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1.
Patterns in diversity, species replacement and species composition of gammaridean amphipods (Crustacea: Malacostraca) were
studied in two areas on different sides of the Greenland–Iceland–Faeroe Ridge. One was sited south of the Ridge in the North
Atlantic Ocean off southern Iceland and the other north of the Ridge in the Arctic Ocean (subarctic and arctic waters of the
Iceland Sea) off northern Iceland. Samples were taken with a Rothlisberg–Pearcy epibenthic sled within the depth range of
about 50 to 1200 m at a total of 28 stations. In all 21 150 individuals were found belonging to 156 species. Of these 102
were found in the northern area with 64 of the species restricted to this area. In all 94 species were found in the southern
area with 52 of the species restricted to this area. This suggests a similar regional diversity, but a different faunal composition.
The amphipods showed similar species replacement patterns with depth on both sides of the Ridge, while the diversity patterns
differed between the areas. In the North Atlantic the number of species increased with depth, while in the Arctic there seemed
to be no pattern at all. It is suggested that diversity patterns of amphipods on each side of the Ridge are shaped by different
factors, and these may not be the same as those determining diversity patterns of other groups in the area. Salinity (as indicative
of water masses) was found to be the most important environmental variable in explaining the species composition when both
areas were considered, suggesting a number of contributing factors (adaptation to water masses, dispersal, etc.). Water temperature
was the most important variable in explaining the variance in the species composition in the northern area, while depth was
the most important variable in explaining the variance in the species composition of the southern area.
Received: 9 March 1997 / Accepted: 10 December 1997 相似文献
2.
3.
Takeo Kurihara 《Marine Biology》2007,153(1):61-70
Spatial and temporal variations of benthic fauna over a wide region (>1,000 km) that includes complex ocean currents have
seldom been quantitatively studied. The present study revealed malacofaunal variations on Japanese rocky shores affected by
the Soya, Tsushima, Oyashio, and Kuroshio currents, and in the Inland Sea. On 29 shores in seven regions in these sea areas,
previous researchers have recorded the number of molluscs in quadrats in spring and summer of 1978 and 1984–1986. Reanalyses
of these records revealed the following patterns. (1) Shore-to-shore variation in malacofauna was correlated with shore-to-shore
geographical distance less clearly for more southern regions. This might show that in southern regions many taxa with low
relative abundance are haphazardly recorded on some shores and blur the effect of shore-to-shore distance on malacofaunal
dissimilarity. (2) Region-to-region variation in malacofauna was significantly correlated with region-to-region geographical
distance. This suggests the influences of environments and paleontological events specific to each current surrounding each
region. (3) The pattern of dissimilarity between the Inland Sea and the other sea areas greatly changed from the 1970s to
1980s. This was due in part to the following density fluctuations on some shores in the Inland Sea: increases in the non-indigenous
mussel Mytilus galloprovincialis, cultured oyster Crassostrea gigas, and littorinid Littorina brevicula reportedly abundant in sheltered areas; and decreases in the littorinid Nodilittorina radiata reportedly abundant in exposed areas and muricid gastropods Thais spp. showing imposex. This suggests an increase of anthropogenic perturbations during the study period in the Inland Sea
which is surrounded by large cities and ports.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Anne Marie Power Karen McCrann David McGrath Ruth M. O’ Riordan Christina Simkanin Alan A. Myers 《Marine Biology》2011,158(10):2149-2160
This study examined how the species composition of an intertidal barnacle guild varied according to physical gradients in
the environment at small scales governed by microclimates, medium scales of wave exposure and large scales of latitude. Barnacle
distributions at small and medium scales were sampled in Ireland between 51°29′ and 52°44′N and 6°50′ and 10°08′W. Sampling
on European shores spanned ~18° latitude from 37°05′ to 55°16′N. Barnacle surveys mainly took place in 2003–2004. An index
of wave fetch was calculated along the wave exposure gradient using a digital coastline-based model that was supported by
a biological exposure scale. A ‘dryness’ index was defined according to mean monthly wind speed, fetch along the average wind
direction and mean monthly air or sea surface temperatures for 2 years (January 2001–December 2002) which is the period when
the most recent adults in the barnacle community would have settled and grown to adulthood. The proportion of the dry-loving
barnacle Chthamalus montagui Southward increased within the barnacle guild at all scales as the habitat became warmer and drier. Barnacle densities were
high in all habitats, mean densities ranged from a minimum of 4.16 cm−2 on moderately exposed shores to a maximum of 6.27 cm−2 in sunlit or south-facing microclimates. Percentage cover of barnacles across the gradient of latitudes was usually >70%.
