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1.
Gravel occurred in. the stomachs of 17.8% of 924 Galaxias vulgaris and 2.8% of 430 Philypnodon breviceps taken from the Glentui River, Canterbury, between June 1970 and November 1971. It is suggested that differences in feeding habits and feeding locality are responsible for the difference in occurrence of gravel in the stomachs of the two fish species. Galaxias vulgaris feeds in the water column in riffles and, being a drift feeder, is more likely to ingest inedible material by accident than is P. breviceps, which feeds on the bottom in sheltered or quiet stretches of the river.  相似文献   

2.
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.  相似文献   

3.
Inanga (Galaxias maculatus Jenyns) are the basis of an important recreational and commercial freshwater fishery that has declined over the past 100 years, probably because of habitat degradation in developed areas. Maintenance of suitable stream flows for inanga is one means of protecting the fishery. Observations of habitat use by drift‐feeding inanga were made in three streams. Most feeding inanga were stationary in the current taking food items from the drift and sometimes from the surface. Drift‐feeding locations were related to current patterns and water velocity, with inanga feeding at locations where the current concentrated food, and where water velocities were sufficiently low to allow the fish to hold position. The mean feeding velocity did not vary significantly between streams, although the range of velocities used did. Optimum feeding velocities were 0.03–0.07 m s‐1, and were comparable with brown trout (Salmo trutta) feeding velocities, when adjusted for the differences in fish size. Depth use was very different between streams and this was attributed to the variation in available habitat. Depths greater than 0.3 m were optimum, with some use of depths between 0.1 and 0.3 m. It is suggested that inanga suitability criteria are dictated by biological factors, such as swimming ability and bio‐energetic requirements, rather than the river the fish is living in and that it is necessary to collect habitat use and availability data in a wide range of stream types to define optimal habitat and suitability criteria for generalised application.  相似文献   

4.
Food and feeding of small fish in the Rakaia River,New Zealand   总被引：1，自引：1，他引：0  
Benthic macroinvertebrates and fish species were collected at monthly intervals during a 12‐month period, from 3 areas of the lower Rakaia River. The composition and abundance of the benthos and stomach contents of the fish were analysed for seasonal trends, food niche breadth and overlap between pairs of fish species, and overlap between the benthos and the diet of each fish species. The diets of bluegilled bully (Gobiomorphus hubbsi), upland bully (G. breviceps), juvenile longfinned eel (Anguilla dieffenbachii), Galaxias brevipinnis, G. paucispondylus, and juvenile brown trout (Salmo trutta) were similar to the proportions of prey species in the benthos. Deleatidium and chironomid larvae dominated the benthos in all seasons and formed the majority of food items in the diet of these species. Food niche overlap between these species was high, indicating potential competition, but preferred habitat and feeding habit differences plus low fish population density and abundance of main prey items probably eliminate the occurrence of any serious competition. The diet of the other fish species differed from this pattern. The common bully (Gobiomorphus cotidianus) ate proportionally more chironomid larvae and fish eggs than occurred in the benthos; torrentfish (Cheimarrichthys fosteri) ate proportionally more chironomid larvae than occurred in the benthos; and quinnat salmon (Oncorhynchus tshawytscha) depended largely upon prey species of terrestial origin, such as adult Deleatidium and dipterans.  相似文献   

5.
Galaxias divergent Stokell is a small, bottom‐dwelling fish inhabiting streams in the North Island and the northern part of the South Island. Its ecology is similar in many respects to that of G. vulgaris. The fry develop in the same environment as the adults, unlike the sea‐going young of several other Galaxias spec'es. Spawning occurs in spring and summer, and at least some of the fish mature at the beginning of their second year. The maximum age attained seems to be about 3 years, and the fish can reach a length of about 80 mm in this time. The food consists mostly of small benthic invertebrates taken from both the stream bed and the drift fauna.  相似文献   

6.
Drift was collected over 24‐h periods in five rivers in South Island, New Zealand, to determine whether diel periodicity was consistent across a range of river types, and whether the pattern was similar for different life stages/sizes of selected taxa. Total drift density (numbers per 100 m3 ) of aquatic invertebrates was greater at night than during the day in all rivers; peak abundance occurred shortly after sunset in clear water rivers and shortly before sunrise in a turbid, glacier‐fed river. Densities of drifting Deleatidium spp., Nesameletus spp. (both Ephemeroptera), Aoteapsyche spp., and Hydrobiosidae (both Trichoptera), were generally greater at night than during the day. However, the timing of peak abundance in the drift for other common taxa varied between rivers. Larger Deleatidium spp. larvae (> 1.00 mm head width) were more common in the drift at night than during the day in all rivers. However, this was not apparent for Aoteapsyche spp. and Hydrobiosidae, for which diel differences in the size of drifting animals were not consistent even within the same river. The propensity for some aquatic invertebrates to drift at night may influence fish feeding behaviour, particularly with respect to the timing of feeding and the species or life history stages of their prey.  相似文献   

