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1.
A benthological survey in the Benguela upwelling area off northern Namibia (located at 17.3°S and water depth ranging between
26 and 117 m) showed the concentration of dissolved oxygen and the accumulation of organic-rich sediments to control macrozoobenthic
community patterns. In contrast to highly biodiverse nearshore areas with well-structured shell deposits of the brachiopod
Discinisca tenuis (Sowerby 1847), the benthic community in the oxygen minimum zone (OMZ) decreased strongly in species numbers. Nevertheless,
a well-established community ranging from 13 to 31 species persisted. Species densities (300–3,350 ind m−2) and biomass (4–109 g afdw/m2) were surprisingly high for areas with near bottom oxygen concentrations from 0.06 to 0.88 ml l−1. In contrast to OMZ’s of other upwelling areas, where the benthic macrofauna is generally dominated by small-bodied polychaetes,
off Namibia larger key organisms like the bivalve Nuculana bicuspidata (Gould 1845) and the snail Nassarius vinctus (Marrett 1877) accounted for a large proportion of the macrozoobenthos >1 mm. This is supposed to have a distinct effect
on the functional properties of the sediments.
相似文献
Michael Lothar ZettlerEmail: |
2.
The influence of multiple anchored fish aggregating devices (FADs) on the spatial behavior of yellowfin (Thunnus albacares) and bigeye tuna (T. obesus) was investigated by equipping all thirteen FADs surrounding the island of Oahu (HI, USA) with automated sonic receivers
(“listening stations”) and intra-peritoneally implanting individually coded acoustic transmitters in 45 yellowfin and 12 bigeye
tuna. Thus, the FAD network became a multi-element passive observatory of the residence and movement characteristics of tuna
within the array. Yellowfin tuna were detected within the FAD array for up to 150 days, while bigeye tuna were only observed
up to a maximum of 10 days after tagging. Only eight yellowfin tuna (out of 45) and one bigeye tuna (out of 12) visited FADs
other than their FAD of release. Those nine fish tended to visit nearest neighboring FADs and, in general, spent more time
at their FAD of release than at the others. Fish visiting the same FAD several times or visiting other FADs tended to stay
longer in the FAD network. A majority of tagged fish exhibited some synchronicity when departing the FADs but not all tagged
fish departed a FAD at the same time: small groups of tagged fish left together while others remained. We hypothesize that
tuna (at an individual or collective level) consider local conditions around any given FAD to be representative of the environment
on a larger scale (e.g., the entire island) and when those conditions become unfavorable the tuna move to a completely different
area. Thus, while the anchored FADs surrounding the island of Oahu might concentrate fish and make them more vulnerable to
fishing, at a meso-scale they might not entrain fish longer than if there were no (or very few) FADs in the area. At the existing
FAD density, the ‘island effect’ is more likely to be responsible for the general presence of fish around the island than
the FADs. We recommend further investigation of this hypothesis.
相似文献
Laurent Dagorn (Corresponding author)Email: |
Kim N. HollandEmail: |
David G. ItanoEmail: |
3.
F. Badalamenti C. J. Sweeting N. V. C. Polunin J. Pinnegar G. D’Anna C. Pipitone 《Marine Biology》2008,154(5):765-773
Trawling has a significant effect on the structure of marine communities, yet the ubiquity of trawling impacts makes testing
such effects difficult. This study examines trawling impacts on trophodynamics of three fishes among the Gulfs of Castellammare
and Termini Imerese (northern Sicily), the first of which has been subject to a trawling ban since 1990 that initially resulted
in an eightfold increase in total fish biomass. The Gulf of Termini Imerese remains heavily fished and was treated as a control
site. Nitrogen and carbon stable isotope data were used to assess fishing induced changes in trophic levels or source of production
supporting three demersal fish species; Mullus barbatus,
Merluccius merluccius and Lophius budegassa following a control-impact approach. The exclusion of trawling resulted in only small alteration of δ15N in two of the three-three species. There were no systematic changes in the δ13C of any species sampled. Thus, a large influence of trawling on the trophodynamics of the studied species at sampled size
was discounted. Although stable isotopes do not have spatial or temporal resolution to identify detailed shifts in diet composition,
their integrative nature highlights that the trophic role these species play is robust to fishing impacts at scales over which
the fishery operates. This is despite a significant increase in the abundance of these species and of total fish biomass within
the protected area.
