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1.
Nicole B. Richoux Sébastien Jaquemet Bo T. Bonnevie Yves Cherel Christopher D. McQuaid 《Marine Biology》2010,157(8):1755-1766
During chick-rearing, albatrosses can alternate between long foraging trips that provide the main source of food for the adults
and short foraging trips that they use to feed their young. This flexibility in foraging behaviour can lead to differences
in diet composition between adults and chicks and implies that they may be vulnerable in different ways to food shortages.
The trophic ecology of the Grey-headed albatross Thalassarche chrysostoma was investigated at the sub-Antarctic Prince Edward Islands during the chick-rearing period in April 2006 using a combination
of approaches. Diets of adults and chicks were assessed using stable isotope ratios and fatty acid (FA) profiles of blood
and/or stomach oils, in addition to stomach contents analysis. Fish from the family Macrouridae and cephalopods (particularly
the onychoteuthid Kondakovia longimana) were the primary prey, whereas crustaceans (krill Euphausia superba) represented a smaller proportion of the stomach contents. Stomach oil FA profiles contained more monounsaturated FA than
the profiles of plasma, which were richer in saturated FA and arachidonic acid (20:4n-6). There was also a distinct separation
of adults from chicks, with higher levels of monounsaturates in chick plasma, and higher saturated FA levels (particularly
16:0) in the adult plasma. Stable carbon isotope ratios of whole blood were similar in adults and chicks, whereas stable nitrogen
isotope ratios showed significant enrichment by >1‰ in chicks. The combined FA, stable isotopes and stomach contents analyses
suggest clear differences in diet quality between adults and chicks, with chicks feeding at a higher trophic position through
feeding more on highly nutritious fish and adults keeping much of the less nutritious zooplankton for themselves. 相似文献
2.
Petra Quillfeldt Andreas Michalik Gritta Veit-Köhler Ian J. Strange Juan F. Masello 《Marine Biology》2010,157(9):2043-2050
Central place foragers are constrained in their foraging distribution by the necessity to return to their nest site at regular
intervals. In many petrels that feed on patchily distributed prey from the sea surface over large foraging areas, alternating
long and short foraging trips are used to balance the demands of the chick with the requirements of maintaining adult body
condition. When the local conditions are favourable for prey density and quality, adults should be able to reduce the number
of long foraging trips. We studied the flexibility in foraging trip lengths of a small pelagic petrel, the thin-billed prion
Pachyptila belcheri, over three breeding seasons with increasingly favourable, cold-water conditions. During a warm-water influx in February
2006, chicks were fed less frequently and adults carried out foraging trips of up to 8 days. When conditions became more favourable
with colder water temperatures in 2007 and 2008, thin-billed prions decreased trip lengths, more often attended their chick
every day, and long foraging trips of six to eight days were not registered during 2008. Chick growth rates mirrored this,
as chicks grew poorly during 2006, intermediate during 2007 and best during 2008. Thin-billed prions preyed mainly on squid
during incubation and mainly on amphipods and euphausiids during chick-rearing. In the poorest season only, the diet was substantially
supplemented with very small copepods. Together, the present results indicate that during warm-water conditions, thin-billed
prions had difficulties in finding sufficient squid, amphipods or euphausiids and were forced to switch to lower trophic level
prey, which they had to search for over large ocean areas. 相似文献
3.
We examined the isotopic signatures (δ13C, δ15N) of adult body feathers from southern giant petrels Macronectes giganteus collected at two breeding colonies in Antarctica (Potter Peninsula and Cape Geddes) and one in southern Patagonia (Observatorio
Island), as well as in whole blood collected from adults of both sexes at each Antarctic colonies and from chicks at Potter
Peninsula. As body feather moult is a continuous process in giant petrels, feathers provide an integrated annual signal of
an adult’s diets and foraging habitats. In contrast, the stable isotope values of adult and chick blood are reflective of
their diets during the breeding season. We found that sex-specific dietary segregation in adults breeding in Antarctica was
notable during the breeding season (blood samples) but absent when examined across the entire year (feather samples). In addition,
blood stable isotope values differed between chicks and adults, indicating that adults provision their offspring with a relatively
higher amount of penguin and seal prey that what they consume themselves. This finding confirms previous work that suggests
that chicks are preferentially fed with prey of presumably higher nutritional value such as carrion. Finally, based on isotopic
differences between major oceanographic zones in the Southern Ocean, our data indicate population-specific differences in
foraging distribution, with Antarctic populations move seasonally between Antarctic and subantarctic zones, while Patagonian
populations likely forage in subtropical waters and in continental shelf habitats year-round. 相似文献
4.