The results suggest that the distribution and abundance of interacting barnacle species on European coasts is strongly controlled
by abiotic factors, most likely temperature and desiccation. 相似文献
5.
Large-scale patterns of shell variation in Littorina striata, a planktonic developing periwinkle from Macaronesia (Mollusca: Prosobranchia) 总被引:2,自引:1,他引:1
Littorina striata King and Broderip, 1832 is a strictly Macaronesian, intertidal periwinkle with planktonic development. The species displays
a high degree of shell variation involving size and sculpture (nodulose vs smooth shells). The present work provides a preliminary
account of some aspects of this shell variation on wave-exposed shores over the entire geographical range of the species.
Based on morphological patterns observed among other prosobranchs it was predicted that southern specimens of L. littorina should on the average be larger, heavier, more nodulose, and should show more shell repair marks, than northern specimens.
These expectations were confirmed for shell size and weight. In contrast, there was no consistent pattern in nodulosity between
archipelagos, even though there were differences at much smaller scales. Shell repair marks were more prevalent in northern
populations, but this trend was only due to a significant N–S difference among nodulose shells. This is surprising as nodulose
shells displayed significantly fewer shell repair marks than smooth shells. These observations were tentatively interpreted
as a function of presumed differential N–S patterns of wave action and ambient temperatures. In this context, wave action
in Macaronesia seems to increase in the south (contrary to what current theories predict). This atypical situation may confound
the interpretation of morphological patterns in L. striata so that firm conclusions cannot be drawn without further experimental work at different spatial scales. Nevertheless, it
seems that generalisations about macrogeographic shell morphology patterns, based on interspecific comparisons, are not directly
applicable to intraspecific patterns, and may strongly depend on local conditions which make adequate sampling and data treatment
very difficult.
Received: 10 September 1997 / Accepted: 15 January 1998 相似文献
6.
The effects of various concentrations of a synthetic estrogen, ethynylestradiol (EER), and an estrogenic compound, bisphenol
A (BPA), on the development of two sea urchin species, Hemicentrotus pulcherrimus and Strongylocentrotus nudus, were examined. At concentrations of 2.5 μM or higher of EER the zygotes did not hatch; at 0.98–1.25 μM they developed but had abnormal morphology;
and at concentrations lower than 1 μM there was no effect on embryogenesis. The dose dependency was the same for both species,
but more embryos of S. nudus showed exogastrulation at 3–10 μM EER. The effect of BPA on early development was less remarkable than that of EER; most
embryos developed normally even in the presence of 2.5 μM BPA. The feeding larvae progressed and finally metamorphosed into
juveniles even at 0.1–3 μM EER. The chemicals had opposing effects on the growth of the juveniles. A low dose of EER (0.1–1 μM)
promoted growth and the average diameter of the test was bigger than that of the control group; the same dose of BPA suppressed
growth and the test was smaller than that of the control group. These results show that the sensitivity and response to endocrine
disrupter chemicals changes markedly during the ontogeny of sea urchins.
Physical and Chemical Impacts on Marine Organisms, a Bilateral Seminar Italy-Japan held in November 2004 相似文献
7.