相似文献
C. J. SweetingEmail: |
4.
Chang Xuan Mao 《Environmental and Ecological Statistics》2007,14(4):473-481
Consider the removal experiment used to estimate population sizes. Statistical methods towards testing the homogeneity of
capture probabilities of animals, including a graphical diagnostic and a formal test, are presented and illustrated by real
biological examples. Simulation is used to assess the test and compare it with the χ2 test.
相似文献
Chang Xuan MaoEmail: |
5.
Direct observations of the plankton vertical distribution performed from a manned submersible were made in the Charlie-Gibbs Fracture Zone (Atlantic Ocean). Plankton was counted using a standard 3-m2 frame in the depth layer from 170 to 4361 m and plotted for every 50 m. The most abundant components of the macroplankton were pelagic shrimps, chaetognaths and gelatinous animals, with peak of densities corresponding to the main pycnocline. Mucous houses of appendicularians were abundant at 150 m above the seabed—up to 0.07–0.09 m–3, compared to 0–0.006 m–3 in the upper layers. The new observations confirm that the near-bottom peak of appendicularian abundance is characteristic of at least the entire Central Atlantic, and it is not associated with certain biotopes on the bottom.Communicated by O. Kinne, Oldendorf/Luhe
相似文献
G. M. VinogradovEmail: |
6.
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: |
7.
M. M. Manzano-Sarabia E. A. Aragón-Noriega C. A. Salinas-Zavala D. B. Lluch-Cota 《Marine Biology》2007,152(5):1021-1029
Life histories of penaeid shrimp have been classified according to the preferred habitats of postlarval, juvenile, and adult
stages, ranging from exclusively estuarine to exclusively offshore waters. Brown shrimp Farfantepenaeus californiensis migrate to an offshore habitat at the juvenile stage or even a smaller body size. This paper presents results of monthly
samplings from 24 stations over 1 year in the Agiabampo Lagoon complex, a hypersaline lagoon in northwestern Mexico. Five
species of penaeid shrimp were identified, with brown shrimp the most abundant during the year of sampling. Results suggest
that residency of brown shrimp inside this lagoon is longer than reported in previous studies. An interaction between length
and environmental variables (near-surface temperature, salinity, and rainfall) appear to be cues concerning migration.
相似文献
C. A. Salinas-ZavalaEmail: |
8.
Bruce C. Glavovic 《Journal of Coastal Conservation》2008,12(3):125-134
Hurricanes devastated the Gulf coast of the USA in 2005. Hurricane Katrina, in particular, highlighted the compelling need
to build more sustainable and hazard-resilient communities. Much can be learned from recovery efforts to rebuild the Gulf
coast. Personal observations and interviews with planners, academics and others involved in recovery efforts inform this analysis,
which focuses on New Orleans. A conceptual framework is developed and principles and operational imperatives outlined to guide
action for building sustainable, hazard-resilient communities. Such communities will remain elusive unless ‘business as usual’
is confronted by a transformational process of developmental planning. Sustainable, hazard-resilient coastal communities are
founded upon robust ‘critical infrastructure’ that is secured by planning and decision-making processes that enable coastal
communities to build ‘layers of resilience’ to overcome ‘waves of adversity’. Planners need to take on a redefined role—as
‘new naval architects’—to design and build communities that are ‘sea-worthy’ in this age of coastal storms.
相似文献
Bruce C. GlavovicEmail: |
9.
When animals die in traps in a mark-recapture study, straightforward likelihood inferences are possible in a class of models.
The class includes M0, Mt, and Mb as reported by White et al. (Los Alamos National Laboratory, LA-8787-NERP, pp 235, 1982), those that do not involve heterogeneity.
We include three Markov chain “persistence” models and show that they provide good fits in a trapping study of deer mice in
the Cascade-Siskiyou National Monument of Southern Oregon where trapping mortality was high.
相似文献
Fred L. RamseyEmail: |
10.
Monica R. Lara 《Marine Biology》2008,154(1):51-64
Larval fishes likely use a variety of settlement cues to locate and navigate toward the habitats they will inhabit as juveniles.
