共查询到20条相似文献,搜索用时 31 毫秒
1.
The pattern and characteristics of diving in 14 female northern rockhopper penguins, Eudyptes chrysocome moseleyi, were studied at Amsterdam Island (37°50′S; 77°31′E) during the guard stage, using electronic time–depth recorders. Twenty-nine
foraging trips (27 daily foraging trips and two longer trips including one night) with a total of 16 572 dives of ≥3 m were
recorded. Females typically left the colony at dawn and returned in the late afternoon, spending an average of 12 h at sea,
during which they performed ∼550 dives. They were essentially inshore foragers (mean estimated foraging range 6 km), and mainly
preyed upon the pelagic euphausiid Thysanoessa gregaria, fishes and squid being only minor components of the diet. Mean dive depth, dive duration, and post-dive intervals were 18.4 m
(max. depth 109 m), 57 s (max. dive duration 168 s), and 21 s (37% of dive duration), respectively. Descent and ascent rates
averaged 1.2 and 1.0 ms−1 and were, together with dive duration, significantly correlated with dive depth. Birds spent 18% of their total diving time
in dives reaching 15 to 20 m, and the mean maximum diving efficiency (bottom time:dive cycle duration) occurred for dives
reaching 15 to 35 m. The most remarkable feature of diving behaviour in northern rockhopper penguins was the high percentage
of time spent diving during daily foraging trips (on average, 69% of their time at sea); this was mainly due to a high dive
frequency (∼44 dives per hour), which explained the high total vertical distance travelled during one trip (18 km on average).
Diving activity at night was greatly reduced, suggesting that, as other penguins, E. chrysocome moseleyi are essentially diurnal, and locate prey using visual cues.
Received: 9 December 1998 / Accepted: 3 March 1999 相似文献
2.
Satellite telemetry was used to study the movements and behaviour of ten blue sharks and one individual each of shortfin mako,
thresher and bigeye thresher off eastern Australia. The tracks showed latitudinal movements of up to 1,900 km, but none of
the sharks travelled away from the eastern Australian region. Tracking periods did not exceed 177 days. All species showed
oscillatory dive behaviour between the surface layers to as deep as 560–1,000 m. Blue sharks spent 35–58% of their time in
<50 m depths and 10–16% of their time in >300 m. Of these four species, the bigeye thresher spent the least time in the surface
layers and the most time at >300 m depth. All four species showed clear diel behaviour generally occupying shallower depths
at night than during the day. Blue sharks were mainly in 17.5–20.0°C water, while the thresher sharks showed a more bimodal
temperature distribution. 相似文献
3.
The post-release behaviour of eight black marlin (Makaira indica), caught by standard sportfishing techniques off the Great Barrier Reef, Australia, was investigated using ultrasonic telemetry.
Five marlin between 100 and 420 kg were successfully tracked for periods of 8 to 27 h. Of the three others tagged, one was
killed by a shark and two shed their tags, probably as the result of poor attachment. The black marlin spent most of their
time within 10 m of the surface, both day and night. During the day, however, they also spent some time between 40 and 140 m
depth. They rarely penetrated the thermocline, and then only briefly, remaining at temperatures no more than 8 C° below that
of surface waters. The deepest dives were to 178 m. Four of the five marlin tracked, initially moved offshore before heading
parallel to the shore, whereas the other marlin stayed close to the reef edge. The average mean swimming speeds over the ground
for entire tracks ranged from 0.7 to 1.02 m s−1.
Received: 17 January 1997 / Accepted: 16 June 1999 相似文献
4.