Growth parameters of deep-water decapod crustaceans in the Northwestern Mediterranean Sea: a comparative approach 总被引:1,自引:1,他引:0
Relative and absolute growth were studied in 17 species of deep-water decapod crustaceans, spanning nine families of six
different infra-orders, in the Northwestern Mediterranean Sea. The overall maximum abundance of these species lay between
200 m and 750 m (i.e. upper- and mid-slope species). Relative and absolute growth rates were compared by contrasting the slopes
of the size–weight relationships for the different species and calculating the von Bertalanffy growth-equation parameters
asymptotic length (L
∞
) and growth rate (k). The size–weight relationships differed significantly as function of the species' life habits. The results revealed a significant
decrease in weight relative to size in mesopelagic species (which carry out diel vertical migrations), an almost isometric
relationship between size and weight in the less mobile nektobenthic species, and a significant increase in weight relative
to size in strictly benthic species. The mean allometric coefficient for each group increased significantly from mesopelagic
to benthic species. However, no general trend was observed in the growth-performance index, Φ (an index used to compare absolute
growth rates between species, as a function of habit and depth of maximum abundance for all species combined), suggesting
that the deep-water decapod crustaceans studied have similar absolute growth rates. Nevertheless, comparison of growth-parameter
and growth-performance index values within families did reveal differences. Mesopelagic species of the families Sergestoidae
and Pasiphaeidae showed slightly increased growth rates with increasing depth of distribution. Nektobenthic species of the
genus Plesionika followed a trend opposite to that shown by mesopelagic species, with a higher growth rate for the shallowest-dwelling species
(P. heterocarpus) than the deepest-dwelling species (P. acanthonotus). Taking growth as one of the major components of an organism's energy budget, the growth rates for the decapod crustacean
species in this study were significantly lower than those reported in the literature for shallow-water penaeid crustacean
species (which are distributed in higher-temperature habitats than deep-water Mediterranean crustaceans) and higher than those
reported for mesopelagic myctophid fish species. Hence, the well-defined growth trends shown by deep-water decapod crustacean
species in the Northwestern Mediterranean Sea, compared to the less well-defined trends in the other taxa, is discussed in
the framework of the overall dynamics of their ecosystem.
Received: 25 May 1998 / Accepted: 27 September 1999 相似文献
8.
During oxygen crises, benthic faunas exhibit a series of behavioural patterns that reflect the duration and severity of the
event. During artificially induced oxygen deficiencies at 24 m depth in the Northern Adriatic Sea, we photographically documented
predation by the sea anemones Cereus pedunculatus (Pennant, 1777) and Calliactis parasitica (Couch, 1842) on the brittle star Ophiothrix quinquemaculata (DelleChiaje, 1828). Five predatory events were recorded with four anemones during nine deployments totalling 817 h of observation. Under near-anoxic
conditions, individuals of both actinians made contact with, pulled in and consumed the brittle stars. The duration of each
predatory event was 1.5–7.5 h. In three of the five events, brittle star remains were regurgitated after an additional 2.0–12.5 h
of digestion by the anemones. Our time-lapse sequences demonstrate that oxygen deficiency, beyond eliciting a series of specific
behaviours in members of each species, also promotes previously unobserved interspecific interactions. Our results show that
sea anemones are not only highly resistant to anoxia, but may also benefit by taking advantage of prey that are more vulnerable
to anoxic conditions. 相似文献
9.
In south-western Australia, the isopod Limnoria agrostisa commonly burrows into leaf clusters and immature shoots of Amphibolis griffithii. The isopod also burrows into the sheath and rhizomes of Posidonia species. In A. griffithii, the isopod consumes new tissue within the sheath, damaging or destroying the meristem. This results in malformation of new
leaves or destruction of whole leaf clusters with the potential to reduce the photosynthetic area of a shoot. The isopod has
been found in all but one meadow of A. griffithii examined over 1,000 km of the Western Australian coastline. It was present throughout the year and showed little variation
in abundance. Young were produced year round, but were more abundant in the summer months. Females, 3.5 mm in length or larger,
produced 2–5 young that were brooded within the leaf cluster or base of an immature shoot. Within a meadow, 40–70% of shoots
and 10–20% of leaf clusters were damaged by isopods. Seasonal trends were not consistent, but damage appeared to be higher
in summer when isopod abundance was higher. Approximately 40% of clusters were destroyed by isopod damage. Isopods attack
shoots of all ages, but damage was often located on apical clusters. There was no evidence that isopod damage initiated branching
or leaf cluster formation. Estimations of clusters damaged or destroyed may be conservative, as only those clusters remaining
on a shoot could be counted, and cluster loss could not be quantified. Examination of defoliated stems on upright shoots and
horizontal rhizomes indicated that many were destroyed by isopods. The effect of L. agrostisa although substantial appears to be a feature of healthy seagrasses throughout southern Australia. 相似文献
10.
Under natural conditions, sea bass eggs hatch in the open sea and young-of-the-year sea bass are found close to estuaries
and enter brackish and even freshwater lagoons in the Mediterranean and the eastern Atlantic. The ontogeny of osmoregulation
in the European sea bass, Dicentrarchus labrax (Linnaeus, 1758), was studied in different developmental stages, from hatching to large juveniles, exposed to a range of
salinities at 17 °C. The experiments were carried out from March to August 1998 in southern France. The type of hyper-hypo-osmotic
regulation did not change during development. All stages hyper-regulated at low salinity (under 10–11‰) and hypo-regulated
at higher salinities. The acquisition of the full ability to hypo-regulate occurred in four steps. Osmoregulatory capacity
was size- and age-dependent and reached its maximum for fish 17–26 mm long, 63–86 days after hatching. The iso-osmotic salinity
was 10.2–11.6‰. Our results suggest that early development of osmoregulatory ability, and thus of salinity tolerance in sea
bass, may provide an advantageous flexibility for the timing of migration towards low-salinity habitats.
Received: 22 May 2000 / Accepted: 18 December 2000 相似文献
11.
M. Matabos E. Thiébaut D. Le Guen F. Sadosky D. Jollivet F. Bonhomme 《Marine Biology》2008,153(4):545-563
Three different molecular markers (i.e. seven allozyme loci, two nuclear gene loci and, mtCOI DNA sequences) were used to
assess the genetic structure of the vent gastropod Lepetodrilus elevatus collected from three vent fields along the East Pacific Rise (13°N, 9°50′N and 17°S). While allozymes and nuclear loci suggested
a strong stepping-stone pattern, a multivariate analysis performed on allozymic frequencies showed the presence of two distinct
evolutionary lineages: the first situated in the north from 13°N to 9°50′N and the second in the south from 9°50′N to 17°S.
The analysis of mitochondrial DNA sequences confirmed the separation of L. elevatus into two distinct clades with a divergence of 6.5%, which is consistent with the interspecific level of sequence variation
in other vent species. A divergence time of 6–14 Mya was estimated between the two clades from previous clock calibrations.
Our results suggest that these taxa followed an allopatric speciation between the northern and southern parts of the EPR with
a recent demographic expansion of the southern clade to the north and a subsequent secondary contact (clade hybridisation).
This speciation was probably reinforced by a habitat specialisation of the two cryptic species because the southern clade
was mainly found associated with mussel-dominated communities and the northern clade with tubeworm-dominated communities.
However, the analysis of shell morphology failed to separate the two cryptic species based on this sole criterion although
they differed from Lepetodrilus elevatus galriftensis (Galapagos population) by a higher shell elevation. Within each clade, genetic differentiation was not related to the distance
across populations and could be within vent field as important as between fields. While both clades appear to be in expansion
since their speciation, significant excesses in heterozygotes suggest a very recent and local bottleneck at 17°S, probably
due to massive site extinction in this region. 相似文献
12.
Individual specialisation is increasingly recognised to be an ecological and evolutionary process having important consequences for population dynamics of vertebrates. The South American fur seal (SAFS) and the South American sea lion (SASL) are two otariid species with similar ecology that coexist in sympatry in the Uruguayan coast. These two species have contrasting trends and widely different population sizes. The underlying reasons for these population trends, unique in their geographical ranges, remain unknown. We studied the foraging ecology of these otariid species over 2 years at the individual- and population levels using the isotopic ratios (δ13C–δ15N) in whiskers of both sexes. We compared the isotope ratios between species and sexes and used several metrics to characterise the degree of overlap and distinctiveness in the use of isotopic niche space at the individual- and population levels. Interspecific trophic niche overlap was minimal, thus ruling out interspecific competition as the cause for the contrasting population trends of both species. At the intraspecific level, both species had sexual segregation in their foraging areas, but each species had a large overlap in the isotopic niches between sexes. While SAFS had a wider niche and generalist individuals, SASL had the narrower niche with a higher degree of individual specialisation. Behavioural constraints during the breeding season, intraspecific competition and a major dependence on resources of the Uruguayan coastal shelf may explain why SASL had a higher trophic individual specialisation and a larger vulnerability in a heavily exploited habitat by fisheries and, by consequence, a locally declining population trend. 相似文献
13.
