A. dieffenbachiiandCheimarrichthys fosteri. This suggests New Zealand species are able to thrive within a wide temperature range.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516630

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Floods are often considered one of the major regulators of fish populations, but there are few observations of fish behaviour or habitat use at such times. To investigate habitat use and fish movement during floods, two locations on the Pohangina River, North Island, were sampled at the peak of a small flood. Habitat use at normal flows was determined by repeating the same sampling procedure in runs and riffles on the Pohangina and two nearby rivers. The sampling procedure was to electrofish runs and riffles in lanes, stratified by depth (0–0.125 m, 0.125–0.25 m, 0.25–0.5 m, and 0.5–0.75 m). Water depths and velocities were measured in each sampling lane. Fish were most abundant along the river margins less than 0.25 m deep, both during the flood and in normal flows. Two days after the flood, these shallow areas, that had been occupied by fish during the flood, were dry again. This suggests that the edge‐dwelling fish species in these rivers respond quickly to flow changes, moving with the river margins to minimise any change in depth. Response to changes in velocity were less apparent and the water velocity in the areas occupied by edge‐dwelling fish during the flood was sub‐optimal in terms of normal habitat preference. The response of fish to flow and habitat change and the use of sub‐optimal habitat for short periods of time highlights the difficulty of interpreting a time series of weighted usable area.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516631

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor