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1.
The mechanical basis of prey capture by scyphomedusae has been largely ignored, despite the importance of these predators in a variety of planktonic ecosystems. Interactions between swimming, fluid motions, and prey capture were examined during 1991–1992 for a species from the three scyphozoan orders having planktonic medusae: Rhizostomeae, Stomolophus meleagris Agassiz, 1862; Coronatae, Linuche unguiculata (Schwartz, 1788); and Semaeostomeae, Cyanea capillata (Linnaeus, 1758). All three species used flow created during bell pulsation to capture prey, but the type of flow used for prey capture and the capture surface morphology were different for each species. The mechanics of capture by these species of diverse morphology and taxonomic affinity suggests that the use of bell pulsation-induced flow for prey entrainment and capture is widespread among the scyphomedusae. 相似文献
2.
Although medusan predators play demonstrably important roles in a variety of marine ecosystems, the mechanics of prey capture and, hence, prey selection, have remained poorly defined. A review of the literature describing the commonly studied medusa Aurelia aurita (Linnaeus 1758) reveals no distinct patterns of prey selectivity and suggests that A. aurita is a generalist and feeds unselectively upon available zooplankton. We examined the mechanics of prey capture by A. aurita using video methods to record body and fluid motions. Medusae were collected between February and June in 1990 and 1991 from Woods Hole, Massachusetts and Narragansett Bay, Rhode Island, USA. Tentaculate A. aurita create fluid motions during swimming which entrain prey and bring them into contact with tentacles. We suggest that this mechanism dominates prey selection by A. aurita. In this case, we predict that medusae of a specific diameter will positively select prey with escape speeds slower than the flow velocities at their bell margins. Negatively selected prey escape faster than the medusan flow velocity draws them to capture surfaces. Faster prey will be captured by larger medusac because flow field velocity is a function of bell diameter. On the basis of prey escape velocities and flow field velocities of A. aurita with diameters of 0.8 to 7.1 cm, we predict that A. aurita will select zooplankton such as barnacle nauplii and some slow swimming hydromedusae, while faster copepods will be negatively selected. 相似文献
3.
Scyphomedusae are ubiquitous in marine and estuarine systems, where they frequently play an important role in trophodynamics. Many scyphomedusae are cruising predators, and feeding rates depend, in part, on swimming behavior. Yet, no model of medusa swimming exists. An individual-based correlated random walk (CRW) model of medusa swimming behavior in three dimensions was developed. The model was validated using a previously published dataset of the swimming of 19 Chrysaora quinquecirrha (Desor, 1848) medusae that were observed in the presence or absence of zooplankton prey in laboratory mesocosms in August–October 1998 (Matanoski et al. in Mar Biol 139:191–200, 2001). In the presence of prey, medusae swam at a constant moderate rate in looping trajectories. In the absence of prey, medusae alternated periods of slow and fast swimming in more linear trajectories. In the model, looping trajectories were reproduced only when changes in movement by a medusa were oriented to its current position and orientation; more linear trajectories were reproduced by movement oriented to a fixed framework. This suggests that medusae change from swimming behavior oriented to local stimuli (e.g., contact with prey) to long-range stimuli (e.g., gravity) depending on the availability of prey. The model reproduced cyclical changes in swimming speeds by medusae in the absence of prey by simulating switching in the behavior controlling the strength of swimming bell pulsations using a probabilistic function. Model results also demonstrated that medusae tend to swim toward the surface, avoid contact with the bottom, increase time spent in prey patches if they alter swimming patterns in the presence of prey, and exhibit significant periodicities in swimming patterns that are the result of deterministic behavior. The model will permit the simulation of the complex behavior of medusae. 相似文献
4.
Phyllorhiza
punctata, commonly called the Australian white spotted jellyfish, invaded the Caribbean in the 1960s, becoming established there and
subsequently in the United States in the northern Gulf of Mexico (by 2000) and eastern Florida (2001). With the prevailing
Loop Current flowing clockwise around the Gulf of Mexico and joining the Gulf Stream along eastern Florida, potential transport
of P. punctata along the eastern seaboard of the USA could be facilitated. P. punctata medusae were collected in small numbers along the entire Georgia coast during May–November in 2007 and 2008. Medusa bell
diameters increased both years from ca. 10 cm in May to ca. 33 cm in autumn. Specimens lacked zooxanthellae, as reported for
medusae in the northern Gulf of Mexico and Florida. It is possible that the P. punctata medusae observed were transported from established populations to the south; however, whether or not this species is established
along the Georgia coast has yet to be determined. 相似文献
5.
