共查询到20条相似文献,搜索用时 312 毫秒
1.
Estimating abundance of killer whales in the nearshore waters of the Gulf of Alaska and Aleutian Islands using line-transect sampling 总被引:1,自引:0,他引:1
Alexandre N. Zerbini Janice M. Waite John W. Durban Rick LeDuc Marilyn E. Dahlheim Paul R. Wade 《Marine Biology》2007,150(5):1033-1045
Killer whale (Orcinus orca Linnaeus, 1758) abundance in the North Pacific is known only for a few populations for which extensive longitudinal data
are available, with little quantitative data from more remote regions. Line-transect ship surveys were conducted in July and
August of 2001–2003 in coastal waters of the western Gulf of Alaska and the Aleutian Islands. Conventional and Multiple Covariate
Distance Sampling methods were used to estimate the abundance of different killer whale ecotypes, which were distinguished
based upon morphological and genetic data. Abundance was calculated separately for two data sets that differed in the method
by which killer whale group size data were obtained. Initial group size (IGS) data corresponded to estimates of group size
at the time of first sighting, and post-encounter group size (PEGS) corresponded to estimates made after closely approaching
sighted groups. ‘Resident’-type (fish-eating) killer whales were more abundant than the ‘transient’-type (mammal-eating).
Abundance estimates of resident killer whales (991 [95% CI = 379–2,585] [IGS] and 1,587 [95% CI = 608–4,140] [PEGS]), were
at least four times greater than those of the transient killer whales (200 [95% CI = 81–488] [IGS] and 251 [95% CI = 97–644]
whales [PEGS]). The IGS estimate of abundance is preferred for resident killer whales because the estimate based on PEGS data
may show an upward bias. The PEGS estimate of abundance is likely more accurate for transients. Residents were most abundant
near Kodiak Island in the northern Gulf of Alaska, around Umnak and Unalaska Islands in the eastern Aleutians, and in Seguam
Pass in the central Aleutians. This ecotype was not observed between 156 and 164°W, south of the Alaska Peninsula. In contrast,
transient killer whale sightings were found at higher densities south of the Alaska Peninsula between the Shumagin Islands
and the eastern Aleutians. Only two sightings of ‘offshore’-type killer whales were recorded during the surveys, one northeast
of Unalaska Island and the other south of Kodiak Island. These are the first estimates of abundance of killer whale ecotypes
in the Aleutian Islands and Alaska Peninsula area and provide a baseline for quantifying the role of these top predators in
their ecosystem.
Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.
相似文献
Alexandre N. ZerbiniEmail: |
2.
E. L. Carroll N. J. Patenaude S. J. Childerhouse S. D. Kraus R. M. Fewster C. S. Baker 《Marine Biology》2011,158(11):2565-2575
The abundance of New Zealand subantarctic southern right whales (Eubalaena australis) was estimated for the first time using mark-recapture methods based on photo-identification and microsatellite genotyping
(13 loci). Individual identification photographs of 383 whales and microsatellite genotypes of 235 whales were collected during
annual austral winter field surveys from 1995 to 1998. Given the 4-year survey period and lack of geographic and demographic
closure, we estimated super-population abundance using the POPAN Jolly-Seber model implemented in the software programme MARK.
Models with constant survivorship but time-varying capture probability and probability of entry into the population were the
most suitable due to the survey design. This provided estimates of abundance in 1998 of 908 non-calf whales (95% C.L. = 755,
1,123) for the photo-identification and 910 non-calf whales (95% C.L. = 641, 1,354) for the microsatellite genotype data sets.
The current estimate of 900 whales may represent less than 5% of the pre-whaling abundance in New Zealand waters. 相似文献
3.
