Swimming behaviour in a pycnogonid (note)

Four adult specimens of the pycnogonid Ammothea magniceps were observed swimming at the sea surface at night at Kaikoura. Even after capture the animals continued to swim at the surface of the water for over an hour. Such swimming behaviour is considered important in explaining the presence of “benthic” animals in plankton samples.     

Heavy metal pollution in Wellington Harbour

Heavy metal analysis of the < 20 μm fraction of marine sediments from Wellington Harbour and Waiwhetu Stream have shown that the Waiwhetu Stream is easily the most polluted area in the Wellington Harbour system with Pb and Zn in the extremely polluted category and Cu, Cd, and Hg in the moderately to strongly polluted category. These elements have different distributions in the stream sediments reflecting their different sources from adjacent factories. In Wellington Harbour itself, the central basin of the harbour suffers from minimal pollution. Pb, and to a lesser extent Zn and Cu, are the main pollutants and local enrichment of these elements is noted in Lambton Harbour basin, off Pencarrow and Moa Point outfalls, in Evans Bay, and off Petone and Kaiwharawhara. The geochemical data do not enable us to identify the source of the pollutants unambiguously. A summary of the history of waste discharges into the harbour suggests that heavy metal pollution may have been higher in the past.     

Circulation and mixing in Lake Rotongaio and Lake Okaro under conditions of light to moderate winds: Preliminary results

I report on a group of orca (Orcinus orca (Linnaeus, 1758)) near the Bay of Islands, New Zealand, which were a lighter coloration than orca usually seen in these waters. Differences in pigmentation included a light grey caudal peduncle area and a dorsal cape, which has previously only been described for Antarctic orca. The size and shape of the eye patches were not consistent with orca photo‐identified in New Zealand. I suggest that this group of orca, although observed in New Zealand waters, were of Antarctic origin.     

Nyctiphanes australis (Euphausiacea) and an upwelling plume in western Cook Strait,New Zealand

Quantitative data are presented on the distribution of adult and larval stages of the euphausiid Nyctiphanes australis G. O. Sars, in western Cook Strait, New Zealand, an area influenced by an upwelling plume. The behaviour of N. australis in the Kahurangi Point region at different stages of its life history appears to ensure its maintenance, in general, over the continental shelf on an upwelling coast. Population structure at the source of the upwelling near Kahurangi Point differed from that in regions “down stream” from the plume. Nyctiphanes australis was most abundant at the “downstream” eastern end of the upwelling plume, and the evidence suggesting that the dense populations there may be resident is discussed. Possible reasons for low densities of furcilia II and III stages in the eastern plume region are considered.     

Sink rate of baited hooks during deployment of a pelagic longline from a New Zealand fishing vessel

The sink rate of baited hooks during the deployment of a pelagic longline was determined using time depth recorders. This study was undertaken to determine how long baited hooks are within the known diving ranges of seabirds. During the vessel's normal fishing operations the unweighted baited hooks reached a mean depth of 5.57 m, 30 s after being deployed. The tori line aerial section covered the longline for a mean time of 29.3 s. With the addition of a 60 g lead swivel, the mean baited hook depth attained more than doubled to 13.44 m, and a further trial using a lead core cord in the snood configuration showed a small but significant increase in hook depth over the unweighted control (7.27 m). An increase in wind speed caused the baited hooks to sink faster (0.54 m for each Beaufort unit increase in wind speed). There was also evidence that the apparent wind direction while the vessel is setting also has an effect on the depths realised, but swell height had no detectable effect. The temperature of the bait also significantly affected the hook depth: partially thawed baits sank faster than thawed baits. A 1°C rise in bait temperature reduced the depth by 0.19 m. During normal line setting on this vessel using unweighted branchlines and a tori line, a considerable proportion of the baited hooks are within the known diving range of sooty shearwaters (Puffinus griseus), white chinned petrels (Procellaria aequinoctialis), shy albatross (Thalassarche cauta), black browed albatross (T. melanophrys), grey headed albatross (T. chrysostoma), and light mantled sooty albatross (Phoebetria palpebrata). The addition of a 60 g weight removes the baited hooks from the recorded diving range of all of these species except sooty shearwaters. Investigating the behaviour of different gear configurations along with evaluating the effect that environmental conditions have on the deployment of a longline will greatly add to our understanding of why some seabirds are caught.     