Mesozooplankton (<5 mm) collected by stratified oblique tows with a 1-m2 MOCNESS was examined at four stations in the Arabian Sea, with special reference to the bathypelagic zone. The profiles commenced
about 20 m above bottom, at 4430 m as a maximum depth. The highest mesozooplankton biomass concentrations (wet weight per
cubic meter) were obtained from the surface layer during night. A secondary maximum was situated between 150 and 450 m, with
maximum concentrations at daytime. This layer coincided with the daytime residence depth of the deep scattering layer. The
standing crop of the mesozooplankton in the upper 1000 m was highest at station WAST at 16°N; 60°E (ca. 47 000 mg m−2); station CAST at 14°N; 65°E ranked second (ca. 22 500 mg m−2), followed by station SAST at 10°N; 65°E (11 420 mg m−2). The differences can be related to different productivity regimes at the sea surface generated by the Findlater Jet during
the SW monsoon. The differences in surface production were also reflected below 1000 m depth, in the bathypelagic zone, with
mesozooplankton wet weights of 5330 mg m−2 at WAST, 3210 mg m−2 at CAST, 3390 mg m−2 at EAST (15°N; 65°E) and 2690 mg m−2 at SAST. The decrease of mesozooplankton concentration with depth in the oxygen minimum zone (OMZ) was stronger than in comparable
depths of open-ocean areas where an OMZ is absent. Among the discriminated four size classes of mesozooplankton, the largest
fraction (2 to 5 mm) indicated a biomass peak at 1200 m depth, which coincided with the lower boundary layer of the OMZ. The
rate of decrease of mesozooplankton biomass with depth in the bathypelagic zone was statistically similar between the sites,
even though the absolute zooplankton biomass at the sites was different. There is no evidence that the presumed lower carbon
degradation rates in the OMZ of the Arabian Sea caused a larger standing crop and less of a decrease in biomass with depth
in the bathypelagic zone in comparison to other seas.
Received: 16 May 1997 / Accepted: 5 June 1997 相似文献
5.
One concept of evolutionary ecology holds that a living fossil is the result of past evolutionary events, and is adapted
to recent selective forces only if they are similar to the selective forces in the past. We describe the present environment
of the living coelacanth Latimeria chalumnae Smith, 1939 at Grande Comore, western Indian Ocean and report depth-dependent cave distribution, temperature, salinity and
oxygen values which are compared to the fish's distribution and its physiological demands. We studied the activity pattern,
feeding behaviour, prey abundance and hunting success to evaluate possible links between environmental conditions, feeding
ecology and evolutionary success of this ancient fish. Transmitter tracking experiments indicate nocturnal activity of the
piscivorous predator which hunts between approximately 200 m below the surface to 500 m depth. Fish and prey density were
measured between 200 and 400 m, both increase with depth. Feeding tracks and feeding strikes of the coelacanth at various
depths were simulated with the help of video and laser techniques. Along a 9447 m video transect a total of 31 potential feeding
strikes occurred. Assuming 100% hunting success, medium-sized individuals would obtain 122 g and large females 299 g of prey.
Estimates of metabolic rates revealed for females 3.7 ml O2 kg−1 h−1 and for males 4.5 ml O2 kg−1 h−1. Today coelacanths are considered to be a specialist deep-water form and to inhabit, with their ancient morphology, a contemporary
environment where they compete with advanced, modern fish.
Received: 5 July 1999 / Accepted: 11 November 1999 相似文献
6.
Seasonal sampling was carried out based on day/night, vertically stratified tows (100 or 125 m strata) in the upper 900 m
of the water column over the mid-slope commercial fishing grounds south of Tasmania. A large midwater trawl (105 m2 mouth area) was used with an opening/closing cod-end. Subtropical convergence and subtropical species dominated the fauna,
but many less abundant, more widely-distributed species were also present. Fishes, which contributed 89% of micronekton biomass
and 135 of 178 species, were dominated by the Myctophidae (48% biomass and 48 species). Twenty micronekton species made up
80% of the total biomass. Overall, the micronekton fish biomass in this region was 2.2 g m−2 wet weight. A pronounced day/night shift in the distribution of biomass was attributable to diel migratory species. During
the day, <0.2% of the total micronekton biomass was found in 0 to 300 m; most biomass was below 400 m, with peaks at 400 to
525 m and 775 to 900 m. At night, 53% of the biomass was found in 0 to 300 m, with progressively less in each deeper stratum.
The vertical ranges of individual species typically exceeded 400 to 500 m during the day and night and were non-coincident,
although nyctoepipelagic migrators were concentrated in the surface 200 m at night. Distinct epipelagic, lower and upper mesopelagic
assemblages were identified, and patterns of epipelagic migration, limited migration and non-migration were categorised for
species from each of the lower and upper mesopelagic assemblages. The vertical distribution of these assemblages was coincident
with the primary water masses: subantarctic mode water (∼250 to 600 m) and antarctic intermediate water (below ∼700 m). The
flux of migrating micronekton, estimated at 0.94 to 3.36 g C m−2 yr−1 to the lower mesopelagic and 1.14 to 4.06 g C m−2 yr−1 to the upper mesopelagic, appeared to be considerably outweighed by the consumption needs of aggregated mid-slope benthopelagic
predators. We suggest that advection of mesopelagic prey in antarctic intermediate water may sustain aggregated populations
of orange roughy (Hoplostethus atlanticus) and other predators on the micronekton in mid-slope depths at this site.