Sexual reproduction of the scyphomedusa Aurelia aurita in relation to temperature and variable food supply 总被引:1,自引:0,他引:1
The effects of food availability and temperature on sexual maturation and female reproductive output of the scyphomedusa
Aurelia aurita was examined in two populations from the contrasting environments of Southampton Water and Horsea Lake, England. Trends in
oogenesis and subsequent reproductive output differed markedly between the two populations. In Southampton Water, the onset
of sexual maturation occurred earliest in the larger medusae, but eventually all females became ripe, the smallest being 45 mm
bell diameter (BD). The decrease in minimum size at maturity was correlated with increasing temperature. In A. aurita from Horsea Lake, size at maturity varied on a seasonal basis, with the smallest ripe female being only 19 to 20 mm BD. There
were spring and autumn periods of sexual maturation in this population. During the autumn period, it is likely that food limitation
was playing a more critical role in determining medusa size, with decreasing temperature indirectly affecting A. aurita by limiting primary and secondary production. In similar-sized ripe medusae, fecundity was greater in Southampton Water,
but the planula larvae produced were significantly smaller than those in Horsea Lake. It is suggested that in Horsea Lake,
the quality of the larvae are greater in terms of biochemical content to ensure survival of the few gametes produced (i.e.
K-strategy). Comparison of the reproductive effort of the two A. aurita populations revealed that medusae from Southampton Water, which experience greater food availability, are able to direct
more energy to reproduction than Horsea Lake medusae. In the latter, A. aurita medusae appear to partition the available food resources into either somatic growth (and therefore increased future fecundity)
when food is abundant, or reproductive growth when food is scarce.
Received: 24 June 1997 / Accepted: 23 March 1998 相似文献
6.
Although scyphomedusae have received increased attention in recent years as important predators in coastal and estuarine
environments, the factors affecting zooplankton prey vulnerability to these jellyfish remain poorly understood. Current models
predicting feeding patterns of cruising entangling predators, such as Chrysaora quinquecirrha (Desor, 1948), fail to account for the selection of fast-escaping prey such as copepods. Nevertheless, our analysis of gastric
contents of field-collected medusae showed that this scyphomedusa fed selectively on the calanoid copepod Acartia tonsa (Dana, 1846) and preferentially ingested adult over copepodite stages. We measured feeding rates in a planktonkreisel while
simultaneously videotaping predator–prey interactions. C. quinquecirrha consumed adult A. tonsa ten times faster than copepodites. Differences in prey behavior, in the form of predator–prey encounter rates or post-encounter
escape responses, could not account for the elevated feeding rates on adults. Prey size, however, had a dramatic impact on
the vulnerability of copepods. In experiments using heat-killed prey, feeding rates on adults (1.5 times longer than copepodites)
were 11 times higher than on copepodites. In comparison, medusae ingested heat-killed prey at only two to three times the
rate of live prey. These results suggest that during scyphomedusan–copepod interactions, prey escape ability is important,
but ultimately small size is a more effective refuge from predation.
Received: 26 September 1997 / Accepted: 20 May 1998 相似文献
7.