Rosborg I Nihlgård B Gerhardsson L Sverdrup H 《Environmental geochemistry and health》2006,28(3):215-229
The water chemistry of 20 municipal water treatment plants in southern Sweden, representing various bedrock situations, and water qualities, were investigated. Four water samples, raw and treated, were collected from each plant and analyzed by predominantly ICP-OES and ICP-MS at four occasions from June to December, 2001. The concentrations of Ca, Mg, K, Na, HCO3 and a number of micronutrients, varied considerably in treated waters from the studied plants (ranges; Ca: 9.1–53.7 mg L−1, Mg: 1.4–10.9 mg L−1, K: 1.1–4.8 mg L−1, Na; 5.4–75.6 mg L−1, HCO3: 27–217 mg L−1). The elimination of Fe and Mn from raw water was efficient in all treatments investigated, giving concentrations in treated waters below the detection limits at some plants. Softening filters gave waters with Ca-concentrations comparable to the softest waters in this study. Adjustment of pH by use of chemicals like lye, soda or lime, modified the consumer water composition significantly, besides raising the pH. It was estimated that drinking water contributed to approximately 2.2–13% of the daily Ca uptake, if the gastrointestinal uptake efficiency from food and water was estimated to be around 50%. The corresponding figures for Mg was 1.0–7% and for F 0–59%. None of the studied elements showed any significant time trends in raw or treated waters during the follow-up period. The concentrations of potentially toxic metals such as Al, Pb and U were low and did not indicate risks for adverse health effects (ranges; Al: 0.5–2.3 μg L−1, Pb: 0–0.3 μg L−1, U: 0.2.5 μg L−1). 相似文献
14.
J. W. Fourqurean N. Marbà C. M. Duarte E. Diaz-Almela S. Ruiz-Halpern 《Marine Biology》2007,151(1):219-232
Morphology, elemental content and isotopic composition of leaves of the seagrasses Posidonia oceanica and Cymodocea nodosa were highly variable across the Illes Balears, a Spanish archipelago in the western Mediterranean, and varied seasonally
at one site in the study area. The data presented in this paper generally expand the reported ranges of nitrogen, phosphorus,
iron and arsenic content and δ13C and δ15N for these species. Nitrogen and phosphorus content of P. oceanica leaves also showed significant seasonal variability; on an annual basis, P. oceanica leaves averaged 1.55% N and 0.14% P at this monitoring site. Both N and P were more concentrated in the leaves in winter
than in summer, with winter maxima of 1.76% N and 0.17% P and summer minima of 1.34% N and 0.11% P. There was no significant
annual pattern observed in the δ13C of P. oceanica leaves, but there was a repeated 0.6‰ seasonal fluctuation in δ15N. Mean annual δ15N was 4.0‰; δ15N was lowest in May and it increased through the summer and autumn to a maximum in November. Over the geographic range of
our study area, there were interspecific differences in the carbon, nitrogen and phosphorus content of the two species. Posidonia oceanica N:P ratios were distributed around the critical value of 30:1 while the ratios for C. nodosa were lower than this value, suggesting P. oceanica we collected was not consistently limited by N or P while C. nodosa tended toward nitrogen limitation. Nutrient content was significantly correlated to morphological indicators of plant vigor.
Fe content of P. oceanica leaves varied by a factor of 5×, with a minimum of 31.1 μg g−1 and a maximum of 167.7 μg g−1. Arsenic was present in much lower tissue concentrations than Fe, but the As concentrations were more variable; the maximum
concentration of 1.60 μg g−1 was eight times as high as the minimum of 0.20 μg g−1. There were interspecific differences in δ13C of the two species; C. nodosa was consistently more enriched (δ13C = −7.8 ± 1.7‰) than P. oceanica (−13.2 ± 1.2‰). The δ13C of both species decreased significantly with increasing water depth. Depth related and regional variability in the δ13C and δ15N of both species were marked, suggesting that caution needs to be exercised when applying stable isotopes in food web analyses. 相似文献
15.