7.
Galaxias vulgaris Stokell is a totally freshwater fish species and the adults usually live a cryptic life under stones. The life history of this species, with special emphasis on its embryology, growth rate, and sex ratio, is described. Comparisons are made with other members of the family Galaxiidae, especially G. maculatus attenuatus  相似文献   

8.
The muscle myogen proteins of 10 species of the family Galaxiidae exhibited a high degree of species specificity when separated by starch gel electrophoresis. Non‐diadromous, non‐lacustrine species had some variation in the proteins present, while diadromous and lacustrine species, except for Galaxias maculatus, had remarkably uniform muscle myogen electrophero‐grams. The variation can be explained by polymorphism and mosaic evolution of isolated freshwater populations. It was found that previously erected specific and generic categories, except for G. vulgaris, are clearly defined by differences in muscle protein. The standardised electropherogram types obtained were subjected to cluster analysis using both squared Euclidean distance and the complement of Jacard's coefficient with average sorting strategy. A principal component analysis was also carried out. The first two components of the principal component analysis widely spaced the three genera included in this study (Salmo, Galaxias, and Neochanna), with N. burrowsius occupying an intermediate position between Galaxias and Neochanna. Previous workers have considered this species to be a connecting link between the two genera. The dendrogram produced by using squared Euclidean distance (which included all available information) first clustered the types into Salmoniidae and Galaxiidae. The latter were split into the genus Neochanna and the genus Galaxias which was then subdivided into stout‐bodied species (G. argenleus and G. jasciatus) and slender‐bodied species. G. brevipinnis and G. vulgaris types were further separated from the three alpine Galaxias species and G. maculatus. The substantial agreement of these results with previous taxonomic efforts indicates that electrophoretic data can be a valid taxonomic tool.  相似文献   

9.
Food differentiation among coexistent species in the field is important strategy for copepods to acquire materials and maintain population stabilization.In situ diet analysis of co-occurring six copepod species in coral waters of the Sanya Bay was conducted using a PCR protocol based on 18 S ribosomal gene.Various prey organisms were uncovered,including dinoflagellate,diatom,green algae and plant,protozoa and metazoan.All these spatially coexisting six species showed different dietary diversity,with the food niche breadth(B)ranging from 1.00(Temora turbinate in morning)to 10.68(Calanopia elliptica in night).While food overlap between all these copepods were low,with the average value of the diet niche overlap index being approximately 0.09.Even temporally co-existing species sampled from the same time point fed on different groups of prey items with the food overlap index of 0.04 to 0.07 in midday and night but 0 in morning.As the most important dominant copepod in the Sanya Bay,Subeucalanus subcrassus seems to be capable to regulate its feeding,by exhibiting a rhythm of herbivorous feeding in midday and carnivorous feeding in morning and night,to better coordinate with other competitors for utilization of food resources.For most copepods,none of the prey items belonged to the dominant phytoplankton in the ambient water,indicating that copepod can better their survival by widening the choice of potential food resources in food limited environment.The dietary separation observed here might be important strategy for copepod to maintain population stabilization and thriving in the Sanya coastal waters.  相似文献   

10.
The larvae and larval development of Galaxias maculatus are described from a freshwater lake and a saline river in southwestern Western Australia. The size at hatching (7.0 mm total length) was similar to that recorded elsewhere for G. maculatus and the sequence of fin development (i.e., caudal, dorsal, anal, pectoral, and pelvic fins) was identical to that recorded for galaxiids generally. There were relative increases in the proportions of head length and body depth with larval growth and a decrease in proportion of pre‐anal length. Larvae from river habitats were smaller throughout larval stages of development than those from the lake. Fins of riverine fish began and completed development at a smaller size of fish than the lacustrine population, presumably as a response to the need for great motility at a smaller fish size in lotic environments.  相似文献   