Information about the morphology and state of development of the sensory organs of larval stages of fishes provides insight
into their capabilities at the time of settlement. The peripheral olfactory organ of wild-caught late-stage larvae and early
juveniles and some adults of 14 species of the Caribbean reef fishes wrasses (Labridae), parrot fishes (Scaridae) and damselfish
(Pomacentridae) were examined using scanning electron microscopy and compared in terms of settlement specificity. Ages in
days after hatching and days post-settlement were determined from the otoliths. Morphology of the nares and the olfactory
epithelium are described for these species by stage. The separation of the anterior and posterior nares occurred before settlement
in the labrids but in some specimens of scarids this separation was not complete by the time of settlement. Densities of ciliated
and microvillous receptor cells and non-sensory ciliated epithelial cells were calculated. Densities of ciliated receptor
cells ranged from 0.389 μm−2 in a specimen of Thallasoma bifasciatum to 0.0057 μm−2 in Bodianus rufus and of microvillous receptor cells from 0.038 μm−2 in a Clepticus parrae juvenile to 0.266 μm−2 in a juvenile Doratonotus megalepis. Densities of non-sensory cilia, also associated with high olfactory ability, were also high. The olfactory organ in wrasses
is well developed prior to settlement and is comparable to that of adult fishes. The possible role of olfaction in larval
schooling, reef cue detection and orientation toward habitat at settlement is discussed.
相似文献
Monica R. LaraEmail: |
11.
Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico 总被引:4,自引:2,他引:2
Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA
waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic
differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci
within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence
for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations,
two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (R
ST=0.096, P≤0.0001) and mitochondrial DNA (Φ
ST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation
coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence
of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes
of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species
is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas
where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance
of genetic diversity in this species in regions where incidental human-induced mortality occurs.
相似文献
Lara D. AdamsEmail: |
12.
Marine communities are experiencing unprecedented rates of species homogenization due to the increasing success of invasive
species, but little is known about the mechanisms that allow a species to invade and persist in a new habitat. In central
California, native (Mytilus trossulus Gould 1850) and invasive (Mytilus galloprovincialis Lamarck 1819) blue mussels and their hybrids co-exist, providing an opportunity to analyze the mechanisms that determine
the distributions of these taxa. Spatial and temporal variation in temperature and salinity and the relative frequencies of
these mussel taxa were examined between 2000 and 2004 at four sites in San Francisco Bay and four in Monterey Bay, which were
chosen for their different positions along inferred estuarine/oceanic gradients in the hybrid zone. Mussels were genetically
identified as the parent species or hybrids by amplifying regions of two species-specific loci: the adhesive byssal thread
protein (Glu-5′) and the internal transcribed spacer region of ribosomal DNA (ITS 1). The proportion of M. trossulus at the eight hybrid zone sites correlated negatively with average salinity (R
2=0.60) and positively with maximal temperature (R
2≥0.72), a somewhat unexpected result given what is known about the phylogeography of this species. The proportion of M. galloprovincialis showed the opposite pattern. The proportion of hybrids was correlated neither with habitat temperature nor salinity. Genotypes
of mussel populations at an additional 13 sites from Coos Bay, Oregon (latitude 43.35°N) to Long Beach, California (latitude
33.72°N), sampled at various intervals between 2000 and 2004, were also determined. This survey confirmed previous reports
that the hybrid zone lies between Monterey and the Cape Mendocino region (latitudes 36.63°N–40.5°N). Within Monterey and San
Francisco Bays, however, the temporal comparisons (1990s vs. 2000s) revealed abrupt changes in the proportions of the two
parent species and their hybrids on annual and decadal time scales. These changes indicate that the blue mussel populations
are in a highly dynamic state. The survey also showed that, regardless of habitat, M. trossulus is consistently of smaller average size than either M. galloprovincialis or hybrids.
相似文献
Caren E. BrabyEmail: |
13.
R. Webster West Daniela K. Nitcheva Walter W. Piegorsch 《Environmental and Ecological Statistics》2009,16(1):63-73
A primary objective in quantitative risk assessment is the characterization of risk which is defined to be the likelihood
of an adverse effect caused by an environmental toxin or chemcial agent. In modern risk-benchmark analysis, attention centers
on the “benchmark dose” at which a fixed benchmark level of risk is achieved, with a lower confidence limits on this dose
being of primary interest. In practice, a range of benchmark risks may be under study, so that the individual lower confidence
limits on benchmark dose must be corrected for simultaneity in order to maintain a specified overall level of confidence.