We studied foraging activity of giant petrels during the incubation period, by simultaneously deploying activity recorders and satellite transmitters on northern (Macronectes halli) and southern giant petrels (Macronectes giganteus) at Bird Island (South Georgia, Antarctica) between 29 October and 26 December 1998. Satellite tracking showed two types of trips: (1) coastal trips, all undertaken by male northern giant petrels, to the nearby South Georgia mainland, presumably foraging on seal and penguin carcasses on beaches, and (2) pelagic trips, foraging at sea for marine prey or potentially scavenging on distant archipelagos (e.g. South Sandwich, Falkland or South Orkney Islands). Activity recorder data were consistent with the types of trip defined by the satellite tracking data, with median wet activity (time spent at the sea surface) during pelagic trips being 41%, but only 14% on coastal trips. On pelagic trips, there was a significant negative correlation between the duration of wet periods and the speed of travel between satellite uplinks. Mean travelling speed between uplinks was greater during day than night for both types of trips, suggesting that giant petrels prefer to travel during daylight and are less active at night. The scarcity of wet periods during the night in giant petrels foraging to the South Georgia coast (median=3%, range=1-9%) indicates that such birds spent almost all night on land. Likewise, the scarcity of wet periods at night for three birds foraging 700-1,000 km south of Bird Island, where there is no land but abundant icebergs, suggests these birds were resting on the icebergs at night. In addition to the adaptations to scavenging on carrion, pelagic trips by giant petrels contain elements similar to those of albatrosses, indicating a complexity to giant petrel lifestyle hitherto unrecognised. 相似文献
5.
The fatty acid and alcohol composition of the pelagic amphipod, Themisto libellula, was monitored during the 5 first months of its life cycle (4–20 mm length) in an Arctic fjord, Kongsfjorden, Svalbard. Fatty
acids of the three major lipid classes, polar lipids (PL), triacylglycerol (TAG), and wax esters (WE), were analyzed to highlight
ontogenic changes in their diet and metabolism. The PL composition of T. libellula did not show any strong variations along their growth except during the first month where an important increase of 20:5(n-3)
(EPA) and 22:6(n-3) (DHA) was observed. The TAG composition revealed a clear gradient corresponding to a diet shift from omnivorous
juveniles toward carnivorous sub-adults and adults. Indeed, fatty acid trophic markers of diatoms were dominant in the juveniles,
whereas 20:1(n-9) and 22:1(n-11), the Calanus sp. trophic markers, overwhelmed in the older stages. The WE composition highlighted the same general trend, however, differences
were found with the TAG and are discussed as a result of differences in turnover rates and assimilation pathways between the
two lipid classes. 相似文献
6.
Elizabeth K. Mackley Richard A. Phillips Janet R. D. Silk Ewan D. Wakefield Vsevolod Afanasyev Robert W. Furness 《Marine Biology》2011,158(2):429-438
Despite the recent burgeoning in predator tracking studies, few report on seabird activity patterns, despite the potential
to provide important insights into foraging ecology and distribution. In the first year-round study for any small petrel,
we examined the activity patterns of the white-chinned petrel Procellaria aequinoctialis based on data from combination geolocator-immersion loggers deployed on adults at South Georgia. The petrels were highly
nocturnal, flying for greater proportions of darkness than any large procellarid studied so far, except the light-mantled
albatross Phoebetria palpebrata. Flight bout durations were short compared with other species, suggesting a dominant foraging mode of small-scale searching
within large prey patches. When migrating, birds reduced the proportion of time on the water and increased flight bout duration.
Activity patterns changed seasonally: birds flew least during the nonbreeding period, and most frequently during chick-rearing
in order to meet higher energy demands associated with provisioning offspring. The degree of their response to moonlight was
also stage dependent (greatest in nonbreeding, and weakest in incubating birds), a trait potentially shared by other nocturnal
petrels which will have repercussions for feeding success and prey selection. For the white-chinned petrel, which is commonly
caught in longline fisheries, these results can be used to identify periods when birds are most susceptible to bycatch, and
therefore when use of mitigation and checking for compliance is critical. 相似文献
7.