Received: 2 April 1997 / Accepted: 21 August 1997 相似文献
7.
R. W. Brill B. A. Block C. H. Boggs K. A. Bigelow E. V. Freund D. J. Marcinek 《Marine Biology》1999,133(3):395-408
We measured the horizontal and vertical movements of five adult yellowfin tuna (Thunnus albacares, estimated body mass 64 to 93 kg) near the main Hawaiian Islands, while simultaneously gathering data on oceanographic conditions
and currents. Fish movements were recorded by means of ultrasonic depth-sensitive transmitters. Depth–temperature and depth–oxygen
profiles were measured with vertical conductivity–temperature–depth (CTD) casts, and the current-velocity field was surveyed
using an acoustic Doppler current profiler (ADCP). Large adult yellowfin tuna spent ≃60 to 80% of their time in or immediately
below the relatively uniform-temperature surface-layer (i.e. above 100 m), a behavior pattern similar to that previously reported
for juvenile yellowfin tuna, blue marlin (Makaira nigricans), and striped marlin (Tetrapturus audax) tracked in the same area. In all three species, maximum swimming depths appear to be limited by water temperatures 8 C°
colder than the surface-layer water temperature. Therefore, neither large body mass, nor the ability to maintain elevated
swimming-muscle temperatures due to the presence of vascular counter-current heat exchangers in tunas, appears to permit greater
vertical mobility or the ability to remain for extended periods below the thermocline. In those areas where the decrease in
oxygen with depth is not limiting, the vertical movements of yellowfin tuna, blue marlin and striped marlin all appear to
be restricted by the effects of water temperature on cardiac muscle function. Like juvenile yellowfin tuna, but unlike blue
marlin and striped marlin, adult yellowfin tuna remained within 18.5 km of the coast and became associated with floating objects,
including anchored fish-aggregating devices (FADs) and the tracking vessel. Like juvenile yellowfin tuna, large adult yellowfin
repeatedly re-visit the same FAD, and appear able to navigate precisely between FADs that are up to 18 km apart. The median
speed over ground ranged from 72 to 154 cm s−1. Neither speed nor direction was strongly influenced by currents.
Received: 27 March 1998 / Accepted: 13 November 1998 相似文献
8.
A method for attaching acoustic transmitters externally to deep-water fishes in situ is described. Tags, each comprising
a transmitter connected to a dart, were fired at fish from a pneumatic gun held by the manipulator arm of a submersible. The
method was applied successfully for tagging coelacanths and may have application for use with other species of fishes living
at depths to about 1000 m. The usefulness of direct observation for monitoring the effects of tags on fish is evaluated in
relation to the effects of the tagging method on coelacanths.
Received: 3 January 1997 / Accepted: 25 January 1997 相似文献
9.
The aim of this study was to determine whether the composition of the demersal fish fauna in coastal marine waters in temperate
Australia changes markedly with increasing water depth and distance from the shore and whether the composition of the fish
fauna in water depths of 5 to 35 m undergoes cyclic, seasonal changes. Samples of demersal fishes were therefore collected
by trawling over the predominantly sandy substrate at nine sites located in water depths of 5 to 15 m or 20 to 35 m and within
20 km of the shore in four regions along ∼200 km on the lower west coast of Australia. The sampling regime involved trawling
for fishes at each site at night in seven consecutive seasons between the summer of 1990/1991 and winter of 1992. A total
of 72 435 fishes, representing 77 families, 143 genera and 172 species was caught. The compositions of the fish faunas in
offshore waters with depths of 5 to 35 m were shown to differ markedly from those previously recorded for nearshore marine
waters in the same regions. However, as some species, such as Sillago burrus, S. vittata, S. bassensis and Rhabdosargus sarba, increase in size, they move out from their nursery areas in nearshore waters into deeper and more offshore waters, where
spawning occurs. Ordination showed that, in each of the four regions, the composition of the fish fauna in depths of 5 to
15 m differs from that in depths of 20 to 35 m. This difference is attributable to the fact that some species, such as S. burrus, S. vittata and Upeneichthys lineatus, are far more abundant in depths of 5 to 15 m, whereas other species, such as S. robusta, U. stotti and Lepidotrigla modesta, occur predominantly in depths of 20 to 35 m. However, the samples collected from the single site that was inshore but in
deeper water demonstrate that the composition of the fish fauna is influenced by distance from shore as well as by water depth.