For the case of quantal data, simultaneous methods have been constructed that appeal to the large sample normality of parameter
estimates. The suitability of these methods for use with small sample sizes will be considered. A new bootstrap technique
is proposed as an alternative to the large sample methodology. This technique is evaluated via a simulation study and examples
from environmental toxicology.
相似文献
R. Webster WestEmail: |
14.
Fiat boundaries: some implications for interpretation,decision-support,and multi-temporal analysis 总被引:1,自引:0,他引:1
Kim Lowell 《Environmental and Ecological Statistics》2008,15(4):369-383
Polygon-based thematic maps can be composed of boundaries that exist by definition—i.e., bona fide boundaries—or those that
exist relative to a specific interpretation of a spatial phenomenon—i.e., fiat boundaries. The construction of maps composed
of fiat boundaries is usually based on a subjective interpretive methodology that is affected by the data used to construct
the map and the minimum mapping unit employed. That fiat boundaries are not the same as bona fide boundaries affects their
use in computer-based spatial decision support tools. This is discussed both in terms of an analysis conducted at one specific
moment, and in respect to increasingly common multi-temporal analysis.
相似文献
Kim LowellEmail: |
15.
John E. Hathaway G. Bruce Schaalje Richard O. Gilbert Brent A. Pulsipher Brett D. Matzke 《Environmental and Ecological Statistics》2008,15(3):313-327
Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum
number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a method is
developed which accounts for different sources of variation in compositing and data analysis. This method is used to define
and understand the process of determining the optimum number of increments that should be used in forming a composite. The
blending variance is shown to have a smaller range of possible values than previously reported when estimating the number
of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated
number of increments.
相似文献
John E. HathawayEmail: |
16.
The size-specific burrowing capacity of Olivella semistriata, an extremely abundant surfing gastropod of exposed sandy beaches in the tropical East Pacific, was investigated in terms
of sediment grain size. For all investigated sand classes, there was a significant increase in burial time with size. Burrowing
was fastest in sand with grain size between 150 and 355 μm, as well as in native sediment (median grain size 209 μm) and in
field conditions (median grain size 223 μm). Values of the burrowing rate index (BRI) were found to be between 3 and 7, rating
the burrowing capacity of O. semistriata to be fast to very fast. Data from previous qualitative and quantitative sampling campaigns were used to identify the macroscale
(i.e., between beaches) distribution of O. semistriata in terms of sediment grain size and swash conditions. Swash period was shorter than burial time, excluding this as a factor
limiting the distribution. Swash standstill time (the time between uprush and backwash), however, was just long enough on
the beaches, where O. semistriata was present to allow for securing firm anchorage. On reflective beaches, the swash standstill time is as short as 1 or 2 s,
denying O. semistriata the time to burry itself before being swept away by the backwash. As such, swash standstill time is advocated as a valuable
part of the swash exclusion hypothesis. A survey of the available literature on the burrowing of surfers shows that mole crabs
are by far the fastest burrowers and the only surfers that burrow sufficiently fast to withstand the extremely short swash
standstill time on reflective beaches. Burrowing ability of surfing gastropods is found in the same range as surfing bivalves,
both being insufficient to cope with coarse sediment on steep beaches. Finally, we suggest that neither burial time nor BRI,
yet rather the minimal burial time—the time needed to anchor securely in a certain sand at a given swash velocity—should be used to judge the limitations of
burial in terms of sediment and swash conditions.
相似文献
T. VanagtEmail: |
17.
Ferenc Csillag Sándor Kabos Tarmo K. Remmel 《Environmental and Ecological Statistics》2008,15(4):385-401
We revisit one of the classical problems in geography and cartography where multiple observations on a lattice (N) need to be grouped into many fewer regions (G), especially when this number of desired regions is unknown a priori. Since an optimization through all possible aggregations
is not feasible, a hierarchical classification scheme is proposed with an objective function sensitive to spatial pattern.