During various seasons from May 2001 until July/August 2003, the lipid dynamics of the pteropod Clione limacina from Kongsfjorden, Svalbard, were investigated with respect to ontogenetic development and life-cycle. Polytrochous larvae, which were dominant in spring (April, May), composed the lipid-richest specimens of the population, with total lipid of about 50% of dry mass (%DM). Major lipid classes were triacylglycerols (TAG) and 1-O-alkyldiacylglycerol ethers (DAGE), accounting on average for 53.1 and 21.9% of total lipid, respectively. Until summer, larvae grew to adults by utilising their storage lipids. In July/August, lipids were depleted to about 10%DM due to maturation and reproduction. Almost all animals in autumn (September) were mature and able to replenish their lipid deposits by accumulating DAGE (26.7%) and TAG (39.6%). This is probably the prerequisite for successful overwintering.Principal component analysis (PCA), based on the fatty acid compositions, revealed ontogenetic differences between polytrochous larvae, and small and full-grown adults. Higher proportions of 18:4(n-3) and 14:0 were found in polytrochous larvae and smaller adults during spring. Both fatty acids were highly significantly correlated with the proportions of TAG, which were used for growth and development because they are presumably easier to metabolise. PCA also divided C. limacina specimens into DAGE-rich and DAGE-poor. We suggest that DAGE are a long-term energy store and hypothesise that they are necessary during periods of food scarcity, but may also serve as an energy source for reproduction. The fatty acids 17:1(n-8), 15:0, 16:1(n-7) and 18:1(n-7) were significantly correlated with the proportion of DAGE but not with TAG. These fatty acids, which do not originate from their only prey, Limacina helicina, are synthesised de novo. Their abundance reflects an efficient lipid production by C. limacina. Based on the results of lipid biosynthesis and accumulation in combination with the population structure, we suggest that C. limacina has at least a 2-year life-cycle in Svalbard waters.Communicated by M. Kühl, Helsingør 相似文献
8.
Pelagic seabirds are central place foragers during breeding and variation in foraging trip duration and range reflect differences
in diet and chick provisioning, through the exploitation of divergent habitats of varying productivity. We tested whether
these relationships hold in small procellarriids by equipping chick-rearing Cook’s petrel Pterodroma cookii (200 g) with geolocation-immersion loggers, conducting isotope analysis of blood and measuring chick meal mass following
foraging trips of varying duration. Cook’s petrel tracked during chick rearing from Little Barrier Island (LBI) and Codfish
Island (CDF), New Zealand had larger maximum ranges during longer foraging trips. Blood nitrogen isotope signatures (δ15N) of adults were significantly higher after foraging trips of longer duration, but not of greater maximum range. There was
no significant relationship between blood carbon isotope signatures (δ13C) and foraging trip characteristics. Proportion of time spent on the sea surface and the mass of the meal brought back to
chicks were consistently greater for Cook’s petrel with larger maximum ranges, which in the case of birds from CDF coincided
with productive subtropical convergence zone habitats. As predicted, trip duration reflected divergent foraging behaviours
in Cook’s petrel during breeding. We suggest that the availability of different prey is a key factor governing at-sea distributions
and dietary composition of this species. 相似文献
9.
John M. Logan Enrique Rodríguez-Marín Nicolas Goñi Santiago Barreiro Haritz Arrizabalaga Walter Golet Molly Lutcavage 《Marine Biology》2011,158(1):73-85
Atlantic bluefin tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades.
Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food
webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved
fork length) bluefin tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic
Ocean. In the Mid-Atlantic Bight, bluefin tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies
apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed
that juvenile bluefin tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic
Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed <10% of the
prey weights based upon traditional stomach content analyses. Trophic position was similar to juvenile fish sampled in the
NW Atlantic but lower than juveniles sampled in the Mediterranean Sea in previous studies. Our findings indicate that juvenile
bluefin tuna targeted a relatively small range of prey species and regional foraging patterns remained consistent over time
in the Mid-Atlantic Bight but changed in relation to local prey availability in the Bay of Biscay. 相似文献
10.
