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1.
The first mid-Atlantic diet of Mesoplodon beaked whales is presented, from ten Sowerby's Mesoplodon bidens stranded in the Azores region between 2002 and 2009. This doubles the worldwide number of stomachs sampled, and reveals new feeding habits for this species. The mean number of prey items per stomach was 85±89 (range: 12–238), with fish accounting for 99.3% and cephalopods contributing less than 1% of total prey. Fish otoliths from 15 families and cephalopod lower mandibles from three families were identified, representing 22 taxa. The diet consisted mainly of small mid-water fish, the most numerous being Diaphus sp., Lampanyctus sp. and Melamphaidae species. Myctophids were present in all stranded individuals, followed by Diretmidae, Melamphaidae and Opisthoproctus soleatus, while the remaining fish species were scarce or single occurrences. Consistency of diet in four different years reveals a divergence from all previous records in continental areas, where mainly neritic and shelf-break benthopelagic fish species have been reported. Mid-Atlantic Sowerby's beaked whales' showed dietary plasticity, feeding on the most abundant mid-water groups occurring between 0 and750 m. Trophic level from prey numerical frequency was estimated at 4.4±0.46.  相似文献   

2.
The striped dolphin, Stenella coeruleoalba, is an oceanic species that occasionally occurs in neritic habitats; in the Bay of Biscay it is abundant offshore and erratic in occurrence over the shelf. Given that prey assemblages differ widely among these habitats both in terms of taxonomic composition and of ecology, this would suggest that striped dolphins are able to shift from vertically migrating meso-pelagic prey to neritic or coastal prey types. We investigated the striped dolphin's dietary plasticity by examining the stomach contents of individuals stranded along the French Atlantic coast. 1109 prey items were identified belonging to 30 distinct taxa and their biomass was calculated. Fish accounted for 91% of the diet by number and 61% by mass; the rest was mostly cephalopods, crustaceans being present as trace. Specific composition included both oceanic (myctophid and sternoptychid fish; histioteuthid, gonatid and brachioteuthid cephalopods), neritic (gadids and anchovy; loliginid, sepiolid and sepiid cephalopods) and even coastal (atherinid fish) prey types, showing that these animals had changed their diet as they moved over the shelf.  相似文献   

3.
Records of four species of Delphinidae, Delphinus delphis, Lissodelphis peroni, Lagenorhynchus obscurus, and Lagenorhynchus cruciger in waters to the east and south‐east of New Zealand are discussed in relation to surface temperatures.

In this region D. delphis appears to be largely confined north of the Subtropical Convergence and a minimum surface temperature of about 14°c, and near New Zealand from Hawke Bay southward in the warm water of the East Cape Current; L. peroni to the Subtropical Convergence and the subantarctic water to the south of it, between surface temperatures of 9°c and 16°c; L. obscurus to the immediate vicinity of the Subtropical Convergence and surface temperatures in summer of about 14° to 15°c, and L. cruciger across the Antarctic Convergence region, in a surface temperature range of 2° to 9°c.  相似文献   

4.
柔鱼亚科(Ommastrephinae)近缘种鸢乌贼(Sthenoteuthisoualaniensis)和茎柔鱼(Dosidicus gigas)为重要的大洋性经济头足类,二者在东太平洋赤道海域均有分布。研究以同一航次捕获的两种头足类为研究对象,结合传统胃含物分析和DNA条形码技术对二者食物组成及其差异开展研究,以分析同域近缘头足类间的摄食习性及差异。结果表明,鸢乌贼和茎柔鱼均以鱼类、头足类和甲壳类为主要食物来源,ANOVA显示,两者在Shannon多样性指数和饵料生物头足类和鱼类N%上均存在显著差异, SIMPER分析进一步表明,种间胃含物组成差异最主要体现在鱼类的种类组成和个数百分比上。研究结论直观反映了同域近缘头足类物种食物特化的现象,为后续探究头足类近缘种共存机制提供了数据支持。  相似文献   