The objective function to be minimized during the assignment of observations to regions (classification) consists of two terms:
the first characterizes accuracy and the second, model complexity. For the latter, we introduce a spatial measure that characterizes
the number of homogeneous patches rather than the usual number of classes. A simulation study shows that such a classification
procedure is less sensitive to random and spatially correlated error (noise) than non-spatial classification. We also show
that for conditional autoregressive error (noise) fields the optimal partitioning is the one that has the highest within-units
generalized Moran coefficient. The classifier is implemented in ArcView to demonstrate both a socio-economic and an environmental
application to illustrate some potential applications.
相似文献
Tarmo K. Remmel (Corresponding author)Email: |
18.
In this commentary, we discuss recent experiments on the reliability of bird song as a signal of aggressive intent during
territorial conflicts. We outline relevant theoretical views on honest signaling, highlighting the vulnerability handicap
hypothesis as a possible explanation for soft song’s reliability in predicting attack. We also sketch possible methods of
testing whether soft song agrees with key predictions of the vulnerability handicap hypothesis. Finally, we suggest possible
empirical refinements that may be useful in future studies of signals of intent, both in birds and in animals broadly. In
particular, we argue that future studies of intent should strive to incorporate the following elements into their experimental
design: (1) multi-modal signal components, (2) interaction dynamics, and (3) minimal time intervals. Simulated exchanges using
dynamically interactive models may provide a powerful means of incorporating all three of these design features simultaneously.
相似文献
Mark E. LaidreEmail: |
19.
Ruth M. Casper Simon N. Jarman Nicholas J. Gales Mark A. Hindell 《Marine Biology》2007,152(4):815-825
The diet of pinnipeds is most commonly inferred from morphologically diagnostic remains of prey in their scats. Although this
method can generate quantitative estimates of diet simply, important prey types may not always be detected. DNA-based methods
improve detection of prey in scats, but they are not quantitative. While some studies have combined morphological and DNA-based
methods, these have only assessed prey that are represented by their hard remains in scats. To overcome this bias, we apply
molecular and morphological analyses to the soft and hard portions of faecal samples respectively, to estimate the diet of
lactating Antarctic fur seals (Arctocephalus gazella) on Heard Island. The diet of this population is of particular interest because it is expanding rapidly and may rely to some
extent on mackerel icefish (Champsocephalus gunnari), which are subject to commercial fisheries. Based on results from morphological analysis and likely important prey types,
we tested for DNA remains of C. gunnari, myctophids and squid in faecal samples. The proportion of samples (n = 54) yielding no dietary information was reduced from around 25.9% using either method alone, to 9.3% when combined. Detection
of all prey types tested for was notably improved by integrating molecular and morphological data. Data from either method
alone would have underestimated the number of animals consuming C. gunnari by around 25.7%. Detection of multiple prey types in samples increased from 9.3% when using morphological analysis only,
to 33.3% when using DNA only, to 46.3% when using both methods. Taken in isolation, morphological data inferred that individual
seals consume either C. gunnari or myctophids, probably foraging in separate locations characteristic of those prey. Including molecular data demonstrated
that while this may be true of some individuals, many other seals consume a mixed diet of at least C. gunnari, myctophids and squid. This new approach of combining DNA-based and morphological analyses of diet samples markedly increased
the number of samples yielding dietary information, as well as increasing the amount of information attained from those samples.
Our findings illustrate the broad potential of this technique to improve insight into trophic interactions in marine ecosystems.
相似文献
Ruth M. CasperEmail: |
20.
Dimitris Karlis Vassilis G. S. Vasdekis Maria Banti 《Environmental and Ecological Statistics》2009,16(3):355-367
Heteroscedastic additive and multiplicative models are proposed to disaggregate household data on water consumption from Athens
and provide individual consumption estimates. The models adjust for heteroscedasticity assuming that variances relate to covariates.
Household characteristics that can influence consumption are also included into models in order to allow for a clearer measurement
of individual characteristics effects. Estimation is accomplished through a penalized least squares approach. The method is
applied to a sample of real data related to domestic water consumption in Athens. The results show a greater consumption of
water for males while the single-female households are these that use the lowest quantities of water. The consumption curves
by age and gender are constructed presenting differences between the two sexes.
相似文献
Vassilis G. S. VasdekisEmail: |