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1.
Long-finned pilot whales (Globicephala melas), Risso's dolphins (Grampus griseus), melon-headed whales (Peponocephala electra), Cuvier's beaked whales (Ziphius cavirostris), Sowerby's beaked whales (Mesoplodon bidens), northern bottlenose whales (Hyperoodon ampullatus), sperm whales (Physeter macrocephalus), dwarf sperm whales (Kogia sima) and pygmy sperm whales (Kogia breviceps) make up the large community of deep-diving odontocetes occurring off the Bay of Biscay, northeast Atlantic. The ecology of these toothed cetaceans is poorly documented worldwide. The present study described their prey preferences from stomach content analysis and showed resource partitioning within the assemblage. The majority of the species appeared to be mostly teutophageous. Fish was an important food source only for the Sowerby's beaked whale and, to a lesser extent, for the long-finned pilot whale. In terms of foraging habitats inferred from prey composition, either pelagic oceanic or demersal neritic habitats were exploited by toothed whales in the Bay of Biscay, with only the long-finned pilot whale foraging in the two habitats. Finally, with more than 14,000 identified cephalopods from 39 species, the present study highlighted also the poorly known deep-sea cephalopod community off the Bay of Biscay using top predators as biological samplers.  相似文献   

2.
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3.
The sequential megafaunal collapse hypothesis: Testing with existing data   总被引：4，自引：1，他引：4  
Springer et al. [Springer, A.M., Estes, J.A., van Vliet, G.B., Williams, T.M., Doak, D.F., Danner, E.M., Forney, K.A., Pfister, B., 2003. Sequential megafaunal collapse in the North Pacific Ocean: an ongoing legacy of industrial whaling? Proceedings of the National Academy of Sciences 100 (21), 12,223–12,228] hypothesized that great whales were an important prey resource for killer whales, and that the removal of fin and sperm whales by commercial whaling in the region of the Bering Sea/Aleutian Islands (BSAI) in the late 1960s and 1970s led to cascading trophic interactions that caused the sequential decline of populations of harbor seal, northern fur seal, Steller sea lion and northern sea otter. This hypothesis, referred to as the Sequential Megafaunal Collapse (SMC), has stirred considerable interest because of its implication for ecosystem-based management. The SMC has the following assumptions: (1) fin whales and sperm whales were important as prey species in the Bering Sea; (2) the biomass of all large whale species (i.e., North Pacific right, fin, humpback, gray, sperm, minke and bowhead whales) was in decline in the Bering Sea in the 1960s and early 1970s; and (3) pinniped declines in the 1970s and 1980s were sequential. We concluded that the available data are not consistent with the first two assumptions of the SMC. Statistical tests of the timing of the declines do not support the assumption that pinniped declines were sequential. We propose two alternative hypotheses for the declines that are more consistent with the available data. While it is plausible, from energetic arguments, for predation by killer whales to have been an important factor in the declines of one or more of the three populations of pinnipeds and the sea otter population in the BSAI region over the last 30 years, we hypothesize that the declines in pinniped populations in the BSAI can best be understood by invoking a multiple factor hypothesis that includes both bottom–up forcing (as indicated by evidence of nutritional stress in the western Steller sea lion population) and top–down forcing (e.g., predation by killer whales, mortality incidental to commercial fishing, directed harvests). Our second hypothesis is a modification of the top–down forcing mechanism (i.e., killer whale predation on one or more of the pinniped populations and the sea otter population is mediated via the recovery of the eastern North Pacific population of the gray whale). We remain skeptical about the proposed link between commercial whaling on fin and sperm whales, which ended in the mid-1960s, and the observed decline of populations of northern fur seal, harbor seal, and Steller sea lion some 15 years later.  相似文献   

4.
The ampeliscid amphipod community in the Chirikov Basin of the northern Bering Sea was a focus of study during the 1980s because they were a major food for the Eastern North Pacific (ENP) population of gray whales Eschrichtius robustus. Information from the 1980s benthic investigations, published accounts of ENP gray whale population trends and the occurrence in 1999–2000 of an unusual number of gray whale mortalities prompted concern that the whale population may have exceeded the carrying capacity of its food base. Therefore, during two cruises per year between June and September, 2002 and 2003, we resampled the 20 stations occupied during the 1980s, to determine if there had been any significant changes in ampeliscid abundance and biomass. During 2002–2003, average ampeliscid dry weight biomass was about 28±10 g m−2 (95% confidence interval), a decline of nearly 50% from maximum values in the 1980s. Amphipod length measurements indicated that the declines were due mainly to the absence of the larger animals (20–30 mm length). Two hypotheses were considered regarding the amphipod declines: gray whale predation and climate. Ampeliscid production (105 kcal m−2 yr−1) and gray whale energy requirements (1.6×108 kcal individual−1 yr−1) indicated that as little as 3–6% of the current estimate of the ENP gray whale population could remove 10–20% of the annual ampeliscid production from the study site in 2002–2003, a finding consistent with the hypothesis that top-down control by foraging whales was the primary cause of the observed declines. A 10-yr time series of temperature near the bottom in the Bering Strait and northward transport did not reveal a consistent trend between 1990 and 2001, suggesting that climate influences were not the major cause of the observed declines. Arctic ampeliscids have slow growth rates and long generation times; therefore the ampeliscid community may require decades to recover to densities observed in the 1980s. Predicted warming trends in the northern Bering Sea could impact ampeliscid recovery by lowering primary production or altering the community composition of the benthos.  相似文献   