5.
This study provides one of the first quantitative assessments of a fish community within a pre-operational deep-water port system. Between September 2006 and September 2007 a total of 4 559 fish, representing 47 species and 27 different families, were caught within the Port of Ngqura, Africa's deepest port, in 1 713 h of shore-angling (2.3 fish angler?1 h?1) and 239 h of boat-based angling (2.8 fish angler?1 h?1). Catches included species representative of both estuarine and shore fisheries. The majority (83.0%) of species caught were marine and most were less than size-at-50% maturity (71.4%). The most abundantly caught species were dusky kob Argyrosomus japonicus (25.5%), elf Pomatomus saltatrix (24.9%), garrick Lichia amia (17.7%) and dusky sharks Carcharhinus obscurus (10.7%). Fish assemblages differed significantly (p < 0.05) between three habitats within the port: Dolosse, Quay Wall and Sandy Shore. The Dolosse habitat supported the greatest abundance (3.1 fish angler?1 h?1) and diversity (43) of fish species. The Port of Ngqura is thus functioning as an important habitat for both juvenile and adult fish. The diversity and abundance of fish suggests the potential use of ports and other artificial structures for enhancing local fisheries in South Africa.  相似文献   

6.
The diets of 15 species of squaloid sharks caught between Walvis Bay and Cape Agulhas over a depth range of 50–1 016 m are analysed. The most common prey items were fish and cephalopods. Hake Merluccius spp. were common in the diets of Centrophorus squamosus, Squalus acanthias, and S. cf. mitsukurii. Myctophids were extensively preyed on by Centroscyllium fabricii, Deania calcea, D. profundorum, Etmopterus cf. brachyurus, E. compagnoi, S. acanthias and S. megalops, among others. The most common cephalopods in shark stomachs were Histioteuthis miranda, Lycoteuthis ?diadema, Octopus vulgaris and Todarodes angolensis. Crustaceans were uncommon prey of most species, except for Centroscyllium fabricii and Etmopterus cf. granulosus. Centroscymnus coelolepis was the only squaloid with cetacean remains in the stomach. That species appears to parasitize its cetacean victims.  相似文献   

7.
根据2019年1月、4月、7月和10月四个季度10个站位定置张网调查资料, 对福建三沙湾游泳动物的种类组成及季节变化进行分析研究。结果表明: 调查共获得游泳动物209种, 隶属于3门4纲19目73科144属, 其中鱼类154种, 甲壳类48种, 头足类7种。游泳动物种类数以秋季出现最多, 四个季节共同出现的种类有42种。鲈形目种类最多, 其次是十足目。鱼类适温性以暖水性种类居多, 占71.43%, 暖温性种类次之(27.92%); 生态类型以底层、近底层鱼类居多, 两者合占75.97%。鹰爪虾(Trachypenaeus curvirostris)、大黄鱼(Larimichthys crocea)、棘头梅童鱼(Collichthys lucidus)、红星梭子蟹(Portunus sanguinolentus)和日本蟳(Charybdis japonica)等14个种类是三沙湾游泳动物的优势种类, 季节性优势种居多。三沙湾定置张网调查渔业资源质量密度为111.09 kg/km2, 尾数密度为13.72×103 ind./km2, 均以夏季最高, 春季最低。应该进一步加强对三沙湾渔业资源的合理利用和有效保护, 同时重视对外来物种的监测。  相似文献   

8.
The stomach contents of 36 South African fur seals beached over a 20 year period along the south-east coast of South Africa were examined. In all, 15 fish and nine cephalopod prey types were identified. Five species of fish (Merluccius capensis, Trachurus trachurus capensis, Cynoglossus zanzibarensis, Pterogymnus laniarius, Austroglossus pectoralis) and two cephalopods (Loligo vulgaris reynaudii, Octopus sp.) were of major importance in the diet. The proportion of demersal species in the diet is higher than previously reported, suggesting that the seals forage extensively on the sea floor. The most important fish species in the diet was M. capensis, and the most important cephalopod was L. v. reynaudii. Male and female seals showed distinct prey selection, suggesting possible intraspecific resource partitioning. There is no evidence of competition between seals and other top predators.  相似文献   

