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1.
Electronic tagging and remotely sensed oceanographic data were used to determine the oceanographic habitat use and preferences
of Atlantic bluefin tuna (Thunnus thynnus L.) exhibiting behaviors associated with breeding in the Gulf of Mexico (GOM). Oceanographic habitats used by 28 Atlantic
bluefin tuna exhibiting breeding behavior (259 days) were compared with available habitats in the GOM, using Monte Carlo tests
and discrete choice models. Habitat utilization and preference patterns for ten environmental parameters were quantified:
bathymetry, bathymetric gradient, SST, SST gradient, surface chlorophyll concentration, surface chlorophyll gradient, sea
surface height anomaly, eddy kinetic energy, surface wind speed, and surface current speed. Atlantic bluefin tuna exhibited
breeding behavior in the western GOM and the frontal zone of the Loop Current. Breeding areas used by the bluefin tuna were
significantly associated with bathymetry, SST, eddy kinetic energy, surface chlorophyll concentration, and surface wind speed,
with SST being the most important parameter. The bluefin tuna exhibited significant preference for areas with continental
slope waters (2,800–3,400 m), moderate SSTs (24–25 and 26–27°C), moderate eddy kinetic energy (251–355 cm2 s−2), low surface chlorophyll concentrations (0.10–0.16 mg m−3), and moderate wind speeds (6–7 and 9–9.5 m s−1). A resource selection function of the bluefin tuna in the GOM was estimated using a discrete choice model and was found
to be highly sensitive to SST. These habitat utilization and preference patterns exhibited by breeding bluefin tuna can be
used to develop habitat models and estimate the probable breeding areas of bluefin tuna in a dynamic environment. 相似文献
2.
Pop-up satellite archival tags were implanted into 68 Atlantic bluefin tuna (Thunnus thynnus Linnaeus), ranging in size from 91 to 295 kg, in the southern Gulf of Maine (n=67) and off the coast of North Carolina (n=1) between July 2002 and January 2003. Individuals tagged in the Gulf of Maine left that area in late fall and overwintered in northern shelf waters, off the coasts of Virginia and North Carolina, or in offshore waters of the northwestern Atlantic Ocean. In spring, the fish moved either northwards towards the Gulf of Maine or offshore. None of the fish crossed the 45°W management line (separating eastern and western management units) and none traveled towards the Gulf of Mexico or the Straits of Florida (known western Atlantic spawning grounds). The greatest depth recorded was 672 m and the fish experienced temperatures ranging from 3.4 to 28.7°C. Swimming depth was significantly correlated with location, season, size class, time of day, and moon phase. There was also evidence of synchronous vertical behavior and changes in depth distribution in relation to oceanographic features.Communicated by J.P. Grassle, New Brunswick 相似文献
3.
M. E. Lutcavage R. W. Brill G. B. Skomal B. C. Chase J. L. Goldstein J. Tutein 《Marine Biology》2000,137(2):347-358
Ultrasonic, depth-sensitive transmitters were used to track the horizontal and vertical movements, for up to 48 h, of 11
adult (136 to 340 kg estimated body mass) North Atlantic bluefin tuna (Thunnus thynnus Linnaeus). Fish were tracked in October 1995, September and October 1996, and August and September 1997 in the Gulf of Maine,
northwestern Atlantic. The objective was to document the behavior of these fish and their schools in order to provide the
spatial, temporal, and environmental information required for direct (i.e. fishery-independent) assessment of adult bluefin
tuna abundance using aerial surveys. Transmitters were attached to free-swimming fish using a harpoon attachment technique,
and all fish remained within the Gulf of Maine while being followed. Most of the bluefin tuna tagged on Stellwagen Bank or
in Cape Cod Bay (and followed for at least 30 h) held a predominately easterly course with net horizontal displacements of
up to 76 km d−1. Mean (±SD) swimming depth for all fish was 14 ± 4.7 m and maximum depth for individuals ranged from 22 to 215 m. All but
one fish made their deepest excursions, often single descents, at dawn and dusk. In general, adult bluefin tuna spent <8%
of their time at the surface (0 to 1 m), <19% in the top 4 m, but >90% in the uppermost 30 m. Mean (±SD) speed over ground
was 5.9 km h−1, but for brief periods surpassed 20 to 31 km h−1. Sea surface temperatures during tracking were 11.5 to 22.0 °C, and minimum temperatures encountered by the fish ranged from
6.0 to 9.0 °C. Tagged bluefin tuna and their schools frequented ocean fronts marked by mixed vertebrate feeding assemblages,
which included sea birds, baleen whales, basking sharks, and other bluefin schools.