Comparison of feeding habits of myctophid fishes and juvenile small epipelagic fishes in the western North Pacific 总被引:1,自引:0,他引:1
Kaori Takagi Akihiko Yatsu Hiroshi Itoh Masatoshi Moku Hiroshi Nishida 《Marine Biology》2009,156(4):641-659
To examine the potential trophic competition between myctophids and small epipelagic fishes in the nursery grounds in spring,
we compared the stomach contents of dominant myctophids (Symbolophorus californiensis, Ceratoscopelus warmingii and Myctophum asperum; n = 179) and juvenile epipelagic fishes (Japanese sardine, Sardinops melanostictus, Japanese anchovy, Engraulis japonicus, chub mackerel, Scomber japonicus, and spotted mackerel, S. australasicus; n = 78) that were simultaneously collected at nighttime with a midwater trawl net around the Kuroshio-Oyashio transition zone
in the western North Pacific. It was clear that the neritic copepod Paracalanus parvus s.l. was the most abundant species in NORPAC samples (0.335 mm mesh size) taken at the same stations. Diets of dominant myctophid
fishes differed from those of the juvenile epipelagic fishes; Japanese sardine and anchovy mostly preyed upon P. parvus s.l. (23.6% of stomach contents in volume) and Corycaeus affinis (16.1%), respectively. Both chub and spotted mackerels mainly preyed upon the seasonal vertical migrant copepod, Neocalanus cristatus (15.9 and 14.7%, respectively). On the contrary, myctophid fishes probably do not specifically select the abundant neritic
copepods. Namely, S. californiensis mostly preyed upon a diel vertical migrating copepod, Pleuromamma piseki (22.7 and 30.6% in stomach of juvenile and adult, respectively), while C. warmingii and M. asperum preyed on Doliolida (43.0% in stomach of juvenile C. warmingii), appendicularians (11.0% in stomach of juvenile M. asperum), and Ostracoda (6.3% in stomach of adult C. warmingii). Feeding habits of myctophid fishes seem adapted to their prey animals; low rate of digested material (less than 30% in
volume) in stomachs of S. californiensis may be linked to the movement of P. piseki, hence S. californiensis can easily consume this copepod at night since they are more concentrated at night than daytime. High rate of digested material
(over 40%) of M. asperum and adult C. warmingii suggest that they feed not only at night but also during the daytime in the midwater layer. Thus, myctophid fishes actually
fed in the surface layer but less actively than the small epipelagic fishes. These results suggest that the potential for
direct food competition between myctophids and small epipelagic fishes is low in the nursery ground, but there remains a possibility
of indirect effects through their prey items, since the above gelatinous animals feed on common prey items as juveniles of
Japanese sardine and anchovy. 相似文献
11.
Fatty acid evidence for the importance of myctophid fishes in the diet of king penguins, Aptenodytes patagonicus 总被引:1,自引:0,他引:1
We tested the usefulness of the fatty acid signature-method in investigating the diet of seabirds in conjunction with the
conventional technique of stomach-content analysis. We compared the fatty acid composition of subcutaneous white adipose tissue
(SWAT) of king penguin chicks (Aptenodytes patagonicus) during fattening periods to that of total lipids from their food. In both spring and autumn, the fatty acid composition
of chick SWAT was identical to that of the dietary lipids. Because the diet of adult king penguins feeding for self-maintenance
(i.e. not for their chicks) was essentially unknown, we subsequently analysed their SWAT fatty acid patterns after premolting
and prebreeding foraging trips (during which they build up large energy reserves). The fatty acid composition of SWAT from
adults was identical to that of chick adipose tissue and food. King penguin diet and SWAT were characterized by high levels
of very long-chain mono-unsaturated fatty acids (20 to 24 carbon atoms, 16 to 23% by mass) and (n-3) poly-unsaturated fatty acids (19 to 27%); these consisted mainly of 20:1n-9 (5 to 8%) and 22:1n-11 (5 to 8%), and 22:6n-3 (10 to 13%) and 20:5n-3 (3 to 9%), respectively. Prey items identified from chick stomach contents indicated that the bulk of the food was oceanic
myctophid fishes, mainly Electrona carlbergi, Krefftichthys anderssoni and Protomyctophum tenisoni. The fatty acid composition of four other species of myctophid fishes was similar to that of penguin diet and SWAT, but markedly
different from that measured for a squid species and that reported for crustaceans. These findings indicate that adult king
penguins prey on myctophid fish not only to feed their chicks but also for their own nutrition. The fatty acid signature-technique
is therefore a reliable method to gain information on the food and feeding ecology of seabirds when more conventional techniques
are of limited value. Such information is important to the understanding of trophic relationships between key species of the
ecosystems, and also to provide insight into the nature of avian adaptations to the marine environment.