9.
The shark species Carcharhinus brachyurus, C. obscurus and Sphyrna zygaena, which attain more than 2 m when adult, occur in coastal waters of the Southern Cape as juveniles. They use these coastal waters as nursery areas and their relative abundance there varies through the year, possibly because of seasonally varying oceanographic conditions. Adult C. brachyurus occur in the same geographic area but usually deeper, although there is some overlap in juvenile and adult depth ranges. Adult C. obscurus prefer the warmer subtropical and tropical waters north of the study area. Adult S. zygaena are found over deep reefs at the edge of the continental shelf. There was considerable dietary overlap between the three species, the prey of all three being dominated by small schooling fish, such as pilchard, and squid. For the three species, animals of total length >2 m took larger prey, such as elasmobranchs, with greater frequency, although they continued to prey on squid and schooling fish. It is postulated that the nursery areas are in the study area because of the abundance of food there, and that avoidance of cannibalism would be enhanced by the use of such nurseries.  相似文献   

10.
The shore stranding of mesopelagic fauna is a recurrent phenomenon in the Strait of Messina (Central Mediterranean Sea). The aim of this paper is to test the influence of lunar phases, winds and seasons upon the frequency of occurrence of strandings of mesopelagic fish. Species abundance in relation to these factors was quantified for the first time. Specimens were collected stranded on the shore along the Sicilian coast of the Strait of Messina between 2008 and 2016. Overall 32 species belonging to seven families (Gonostomatidae, Microstomatidae, Myctophidae, Paralepididae, Phosichthyidae, Sternoptychidae, Stomiidae) were found stranded. Myctophidae was the family including the highest number of species (16), whereas Gonostomatidae was the most abundant in terms of total number of individuals (47.2%), mainly thanks to the species Cyclothone braueri. The moon, which influences the strength of currents (highest during full and new moon phases) and irradiance (higher in some lunar phases, such as the full moon), affected the abundance of stranded mesopelagic fish in the study area. The highest number of stranding events was recorded during the new moon: 34.6% of the total relative abundance of stranded mesopelagic fish. Wind blowing from the sea towards the coastline (southeasterly and easterly winds) created the best conditions for strandings. The highest abundance of stranded specimens was recorded during the winter season.  相似文献   

11.
Aside from gender differences, a principal components analysis of skull measurements of 72 adult common dolphins from South Africa failed to distinguish more than one form of Delphinus. Plots of rostral length against zygomatic width indicated most could be referred to the long-beaked form D. capensis, but three individuals lay outside this range, two of which were within the range for the short-beaked form D. delphis from the North Pacific. These were smaller individuals with significantly shorter beaks, longer flippers and wider flukes, and the colour patterns of two agreed completely or mostly with criteria for delphis. Their tooth counts were within (but close to the upper end of) the range for D. delphis, whereas other common dolphins in the region were within the range for D. capensis. Vertebral counts for all Delphinus from South Africa were similar and were well below those for D. capensis from the North Pacific. It is concluded that a smaller form of Delphinus, with characteristics mostly resembling those of D. delphis, occurs in South African waters, but (because of small sample size and the lack of complete agreement with published criteria for D. delphis from the North Pacific) its exact taxonomic relationship to D. capensis in this region is unclear.  相似文献   

12.
The diet of the squid Nototodarus sloanii was determined from examination of stomach contents of 388 specimens of 14.3–41.0 cm dorsal mantle length sampled at depths of 211–760 m on the Chatham Rise, New Zealand. Prey items were predominantly mesopelagic fishes, with some crustaceans and cephalopods. The most important prey species identified was Maurolicus australis, followed by Lampanyctodes hectoris, and unidentified squids (Teuthoidea). Multivariate analyses using distance‐based linear models, non‐parametric multi‐dimensional scaling, analysis of similarities, and similarity percentages, indicated crustaceans were more important in the diet of smaller squid (83–480 g), the fish component of the diet was dominated by L. hectoris on the east Chatham Rise and M. australis on the west Chatham Rise, and there may be a difference in diet with sex, with crustaceans and cephalopods more important for females. The results indicated that N. sloanii, similar to other ommastrephid squids, foraged primarily in the mesopelagic layers.  相似文献   