Kevin P. Robinson Michael J. Tetley E. Gay Mitchelson-Jacob 《Journal of Coastal Conservation》2009,13(1):39-48
The coastal waters of the Moray Firth in northeast Scotland (57o41’N 2o40’W) provide rich, inshore feeding grounds for minke
whales (Balaenoptera acutorostrata) during the summer and autumnal months. In order to better understand the habitat selection, movements and feeding ecology
of the animals utilising this North Sea region, distribution data from the southern coastline of the outer Moray Firth were
subsequently examined with respect to the marine physiography of the area, specifically the environmental variables water
depth, slope, aspect and sediment-type. A total of 305 minke whale encounters – collected from dedicated boat surveys conducted
between May and October 2001 to 2006 inclusive – were used in the construction of a Geographic Information System (GIS) for
the 860 square-km study site. The subsequent analysis revealed a strong spatial preference by whales in this location for
water depths between 20 and 50 metres (mean 46.9 m, SD = 30.9), steep slopes (mean 75.7 degrees, SD = 8.9), a northerly-facing
aspect and sandy-gravel sediment type. Kruskal-Wallis tests for variance confirmed that the distribution of B. acutorostrata was significantly different across each of these physiographic features examined (P < 0.05). In particular, water depth and sediment type were shown to be highly correlated with the frequency of whales observed
(Spearman’s Rank Correlation P < 0.05 for depth and sediment respectively). From these results, we conclude that sea bottom characteristics may be used to
predict the fine-scale distribution of minke whales on their feeding grounds; the physiographic features identified providing
valuable proxies for inferring prey distributions in the absence of fisheries data. However, an appreciation of both abiotic
and biotic factors (using a combination of GIS and remote sensing outputs) is clearly desirable for ecosystem-based management
approaches for the coastal conservation of these whales. The application of GIS capacities to ecological studies based largely
on field data of these marine mammals is highly recommended in the present study to cetologists, environmental modellers and
conservation managers alike. 相似文献
4.
Holly Fearnbach John W. Durban David K. Ellifrit Janice M. Waite Craig O. Matkin Chris R. Lunsford Megan J. Peterson Jay Barlow Paul R. Wade 《Marine Biology》2014,161(2):459-472
The productive North Pacific waters of the Gulf of Alaska, Aleutian Islands and Bering Sea support a high density of fish-eating “Resident” type killer whales (Orcinus orca), which overlap in distribution with commercial fisheries, producing both direct and indirect interactions. To provide a spatial context for these interactions, we analyzed a 10-year dataset of 3,058 whale photo-identifications from 331 encounters within a large (linear ~4,000 km) coastal study area to investigate the ranging and social patterns of 532 individually identifiable whales photographed in more than one encounter. Although capable of large-scale movements (maximum 1,443 km), we documented ranges generally <200 km, with high site fidelity across summer sampling intervals and also re-sightings during a winter survey. Bayesian analysis of pair-wise associations identified four defined clusters, likely representing groupings of stable matrilines, with distinct ranging patterns, that combined to form a large network of associated whales that ranged across most of the study area. This provides evidence of structure within the Alaska stock of Resident killer whales, important for evaluating ecosystem and fisheries impacts. This network included whales known to depredate groundfish from longline fisheries, and we suggest that such large-scale connectivity has facilitated the spread of depredation. 相似文献
5.
ROB WILLIAMS SHARON L. HEDLEY TREVOR A. BRANCH MARK V. BRAVINGTON ALEXANDRE N. ZERBINI KEN P. FINDLAY 《Conservation biology》2011,25(3):526-535
Abstract: Often abundance of rare species cannot be estimated with conventional design‐based methods, so we illustrate with a population of blue whales (Balaenoptera musculus) a spatial model‐based method to estimate abundance. We analyzed data from line‐transect surveys of blue whales off the coast of Chile, where the population was hunted to low levels. Field protocols allowed deviation from planned track lines to collect identification photographs and tissue samples for genetic analyses, which resulted in an ad hoc sampling design with increased effort in areas of higher densities. Thus, we used spatial modeling methods to estimate abundance. Spatial models are increasingly being used to analyze data from surveys of marine, aquatic, and terrestrial species, but estimation of uncertainty from such models is often problematic. We developed a new, broadly applicable variance estimator that showed there were likely 303 whales (95% CI 176–625) in the study area. The survey did not span the whales' entire range, so this is a minimum estimate. We estimated current minimum abundance relative to pre‐exploitation abundance (i.e., status) with a population dynamics model that incorporated our minimum abundance estimate, likely population growth rates from a meta‐analysis of rates of increase in large baleen whales, and two alternative assumptions about historic catches. From this model, we estimated that the population was at a minimum of 9.5% (95% CI 4.9–18.0%) of pre‐exploitation levels in 1998 under one catch assumption and 7.2% (CI 3.7–13.7%) of pre‐exploitation levels under the other. Thus, although Chilean blue whales are probably still at a small fraction of pre‐exploitation abundance, even these minimum abundance estimates demonstrate that their status is better than that of Antarctic blue whales, which are still <1% of pre‐exploitation population size. We anticipate our methods will be broadly applicable in aquatic and terrestrial surveys for rarely encountered species, especially when the surveys are intended to maximize encounter rates and estimate abundance. 相似文献
6.