The potential impact of future sea level rise and climate change on 15 Welsh coastal dune systems has been investigated. Historical
Trend Analysis was undertaken using Ordnance Survey maps to quantify past shoreline change and to permit extrapolation of
past trends to predict possible future shoreline positions by 2080–2100. Predictions were also made using the Bruun Rule relationship
between sea level rise and shoreline response and an integrated method of assessment, Expert Geomorphological Assessment (EGA),
which provides a ‘best estimate’ of future coastline change, taking into account such factors as geological constraints, the
nature of past, present and future environmental forcing factors, and known coastal process–response relationships. The majority
of the 15 systems investigated experienced a net increase in dune area over the last 100–120 years. Only one (Whiteford Burrows)
experienced significant net area loss (>5 ha). EGA predictions suggest that several systems are likely to experience significant
net loss of dune habitat over the next century, whilst continued net gain is likely to occur for systems where sediment supply
rates remain high. Little net change is predicted in some systems. Considering the 15 dune systems together, it is considered
unlikely that net dune habitat loss will exceed net gain over the next 100 years provided that there are no major disruptions
to sediment supply and natural coastal processes. 相似文献
16.
Breeding Distributions of North American Bird Species Moving North as a Result of Climate Change 总被引:2,自引:0,他引:2
Abstract: Geographic changes in species distributions toward traditionally cooler climes is one hypothesized indicator of recent global climate change. We examined distribution data on 56 bird species. If global warming is affecting species distributions across the temperate northern hemisphere, these data should show the same northward range expansions of birds that have been reported for Great Britain. Because a northward shift of distributions might be due to multidirectional range expansions for multiple species, we also examined the possibility that birds with northern distributions may be expanding their ranges southward. There was no southward expansion of birds with a northern distribution, indicating that there is no evidence of overall range expansion of insectivorous and granivorous birds in North America. As predicted, the northern limit of birds with a southern distribution showed a significant shift northward (2.35 km/year). This northward shift is similar to that observed in previous work conducted in Great Britain: the widespread nature of this shift in species distributions over two distinct geographical regions and its coincidence with a period of global warming suggests a connection with global climate change. 相似文献
17.
The cosmopolitan polychaete Capitella capitata, known as a complex of opportunistic sibling species, usually dominates the macrobenthos of polluted or unpredictable environments.
A population of C. capitata, termed Capitella sp. M, was found in a shallow water hydrothermal vent area south of Milos (Greece). Here, this population occurs close to
vent outlets (termed the “transition zone”), an environment with steep gradients of temperature, salinity and pH and increased
sulphide concentrations of up to 710 μM. The field distribution of C. capitata in relation to sulphide concentrations around the vent outlets was investigated and sulphide tolerance experiments were conducted
on laboratory-cultured worms to elucidate possible adaptations of Capitella sp. M to these extreme environmental conditions. In order to investigate whether the population from the Milos hydrothermal
vent area can be considered a distinct sibling species within the C. capitata complex, crossbreeding experiments and analysis of general protein patterns were conducted with Capitella sp. M and three other C. capitata populations of different ecological ranges. Capitella sp. M showed high resistance (median survival time: 107 ± 38 h) to anoxia plus high sulphide concentrations of 740 μM. It seems that the ability to survive high-sulphide conditions in combination with reduced interspecific competition enables
the polychaete to maintain a continuous population in this rigorous habitat. From the extremely high tolerance to anoxia and
sulphide, shown in both the crossbreeding experiments and the analysis of total proteins, it can be concluded that Capitella sp. M from the Milos hydrothermal vent area represents a separate sibling species within the C. capitata complex.
Received: 3 March 1997 / Accepted: 12 September 1997 相似文献
18.
Recruitment variability plays a critical role in determining local population densities of benthic organisms, but extreme
vulnerability at the onset of juvenile life is a trait that is largely responsible for population survivorship trends. The
aim of the present study was to determine the role of juvenile recruitment in the population structure of Necora puber. Juveniles of N. puber were collected from the lower intertidal of rocky shores of Plymouth Sound (southwest coast of the UK) and monthly size–frequency
distribution were used to determine the dynamics and the growth of the population. The parameters of the von Bertalanffy growth
function were estimated (K=0.281 year−1; t
0=0.043; C=0.103; and t
s=0.268) assuming a L
∞=105 mm. Growth was markedly seasonal and present results indicated a slower juvenile growth rate than described previously
for N. puber. The recruitment period was extensive and was two times higher in 2001 than in 2000 at the start of the 1+ year, but levelled
off at the end of the 1+ year class on three of the four shores studied. Instantaneous mortality as high as 5.1 year−1(99.4% year−1) was observed during the higher recruitment year. Early juvenile mortality appears to be density dependent and a demographic
bottleneck appears to limit the number of juveniles on some shores. 相似文献
19.