The compositions of the fish faunas differed with latitude, largely due to the fact that some subtropical species, such as
Polyspina piosae, S. burrus and S. robusta, did not extend down into the more southern regions. Ordination also showed that the composition of the fish faunas at all
but one of the nine sites underwent pronounced and consistent cyclic, seasonal changes. This seasonal cyclicity at the different
sites was attributable to sequential patterns of immigrations and emigrations by a number of fish species during the course
of the year. These seasonal migrations involved, inter alia (1) movements of certain species from their nursery areas into
these deeper waters, e.g. S. bassensis and Scobinichthys granulatus; (2) migrations into and off the sandy areas of the inner continental shelf, e.g. Arnoglossus muelleri; (3) migrations to spawning areas, e.g. Sillago robusta; and (4) movements into areas where detached macrophytes accumulate in winter, e.g. Cnidoglanis macrocephalus and Apogon rueppellii.
Received: 21 August 1998 / Accepted: 9 February 1999 相似文献
10.
Late larvae of the serranid coral trout Plectropomus leopardus (Lacepède), captured in light traps, were released during the day both in open water and adjacent to two reefs, and their
behaviour was observed by divers at Lizard Island, northern Great Barrier Reef. Coral trout larvae (n = 110) were present in light-trap catches from 18 November to 3 December 1997, including new moon (30 November). The swimming
speed of larvae in open water or when swimming away from reefs was significantly greater (mean 17.9 cm s−1) than the speed of larvae swimming towards or over reefs (mean 7.2 cm s−1). Near reefs, larvae swam at average depths of 2.7 to 4.2 m, avoiding 0 to 2 m. In open water, swimming depth varied with
location: larvae >1 km east of Lizard Island swam steeply downward to >20 m in 2 to 4 min; larvae >1 km west oscillated between
2.6 and 13 m; larvae 100 to 200 m east of Lizard Island oscillated between 0.8 and 15 m. Nearly all larvae swam directionally
in open water and near reefs. In open water, the average swimming direction of all larvae was towards the island, and 80%
(4 of 5) swam directionally (p < 0.05, Rayleigh's test). Larvae swam directionally over the reef while looking for settlement sites. The frequency of behaviours
by larvae differed between two reefs of different exposure and morphology. Depending on site, 26 to 32% of larvae released
adjacent to reefs swam to open water: of these, some initially swam towards or over the reef before swimming offshore. In
some cases, offshore-swimming seemed to be due to the presence of predators, but usually no obvious cause was observed. Depending
on the reef, 49 to 64% of the larvae settled. Non-predatory reef residents aggressively approached 19% of settlers. Between
5 and 17% of the larvae were eaten while approaching the reef or attempting to settle, primarily by lizardfishes but also
by wrasses, groupers and snappers. A higher percentage of larvae settled in the second week of our study than in the first.
Average time to settlement was short (138 s ± 33 SE), but some larvae took up to 15 min to settle. Average settlement depth
was 7.5 to 9.9 m, and differed between locations. No settlement took place on reef flats or at depths <4.2 m. Larvae did not
appear to be selective about settlement substrate, but settled most frequently on live and dead hard coral. Late-stage larvae
of coral trout are capable swimmers with considerable control over speed, depth and direction. Habitat selection, avoidance
of predators and settlement seem to rely on vision.
Received: 7 July 1998 / Accepted: 26 January 1999 相似文献
11.