13.
Records are presented of sightings of 6 cetacean species (15 common dolphins, Delphinus delphis Linnaeus, over 5000 dusky dolphins, Lagenorhynchus obscurus (Gray), approximately 74 bottlenose dolphins, Tursiops truncatus (Montagu), 8 sperm whales, Physeter catodon Linnaeus, 6 southern humpback whales, Megaptera novaeangliae lalandi (Fischer), and 36 southern pilot whales. Globi‐cephala melaena edwardii (Smith)) from m.v. Lloret Lopez II between 8 January and 2 April 1970. A large school of dusky dolphins was observed south of Solander Island. Monthly water temperatures in the summer of 1970 were high and in January ranged from 15.4°c (9.2 km west of Fiordland) and 21.6°c (55 km west of Cape Farewell), in February from 16.2°c (Fiordland) and 20.4°c (Cape Farewell), and in March from 16.0°c (Fiordland) and 20.5°c (Cape Farewell).  相似文献   

14.
The species composition, seasonal abundance, and vertical distribution of mesopelagic fish larvae are described based on discrete depth sampling from the surface down to 1000 m depth during four cruises at a fixed sampling station in Sagami Bay. The abundances of total mesopelagic fish larvae in April, July, September, and December were 65.7, 13.6, 118.9, and 17.2 individuals per 10 m2 sea surface, respectively. Twenty species or types of mesopelagic fish larvae belonging to 10 families were collected. Diaphus garmani, Lipolagus ochotensis, Diogenichthys atlanticus, Sigmops gracile, and Maurolicus japonicus were the five most abundant larvae and accounted for 43.1, 14.5, 7.4, 6.3, and 5.9% of the total mesopelagic fish larvae, respectively. These five species showed clear seasonal changes in abundance, i.e. L. ochotensis, D. atlanticus, and S. gracile larvae mainly occurred during winter— spring; D. garmani and M. japonicus were collected during summer—autumn. No obvious diel vertical migration was found in these larvae. The larvae of D. garmani and M. japonicus were concentrated in the 25–50 and 50–100 m depth layers, respectively. The transforming stage of L. ochotensis, S. gracile, and D. atlanticus occurred at 400–1000 m depth, while their larvae (<8 mm standard length) occurred in the upper 100 m layer, indicating that metamorphosis of these species takes place in the 400–1000 m layer. Based on the occurrence of mesopelagic fish larvae and oceanographic processes in Sagami Bay, with the exception of D. garmani and M. japonicus, most larvae are considered to originate from the Kuroshio region where their main spawning grounds are formed.  相似文献   

15.
Literature on trophic relationships in the Benguela ecosystem has stressed the importance of cephalopods as prey of groundfish. The groundfish community of the shelf and upper slope of southern Africa is dominated by the Cape hakes, and the results presented (1984–1991) confirm that both species of hake are important predators of cephalopods, especially taking into consideration the abundance of hake in the ecosystem. However, geographic, seasonal and species variability are evident in the patterns observed. The main prey species are Sepia spp. (predominantly Sepia australis), Loligo vulgaris reynaudii, Todaropsis eblanae and Lycoteuthis ?diadema. The last-named is an important food organism for fish. Its systematic status needs revision, however. Qualitative results of studies of cephalopod predation are also provided for kingklip and monkfish.  相似文献   

16.
根据2011年4月、5月与6月对浙江南部沿岸产卵场进行的共3个航次的调查资料,对该海域的鱼卵、仔稚鱼的种类组成和数量分布进行了分析,结果表明,共发现鱼卵、仔稚鱼72个种类,分别隶属11目38科48属。其中鱼卵29种,分别隶属6目18科24属;仔稚鱼55种,分别隶属10目29科40属。4—6月仔稚鱼数量呈逐月递减的趋势,而鱼卵数量6月最多,5月最少。鱼卵优势种4月以斑鰶、棱鱚、小黄鱼与蓝点马鲛为主,5月以斑鰶、鳀、龙头鱼、银鲳、蓝点马鲛与石首鱼科为主,6月以鳀、龙头鱼、多鳞鱚与鲱科鱼类为主;仔稚鱼优势种4月以虾虎鱼类、褐菖鲉与平鲉科为主,5月以鳀、虾虎鱼类、棱鱚、斑鰶与长鳍篮子鱼为主,6月以鳀与虾虎鱼类为主。斑鰶、鲳鱼、小黄鱼、棱鱚、蓝点马鲛与褐菖鲉的产卵盛期为4月,而鳀与龙头鱼的产卵盛期为6月。  相似文献   

