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B. Ben Bohlool 《新西兰海洋与淡水研究杂志》2013,47(3):271-275
Abstract Nitrogen fixing potential was measured in summer 1975 by acetylene reduction in situ at 5 stations on the intertidal flats of the Waimea Inlet, Nelson, New Zealand, which receive nutrients from several sources. Highest values (644 μmol?m?2.d?1) were obtained on sediments near an apple cannery effluent discharge and were linear through at least two tidal cycles. The cannery waste had the highest carbon to nitrogen ratio (10.3 : 1.0) of all the effluents examined and exhibited the highest rate of acetylene reduction (14.0 μmol?‐l?1.d?1). Sizeable populations of the nitrogen fixing bacteria Klebsiella pneumoniae were isolated from the cannery effluent (2 × 104 per millilitre) and also from the mud adjacent to the discharge pipe (5 × 105 per millilitrc). The stimulatory effect of the cannery effluent on nitrogen fixation in the sediment was shown to be restricted to close to the discharge point. Sediments in areas affected by slaughterhouse and sewage effluents exhibited the second and third highest rates of acetylene reduction, (130 &; 28 μmol?m?2.d?1 respectively). In both places, the activities were not restricted to the immediate vicinity of the effluent channels. Nitrogen fixation was lowest in sediments fronting a catchment of grazed pasture. Fixation was low also in sediments affected by effluents from the hydraulic debarker of a woodchip mill. 相似文献
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Rainbow trout, Oncorhynchus mykiss, have been stocked in southwestern Australia since the 1930s. Trials at a research station maintained 868 tagged yearling O. mykiss (age: 14 months; standard length: 208 mm) for up to 375 days. The mean tag loss rate was 0.12% ± 0.040% per day for both single- and double-tagged fish. The tag loss rate was used to interpret tag return data from 7030 single-tagged yearlings stocked into three river systems in southwestern Australia. Recaptures indicated that O. mykiss survived into their second season in all rivers, with the maximum time at liberty of 21 months (longevity of at least 35 months). Upstream and downstream movements of O. mykiss increased with time, although 29% of recaptures were reported from the stocking site. Significantly more O. mykiss were recaptured from the Warren River, and differences remained even when corrected for stocking levels; angler effort had a marginal effect on return rates. Higher return rates from the Warren River may be due to availability of suitable habitat (stream cover, cooler water) for O. mykiss. Results allow the stocking regime to be reviewed to improve fishery performance. 相似文献
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Cadet Hand 《新西兰海洋与淡水研究杂志》2013,47(4):493-507
The sea anemones Calliactis conchicola Parry, 1952 and Paracalliactis rosea n.sp. are described. This is the first report of the hormathiid genus Paracalliactis for New Zealand. Calliactis conchicola occurs with living gastropods, hermit crabs, and a true crab, and Paracalliactis rosea occurs with hermit crabs and a true crab. Certain characteristics of each of the two anemones suggest that the genera Calliactis and Paracalliactis may not be as discrete as was indicated by earlier reports. 相似文献
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D. K. Rowe 《新西兰海洋与淡水研究杂志》2013,47(2):115-127
Temporary removal of aquatic plants in Lake Parkinson, a small, eutrophic dune lake, resulted in a number of changes to the population of stocked rainbow trout (Salmo gairdnerii). During each summer the lake stratified and low oxygen levels limited the distribution of trout to shallow (0–4 m) surface waters. In the first summer following weed removal the numbers of black shags (Phallacrocorax carbo) counted at the lake increased, and their predation resulted in a decline in trout density. However, the growth rate and condition of the trout population then exceeded that of trout present before weed removal. During the second summer after weed removal a cladoceran bloom was followed by low phytoplankton levels and high ammonia concentrations. A prolonged calm compounded this situation with the result that oxygen levels in bottom and surface waters dropped below 2 ppm. These low oxygen levels eliminated the trout population, but other fish species present survived. Elimination of aquatic plants affected the population dynamics of other fish species in the lake with potential implications for the trout. The experiment demonstrated the importance of weed beds in maintaining a stable fish community in lakes such as Lake Parkinson. 相似文献