Received: 11 December 1997 / Accepted: 25 July 1998 相似文献
12.
Adrien Chaigne Matthieu Authier Pierre Richard Yves Cherel Christophe Guinet 《Marine Biology》2013,160(4):977-986
Highly dimorphic species like southern elephant seals (Mirounga leonina, SES hereafter) frequently exhibit resource partitioning according to sex and/or age classes. We measured carbon and nitrogen stable isotopes (δ13C and δ15N) of 404 blood samples (136 males and 268 females from Kerguelen Islands, 49°21′S, 70°18′E) from 2004 to 2011. Assuming that the distribution of carbon isotopes (δ13C value) reflects the two main foraging grounds (Polar Frontal and Antarctic Zones), we quantified the proportion of SES foraging within each zone in relation with size, a proxy for their age. We found a clear shift from Polar Frontal to Antarctic waters as male SES aged, but no relation as far as females is concerned. We also observed a widening range of nitrogen isotopic (δ15N) values, suggesting that both males and females expanded their diet spectra with age. Whereas males increased their trophic level, females remained constant on average, with some adult females feeding both at lower and at higher trophic levels than juveniles. 相似文献
13.
Adjustment of parental effort to manipulated foraging ability in a pelagic seabird,the thin-billed prion Pachyptila belcheri 总被引:6,自引:0,他引:6
Henri Weimerskirch Olivier Chastel Luc Ackermann 《Behavioral ecology and sociobiology》1995,36(1):11-16
An experiment was designed to examine in a long-lived seabird, the thin-billed prion (Pachyptila belcheri), how adults adjust their food provisioning strategy when their foraging abilities are reduced and when the chick's needs are increased. To reduce the foraging abilities of adults we impaired their flying ability by removing some flight feathers (handicapped), and to increase the food needs of the chick one parent was retained (single). Birds made either short foraging trips lasting 1–3 days, or long trips lasting 5–9 days. Control birds alternated long and short trips whereas single birds or handicapped birds made several successive short trips and thereafter a long trip. In each treatment, food loads tended to be heavier after long trips than after short trips, and single birds tended to bring heavier loads than control or handicapped birds. Birds in the three treatments lost similar amounts of mass after short trips and gained similar amounts of mass after long trips. However, the mass of handicapped birds declined through the experiment, while that of control and single birds remained stable. Although the proportion of chicks that died during the experiment was similar among the three treatments, the chicks fledged by a single bird were lighter than those in control nests. The results of the experiment suggest that thin-billed prions adjust their breeding effort differently to decreased flying ability or increased food demand by the chick. Single birds increase foraging effort without allowing their condition to deteriorate. Conversely, handicapped birds are unable to maintain their body condition while sustaining the chick at the same rate as control birds. It is suggested that in this long-lived seabird, adults probably adjust their breeding effort so that they do not incur the risk of an increased mortality, this risk being monitored by the body condition. 相似文献
14.
Torkild Tveraa Bernt-Erik Sæther Ronny Aanes Kjell Einar Erikstad 《Behavioral ecology and sociobiology》1998,43(2):73-79
In Procellariiformes, the parents guard the chick after it has attained homeothermy. This strategy may reduce the probability
that a small chick is taken by predators, but is costly as only one parent can forage at a time. The decision to leave the
chick may therefore be a compromise between the chick's vulnerability to predators, the body condition of the parent on the
nest and whether the foraging parent returns in time. We studied how the number of days that parents guarded the chick was
related to the body mass of the parent at the nest and the time the foraging parent spent at sea in the Antarctic petrel Thalassoica antarctica. We also examined how the body mass of the parent on the nest and the duration of the foraging trips influenced the chicks'
body condition at the end of the guarding period. When the foraging parent did not return to the nest in time to relieve its
mate, the number of days the parent on the nest kept guarding the chick was positively related to its body mass on arrival
in the colony. The number of days the foraging parent spent at sea was positively related to the body mass of its mate, but
those that returned in time had a shorter stay at sea relative to their mate's body mass than those that did not return before
their mate had left. Apparently, both the body mass of the parent at the nest and the ability of the foraging parent to adjust
its stay at sea to the mate's body mass is important for the number of days the parents guard the chick and also the chick's
body condition at this point. The inability to return to the nest before the mate has left may be the result of needing a
minimum amount of time at sea to find food, or because some parents having low foraging success and therefore prolong their
stay at sea.