Received: 19 July 1999 / Accepted: 25 March 2000 相似文献
4.
Mitochondrial DNA and electronic tracking reveal population structure of Atlantic bluefin tuna (Thunnus thynnus) 总被引:1,自引:0,他引:1
Population subdivision was examined in Atlantic bluefin tuna (Thunnus thynnus) through sequencing of the control region of the mitochondrial genome. A total of 178 samples from the spawning grounds in
the Gulf of Mexico, Bahamas and Mediterranean Sea were analyzed. Among the samples from these locations were 36 electronically
tagged bluefin tuna that were tagged in the North Atlantic and subsequently traveled to one of these known spawning grounds
during the spawning season. Bluefin tuna populations from the Gulf of Mexico and the Mediterranean Sea were found to be genetically
distinct based on Φst, and sequence nearest neighbor analyses, showing that these two major spawning areas support independent stocks. Sequence
nearest neighbor analysis indicated significant population subdivision among the Gulf of Mexico, western Mediterranean and
eastern Mediterranean Sea. However, it was not possible to find significant pairwise differences between any sampling areas
when using all samples. If only samples that had a high likelihood of assignment to a specific spawning site were used (young
of the year, spawning adults), the differentiation increased among all sampling areas and the Western Mediterranean Sea was
distinct from the Eastern Mediterranean Sea and the Gulf of Mexico. It was not possible to distinguish samples from the Bahamas
from those collected at any of the other sampling sites. These data support tagging results that suggested distinctness of
the Gulf of Mexico, Eastern and Western Mediterranean Sea spawning areas. This level of stock differentiation is only possible
if Atlantic bluefin tuna show strong natal homing to individual spawning grounds. 相似文献
5.
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
6.
Jennifer Goldstein Scott Heppell Andrew Cooper Solange Brault Molly Lutcavage 《Marine Biology》2007,151(6):2063-2075
The reproductive status and body condition of 195 (≥185 cm curved fork length, CFL; assigned age 7 and above) Atlantic bluefin
tuna were assessed in the Gulf of Maine during the commercial fishing season of June–October, 2000–2002. Given the distance
between known spawning and feeding grounds, the prevailing paradigm for Atlantic bluefin tuna (Thunnus thynnus thynnus, L.) suggests that the most likely histological state for females arriving in the Gulf of Maine after spawning would be a
resting or quiescent state with little or no perigonadal fat. Alternatively, the presence of mature or mature-inactive histological
states in some females supports a more varied or individualistic model for bluefin reproduction. No relationship was found
between body condition and reproductive status. Males were found in all reproductive stages, but were more likely to be in
spawning condition (stages 4 and 5) or a mature-inactive state (stage 6) in June and July. Female bluefin tuna were found
in stage 1 (immature or non-spawning) and stage 6 (mature-inactive). Stage 6 females were only present in June and July and
smaller females (<235 cm CFL) were more likely to be in stage 6 than large females (>235 cm CFL) sampled during those same
months. The presence of smaller females in stage 6 arriving at the same time as larger females in stage 1 indicates that Western
Atlantic bluefin tuna may have an asynchronous reproductive schedule and may mature at a smaller size than the currently accepted
paradigm suggests. 相似文献
7.
Sixty-eight yellowfin tuna, Thunnus albacares, (60-135 cm fork length) were caught and released with implanted archival tags offshore off Baja California, Mexico, during
October 2002 and October 2003. Thirty-six fish (53%) were recaptured and the data were downloaded from all 36 recovered tags.