Moerisia lyonsi Boulenger (Hydrozoa) medusae and benthic polyps were found at 0 to 5‰ salinity in the Choptank River subestuary of Chesapeake
Bay, USA. This species was introduced to the bay at least 30 years before 1996. Medusae and polyps of M. lyonsi are very small and inconspicuous, and may occur widely, but unnoticed, in oligohaline waters of the Chesapeake Bay system
and in other estuaries. Medusae consumed copepod nauplii and adults, but not barnacle nauplii, polychaete and ctenophore larvae
or tintinnids, in laboratory experiments. Predation rates on copepods by medusae increased with increasing medusa diameter
and prey densities. Feeding rates on copepod nauplii were higher than on adults and showed no saturation over the range of
prey densities tested (1 to 64 prey l−1). By contrast, predation on copepod adults was maximum (1 copepod medusa−1 h−1) at 32 and 64 copepods l−1. Unexpectedly, M. lyonsi colonized mesocosms at the Horn Point Laboratory during the spring and summer in 4 years (1994 to 1997), and reached extremely
high densities (up to 13.6 medusae l−1). Densities of copepod adults and nauplii were low when medusa densities were high, and estimated predation effects suggested
that M. lyonsi predation limited copepod populations in the mesocosms. Polyps of M. lyonsi asexually produced both polyp buds and medusae. Rates of asexual reproduction increased with increasing prey availability,
from an average total during a 38 d experiment of 9.5 buds polyp−1 when each polyp was fed 1 copepod d−1, to an average total of 146.7 buds polyp−1 when fed 8 copepods d−1. The maximum daily production measured was 8 polyp buds and 22 medusae polyp−1. The colonizing potential of this hydrozoan is great, given the high rates of asexual reproduction, fairly wide salinity
tolerance, and existence of a cyst stage.
Received: 29 October 1998 / Accepted: 3 March 1999 相似文献
8.
Predation by the medusa Aurelia aurita L. on early first-feeding stage larvae of the herring clupea harengus L. was studied in the laboratory. The medusae were captured in Loch Etive, Scotland. Herring larvae were reared from the extificially fertilized eggs of spawning Clyde herring caught in March, 1982. Swimming speeds, volume searched”, capture efficiency and predation rates increased as medusa size increased. Predation rates on fish larvae increased with prey density, but appeared to approach a maximum at high prey densities; in 1 h experiments, a maximum rate of predation of 6.64 larvae h-1 was estimated by fitting an Ivlev function. A model to predict predation rates was constructed from swimming speeds, sizes and densities of medusae and larvae, and capture efficiency. The rates of predation predicted from the model fell within the range of experimental data, but tended to underestimate rates and did not account for saturation of medusae. Swimming patterns of medusae changed after prey capture: (a) before capture, encounter rates were low and medusae were relatively less active; (b) after capture of 1 larva, encounter rates doubled, with the stimulated medusae exhibiting increased activity and an aftered “searching” path; and (c) after capture of many larvae, swimming speeds and encounter rates of medusae decreased. 相似文献
9.
We describe feeding behavior of Aurelia aurita (Linnaeus) using gut content analyses of field-collected specimens and a mesocosm experiment. The field studies were conducted in Narragansett Bay, Rhode Island, USA from March to April 1988, and the mesocosm studies were done at the Marine Ecosystems Research Laboratory at the University of Rhode Island. Patterns of prey selection changed with medusa diameter. Smaller medusae (12 mm diameter) consumed mostly hydromedusan prey whereas larger medusae (up to 30 mm diameter) ingested greater numbers of copepod prey. While larger medusae did feed on copepods, their diet also contained more barnacle nauplii and hydromedusae than expected from the relative abundances of these prey types in plankton samples. A marginal flow mechanism of feeding by A. aurita provided an explanation for the patterns of prey selection we observed in medusae of different sizes and among widely divergent prey types. Our data indicated that large prey, with escape speeds slower than the marginal flow velocities around the bell margins of A. aurita, made up a substantial fraction of the daily ration when they were available. Such prey species may be more important to nutrition than the more abundant copepods and microzooplankton. Successful development of young medusae may depend upon an adequate supply of slowly escaping prey. 相似文献
10.
The reproductive biology of the jellyfish Catostylus mosaicus (Quoy and Gaimard 1824) (Scyphozoa: Rhizostomeae) was investigated in New South Wales, Australia. Medusae were gonochoristic.
There was a 1:1 ratio of male and female medusae and there was no evidence of sexual dimorphism. Oocytes arose from the gastrodermis
and maintained contact with the gastrodermis, via trophocytes, throughout gametogenesis. Spermatogenesis occurred within follicles
that arose from invagination of the gastrodermis. Detailed sampling of gonads over a period of 3.25 yr in Botany Bay, and
over 2.5 yr in Lake Illawarra, indicated that gametogenesis occurred almost continuously during the year. Oocytes were smaller,
or were absent from the ovaries during 3 of the 4 winters sampled at Botany Bay and during all 3 winter periods sampled at
Lake Illawarra. Comparisons were made with other locations, although these were sampled less frequently. When medusae were
present at a location, similar trends were observed. The size at which medusae matured varied, but during non-winter periods
and at two locations, all medusae exceeding 130 mm diam were considered mature.