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This study examined the diet of sympatric populations of migratory juvenile rainbow trout and landlocked koaro in the Waipehi and Omori Streams, Lake Taupo, New Zealand. In both species, diet was dominated, both numerically and by weight, by aquatic prey: Ephemeroptera, Trichoptera, and Diptera larvae were the most numerous prey items. Adult koaro and juvenile rainbow trout both fed on small koaro. Terrestrial prey items were present in low numbers in the diets of both koaro and juvenile rainbow trout, but were more important in terms of weight. Resource partitioning was weak although koaro consumed more small benthic invertebrates such as chironomid larvae, whereas the diet of rainbow trout contained more Ephemeroptera larvae and terrestrial insects. In the Waipehi Stream, koaro consumed both rainbow trout ova and koaro ova; in Omori Stream, trout ova were important in the diet of juvenile rainbow trout. Since the diets of koaro and juvenile rainbow trout in some Taupo tributaries are similar, populations may co‐exist by temporal and/or spatial partitioning of food resources, whereas trout predation on small koaro may be a limiting factor for koaro populations. 相似文献
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Underwater census and single‐pass electrofishing were compared for estimating relative abundance of juvenile brown trout in the Kakanui River, South Island, NZ. Mean sampling efficiency was lower, and the variability of sampling efficiency was much greater, for underwater census (0+ trout: x = 0.38, s = 0.368; 1+ trout: x = 0.62, s = 0.822) than for single‐pass electrofishing (0+ trout: x = 0.61, s = 0.143; 1+ trout: x = 0.74, s = 0.171). Sampling efficiency of both methods was dependent on temperature. Electrofishing became less efficient at higher temperatures whereas underwater census became less efficient at colder temperatures. The low, and highly variable, sampling efficiency for underwater census of 0+ brown trout was related to substrate hiding behaviour which is dependent on temperature. A ratio method for comparing relative abundance estimates is presented. Minimum significance values for the ratio (R) were derived for 0+ trout using temperature adjusted sampling efficiencies. To be statistically significant, relative abundance estimates made by underwater census had to differ by a factor of 6–7 times, whereas those made by single‐pass electrofishing had to differ only by about 2 times, depending on the number of fish counted. By confining comparisons of relative abundance estimates made by underwater census to the summer period, differences of about 3.5–4 times could be detected statistically. It was concluded that single‐pass electrofishing is superior to underwater census for estimating the relative abundance of juvenile brown trout in shallow (< 1 m) river habitat, especially when temperature varies widely as with season and time of day. 相似文献
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A small‐scale experiment was done to test the feasibility of thermally marking hatchery‐reared rainbow trout (Oncorhynchus mykiss Walbaum) fry that are released into rivers and impoundments in New South Wales (NSW), Australia. Fry of rainbow trout were exposed to two different 48‐h thermal cycles each of a cold and warm water period. One thermal regime consisted of a cold water period during which the temperature was reduced from 14 to 8°C for 18 h followed by a return to 14°C for 30 h. For the second thermal treatment, water temperature was reduced to 4°C for 10 h followed by a period of 38 h at 14°C. Thermal cycles were repeated 4 and 8 times for each thermal regime, respectively. Following a growth period after treatment, obvious marks were visible on all treated otoliths as distinct from control otoliths. The 10°C differential treatment created the most visible patterns and growth of these fish was not significantly different from control fish. This marking method could be applied to normal hatchery practices to evaluate the effectiveness of large‐scale rainbow trout stockings in NSW. 相似文献
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《Limnologica》2016
The current study is, according to our knowledge, the first study indicating that ion deficit is an important restrictor to the distribution of brown trout populations in very dilute mountain lakes. The brown trout populations in the study lakes may be able to survive solely due to traces of air borne sea salt spray. 相似文献