Vertical movement and habitat of opah (Lampris guttatus) in the central North Pacific recorded with pop-up archival tags 总被引:1,自引:0,他引:1
Data from 11 pop-up archival transmitting tags attached to opah (Lampris guttatus, F. Lampridae) in the central North Pacific between November 2003 and March 2005 were used to describe their vertical movement
and habitat. In the subtropical gyre northwest of the Hawaiian Islands, opah generally inhabited a 50–400 m depth range and
8–22°C temperatures. They were frequently found in depths of 50–150 m at night and in greater depths (100–400 m) during the
day, but were constantly moving vertically within this broad range. At night, excursions below 200 m were not uncommon and
during the day they were very likely to spend some time at depths <175 m. Their vertical speeds were generally <25 cm s−1 but on one occasion an opah descended at a burst speed of 4 m s−1. Vertical habitat use by individual opah apparently varied with local oceanographic conditions, but over a 24-h period the
average temperature experienced was always in the narrow range of 14.7 to 16.5°C.
相似文献
Jeffrey J. PolovinaEmail: |
12.
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
13.
A survey of the distribution and maximum depth of a continuous Fucus vesiculosus belt was carried out in the Gulf of Finland in 1991. F. vesiculosus is widely distributed throughout the Gulf of Finland, including the vicinity of Vyborg Bay, Russia in the east. The maximum
growth depth of F. vesiculosus in the Gulf of Finland reflects two different patterns according to the exposure to wave action. The most robust and continuous
F. vesiculosus belt is observed on exposed shores, where the maximum growth depth is 5 to 6 m, with the optimum at 2 to 3 m. On moderately
exposed shores the maximum growth depth is 3 m, with an optimum growth depth of <2 m. The maximum growth depth also varies
geographically, with a decreasing trend towards the east. Maximum growth depth of F. vesiculosus correlates with light intensity. The compensation point for F. vesiculosus photosynthesis is about 25 μmol m−2 s−1, and photosynthesis is saturated at a light intensity of 300 μmol m−2 s−1. Vertical irradiance attenuation measurements in situ in summer revealed that for F. vesiculosus photosynthesis the quantity of light is optimal (200 to 300 μmol m−2 s−1) at <3 m depth. At depths >5 m the quantity of light is near or below the photosynthesis compensation point and insufficient
for growth. These depth limits of light penetration coincide with measured growth depths of F. vesiculosus in the Gulf of Finland.
Received: 7 May 1999 / Accepted: 18 November 1999 相似文献
14.
Territorial Parma microlepis (Günther) (Pomacentridae) were collected at different depths, at three sites in each of four estuaries near Sydney, Australia.
Element concentrations were measured by induc- tively-coupled–plasma mass spectrometry. Significant differences in concentrations
of Mn and Ba were found in the otoliths of fish sampled in different depth strata, with concentrations generally greatest
in fish found in water <4 m deep. Depth-related differences varied among estuaries (e.g. 0 to 1.2 μg Ba g−1 otolith). In most estuaries there was a negative linear relationship between concentrations of Mn and Ba in otoliths and
actual depth. Great variation was found within an estuary among sites separated by 0.5 to 3 km. In the eye lenses, concentrations
of Rb differed according to depth of capture of fish. The age of fish (1+ to 34 yr) had no influence on the concentrations
of elements in otoliths or lenses. Multivariate comparisons of elemental composition (= fingerprints) detected significant
differences among depth strata. Fish collected from shallow water had the clearest multivariate classification according to
depth. There was a close match between our shallow strata and the average depths reached by low-salinity/high-temperature
estuarine plumes. The element composition of whole otoliths and lenses represents average concentrations experienced by the
fish. The temporal resolution of differences in ambient conditions is likely to be coarse in the fish (i.e. months to years).
Received: 9 April 1999 / Accepted: 29 February 2000 相似文献
15.