Received: 6 January 2000 / Accepted: 3 July 2000 相似文献
11.
C. E. Mills 《Marine Biology》1981,64(2):185-189
Feeding behaviors of the following 4 species of hydromedusae are described from field and laboratory observations: Probosidactyla flavicirrata, Stomotoca atra, Phialidium gregarium and Polyorchis penicillatus. Feeding efficiency of medusae has previously been considered equivalent to fishing with a given amount (combined tentacle length) of adhesive fishing line; however, detailed observation shows that behavior of medusae greatly modifies the fishing capacity of each species. It is hypothesized that in addition to (1) tentacle number and length, the following factors strongly influence feeding efficiency: (2) tentacle posture, (3) velocity of tentacles moving through water (4) swimming pattern of medusa, (5) streamlining effects of medusa bell on water flow, (6) diameter of prey, (7) swimming pattern and velocity of prey. Each species of hydromedusa utilizes the above factors in different combinations.Mailing address 相似文献
12.
Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores 总被引:3,自引:0,他引:3
We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton.
Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m
depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically
longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution
across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter
wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within
this range, colors are well-adapted to the particular environment which the species inhabit.
Received: 27 April 1998 / Accepted: 27 October 1998 相似文献
13.
Effect of amino acids on the swimming activity of newly hatched turbot larvae (Scophthalmus maximus)
The swimming behaviour of newly hatched turbot (Scophthalmus maximus L.) larvae was observed in artificial seawater (ASW) and in solutions of 21 l-amino acids at a concentration of 10−5
M. The behaviour of 20 larvae was analysed in each solution. Each larva was observed for 1 min. Individual movements were recorded
on video and analysed using a computer-assisted program. The larvae swam in convoluted, randomised three-dimensional paths,
rested and started swimming again. There were large variations in the swimming behaviour of turbot larvae during ontogeny.
In ASW the mean frequency of trajectories longer than a body length of 4 mm larva−1 min−1 increased from 1.2 at Day 1, to 10 at Day 4. Analysing the data (Dunnett's method) revealed that the frequency of swimming
trajectories increased in the presence of glycine, histidine and glutamine, and decreased in the presence of proline. The
total distance swum increased for glycine but decreased for proline. The threshold concentration for glycine detected by turbot
larvae was 10−5
M. The straightness index did not change in the presence of the amino acids. The possible role of these changes in behaviour
is discussed.
Received: 12 June 1997 / Accepted: 13 January 1998 相似文献
14.
The ctenophore Mnemiopsis leidyi A. Agassiz, 1865 is known to be eaten by the scyphomedusan Chrysaora quinquecirrha (Desor, 1948), which can control populations of ctenophores in the tributaries of Chesapeake Bay. In the summer of 1995,
we videotaped interactions in large aquaria in order to determine whether M. leidyi was always captured after contact with medusae. Surprisingly, M. leidyi escaped in 97.2% of 143 contacts. The ctenophores increased swimming speed by an average of 300% immediately after contact
with tentacles and 600% by mid-escape. When caught in the tentacles of C. quinquecirrha, the ctenophores frequently lost a portion of their body, which allowed them to escape. Lost parts regenerated within a few
days. The striking ability of M. leidyi to escape from C. quinquecirrha may be critically important in maintaining ctenophore populations in situ.
Received: 14 November 1996 / Accepted: 4 December 1996 相似文献
15.