Time at liberty ranged from 9 to 1,161 days, and the data were analyzed for the 20 fish that were at liberty for 154 or more
days. The accuracy in the position estimates, derived from light-level longitude data and sea-surface temperatures (SSTs)
based latitude, is about 0.41° in longitude and 0.82° in latitude, in this region. The movement paths, derived from position
estimates, for the 20 yellowfin indicated that 19 (95%) remained within 1,445 km of their release locations. The estimated
mean velocity along movement paths was 77 km/day. The southern and northern seasonal movement paths observed for yellowfin
off Baja California are influenced by the seasonal movements of the 18°C SST isotherm. Cyclical movements to and from suitable
spawning habitat (≥24°C SST) was observed only for mature fish. For the 12 fish that demonstrated site fidelity, the mean
95 and 50% utilization distributions were 258,730 km2 and 41,260 km2, respectively. Evaluations of the timed depth records resulted in discrimination of four distinct behaviors. When exhibiting
type-1 diving behavior (78.1% of all days at liberty) the fish remained at depths less than 50 m at night and did not dive
to depths greater than about 100 m during the day. Type-2 diving behavior (21.2% of all days at liberty) was characterized
by ten or more dives in excess of 150 m during the day. Type-2 diving behavior is apparently a foraging strategy for fish
targeting prey organisms of the deep-scattering layer during the day, following nighttime foraging within the mixed layer
on the same prey. Yellowfin tuna exhibited occasional deep-diving behavior, and some dives exceeded 1,000 m, where ambient
temperatures were less than 5°C. Surface-oriented behavior, defined as the time fish remained at depths less than 10 m for
more than 10 min, were evaluated. The mean number and duration of surface-oriented events per day for all fish was 14.3 and
28.5 min, respectively. Habitat utilization of yellowfin, presented as monthly composite horizontal and vertical distributions,
indicates confined geographical distributions, apparently resulting from an affinity to an area of high prey availability.
The vertical distributions indicate greater daytime depths in relation to a seasonally deeper mixed layer and a greater proportion
of daytime at shallower depths in relation to a seasonally shallower mixed layer. 相似文献
8.
The genetic population structures of Atlantic northern bluefin tuna ( Thunnus thynnus thynnus) and albacore ( T. alalunga) were examined using allozyme analysis. A total of 822 Atlantic northern bluefin tuna from 18 different samples (16 Mediterranean, 1 East Atlantic, 1 West Atlantic) and 188 albacore from 5 samples (4 Mediterranean, 1 East Atlantic) were surveyed for genetic variation in 37 loci. Polymorphism and heterozygosity reveal a moderate level of genetic variability, with only two highly polymorphic loci in both Atlantic northern bluefin tuna ( FH* and SOD- 1*) and albacore ( GPI- 3* and XDH*). The level of population differentiation found for Atlantic northern bluefin tuna and albacore fits the pattern that has generally been observed in tunas, with genetic differences on a broad rather than a more local scale. For Atlantic northern bluefin tuna, no spatial or temporal genetic heterogeneity was observed within the Mediterranean Sea or between the East Atlantic and Mediterranean, indicating the existence of a single genetic grouping on the eastern side of the Atlantic Ocean. Very limited genetic differentiation was found between West Atlantic and East Atlantic/Mediterranean northern bluefin tuna, mainly due to an inversion of SOD- 1* allele frequencies. Regarding albacore, no genetic heterogeneity was observed within the Mediterranean Sea or between Mediterranean and Azores samples, suggesting the existence of a single gene pool in this area. 相似文献
9.
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
10.
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
11.
Stable 13C and 15N isotope analyses of scale, bone, and muscle tissues were used to investigate diet and trophic position of North Atlantic bluefin tuna (Thunnus thynnus Linnaeus) during residency in the northwest Atlantic Ocean off the northeast coast of the United States. Adult bluefin tuna scales collected from fish between June and October 2001 were significantly enriched in 13C compared to both muscle and bone across all months, while muscle was significantly enriched in 15N compared to either bone or scale throughout the same period. In muscle tissue, there was evidence of a shift over the summer from prey with 13C values (–17 to –18) that were characteristic of silver hake (Merluccius bilinearis) to species with 13C values of –20 to –21 that were similar to Atlantic herring (Clupea harengus) and sandlance (Ammodytes americanus). Depletion of 15N values in adult scales and bone compared to muscle tissue may be explained by bone and scale samples representing juvenile or life-long feeding habits, isotopic routing, or isotopic differences in amino acid composition of the three tissue types. Adult bluefin tuna were estimated to be feeding at a trophic position similar to pelagic sharks in the northwest Atlantic Ocean, while the trophic positions of yellowfin tuna (Thunnus albacares), albacore tuna (Thunnus alalunga), and juvenile bluefin tuna were indicative of a diet of up to a full trophic position below adult bluefin tuna. The close relationship between the juvenile bluefin 15N values and those of suspension feeders suggests that nektonic crustaceans or zooplankton may contribute significantly to the diet of bluefin tuna, a food source previously overlooked for this species in the northwest Atlantic Ocean.Communicated by J.P. Grassle, New Brunswick 相似文献
12.