Tomoharu Eguchi Jeffrey A. Seminoff Robin A. LeRoux Peter H. Dutton Donna L. Dutton 《Marine Biology》2010,157(8):1869-1877
Longitudinal capture-mark-recapture data were used to estimate abundance and survival rates for green turtles (Chelonia mydas) in San Diego Bay, California, USA. These turtles were closely associated with warm effluent from a power plant during winter
months. The life stage distribution of green turtles in the bay ranged from post-pelagic juveniles to adults (44.0–110.4 cm
straight carapace length). During 99 capture sessions between December 2, 1990, and March 25, 2009, 96 individual green turtles
were caught. To estimate abundance and survival rates, robust-design mark-recapture models were fitted to capture-recapture
histories using software MARK. The estimated annual survival rate was 0.861 (SE = 0.147, 95% CI = 0.356–0.986), whereas annual
abundance ranged from 16 (SE = 6.3, 95% CI = 4–29) to 61 (SE = 13.2, 95% CI = 36–88). This study provides the first survival
rate and abundance estimates for a green turtle foraging population in the highly industrialized San Diego Bay. 相似文献
7.
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
8.
Zooplankton community structure across an eddy-generated upwelling band close to a tropical bay-mangrove ecosystem 总被引:2,自引:0,他引:2
M. Rakhesh A. V. Raman C. Kalavati B. R. Subramanian V. S. Sharma E. Sunitha Babu Nanduri Sateesh 《Marine Biology》2008,154(6):953-972
Mesoscale eddies in the world’s oceans are ubiquitous and bring about episodic pulses of nutrients into the photic zone. Transient
in nature, the role of eddy pumping in coastal enrichment via plankton production, and subsequent organic flux is not yet
fully realised. In the context of a cyclonic cold-core eddy that propagates annually under the influence of the East India
Coastal Current and enriches coastal waters in the western Bay of Bengal north of 16°N, a detailed study on zooplankton community
structure along with phytoplankton composition and associated water quality was undertaken during April–May 2002 coinciding
with the spring intermonsoon. Zooplankton samples were collected at 32 hydrographically different (salinity 24.5–35.6 PSU)
GPS fixed locations representing bay-mangrove areas and nearshore waters (30 m) close to the River Godavari, which is one
of India’s largest estuarine systems. During the study, the bay-coastal waters were typified by elevated nutrient levels (nitrate
10.73–22.04 μM), high salinity (27.98–35.52 PSU), and relatively low temperatures (30.63–31.40°C). Altogether, 95 zooplankton
taxa were encountered with copepods forming the predominant population. Agglomerative Hierarchical Cluster Analysis (AHCA)
and Non-metric Multidimensional Scaling (NMDS) based on Bray–Curtis similarity (PRIMER) analysis revealed appreciable alterations
in zooplankton structure across bay-mangrove locations and coastal waters (Stress 0.11; ANOSIM test Global R: 0.94, P = 0.1%). Similarity Percentage (SIMPER) analysis revealed zooplankton associations through “discriminating species” for each
location (Kakinada Bay, Cluster I, 27.9 ± 3.0 PSU; upwelling band, cluster II, 35.5 ± 0.2 PSU; offshore waters, cluster III,
34.2 ± 0.4 PSU; mangrove outlets, cluster IV, 32.7 ± 1.3 PSU and mangrove creeks, cluster V, 33.5 ± 0.6 PSU). The index of
multivariate dispersion (IMD) illustrated high variability in zooplankton standing stock for mangrove/sea locations relative
to the bay. Concurrent observations on phytoplankton revealed the importance of diatoms (r: 0.640, P ≤ 0.05). Within the eddy-generated band of upwelled water, a significant top-down control of diatoms by herbivorous zooplankton
resulted in a comparative increase in abundance of dinophyceans. Based on zooplankton abundance data and species association
patterns, it was possible to distinguish different zooplankton/copepod communities in accordance with mesoscale variability
in physical, chemical and biological processes under tropical conditions. This was confirmed through canonical correspondence
analysis (CCA) that represented coastal-offshore waters and the Bay environment in this area. 相似文献
9.