Diel swimming behaviors of juvenile anchovies (Anchoa spp.) were observed using stationary hydroacoustics and synoptic physicochemical and zooplankton profiles during four unique
water quality scenarios in the Neuse River Estuary, NC, USA. Vertical distribution of fish was restricted to waters with DO
greater than 2.5 mg O2 l−1, except when greater than 70% of the water column was hypoxic and a subset of fish were occupying water with 1 mg O2 l−1. We made the prediction that an individual fish would select a swim speed that would maximize net energy gain given the abundance
and availability of prey in the normoxic waters. During the day, fish adopted swim speeds between 7 and 8.8 bl s−1 that were near the theoretical optimum speeds between 7.0 and 8.0 bl s−1. An exception was found during severe hypoxia, when fish were swimming at 60% above the optimum speed (observed speed = 10.6 bl s−1, expected = 6.4 bl s−1). The anchovy is a visual planktivore; therefore, we expected a diel activity pattern characteristic of a diurnal species,
with quiescence at night to minimize energetic costs. Under stratified and hypoxic conditions with high fish density coupled
with limited prey availability, anchovies sustained high swimming speeds at night. The sustained nighttime activity resulted
in estimated daily energy expenditure over 20% greater than fish that adopted a diurnal activity pattern. We provide evidence
that the sustained nighttime activity patterns are a result of foraging at night due to a lower ration achieved during the
day. During severe hypoxic events, we also observed individual fish making brief forays into the hypoxic hypolimnion. These
bottom waters generally contained higher prey (copepod) concentrations than the surface waters. The bay anchovy, a facultative
particle forager, adopts a range of behaviors to compensate for the effects of increased conspecific density and reduced prey
availability in the presence of stratification-induced hypoxia. 相似文献
16.
Annual cycles of phytoplankton community-structure and bloom dynamics in the Neuse River Estuary, North Carolina 总被引:6,自引:0,他引:6
The spatiotemporal distributions of major phytoplankton taxa were quantified to estimate the relative contribution of different
microalgal groups to biomass and bloom dynamics in the eutrophic Neuse River Estuary, North Carolina, USA. Biweekly water
samples and ambient physical and chemical data were examined at sites along a salinity gradient from January 1994 through
December 1996. Chemosystematic photopigments (chlorophylls and carotenoids) were identified and quantified using high-performance
liquid chromatography (HPLC). A recently-developed factor-analysis procedure (CHEMTAX) was used to partition the algal group-specific
chlorophyll a (chl a) concentrations based on photopigment concentrations. Results were spatially and temporally integrated to determine the ecosystem-level
dynamics of phytoplankton community-constituents. Seasonal patterns of phytoplankton community-composition changes were observed
over the 3 yr. Dinoflagellates reached maximum abundance in the late winter to early spring (January to March), followed by
a spring diatom bloom (May to July). Cyanobacteria were more prevalent during summer months and made a large contribution
to phytoplankton biomass, possibly in response to nutrient-enriched freshwater discharge. Cryptomonad blooms were not associated
with a particular season, and varied from year to year. Chlorophyte abundance was low, but occasional blooms occurred during
spring and summer. Over the 3 yr period, the total contribution of each algal group, in terms of chl a, was evenly balanced, with each contributing nearly 20% of the total chl a. Cryptomonad, chlorophyte, and cyanobacterial dynamics did not exhibit regular seasonal bloom patterns. High dissolved inorganic-nitrogen
loading during the summer months promoted major blooms of cryptomonads, chlorophytes, and cyanobacteria.
Received: 12 September 1997 / Accepted: 12 December 1997 相似文献
17.
We determined feeding rates of the hydromedusan Nemopsis bachei L. Agassiz in the mesohaline region of Chesapeake Bay, USA during the spring of 1989 and 1990 from gut contents, digestion rates and abundances of medusae and zooplankton. The medusae consumed primarily copepodites of Acartia tonsa, selecting against naupliar stages. The peak abundance of N. bachei medusae was in April to May, when densities averaged more than 10 m-3. Medusa densities were similar in both years, but were greatest (maximum of 132 medusae m-3) along a southern transect sampled only in 1990. At peak densities, N. bachei medusae consumed 30% d-1 of the copepodite standing stocks, but they consumed <1% d-1 at the lower densities typical of late May or early June. The predation effects were generally greater than those reported for other hydromedusan species. But even at peak predation, N. bachei medusae could not have controlled or reduced A. tonsa copepod populations, which had a production rate of 85% d-1 at that time. Medusa feeding rates were highest at nighttime, and were correlated with prey density in the field, but not in the laboratory.Communicated by J. Grassle, New Brunswick 相似文献
18.