5.
To track the diet of minke whale (Balaenoptera acutorostrata) in the East Sea (Japan Sea), a conjoint analysis of fatty acids and C and N stable isotopes was performed on blubber and skin from the whale and its potential prey. The total lipid content in the blubber of minke whales ranged from 37.9% to 82.7% of wet mass (mean ± SD, 63.1 ± 17.2%), with triacylglycerols being the dominant lipids (96.9%–99.2% of total lipids). The lipid and fatty acid (FA) contents were systematically stratified throughout the depth of the blubber layers; contents of the dominant monounsaturated FAs (MUFAs), including 18:1ω9 and 16:1ω7, increased from the innermost layer to the outermost layer, whereas contents of saturated FAs (SFAs) and polyunsaturated FAs (PUFAs) were higher in the innermost layer than in the outermost layer. This stratification is related to the different physiological roles of the blubber layers; e.g., thermoregulation, streaming, and buoyancy. A comparison of the FA compositions of the innermost layer of minke whales with those of potential prey indicates that FA compositions in the whales are similar to those of Pacific herring. In addition, stable isotope ratios (δ13C and δ15N) suggest that minke whale and Pacific herring have the same or similar diets. Therefore, the diets of minke whale from the East Sea (Japan Sea) could be inferred from information on the diet of the Pacific herring, although FA compositions and stable isotope ratios for Pacific herring would not exactly reflect the whale’s diet. Although the very limited number of samples was used in this study, our preliminary findings are very promising to help understand the feeding ecology of minke whales in the East Sea (Japan Sea).  相似文献   

6.
The whales are an interesting group in several aspects of science, including evolutionary biology, marine ecology and toxicology. Some of the whale species, including the minke whale, graze at the top of the food chains, where they become susceptible to the accumulation of marine pollutants ingested by organisms at lower levels. The northern stock of the minke whale grazes in Arctic waters in the summer, an area of increasing interest in the development of new oil fields. Studies on the metabolism, disposition and effects of xenobiotics in marine mammals are few. The only reports in the open literature so far have dealt with these questions in seals.1–3 Although the marine mammals comprise a particularly interesting group in marine ecology and toxicology, no data have to our knowledge been presented on the xenobiotic metabolising enzyme systems of the whales. In this study, components of the microsomal cytochrome P-450 system were measured in liver samples from several females, one male, and two foetal minke whales, caught in the Norwegian whaling season of 1983. Because of the limited number of samples studied we have treated the samples individually and not performed any statistical analysis of the data. The trends discussed below must therefore be considered with this background.  相似文献   

7.
The Norwegian Sea is a migration and feeding ground for fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) in summer. During the last decade, significant structural changes in the prey community, including northerly expansion and movement in the distribution of pelagic fish species, have been reported from this ecosystem. However, little information on whale feeding ecology exists in the Norwegian Sea and surrounding waters. A total of 59 fin whales and 48 humpback whales were sighted during 864 h of observation over an observation distance of about 8200 nmi (15,200 km) in the Norwegian Sea from 15 July to 6 August 2006 and 2007. The fin whale group size, as mean (±SD), varied between one and five individuals (2.1 ± 1.2 ind.) and humpback whale group size varied between one and six individuals (2.5 ± 1.7 ind.). Fin‐ and humpback whales were observed mainly in the northern part of the study area, and were only found correlated with the presence of macro‐zooplankton in cold Arctic water. Humpback whales were not correlated with the occurrence of adult Norwegian spring‐spawning herring (Clupea harengus) except for the northernmost areas. Despite changes in the whale prey communities in the Norwegian Sea, no apparent changes in fin‐ or humpback whale distribution pattern could be found in our study compared to their observed summer distribution 10–15 years ago.  相似文献   

8.
Sighting and catch data on sperm whales accumulated during a whale survey by the New Zealand Marine Department and whaling operations by the Tory Channel whaling company in 1963–4 were examined.