The rate of growth of any population is a quantity of interest in conservation and management and is constrained by biological
factors. In this study, recent data on life-history parameters influencing rates of population growth in humpback whales,
including survival, age at first parturition and calving rate are reviewed. Monte Carlo simulations are used to compute a
distribution of rates of increase (ROIs) taking into account uncertainty in biological parameter estimates. Two approaches
for computing juvenile survival are proposed, which taken into account along with other life-history data, resulted in the
following estimates of the rate of population growth: Approach A: mean of 7.3%/year (95% CI = 3.5–10.5%/year) and Approach
B: mean of 8.6%/year (95% CI = 5.0–11.4%/year). It is proposed that the upper 99% quantile of the resulting distribution of
the ROI for Approach B (11.8%/year) be established as the maximum plausible ROI for humpback whales and be used in population
assessment of the species. Possible sources of positive and negative biases in the present estimates are presented and include
measurement error in estimation of life-history parameters, changes in the environment within the period these quantities
are measured, density dependence or other natural factors. However, it is difficult to evaluate potential biases without additional
data. The methods presented in this study can be applied to other species for which life-history parameters are available
and are useful in assessing plausibility in the estimation of population growth rates from time series of abundance estimates. 相似文献
10.
The spatial distribution patterns of krill, seabirds (penguin, petrel and albatross), fur seals and baleen whales were mapped
in nearshore waters (<50 km from land) to investigate their habitat selection within two adjacent submarine canyons near Livingston
Island, Antarctica. Three shipboard surveys were conducted (February 2005–2007), and an echosounder was used to measure the
distribution and abundance of krill while simultaneously conducting visual surveys to map seabird and marine mammals. Using
a multispecies approach, we test the hypothesis that spatial organization of krill and top predators co-vary according to
fine-scale changes in bathymetry in the nearshore marine environment. GAMs are used to examine the effect of sea depth, slope
and distance to isobaths on the spatial distribution and abundance of krill and predators. Spatial distribution patterns of
krill and predators relate to fine-scale (1–10 km) changes in bathymetry and exhibit cross-shelf gradients in abundance. Krill
were concentrated along the shelf-break and abundant within both submarine canyons. Predators exhibited different preferences
for locations within the submarine canyon system that relates to their foraging behavior. Penguins concentrated closer to
shore and within the head of the east submarine canyon immediately adjacent to a breeding colony. Whales were also concentrated
over the head of the east canyon (overlapping with penguins), whereas albatrosses and fur seals were concentrated in the west
canyon. Fur seals also showed preference for steep slopes and were concentrated along the shelf-break. Petrels exhibited peaks
in abundance throughout both submarine canyons. Owing to their orientation, size and proximity to the coastline, submarine
canyons provide important habitat heterogeneity for krill and a variety of predators. This study highlights the multispecies
approach for studying spatial ecology of top predators and krill and has implications for marine spatial management of the
Scotia Sea. 相似文献
11.