Differential UVB‐sensitivities of five New Zealand freshwater zooplankton species

Abstract

The ultraviolet (UV) sensitivity of five species of freshwater zooplankton (three Cladocera, two Copepoda) were investigated. The animals were exposed to varying levels of UV‐radiation in a sunshine‐simulator and the UV doses for 10 and 50% mortality (LD₁₀, LD₅₀) were estimated using a dose‐response model. To place these doses in context they were compared with modelled clear‐sky surface UV irradiances in New Zealand. The cladocerans Daphnia carinata and Ceriodaphnia dubia were sensitive to levels of UVB irradiance of LD₁₀ = 18–25 kJ m^?2 and LD₅₀ = 35–37 kJ m^?2. These sensitivities are consistent with published values for other cladocera. In contrast a third cladoceran, Bosmina meridionalis, exhibited no higher mortality over the full range of the cumulative UVB‐doses used (3–40 kJ m^?2) than controls receiving no UV exposure. The copepod Boeckella delicata showed the highest UV‐sensitivity of all organisms tested (LD10 = 7 kJ m^?2, LD50 = 33 kJ m^?2) whereas for Boeckella triarticulata, which was more heavily pigmented than B. delicata, no UV‐induced mortality was observed. Under natural conditions UV irradiances of up to 100 kJ m^?2 day^?1 can fall on the surface of New Zealand lakes. Although this is attenuated in natural waters, these data suggest that UVB irradiance may be a significant ecological variable to some zooplankton species.     

Calorific content of New Zealand marine macrophytes

Calorific content was measured in 28 species of New Zealand macroalgae. Values ranged from 1.04 to 3.34 kcal g‐1 dry weight (wt), 3.03–5.18 kcal g‐1 ash‐free dry wt, and 0.13–1.75 kcal g‐1 wet wt. Seasonal variation in calorific content was measured in two of these species, Macrocystis pyrifera and Ulva lactuca, both of which showed clear changes in energy content over a 1‐year period. Factors affecting variation in calorific content between species and during the year are discussed, and the application of the current findings to ecological and aquacultural research on New Zealand seaweeds are considered.     

Distribution and abundance of Abarenicola affinis (Arenicolidae,Polychaeta) in tidal inlets of Otago,New Zealand

Lugworms are important members of the macrobenthos of sheltered intertidal sediments, and this study assessed the abundance and distribution of Abarenicola affinis in Otago, southern New Zealand. Using a faecal cast:lugworm ratio (1.00:1.09) revealed a patchy distribution across inlets, with an overall mean abundance of 11.1 individuals/m² (range: 3.8 to 21.3 individuals/m²). Distribution patterns varied among inlets, with lugworms mostly confined to the high intertidal zone, but spread across all intertidal zones in one inlet. The lugworm habitat was characterised by muddy to medium sand (55–233 µm mean grain size) with low organic matter (< 2%) and chlorophyll a (1–12 µg/g dry sediment) contents. Depending on the inlet, lugworm abundance was related to sediment parameters, indicating that their distribution across Otago inlets is habitat dependent. The present findings also indicate that factors other than those measured contribute to A. affinis distribution and abundance patterns in this region.     

Estimates of size for the large octopus Macroctopus maorum from measures of beaks in prey remains

Macroctopus maorum, also known as Octopus maorum and Pinnoctopus cordiformis, grows to 12 kg and is the largest octopod in Australasia. In New Zealand, this species features in the diets of seals and albatrosses. Beaks of depredated octopus resist digestion and accumulate in the stomach until regurgitated or defecated. Beaks of M. maorum were differentiated reliably from those of other octopods in prey remains for octopus > c.100 g. Previous studies estimated the size of depredated M. maorum from measures of lower beaks using equations derived either from a small sample of M. maorum or from related species. Here, allometric equations to estimate ventral mantle length (4.6–27.5 cm), dorsal mantle length (5.1–29.0 cm), total length (20–198 cm), and body mass (36–12 000 g) were derived from measures of both upper and lower beaks of 90 specimens of M. maorum. These regressions were imprecise and reflected innate variability in octopus morphometrics, a characteristic reflected in the results of analyses of published data for M. maorum from northern New Zealand and for two other large octopods, Octopus vulgaris and Enteroctopus magnificus.     

Short-term survival of severe propeller strike injuries and observations on wound progression in a bottlenose dolphin

Until recently, vessel collisions with small cetaceans were presumed rare, mainly as a consequence of limited reporting. Observations on dolphin wound healing from propeller strike injuries also remain scarce. We present an extreme case of a bottlenose dolphin (Tursiops truncatus) with multiple propeller wounds, including a penetration to the bone, where survival was possible for at least 23 days post injury. We used photographic records in conjunction with field observations to describe wound progression in the absence of treatment. Considering the severity of the wounds, it was surprising that the injuries were not immediately fatal. A practical solution remains to be found for the problem of odontocete vessel collisions, in particular for small highly mobile species using neritic waters. In view of the ongoing problem in the Hauraki Gulf and, indeed, worldwide, we recommend continued evaluation of cases and reporting of incidents, in addition to investigations into mechanisms that may reduce the risk of occurrence of vessel collisions with cetaceans.