Erin A. Falcone Gregory S. Schorr Annie B. Douglas John Calambokidis Elizabeth Henderson Megan F. McKenna John Hildebrand David Moretti 《Marine Biology》2009,156(12):2631-2640
The relationship between beaked whales and certain anthropogenic sounds remains poorly understood and of great interest. Although
Cuvier’s beaked whales (Ziphius cavirostris) are widely distributed, little is known of their behavior and population structure throughout much of their range. We conducted
a series of five combined visual-acoustic marine mammal surveys from 2006 to 2008 in the southern San Nicolas Basin, a site
of frequent naval activity off the southern California coast, west of San Clemente Island. The study area was defined by a
1,800 km2 array of 88 bottom-mounted hydrophones at depths up to 1,850 m. The array was used to vector visual observers toward vocalizing
marine mammal species. Thirty-seven groups of Cuvier’s beaked whales were encountered during the study period. The overall
encounter rate was one group for every 21.0 h of survey effort, and was as high as one group per 10.2 h of effort during the
October 2007 survey. Whales were encountered in the deepest portion of the study area, at a mean bottom depth of 1,580 m (SD
138). The average group size was 3.8 individuals (SD 2.4), which was higher than has been reported from other studies of this
species. Twenty-four groups were observed over multiple surfacings (median = 4 surfacings, range 2–15). The mean encounter
duration of extended sightings was 104 min (SD 98, range 12–466 min) and the mean distance moved over the course of sightings
was 1.66 km (SD 1.56, range 0.08–6.65 km). Temporal surfacing patterns during extended encounters were similar to dive behavior
described from Cuvier’s beaked whales carrying time-depth recording tags. Seventy-eight photographic identifications were
made of 58 unique individuals, for an overall resighting rate of 0.26. Whales were sighted on up to 4 days, with duration
from first to last sighting spanning 2–79 days. For those whales sighted on subsequent days, the mean distance between subsequent
sightings was 8.6 km (SD 7.9). Individuals resighted over 2–3 days were usually in association with previous group members.
Approximately one-third of groups contained more than one adult male, and many of the repeated associations involved adult
males. These observations suggest the basin west of San Clemente Island may be an important region for Cuvier’s beaked whales,
and also one which affords an unusual opportunity to collect detailed data on this species. Given its status as an active
military range, it can also provide the ability to monitor the behavior of individuals in the presence of naval sonar, a critical
step in the management of this and other beaked whale populations worldwide. 相似文献
20.
The tiger shark (Galeocerdo cuvier Peron and Lesueur 1822) is a widely distributed predator with a broad diet and the potential to affect marine community structure, yet information on local patterns of abundance for this species is lacking. Tiger shark catch data were gathered over 7 years of tag and release research fishing (1991–2000, 2002–2004) in Shark Bay, Western Australia (25°45′S, 113°44′E). Sharks were caught using drumlines deployed in six permanent zones (~3 km2 in area). Fishing effort was standardized across days and months, and catch rates on hooks were expressed as the number of sharks caught h−1. A total of 449 individual tiger sharks was captured; 29 were recaptured. Tiger shark catch rate showed seasonal periodicity, being higher during the warm season (Sep–May) than during the cold season (Jun–Aug), and was marked by inter-annual variability. The most striking feature of the catch data was a consistent pattern of slow, continuous variation within each year from a peak during the height of the warm season (February) to a trough in the cold season (July). Annual growth rates of recaptured individuals were generally consistent with estimates from other regions, but exceeded those for populations elsewhere for sharks >275 cm fork length (FL), perhaps because mature sharks in the study area rely heavily on large prey. The data suggest that (1) the threat of predation faced by animals consumed by tiger sharks fluctuates dramatically within and between years, and (2) efforts to monitor large shark abundance should be extensive enough to detect inter-annual variation and sufficiently intensive to account for intra-annual trends. 相似文献