Seasonal aerial surveys were conducted in the waters of the central Spanish Mediterranean from 2001 to 2003 using the line transect sampling methodology to estimate cetacean abundance. The density of the three most abundant species, striped dolphin (Stenella coeruleoalba), bottlenose dolphin (Tursiops truncatus) and Risso’s dolphins (Grampus griseus), was estimated. In the case of the first two species, the density was estimated accounting for the proportion of submerged animals, while for Risso’s dolphin only the surface density could be estimated. The striped dolphin was the most abundant species in the study area with a mean density of 0.489 dolphins km−2 (95% CI = 0.339–0.705) and a mean abundance of 15,778 dolphins (95% CI = 10,940–22,756). This density is comparable to that obtained in the International Ligurian Sea Cetacean Sanctuary. Striped dolphins were observed throughout the whole year and no seasonal changes in the density were detected. The mean density of bottlenose dolphins was an order of magnitude lower than that of striped dolphins (0.041 dolphins km−2; 95% CI = 0.023–0.075) with a mean abundance of 1,333 dolphins (95% CI = 739–2,407). The Risso’s dolphin had a surface estimated density of 0.015 dolphins km−2 (95% CI = 0.005–0.046) and a mean abundance of 493 dolphins (95% CI = 162–1,498). These results provide valuable biological information useful to develop conservation plans and establish a baseline for future population trend studies. 相似文献
12.
Public signaling plays an important role in territorial and sexual displays in animals; however, in certain situations, it
is advantageous to keep signaling private to prevent eavesdropping by unintended receivers. In the northeastern Pacific, two
populations of killer whales (Orcinus orca), fish-eating “resident” killer whales and mammal-eating “transient” killer whales, share the same habitat. Previous studies
have shown that residents use whistles as private signals during close-range communication, where they probably serve to coordinate
behavioral interactions. Here, we investigated the whistling behavior of mammal-eating killer whales, and, based on divergent
social structures and social behaviors between residents and transients, we predicted to find differences in both whistle
usage and whistle parameters. Our results show that, like resident killer whales, transients produce both variable and stereotyped
whistles. However, clear differences in whistle parameters between ecotypes show that the whistle repertoire of mammal-eating
killer whales is clearly distinct from and less complex than that of fish-eating killer whales. Furthermore, mammal-eating
killer whales only produce whistles during “milling after kill” and “surface-active” behaviors, but are almost completely
silent during all other activities. Nonetheless, whistles of transient killer whales may still serve a role similar to that
of resident killer whales. Mammal-eating killer whales seem to be under strong selection to keep their communication private
from potential prey (whose hearing ranges overlap with that of killer whales), and they appear to accomplish this mainly by
restricting vocal activity rather than by changes in whistle parameters. 相似文献
13.
Elizabeth J. Berens McCabe Damon P. Gannon Nélio B. Barros Randall S. Wells 《Marine Biology》2010,157(5):943-942
Prey selection was investigated in wild, resident common bottlenose dolphins, Tursiops truncatus, during the summer months in Sarasota Bay, Florida, USA. Stomach content analyses of 15 dolphins with extensive sighting
histories and well-documented distributions were used to determine prey use. Prey availability was assessed by purse seine
surveys. We compared the relative abundances of prey available to estimates of prey use at closely matching spatial and temporal
scales. G-tests determined that dolphins in this study significantly selected for prey at the species, family, and soniferous/non-soniferous
prey levels (G
adj
= 753.98–1,775.93, df = 1–21, p ≤ 0.01). While comprising only 6.3% of the total available prey, soniferous fishes accounted for 51.9% of the total prey
consumed. Manly’s standardized forage ratios and 95% Bonferroni confidence intervals determined significant positive selection
for soniferous prey and against non-soniferous prey (βS = 0.9461 vs. βNS = 0.0539). Dolphins selected against Gerridae, Clupeidae, and Sparidae (β ≤ 0.0014), as well as against all the species within those families (β ≤ 0.0190). It is likely that passive listening for soniferous prey provides an ecological or energetic advantage to cetaceans
utilizing this specific foraging technique. 相似文献
14.