Jay Willis John Phillips Rachel Muheim Francisco Javier Diego-Rasilla Alistair J. Hobday 《Behavioral ecology and sociobiology》2009,64(1):57-68
Tunas make sharp descents and ascents around dawn and dusk called spike dives. We examine spike dives of 21 southern bluefin
tuna (Thunnus maccoyii) implanted with archival tags in the Great Australian Bight. Using a new way to categorize this behavior, we show that spike
dives are similar among all the fish in the study. The dive profiles are mirror images at dawn and dusk and are precisely
timed with respect to sunrise and sunset. We analyze the possible reasons for spike dives, considering the timing of spike
dives, the characteristic dive profile, and the tuna's magnetic habitat. In addition, we present anatomical evidence for elaboration
of the pineal organ, which is light mediated and has been implicated in navigation in other vertebrates. The new evidence
presented here leads us to suspect that spike dives represent a survey related to navigation. 相似文献
13.
Gilad Heinisch Aldo Corriero Antonio Medina Francisco J. Abascal Jose-Miguel de la Serna Robert Vassallo-Agius Antonio Belmonte Ríos Antonio García Fernando de la Gándara Christian Fauvel Christopher R. Bridges Constantinos C. Mylonas Saadet F. Karakulak Isik Oray Gregorio De Metrio Hanna Rosenfeld Hillel Gordin 《Marine Biology》2008,154(4):623-630
Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided
into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more
about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between
April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods
at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling
point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such
as the total body mass (M
B) and the weights of the gonads (M
G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important
trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean
Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea),
and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal
development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine
Sea BFT population (mean M
B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M
B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat
for young BFT, until they gain a larger M
B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean
Sea cannot be ruled out. 相似文献
14.
April Hedd P. M. Regular W. A. Montevecchi A. D. Buren C. M. Burke D. A. Fifield 《Marine Biology》2009,156(4):741-751
Owing to the necessity of delivering food to offspring at colonies, breeding seabirds are highly constrained in their foraging
options. To minimize constraints imposed by central-place foraging and to optimize foraging behavior, many species exhibit
flexible foraging tactics. Here we document the behavioral flexibility of pursuit-diving common murres Uria aalge when foraging on female capelin Mallotus villosus in the northwest Atlantic. Quite unexpectedly, being visual foragers, we found that common murres dived throughout the day
and night. Twenty-one percent of recorded dives (n = 272 of 1,308 dives) were deep (≥50 m; maximum depth = 152 m, maximum duration = 212 s), bringing murres into sub-0°C water
in the Cold Intermediate Layer (CIL; 40–180 m) of the Labrador Current. Deep dives occurred almost exclusively during the
day when murres would have encountered spatially predictable aggregations of capelin between 100 and 150 m in the water column.
Temperatures within the CIL shaped trophic interactions and involved trade-offs for both predators and prey. Sub-0°C temperatures
limit a fish’s ability to escape from endothermic predators by reducing burst/escape speeds and also lengthening the time
needed to recover from burst-type activity. Thus, while deep diving may be energetically costly, it likely increases certainty
of prey capture. Decreased murre foraging efficiency at night (indicated by an increase in the number of dives per bout) reflects
both lower light conditions and changing prey behavior, as capelin migrate to warmer surface waters at night where their potential
to escape from avian predators could increase. 相似文献
15.