The use of transparency as camouflage in the epipelagic realm is complicated by the presence of ultraviolet radiation, because
the presence of UV-protective pigments decreases UV transparency and may reveal transparent zooplankton to predators and prey
with UV vision. During July 1999, September 1999, and June 2000, transparency measurements (from 280 to 500 nm) were made
on living specimens of 15 epipelagic (collection depth: 0–20 m, average: 11 ± 1 m) and 19 mesopelagic (collection depth: 150–790 m,
average: 370 ± 40 m) species of transparent zooplankton from Oceanographer Canyon and Wilkinson Basin in the Northwest Atlantic
Ocean. In addition, measurements of downwelling irradiance (from 330 to 500 nm) versus depth were made. The tissues from epipelagic
zooplankton had lower UV transparency than those from mesopelagic zooplankton, while the average visible transparency (at
480 nm) of the two groups was not significantly different. Percent transparency was positively correlated with wavelength
over most of the measured range, with a rapid decrease below a certain cutoff wavelength. In mesopelagic tissues, the cutoff
wavelength was generally 300 nm. In epipelagic tissues, the cutoff wavelength was between 300 and 400 nm. Twelve out of 19
epipelagic tissues had transparencies at 320 nm that were half or less than their 480 nm transparency values, versus only
4 out of 21 mesopelagic tissues. The effects of UV absorption on UV visibility and minimum attainable depth were modeled using
contrast theory and the physics of light attenuation. Because UV absorption was generally significantly greater in the UVB
than in the UVA spectrum (where UV vision occurs), and because the highest UV absorption was often found in less transparent
individuals, its modeled effects on visibility were slight compared to its effects on minimum attainable depth.
Received: 14 April 2000 / Accepted: 16 November 2000 相似文献
16.
Depth and muscle temperature of Pacific bluefin tuna examined with acoustic and pop-up satellite archival tags 总被引:1,自引:0,他引:1
David J. Marcinek Susanna B. Blackwell Heidi Dewar Ellen V. Freund Charles Farwell Daniel Dau Andrew C. Seitz Barbara A. Block 《Marine Biology》2001,138(4):869-885
Six Pacific bluefin tuna were tracked with ultrasonic telemetry and two with pop-up satellite archival tags (PSATs) in the
eastern Pacific Ocean in 1997, 1998, and 1999. Both pressure and temperature ultrasonic transmitters were used to examine
the behavior of the 2- to 4-year-old bluefin tuna. The bluefin spent over 80% of their time in the top 40 m of the water column
and made occasional dives into deeper, cooler water. The mean slow-oxidative muscle temperatures of three fish instrumented
with pressure and temperature transmitters were 22.0–26.1 °C in water temperatures that averaged 15.7–17.5 °C. The thermal
excesses in slow-oxidative muscle averaged 6.2–8.6 °C. Variation in the temperature of the slow-oxidative muscle in the bluefin
was not correlated with water temperature or swimming speeds. For comparison with the acoustic tracking data we examined the
depth and ambient temperature of two Pacific bluefin tagged with pop-up satellite archival tags for 24 and 52 days. The PSAT
data sets show depth and temperature distributions of the bluefin tuna similar to the acoustic data set. Swimming speeds calculated
from horizontal distances with the acoustic data indicate the fish mean speeds were 1.1–1.4 fork lengths/s (FL s−1). These Pacific bluefin spent the majority of their time in the top parts of the water column in the eastern Pacific Ocean
in a pattern similar to that observed for yellowfin tuna.
Received: 4 April 2000 / Accepted: 25 October 2000 相似文献
17.
We examined the degree of mesoscale (km), finescale (m), and microscale (cm) patchiness of ciliates and their prey in waters
of varying hydrographic conditions. Samples were taken throughout the water column, along a transect across the Irish Sea
(54°N), at scales ranging from 0.15 to 105 m. We examined physical, chemical, and biological characteristics. The eastern and western Irish Sea were stratified, with
a pycnocline at ∼20 to 30 m. The central waters were mixed and had adjacent frontal regions. Euphotic depth was ∼20 to 35 m.
Generally, the upper waters were nitrogen-limited, with elevated levels associated with frontal regions and deeper waters.
Microphytoplankton exhibited fine-mesoscale patchiness: diatom numbers were low in stratified waters, with higher levels in
mixed and frontal regions; dinoflagellates were abundant in subsurface waters near the fronts. Nanoflagellate numbers and
biomass decreased with depth below the pycnocline, and exhibited microscale distribution in upper waters; these micropatches
may provide increased food levels for ciliates. Microscale distribution of ciliates was rare and only occurred at mixed/frontal
sites; finescale ciliate patches were a more prominent feature of the water column. These finescale patches can be composed
of a variety of taxa but can also be virtually monospecific. Finescale patches may produce localised regions of high productivity
that is available to fishes and copepods, but may also be a sink, as patches can be short-lived and thus unavailable to predators.
Received: 28 September 1998 / Accepted: 26 January 1999 相似文献
18.