11.
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.  相似文献   

12.
Distribution, abundance, and habitat preferences of native fish were investigated down the length of a relatively pristine, medium‐sized, fourth‐order stream on Stewart Island, New Zealand. A limited fish fauna was recorded (six species), including three threatened large galaxiid species (Galaxias argenteus, Galaxias fasciatus, and Galaxias brevipinnis), which have restricted distributions on mainland New Zealand. Results indicated that these large galaxiids occupy diverse habitats including pools and backwaters within the mainstems of this stream. Their extensive distributions and wide habitat usage were attributed to factors such as the intact catchment vegetation, unmodified stream channel, and the absence of introduced fishes, particularly salmonids. Results suggest that some native species have been excluded from mainstem habitats elsewhere in New Zealand. It was also evident that interactions among the native species influenced habitat use; G. brevipinnis avoided backwaters, runs, and pools in reaches occupied by G. fasciatus and Anguilla dieffenbachii; whereas G. fasciatus appeared to avoid habitats occupied by G. argenteus and A dieffenbachii. Maximum densities and biomass of galaxiids and eels occurred in deepwater habitats (>0.75 m). Furthermore the fish inhabiting these deeper waters were larger and more likely to be female. These findings have significant implications for the design and application of sampling protocols for native New Zealand fishes and for the protection of their habitats. If deeper waters are not sampled then species, sex, and size biased data may result.  相似文献   

13.
Numerical data based on stomach content analysis of the zooplanktivorous freshwater fish, Retropinna semoni, were used to examine the effect of fish sample size on mean counts of dominant prey items. Fifty adult R. semoni were collected from throughout the open‐water of Lake Benanee, Australia at each of five times over a diel period. Bootstrapping was used to generate confidence intervals around sample means, and markedly more accurate means were obtained from samples collected in the day than the night. High variation in night samples was the by‐product of a diurnal feeding regime. Traditional sample sizes of 10 to 15 stomachs resulted in reasonable confidence intervals of sample means derived from collections on the first day, corresponding to uniform feeding patterns in the population. However, increased sample sizes were required to describe more complex feeding behaviour on the second day, when a proportion of the population switched to an alternative prey source.  相似文献   

14.
Drifting mysids were sampled to determine diel activity, and whether mysid numbers vary with respect to inflowing and outflowing tides. Samples of drifting mysids were collected at the mouth of the Taieri River, New Zealand, over one 24‐h cycle using five replicate conical drift nets in January 1999. One‐night and 1‐day ebb and flood tide were each sampled. Four species of mysid Tenagomysis macropsis, T. novae‐zealandiae, T. robusta, and an apparently undescribed species of Gastrosaccus sp., were collected over the sampling period. One species, T. robusta, has not previously been collected from estuarine or riverine systems. The undescribed Gastrosaccus sp. was the most abundant of the four species. All four species were more abundant at night, with T. robusta and Gastrosaccus sp. being considerably more abundant in the drift on outflowing tides. In contrast, roughly equal numbers of T. macropsis and T. novae‐zealandiae were observed drifting in and out of the estuary at night.  相似文献   

15.
实验生态条件下研究十溴联苯醚(BDE-209)的急性毒性胁迫对褶皱臂尾轮虫(Branchionus plicatilis)运动行为与摄食行为的影响,探讨可用以表征胁迫-响应的生物标志物。结果表明:(1)BDE-209胁迫24h显著性增加了褶皱臂尾轮虫的运动抑制率,由此得到24h半数有效抑制浓度(24h-EC_(50))为9.084mg/L,但未达到半数致死作用;(2)当分别以四种海洋微藻:小球藻(Chlorella vulgaris)、青岛大扁藻(Platymonas helgolandica)、等鞭金藻8701(Isochrysis galbana)和小新月菱形藻(Cylindrotheca closterium)为单一饵料来源时,褶皱臂尾轮虫对四种饵料单胞藻的滤水率(F)和摄食率(G)均随着胁迫时间和胁迫浓度的增加而不断下降,呈现出明显的浓度依赖性,说明BDE-209胁迫能显著抑制褶皱臂尾轮虫的摄食作用。(3)将其中三种微藻等生物量混合投喂时,褶皱臂尾轮虫对三种微藻的滤水率和摄食率与单一饵料投喂条件相比均发生变化,且对各种微藻的选食率(Sr)和摄食总生物量均随着胁迫时间和浓度的增加呈下降趋势,选择性指数(Si)发生变化,对小球藻的摄食选择性最高。滤水率的变化较其它指标更敏感,可用以指示浮游动物在个体水平上响应外源环境变化的标志物。结果表明,BDE-209胁迫能有效改变褶皱臂尾轮虫的摄食与选食行为,且其最适宜的饵料是小球藻。  相似文献   