At three coastal dune sites at the island of Hiddensee, north-east Germany, vegetation cover was mapped during 2002 and compared
to vegetation surveys from the late 1980s and 1930s. Abiotic and biotic factors, which have been identified as being critical
for coastal dunes in former studies such as disturbance, salt spray or nutrient availability, were measured. Grazing and land-use
history were reviewed by literature and interviews. Tall graminoid communities, mainly Carex arenaria, are a common vegetation unit today. Development, distribution of these dominances and possible causes for its occurrence
have not been analysed. Generally, older successional vegetation units increased and pioneer stages decreased from the 1930s
until 2002. At the geologically youngest site, the southern dunes, grass encroachment by Carex arenaria was highest (ca. 50% cover in 2002), and age and density of trees lower than at the older, central dunes. Land-use changes
such as decrease in grazing pressure, additional feeding of livestock, increase in coastal protection measures and subsequent
decrease in shifting sands as well as varying availability of groundwater and amount of salt spray are relevant factors for
vegetation changes in coastal dunes over the past 70 years. Site-specific land-use differences such as livestock density and
land-use history have a stronger influence than atmospheric N-pollution on the vegetation composition of these acidic, coastal
dunes under low to moderate N-deposition loads of 6–8 kg N ha−1 yr−1. 相似文献
15.
Sergi Pérez Ángel García-López Renaud De Stephanis Joan Giménez Susana García-Tiscar Philippe Verborgh Juan Miguel Mancera Gonzalo Martínez-Rodriguez 《Marine Biology》2011,158(7):1677-1680
We tested the possibility of measuring progesterone levels in bubbler samples collected from free-ranging live bottlenose
dolphins (n = 11) and long-finned pilot whales (n = 2) as a tool to evaluate the pregnancy status of individuals. Samples were collected during January 2004 and September–October
2005 in the Strait of Gibraltar and Gulf of Cadiz and used for sex-determination by genetic methods (skin samples) and for
quantification of progesterone levels by enzyme immunoassay. Photo-identification tracking of females after taking the biopsy
was used to observe the presence of newborns and, in this way, to determine if the female was pregnant at the time of sampling.
Mean progesterone levels from pregnant bottlenose dolphins (n = 2) were around 9 times higher than those from non-pregnant females (n = 9), with no overlap between concentration ranges demonstrating that this method could constitute an effective tool for
determining pregnancy in wild populations of bottlenose dolphins and other cetacean species. 相似文献
16.
G. D’Onghia L. Sion P. Maiorano Ch. Mytilineou S. Dalessandro R. Carlucci S. Desantis 《Marine Biology》2006,149(3):435-446
The population biology and life strategies of Chlorophthalmus agassizii were studied in the Ionian Sea (eastern–central Mediterranean) using the data collected during the experimental trawl surveys carried out from 1995 to 2000. Depth-related trends of both density and size were found. With depth the former decreased while the latter increased. A typical bigger–deeper phenomenon was detected: young-of-the-year individuals occur on the shelf during autumn–winter months and move towards bathyal bottoms as they grow. The sampled population was made up of several size–age groups. The maximum age of 8 years was identified by means of otolith readings. The Von Bertalanffy growth parameters were estimated from the age–length key (L
∞=189.04±5.401 mm; k=0.24±0.021; t
o=−1.20±0.132; φ′=3.94) and modal progression analysis (L
∞=218.33±18.397 mm; k=0.164±0.028; t
o=−1.694±0.171; φ′=3.89). Reproduction of this monoecious fish was observed during summer–early autumn. Considering the female portion of the gonad, the size at attainment of 50% maturity was 115 mm TL. The corresponding age is within the third year of life. The simultaneous occurrence of oocytes in different development stages was shown in the ovary. Both the asynchronous ovary and oocyte size distribution indicate that C. agassizii spawns more than once during a reproductive season (batch spawner). Functional fecundity (on average 3,018 hydrated oocytes) was between 37 and 69% of the absolute fecundity and increased significantly with the individual size. Since adult specimens are mostly distributed on the slope, eggs and larvae develop in epipelagic waters and migrate in-shore where juvenile forms recruit on the shelf. Juveniles migrate ontogenetically towards deeper bottoms and after 2–3 years start to reproduce annually within a life span greater than 10 years. 相似文献
17.