Differential increment-deposition rate in embryonic statoliths of the loliginid squid Loligo vulgaris 总被引:2,自引:0,他引:2
R. Villanueva 《Marine Biology》2000,137(1):161-168
Apart from one study that reported growth of less than one increment per day in statoliths of the squid Alloteuthis subulata, most studies so far have presumed that one increment was laid down per day in the statoliths of the squid species they examined.
The present study provides evidence of differential daily growth rates in embryonic statoliths of the squid Loligo vulgaris Lamarck, 1798, thus confirming a previous report for A. subulata. Incremental growth rates of L. vulgaris statoliths differ as a function of temperature. Squid embryos were incubated in the laboratory at three temperatures (12.0,
15.5 and 21.1 °C), and tetracycline staining was used to follow statolith growth. This growth slowed in squid exposed to the
lowest temperature, but recovered when the squid were returned to warm conditions, indicating statolith adaptation. Statolith
growth rate after incubation at 12 °C was 1.3% d−1 and reached 6.1% d−1 for squids exposed to 21.1 °C. Statoliths from embryos incubated at 15.5 °C yielded a rate of 1 increment d−1 and a mean daily growth of 2.2 μm in the dorsal dome area of the statolith. In contrast, the slow growth of statoliths incubated
at 12 °C yielded a mean daily growth of only 0.9 μm in the dorsal dome and the readings resulted in a less-than-daily increment-deposition
rate.
Received: 9 October 1999 / Accepted: 30 March 2000 相似文献
19.
The origin of the deep-sea benthic fauna is poorly understood and represents an enormous gap in our understanding of basic
evolutionary phenomena. One obstacle to studying evolutionary patterns in the deep sea has been the technical difficulty of
measuring genetic variation in species that are typically minute, rare, and must be recovered from extreme depths. We used
molecular genetic techniques to quantify variation in the 16S rRNA mitochondrial gene within and among populations of the
common protobranch bivalve Deminucula atacellana (Schenck, 1939). We analyzed 89 individuals from nine samples collected in the 1960s along a depth gradient from 1100 to
3800 m in the western North Atlantic. Genetic variability within populations is much lower than between populations, and peak
haplotype numbers occur near the center of its depth distribution. Continental slope (<2500 m) and rise (>2500 m) populations
were genetically distinct despite the lack of any obvious topographic or oceanographic features that would impede gene flow.
These findings indicate that the deep-sea macrofauna can have strong population structure over small (134 km) spatial scales,
similar to that observed in shallow-water and terrestrial organisms. This surprisingly high biodiversity at the genetic level
affords the potential for adaptation and evolutionary diversification, the ultimate historical causes of high species diversity
in the deep-sea benthos.
Received: 24 July 1997 / Accepted: 26 January 1998 相似文献
20.
Daniel P. Cartamil Chugey A. Sepulveda Nicholas C. Wegner Scott A. Aalbers Andres Baquero Jeffrey B. Graham 《Marine Biology》2011,158(4):935-944
The common thresher shark (Alopias vulpinus) is a secondary target species of the California drift gillnet fishery (CA-DGN) and supports a growing recreational fishery
in California waters. This study used archival tags to examine the movement patterns and habitat preferences of common threshers
of the size range captured in the CA-DGN (>120 cm fork length). Depth and temperature-logging archival tags were deployed
on 57 subadult and adult common threshers in the Southern California Bight. Tags from five individuals (8.8%) were recovered,
and 154 days of data were successfully obtained from four of these. By night, shark movements were primarily limited to waters
above the thermocline, which ranged in depth from 15 to 20 m. Sharks were significantly deeper by day, and daytime vertical
distribution consisted of two distinct modes: a ‘shallow mode’ (wherein sharks occupied only the upper 20 m of the water column)
and a ‘deep mode’ (characterized by frequent vertical excursions below the thermocline). This modal switch is interpreted
as relating to regional differences in abundance of surface-oriented prey and prey in deeper water. Maximum dive depth was
320 m, greatest dive duration was 712 min, minimum temperature experienced during a dive was 9.1°C, and dive descent rate
was significantly greater than ascent rate. Sharks inhabited waters corresponding to a sea surface temperature range of 16
to 21°C. The nocturnal depth distribution of common threshers has implications for management of drift gillnet deployment
depths in the CA-DGN. 相似文献