The aim of our investigations was to determine, via oxygen and carbon-dioxide respirometry, how much energy dolphins (Tursiops truncatus) require when swimming at different speeds. Experiments were conducted on two female bottlenose dolphins (mean mass 162 kg)
in the dolphinarium in Nuremberg Zoo, Germany, between March and August 1997. Animals were stationed in a respiration chamber
for a minimum of 90 s after performing a variety of activities. We measured respiration frequency and oxygen requirements
during (1) resting, (2) swimming at various velocities and (3) leaping to various heights. Resting metabolic rate of our bottlenose
dolphins (2.15 W kg−1) was comparable to previously published data. Metabolic rate in swimming dolphins increased to 2.47 W kg−1 at 2 m s−1, while leaps to 2.2 and 3 m height required a power input of 3.5 and 4 W kg−1, respectively. Transport costs of swimming dolphins were lowest (1.16 J kg−1 m−1, corresponding to 0.12 J N−1 m−1) at a speed of 2.5 m s−1, yielding an optimal range speed of between 1.9 and 3.2 m s−1 (corresponding to minimum cost of transport ±10%). Breathing rates during all experiments correlated very well with oxygen
consumption (r
2 > 0.89) and could be used to derive metabolic rates in unencumbered dolphins at sea.
Received: 18 December 1998 / Accepted: 27 April 1999 相似文献
19.
E. J. Buskey 《Marine Biology》1998,130(3):425-431
The cyclopoid copepod Dioithona oculata forms dense swarms within shafts of sunlight that penetrate the mangrove prop-root habitat of islands off the coast of Belize.
Previous studies, based on in situ video recordings and laboratory studies, have shown that D. oculata is capable of maintaining fixed-position swarms in spite of currents of up to 2 cm s−1. The purpose of this study was to examine the energetic costs of maintaining these swarms, in terms of increased metabolic
costs of maintaining position in currents and in terms of reduced feeding rates in densely packed swarms during the day. Using
a sealed, variable-speed flow-through chamber, the respiration rates of D. oculata were measured while swarms maintained position in different current speeds. The results indicate that active metabolism (swimming
at maximum speed to maintain the swarm in a current) is approximately three times greater than routine metabolism (normal
swimming speeds in the absence of currents), indicating a significant metabolic cost of maintaining swarms in the presence
of currents. In addition, gut-pigment analysis indicated that feeding rates of these copepods were often reduced in swarms
during the day compared to when the copepods were dispersed at night. Given the high “cost” of swarming, the adaptive value
of swarming in terms of reduced predation, increased opportunities for mating, and reduced dispersal, must be substantial.
Received: 4 June 1997 / Accepted: 18 September 1997 相似文献
20.
Environmental preferences of yellowfin tuna (Thunnus albacares) at the northern extent of its range 总被引:5,自引:0,他引:5
B. A. Block J. E. Keen B. Castillo H. Dewar E. V. Freund D. J. Marcinek R. W. Brill C. Farwell 《Marine Biology》1997,130(1):119-132
We used acoustic telemetry to examine the small-scale movement patterns of yellowfin tuna (Thunnus albacares) in the California Bight at the northern extent of their range. Oceanographic profiles of temperature, oxygen, currents and
fluorometry were used to determine the relationship between movements and environmental features. Three yellowfin tuna (8
to 16 kg) were tracked for 2 to 3 d. All three fish spent the majority of their time above the thermocline (18 to 45 m in
depth) in water temperatures >17.5 °C. In the California Bight, yellowfin tuna have a limited vertical distribution due to
the restriction imposed by temperature. The three fish made periodic short dives below the thermocline (60 to 80 m), encountering
cooler temperatures (>11 °C). When swimming in northern latitudes, the depth of the mixed layer largely defines the spatial
distribution of yellowfin tuna within the water column. Yellowfin prefer to spend most of their time just above the top of
the thermocline. Oxygen profiles indicated that the tunas encountered oceanic water masses that ranged most often from 6.8
to 8.6 mg O2 l−1, indicating no limitation due to oxygen concentrations. The yellowfin tuna traveled at speeds ranging from 0.46 to 0.90 m
s−1 (0.9 to 1.8 knots h−1) and frequently exhibited an oscillatory diving pattern previously suggested to be a possible strategy for conserving energy
during swimming.
Received: 14 February 1997 / Accepted: 14 April 1997 相似文献