Received: 10 October 1997 / Accepted after revision: 14 March 1998 相似文献
15.
Carnivorous zooplankton is a key element to the energy transfer through the arctic food web, linking lipid rich herbivores
to the top predators. We investigated the growth and lipid dynamic of the Arctic pelagic amphipod Themisto libellula in Kongsfjorden (Svalbard, 79°N) from May to October 2007. Additional samplings were performed in spring and summer 2006
and further north in Rijpfjorden (80°N), in September 2006 and 2007. In Kongsfjorden, the first free-swimming stages (3 mm)
appeared early May and reached their adult length (25 mm), in October. During their first year, they grew according to a Von
Bertalanffy model and most probably constituted a single cohort. Juveniles had the highest growth rate (0.19 mm day−1) and revealed relatively low total lipid (TL) content (about 2.5% wet weight (WW)) with phospholipids as the major lipid
class. Sub-adults showed a distinct decrease of growth rates which coincided with the increase of neutral lipid storage, reflecting
a switch in energy allocation, from somatic growth to lipid storage. Indeed wax esters (WE) increased up to 48.5% TL on average
in adults in 2006 while triacylglycerols (TAG) remained almost constant below 25.2% TL. The absence of lipid accumulation
(in disproportion of the weight) in 2007 could be explained by a higher metabolism of T. libellula or preys of lower quality. In Rijpfjorden, adults in their second year continued accumulating lipid (up to 10% WW) with high
and similar proportions of both lipid classes, WE and TAG. We highlighted that T. libellula exhibited a variable lipid metabolism along its life cycle depending on its physiological needs and environmental conditions. 相似文献
16.
The pelagic yellowtail kingfish Seriola lalandi has become a target species for aquaculture in Asia and Australasia. Australasian production is reliant on larviculture from
eggs of captive brood stock; however, knowledge regarding the nutritional requirements of larvae of this species is still
scarce, particularly in relation to lipids. As a first step in establishing these requirements, eggs and larvae from captive
S. lalandi brood stock were examined for differences in total protein, total lipid and lipid classes between individual spawning events,
over the spawning season, and during larval development from fertilisation to 15 days post hatch. Results indicate that total
protein egg−1 varied significantly between individual spawning events within a season, but neither total lipid nor total protein egg−1 varied significantly across the spawning season. Brood stock egg lipids were made up of approximately 60% phospholipid, 25%
wax and/or sterol esters (WE), 15% triacylglycerol (TAG), and small amounts of sterols and free fatty acids. During the early
larval period, both WE and TAG were utilised concurrently for energy. The larvae experienced very high mortality around 5–7 days
post hatch, which coincided with very low levels of all neutral lipid classes. Although many other factors may also influence
larval mortality, these results indicate that lipid provisioning may be an important factor in larval survival during the
critical period around first-feeding in this species. Examination of ratios of TAG:ST, often used as a condition index in
fish larvae, suggested that some of the larvae were suffering from starvation. However, as egg-derived WE appears to provide
a significant source of energy during the early larval period in S. lalandi, it is suggested that WE should be included in any index of larval nutritional state. 相似文献
17.
Among species where there is a risk to leaving offspring unattended, parents usually take alternating shifts guarding their young. However, they may occasionally exhibit brood neglect by leaving their offspring unattended at the nest. To investigate this phenomenon further, we examined the foraging behavior of the northern gannet (Morus bassanus) during chick-rearing. This species has a prolonged nestling period (13 weeks) and the single chick is usually guarded by one or other of its parents, because unattended chicks are frequently attacked by conspecifics. We tested the prediction that the foraging behavior of adults when they left their offspring alone at the nest (unattended trips) would differ in character to when adults left offspring with their partner (attended trips). Brood neglect typically occurred after a longer-than-average attendance period at the nest. Unattended trips were, on average, about half the duration of attended trips, and therefore much closer to the colony. There was also a difference in departure direction between attended and unattended trips, with unattended trips tending to be northeast of the colony. Chicks were fed by parents after both attended and unattended trips, but the frequency and the duration of unattended trips increased as chicks grew older whereas the duration of attended trips decreased as chicks grew. These results indicate that parents may be making a trade-off between risk of attack to their offspring and food-intake rate, and that the solution to this trade-off is dependent on chick age.Communicated by C. Brown 相似文献
18.