16.
Abstract. The waters surrounding the Pribilof Islands are an important nursery ground for juvenile walleye pollock (Theragra chalcogramma), an important forage fish in the pelagic food web of the productive Bering Sea shelf region. The diet of juvenile pollock was studied in two consecutive years along a transect line crossing from a well‐mixed coastal domain, through a frontal region to stratified water farther offshore. Variability in stomach fullness was high and evidence for increased feeding intensity in the front was weak. Prey diversity and prey size generally increased with increasing fish size, shifting from predominantly small copepods to larger, more evasive prey items such as euphausiids, crab megalopae and fish. The diet of the fish reflected changes in the relative abundance of copepods and euphausiids in the prey fields between years. Juvenile pollock showed increased feeding rates at dusk, and stomach fullness as well as prey condition were generally lowest just before sunrise; however, the proportion of euphausiids increased in the diet of pollock caught at night, suggesting that some food was also ingested during darkness. Juvenile pollock and their euphausiid prey both vertically migrated above the thermocline at night, although each had a different daytime depth.  相似文献   

17.
Data are presented on biomass, mortality, growth, and production of fish populations inhabiting two small streams in the Wairarapa district of the North Island of New Zealand. The main water of both streams contained a mixed population of bullies (Philypnodon breviceps Stokell), brown trout (Salmo trutta Linn.), and eels (Anguilla dieffenbachii Gray, and A. australis schmidtii Phillipps). The headwater tributaries of one of the streams contained a large population of Galaxias divergens Stokell and a few eels, but other fish species were absent. All species of fish appeared to be using the same food supply of small benthic invertebrates, mainly ephemeropteran and dipteran larvae. Biomass of benthos per unit area was appreciably higher in the headwater tributary examined than in the main waters downstream. Mean annual stock of benthos in the tributary (Hinau north branch) was 19.75 g/m2, in the Hinau main water 10.71 g/m2 and in the Hinaki main water 13.47 g/m2 Nevertheless, production per unit area from the nearly monospecific fish population in the Hinau north branch (14.28 g/m2) was less than that of the mixed populations in the main waters (24.17 g/m2 in the Hinau, 73.54 g/m2 in the Hinaki). Possibly fish production in the headwaters might be greater if the species composition of fish was more diverse.  相似文献   

18.
The distribution of fish within eight small streams feeding into the lower Taieri and Waipori Rivers on the east coast of New Zealand's South Island was examined. A total of eight native and two introduced species were recorded. Eels (Anguilla spp.) and giant kokopu (Galaxias argenteus Gmelin) were the most widely distributed species being located in all streams surveyed. Common bullies (Gobiomorphus cotidianus McDowall) and brown trout (Salmo trutta Linnaeus) were also widely distributed being detected in seven and six of the streams respectively. Three streams of potential conservation significance were identified. These were Picnic Gully Creek which contained a significant population of banded kokopu (Galaxias fasciatus Gray), a Category C threatened species, and Cullens and Alex Creeks which contained significant populations of giant kokopu, a Category B threatened species. The population of giant kokopu in Cullens and Alex Creeks currently represents the largest known population of this species on the east coast of New Zealand (excluding Southland). It has been suggested that brown trout may influence the distribution of native galaxiids. The longitudinal distribution of giant kokopu and brown trout in streams was examined at night using a continuous spotlight sampling approach. Distributions of these two species rarely overlapped at a local scale. Coarse habitat use data indicated that brown trout regularly occupied a variety of habitat types including modified agricultural channels. In contrast, giant kokopu rarely used agricultural channels being predominantly located in pool habitats.  相似文献   

19.
By relating catches to area trawled, the population of Uranostoma richei (Freminville, 1813) in 1969–70 in Lyttelton Harbour, South Island, New Zealand, was estimated at 120 000–900 000.

Analysis of 1 5S8 stomachs showed that Uranostoma fed on 58 species from 7 phyla. Arthropods constituted three‐quarters of the food, with the crab Macro‐phthalmus hirtipes contributing over 60%. The remaining food items included polychaetes, brachiopods, chordates, coelenterates, echinoderms, molluscs, debris, and digested matter. Analysis of a further 10 465 stomachs showed that feeding intensity was highest in summer.  相似文献   

20.
The feeding habit of Austrolethops wardi (Gobiidae) in the seagrass beds of Barrang Lompo and Bone Batang Island in the Spermonde Archipelago, South West Sulawesi, Indonesia, was investigated through gut content analysis. The feeding preferences of this species are very similar on both islands: A. wardi, a burrow associate of Neaxius acanthus, was found to feed almost exclusively on seagrass (which was found in 100% of the investigated stomachs and made up >94% of food items). However, seagrass epiphytes (<5% of food items) and animal food (<1% of food items) occurred in the guts as well, the latter predominantly in terms of copepods and to a lesser degree in other small invertebrates. These results indicate that animal food is of little importance for A. wardi. Some specimens even contained no parts of animal food.  相似文献   

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