Fifteen yellow-bellied sea snakes,Pelamis platurus, fitted with pressure-sensitive ultrasonic transmitters, were tracked in the Gulf of Panamá during 1983–1985. Snakes spent up to 99.9% (
= 87%) of the tracking time under water and dived to 50 m. The maximum voluntary submergence time observed was 213 min, and of 202 complete dives logged, 19 exceeded 90 min. Dive durations of tracked snakes were typically longer than expected, based upon their estimated body-oxygen stores, and some were even longer than the reported survival times of forceably submerged snakes. Snakes, however, dived repeatedly and did not spend long periods at the surface between dives, suggesting that they did not develop an oxygen deficit during diving. Diving snakes may be able to avoid anaerobiosis by having a reduced metabolic rate, an enhanced rate of cutaneous oxygen uptake, or both. Surface conditions and subsurface temperatures influence the diving behavior ofP. platurus. Laboratory experiments in Panamá indicated that a larger number of snakes were submerged when surface water was turbulent. During February and March, the period of dry season upwelling in the Gulf of Panamá, sea snakes were found to avoid cooler, subsurface water and to make significantly shallower dives: mean maximum depth 6:8 m (n=76) in contrast to a mean maximum depth of 15.1 m (n=147) during the wet season. The dives during the dry season tended to be of shorter duration, with 44% lasting less than 15 min, compared to only 19% of the dives recorded during the wet season being completed in less than 15 min. General avoidance of subsurface temperatures cooler than 19°C was confirmed by laboratory experiments in the 10 m-deep tank at Scripps Institution of Oceanography. 相似文献
16.
This study is the first report of post-nesting migrations of loggerhead sea turtles (Caretta caretta) nesting in Sarasota County (Florida, USA), their most important rookery in the Gulf of Mexico (GOM). In total, 28 females
(curved carapace length CCL between 82.2 and 112.0 cm) were satellite-tracked between May 2005 and December 2007. Post-nesting
migrations were completed in 3–68 days (mean ± SD = 23 ± 16 days). Five different migration patterns were observed: six turtles
remained in the vicinity of their nesting site while the other individuals moved either to the south-western part of the Florida
Shelf (n = 9 turtles), the Northeast GOM (n = 2 turtles), the South GOM (Yucatán Shelf and Campeche Bay, Mexico, and Cuba; n = 5 turtles) or the Bahamas (n = 6 turtles). In average, turtles moved along rather straight routes over the continental shelf but showed more indirect
paths in oceanic waters. Path analyses coupled with remote sensing oceanographic data suggest that most of long-distance migrants
reached their intended foraging destinations but did not compensate for the deflecting action of ocean currents. While six
out of seven small individuals (CCL < 90 cm) remained on the Florida Shelf, larger individuals showed various migration strategies,
staying on the Florida Shelf or moving to long-distance foraging grounds. This study highlights the primary importance the
Western Florida Shelf in the management of the Florida Nesting Subpopulation, as well as the need of multi-national effort
to promote the conservation of the loggerhead turtle in the Western Atlantic.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
Timothée R. Cook Maike Hamann Lorien Pichegru Francesco Bonadonna David Grémillet Peter G. Ryan 《Marine Biology》2012,159(2):373-387
Knowledge on how divers exploit the water column vertically in relation to water depth is crucial to our understanding of
their ecology and to their subsequent conservation. However, information is still lacking for the smaller-bodied species,
due mostly to size constraints of data-loggers. Here, we report the diving behaviour of a flying diving seabird, the Cape
Cormorant Phalacrocorax capensis, weighing 1.0–1.4 kg. Results were obtained by simultaneously deploying small, high resolution and high sampling frequency
GPS and time-depth loggers on birds breeding on islands off Western South Africa (34°S, 18°E) in 2008. In all, dive category
was assigned to all dives performed by 29 birds. Pelagic dives occurred almost as frequently as benthic dives. Pelagic dives
were shallow (mean: 5 m) and took place over seafloors 5–100 m deep. Benthic dives were deeper, occurring on seafloors mainly
10–30 m deep. Dive shape was linked to dive category in only 60% of dives, while the descent rate, ascent rate and bottom
duration/dive duration ratio of a dive best explained its dive category. This shows that only the concomitant use of tracking
and depth tags can adequately classify diving strategies in a diver like the Cape Cormorant. Diet was mainly Cape Anchovy
Engraulis encrasicolis, suggesting that birds probably displayed two contrasted strategies for capturing the same prey. Flexible foraging techniques
represent an important key to survival inside the highly productive but heterogeneous Benguela upwelling ecosystem. 相似文献
18.