Ruth M. Casper Simon N. Jarman Nicholas J. Gales Mark A. Hindell 《Marine Biology》2007,152(4):815-825
The diet of pinnipeds is most commonly inferred from morphologically diagnostic remains of prey in their scats. Although this
method can generate quantitative estimates of diet simply, important prey types may not always be detected. DNA-based methods
improve detection of prey in scats, but they are not quantitative. While some studies have combined morphological and DNA-based
methods, these have only assessed prey that are represented by their hard remains in scats. To overcome this bias, we apply
molecular and morphological analyses to the soft and hard portions of faecal samples respectively, to estimate the diet of
lactating Antarctic fur seals (Arctocephalus gazella) on Heard Island. The diet of this population is of particular interest because it is expanding rapidly and may rely to some
extent on mackerel icefish (Champsocephalus gunnari), which are subject to commercial fisheries. Based on results from morphological analysis and likely important prey types,
we tested for DNA remains of C. gunnari, myctophids and squid in faecal samples. The proportion of samples (n = 54) yielding no dietary information was reduced from around 25.9% using either method alone, to 9.3% when combined. Detection
of all prey types tested for was notably improved by integrating molecular and morphological data. Data from either method
alone would have underestimated the number of animals consuming C. gunnari by around 25.7%. Detection of multiple prey types in samples increased from 9.3% when using morphological analysis only,
to 33.3% when using DNA only, to 46.3% when using both methods. Taken in isolation, morphological data inferred that individual
seals consume either C. gunnari or myctophids, probably foraging in separate locations characteristic of those prey. Including molecular data demonstrated
that while this may be true of some individuals, many other seals consume a mixed diet of at least C. gunnari, myctophids and squid. This new approach of combining DNA-based and morphological analyses of diet samples markedly increased
the number of samples yielding dietary information, as well as increasing the amount of information attained from those samples.
Our findings illustrate the broad potential of this technique to improve insight into trophic interactions in marine ecosystems.
相似文献
Ruth M. CasperEmail: |
19.
Hany Alonso José P. Granadeiro Vitor H. Paiva Ana S. Dias Jaime A. Ramos Paulo Catry 《Marine Biology》2012,159(6):1197-1207
In pelagic seabirds, who often explore distant food resources, information is usually scarce on the level of trophic segregation
between parents and their offspring. To investigate this issue, we used GPS tracking, stable isotopes and dietary information
of Cory’s shearwaters Calonectris diomedea breeding in contrasting environments. Foraging trips at Selvagem Grande (an oceanic island) mainly targeted the distant African
coast, while at Berlenga island (located on the continental shelf), shearwaters foraged mainly over nearby shelf waters. The
degree of isotopic segregation between adults and chicks, based on δ13C, differed markedly between the two sites, indicating that adult birds at Selvagem fed their chicks with a mixture of shelf
and offshore pelagic prey but assimilated more prey captured on coastal shelf waters. Isotopic differences between age classes
at Berlenga were much smaller and may have resulted from limited dietary segregation or from age-related metabolic differences.
The diet of shearwaters was also very different between the two colonies, with offshore pelagic prey only being detected at
Selvagem Grande. Our findings suggest that spatial foraging constraints influence resource partitioning between pelagic seabirds
and their offspring and can lead to a parent–offspring dietary segregation. 相似文献
20.
Sebastián P. Luque John P. Y. Arnould Edward H. Miller Yves Cherel Christophe Guinet 《Marine Biology》2007,152(1):213-224
The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS:
10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort
or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however,
has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips:
overnight (OFT, <1 day) and long (LFT, >1 day), in common with other results from Macquarie Island. However, diving behaviour
differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour
differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal
attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove
deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species.
Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available
than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant
with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three
myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between
fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of
these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered
to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed
a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant
of foraging efficiency and, consequently, maternal investment. 相似文献