Colonization dynamics in trophic-functional structure of periphytic protist communities in coastal waters 总被引:1,自引:0,他引:1
Wei Zhang Henglong Xu Yong Jiang Mingzhuang Zhu Khaled A. S. Al-Rasheid 《Marine Biology》2012,159(4):735-748
The colonization dynamics in trophic-functional patterns of periphytic protist communities was studied in coastal waters of
the Yellow Sea, northern China, from May to June, 2010. The periphytic protists represented different trophic-functional structures
during colonization process. Only certain trophic-functional groups (e.g., photoautotrophs, algivores and non-selectives)
occurred within the protist communities with low species number and abundance at the initial stage (1–3 days), while more
trophic-functional groups (e.g., photoautotrophs, algivores, non-selectives and raptors) contributed to the communities with
increased and peaked species number and abundance at the transitional (7–10 days) and equilibrium (14–28 days) stages, respectively.
All heterotrophic groups were significantly fitted the MacArthur–Wilson model in colonization curves and represented higher
species number and colonization rates at a depth of 1 m than at 3 m. These results may provide necessary understandings for
ecological researches and monitoring programs using periphytic protists with different colonization ages in marine ecosystems. 相似文献
18.
Scot D. Anderson Taylor K. Chapple Salvador J. Jorgensen A. Peter Klimley Barbara A. Block 《Marine Biology》2011,158(6):1233-1237
Mark-recapture techniques can be used to estimate white shark (Carcharodon carcharias) population abundance. These frameworks are based on assumptions that marks are conserved and animals are present at the
sampling location over the entire duration of the study. Though these assumptions have been validated across short-time scales
for white sharks, long-term studies of population trends are dependent on these assumptions being valid across longer periods.
We use 22 years of photographic data from aggregation sites in central California to support the use of dorsal fin morphology
as long-term individual identifiers. We identified five individuals over 16–22 years, which support the use of dorsal fins
as long-time individual identifiers, illustrate strong yearly site fidelity to coastal aggregation sites across extended time
periods (decades), and provide the first empirical validation of white shark longevity >22 years. These findings support the
use of fin morphology in mark-recapture frameworks for white sharks. 相似文献
19.
Pistón M Silva J Pérez-Zambra R Dol I Knochen M 《Environmental geochemistry and health》2012,34(2):273-278
A multicommutated flow system was designed and evaluated for the determination of total arsenic and selenium by Hydride Generation
Atomic Absorption Spectrometry (HG-AAS). It was applied to the determination of arsenic and selenium in samples of natural
and drinking water. Detection limits were 0.46 and 0.08 μg l−1 for arsenic and selenium, respectively; sampling frequency was 120 samples h−1 for arsenic and 160 samples h−1 for selenium. Linear ranges found were 1.54–10 μg l−1 (R = 0.999) for arsenic and 0.27–27 μg l−1 (R = 0.999) for selenium. Accuracy was evaluated by spiking various water samples and using a reference material. Recoveries
were in the range 95–116%. Analytical precision (s
r
(%), n = 10) was 6% for both elements. Compared with the Standard Methods, APHA, 3114B manual method, the system consumes at least
10 times less sample per determination, and the quantities of acid and reducing agent used are significantly lower with a
reduction in the generation of pollutants and waste. As an additional advantage, the system is very fast, efficient and environmentally
friendly for monitoring total arsenic and selenium levels in waters. 相似文献
20.
Lilia Araujo Noreiva Villa Nuris Camargo Maikellys Bustos Theobaldo Garc��a Avismelsi de Jesus Prieto 《Environmental Chemistry Letters》2011,9(1):13-18
The occurrence of pharmaceuticals in natural waters is a potential threat to human nutrition and ecosystem quality. The persistence
of the acidic pharmaceuticals gemfibrozil, naproxen and mefenamic acid was studied in surface waters of Maracaibo Lake and
Tule reservoir (Venezuela) under laboratory conditions. A quick and easy analytical method was developed for the determination
of the acidic drugs at microgram per liter levels using aqueous derivatization, liquid–liquid extraction and gas chromatography–mass
spectrometry. Pharmaceuticals degradation followed a pseudo first-order kinetic and their half-lives were calculated for every
experimental condition. Under sunlight, naproxen and mefenamic acid were degraded at moderate rates with half-lives from 9.6 ± 0.5
to 27.0 ± 6.6 days, while gemfibrozil had a higher persistence (t
1/2 = 119.5 ± 15.6 − 288.8 ± 61.3 days). 相似文献