Data were retrieved from 25 ocean sunfish (Mola mola) that were tagged with pop-up satellite archival tags in the southern Gulf of Maine (n = 6), off Nantucket Island (n = 17), and off the coast of Georgia (n = 2) between September 2005 and March 2008. Tags remained attached from 7 to 242 days, with a mean attachment period of (X ± SD)
107.2 ± 80.6 days. Ocean sunfish tagged in the Gulf of Maine and southern New England left those areas in the late summer
and early autumn and moved south along the continental shelf break. Fish traveled as far south as the Bahamas and the Gulf
of Mexico. By moving south, sunfish experienced similar mean sea surface temperatures throughout the tagging period. The maximum
straight-line distance traveled by a tagged Mola mola was 2,520 km in 130 days. Two tagged ocean sunfish entered the Gulf of Mexico, one in the December and one in July. Movements
were associated with frontal features created by the Gulf Stream and fish moved farther offshore in 2007 when the Gulf Stream
was deflected from the shelf break. 相似文献
19.
Escolar (Lepidocybium flavobrunneum) is a large, mesopelagic fish that inhabits tropical and temperate seas throughout the world, and is a common bycatch in
pelagic longline fisheries that target tuna and swordfish. Few studies have explored the biology and natural history of escolar,
and little is known regarding its population structure. To evaluate the genetic basis of population structure of escolar throughout
their range, we surveyed genetic variation over an 806 base pair fragment of the mitochondrial control region. In total, 225
individuals from six geographically distant locations throughout the Atlantic (Gulf of Mexico, Brazil, South Africa) and Pacific
(Ecuador, Hawaii, Australia) were analyzed. A neighbor-joining tree of haplotypes based on maximum likelihood distances revealed
two highly divergent clades (δ = 4.85%) that were predominantly restricted to the Atlantic and Indo-Pacific ocean basins.
All Atlantic clade individuals occurred in the Atlantic Ocean and all but four Pacific clade individuals were found in the
Pacific Ocean. The four Atlantic escolar with Pacific clade haplotypes were found in the South Africa collection. The nuclear
ITS-1 gene region of these four individuals was subsequently analyzed and compared to the ITS-1 gene region of four individuals
from the South Africa collection with Atlantic clade haplotypes as well as four representative individuals each from the Atlantic
and Pacific collections. The four South Africa escolar with Pacific mitochondrial control region haplotypes all had ITS-1
gene region sequences that clustered with the Pacific escolar, suggesting that they were recent migrants from the Indo-Pacific.
Due to the high divergence and geographic separation of the Atlantic and Pacific clades, as well as reported morphological
differences between Atlantic and Indo-Pacific specimens, consideration of the Atlantic and Indo-Pacific populations as separate
species or subspecies may be warranted, though further study is necessary. 相似文献
20.
Klemens Pütz Andrea Raya Rey Nic Huin Adrian Schiavini Andrea Pütz Bernhard H. Lüthi 《Marine Biology》2006,149(2):125-137
The diving behaviour of southern rockhopper penguins (Eudyptes c. chrysocome) was studied at two breeding sites in the Southwest Atlantic: the Falkland Islands and Staten Island, Argentina. Incubating and brooding birds were equipped with time-depth recorders to monitor their foraging activities. Rockhopper penguins from Staten Island started their breeding season about 3 weeks earlier than their conspecifics from the Falkland Islands. The foraging area used by incubating males from the Falkland Islands comprised about 150,000 km² to the northeast of the breeding site and was characterised by shelf and slope waters, whereas the foraging area of incubating males from Staten Island comprised 350,000 km² of oceanic waters to the southeast of the breeding site. A number of dive parameters were measured and compared between the four study groups: Incubating males and brooding females from the Falkland Islands, and incubating males and females from Staten Island. In all study groups, dive depth correlated positively to light intensity, dive duration and vertical velocity. However, significant differences between various diving parameters of the study groups were noted, not only in terms of diving performance, but also as regards diving efficiency (DE). A principal component analysis (PCA) on 16 variables revealed that 75% of the variance could be explained by only two principal components: diving pattern (PC1) and diving effort (PC2). PC1 indicated that the birds from Staten Island, both males and females, dived deeper, covered a greater vertical distance per hour and had higher ascent rates, but spent less time underwater and at the bottom of a dive, and had a lower DE than conspecifics from the Falkland Islands. PC2, which included the percentage of foraging dives, the number of dives per hour, dive duration, bottom time and descent rate, differed significantly between incubating males from the Falkland Islands and the other three groups, which were all very similar. Overall, the diving behaviour was notably similar to that of conspecifics from the Indian and Pacific Oceans. The implications of the results in terms of intra-specific adaptations as well as potential threats from human activities are discussed. 相似文献