17.
The spatial size distribution of grunts and snappers have previously indicated the separation of juveniles in nursery habitats from the adults on the coral reef. This implies life cycle migrations from nursery habitats (such as seagrass beds and mangroves) to the coral reef. If diet shifts are related to such migrations, then the diets of these fish must change before or around the fish size at which such migrations take place. A wide size range of juveniles of two grunt species (Haemulon sciurus and Haemulon flavolineatum) and of two snapper species (Lutjanus apodus and Ocyurus chrysurus) were caught in seagrass beds and mangroves, and their gut contents identified and quantified. Regression analysis between fish size and dietary importance of small crustaceans showed a negative relationship in all four species. Positive relations were found for H. sciurus, L. apodus and O. chrysurus between fish length and the dietary importance of decapods, and for L. apodusand O. chrysurus between fish length and prey fish importance. Critical changes in the fish diets with fish size were examined by application of a Canonical Correspondence Analysis (CCA). The CCA yielded three clusters of size-classes of fishes with similar diets, and application of a Mantel test showed that each of these clusters had significantly different diets, and that each cluster diet was significantly specialised. The size at which a fish species ‘switched’ from one cluster to another was compared with size-at-maturity data and with the typical size at which these species migrate from the nursery habitats to the coral reef. H. sciurus and H. flavolineatum may be prompted to migrate from the nursery habitats to coral reef habitats because of dietary changes, or because of the development of the gonads. For L. apodus and O. chrysurus, a dietary changeover forms a more likely explanation for nursery-to-reef migrations than does sexual maturation because these species reach maturity at sizes much larger than the maximum size of individuals found in nursery habitats. Although other factors may theoretically initiate or promote the migration patterns, the results of this study indicate that ontogenetic dietary changes may crucially influence the nursery-to-coral reef migrations of these reef fish species.  相似文献   

18.
Almost 1 000 South African fur seals Arctocephalus pusillus pusillus were collected at sea (inshore and offshore) for examination of stomach contents and other biological parameters. The main prey of seals above the age of one year was teleost fish, of which at least 28 species were identified. Overall, 74,6 per cent of the diet was teleost fish, 16,7 per cent cephalopods, 4,8 per cent crustaceans such as shrimps, prawns, amphipods and isopods and 3,2 percent rock lobster. Within this overall dietary pattern there were marked regional differences. The importance of individual fish species in the diet was investigated from the numbers and the sizes of otoliths occurring in the stomachs, from which the identity and size classes of the prey species could be calculated. Again there were regional differences in the importance of different prey species. On the west coast of South Africa the most important species were anchovy and Cape hakes (each 23% of total diet), whereas on the south coast the important species were anchovy (17%), horse mackerel (14%), pilchard (12%) and Cape hake (14%). Off South West Africa the two dominant species were pelagic goby (52%) and horse mackerel (23%), anchovy and Cape hake constituting only 4 and 5 per cent respectively of total diet. The total annual consumption of anchovy and Cape hake by seals in South African waters was calculated at 125 000 and 120 000 tons respectively.  相似文献   

19.
半滑舌鳎是重要的经济鱼类,已经被广泛推广养殖,致力于养殖方面的研究开展了很多工作,但是对半滑舌鳎生长性状进行准确遗传评估的研究还未见报道。为了对生长性状进行准确的遗传参数估计,本次研究以80个半滑舌鳎家系为研究对象,对半滑舌鳎早期生长性状（包括个体全长、体宽和体质量）进行分析。另外还将鱼体底面纯白与否（命名为底面颜色）作为一个性状进行研究。结果表明,四个性状都属于中等遗传力（全长为0.210、体宽为0.259、体质量为0.268、底面颜色为0.362）。三个生长性状之间具有很高的遗传相关性（0.913-0.959）,表明如果三个性状进行间接选择的话,将会取得较好效果。底面颜色性状与三个生长性状均为正遗传相关,相关系数在0.241-0.353之间,由此可知,对底面颜色进行选择时,可以加强生长性状的选择效果。通过家系育种值排序,初步筛选出了生长性状优良遗传背景丰富的16个全同胞家系,将作为亲鱼繁殖后代。本研究为半滑舌鳎优良品种的成功培育提供了重要基础资料。  相似文献   

20.
We applied DNA‐based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing ~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55–71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard‐parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA‐based analyses and their capabilities to enhance information of trophic interactions.  相似文献   

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