The results showed a unimodal rise and fall in numbers of sperm whales in the Cook Strait region throughout the year. From a peak between December and April whale numbers declined steadily until November, when they rose again sharply.

It is suggested from these results that the best choice for an eight‐month sperm whaling season would be one extending from November to July.

It was concluded that the mean speed of sperm whales in the area was not likely to exceed 1 knot.  相似文献   

9.
Acoustic exposure and behavior of 8 sperm whales were recorded with acoustic and movement-recording tags before, during and after 5 separate 1–2 h controlled sound exposures of industry-provided airgun arrays. None of the 8 whales changed behavioral state (7 foraging, 1 resting) following the start of ramp-up at distances of 7–13 km, or full array exposures at 1–13 km. The most closely approached whale rested throughout exposure but started a foraging dive shortly after the airguns ceased, possibly indicating a delay in foraging during exposure. Using visual tracking and dead-reckoning of tagged animals, we found that their direction-of-movement was random with respect to the airguns, but correlated with their direction-of-movement just prior to the start of exposure, indicating that the tested whales did not show horizontal avoidance of the airguns. Oscillations in pitch generated by swimming movements during foraging dives were on average 6% lower during exposure than during the immediately following post-exposure period, with all 7 foraging whales exhibiting less pitching (p=0.014). Buzz rates, a proxy for attempts to capture prey, were 19% lower during exposure but given natural variation in buzz rates and the small numbers of whales, this effect was not statistically significant (P=0.141). Though additional studies are strongly recommended, these initial results indicate that sperm whales in the highly exposed Gulf of Mexico habitat do not exhibit avoidance reactions to airguns, but suggest they are affected at ranges well beyond those currently regulated due to more subtle effects on their foraging behavior.  相似文献   

10.
The abundance and vertical distribution pattern of a mysidMeterythrops microphthalma were investigated in the Japan Sea. Results from vertical hauls from 602–982 m depth to the surface around Yamato Rise in April 1987 indicated that the dominance (by biomass) ofM. microphthalma was third to fifth of major zooplankton taxa. Vertical distribution investigated at a single station in Toyama Bay in June, September and December 1986 showed that the most part of population of this mysid inhabited consistently below 250 m depth. No marked diurnal vertical migration was evident. Data on body composition and oxygen consumption rate ofM. microphthalma are presented. Water content of the body was 75.6–83.8% of wet weight, and ash was 11.4–20.4% of dry weight. Carbon, hydrogen and nitrogen were 37.9–47.5%, 6.2–7.4% and 9.4–10.1%, respectively, of dry weight. Oxygen consumption rates were 2.2–11.0µl O2 individual–1 hr–1 at 0.5°C, and were directly proportional to body mass. From the comparison with the published data on epipelagic and bathypelagic mysids it is revealed that both body nitrogen composition and oxygen consumption rate expressed as adjusted metabolic rate [AMR02,µl O2 (mg body N)–0.85 hr–1] ofM. microphthalma are intermediate between high epipelagic and low bathypelagic levels, indicating typical mesopelagic features.  相似文献   

11.
The U-Tapao Canal is the main source of freshwater draining into the outer part of Songkhla Lake, which is the most important estuarine lagoon in Thailand. Songkhla Lake is located in southern Thailand between latitudes 7°08' and 7°50' N and longitudes 100°07' and 100°37' E. Acetic acid (HOAc)-soluble Cu, Fe, Mn, Pb, and Zn and the total concentration of these metals along with Al concentration, organic carbon, carbonate, sand, silt, and clay contents were determined in 4 sediment cores obtained at selected intervals from the mouth of the canal to 12 km upstream. Readily oxidizable organic matter in the cores varies from 1.52% to 7.30% and is generally found to decrease seaward. Total concentrations of Al (61.7–99.0 g kg−1; 2.29–3.67 mol kg−1), Cu (12.4–28.2 mg kg−1; 195–444 μmol kg−1), Fe (25.2–42.0 g kg−1; 451–752 mmol kg−1), Mn (0.22–0.49 g kg−1; 4.0–8.9 mmol kg−1), Pb (16.7–43.1 mg kg−1; 80.6–208 μmol kg−1), and Zn (48.6–122.7 mg kg−1; 0.74–1.88 mmol kg−1) vary to a certain extent vertically and seaward in the U-Tapao Canal core sediments. These concentrations are at or near natural levels and show no indication of anthropogenic contamination.Overall, the data show that total metal concentrations in the surface and near surface core sediments are enriched in varying degrees relative to Al in the order of Zn>Mn>Pb>Fe>Cu. Chemical partitioning shows that the enrichment in the surface and near surface sediments is related to the relatively high proportion of the total metal concentrations (Mn>Zn>Fe>Cu>Pb) that occur in the acetic acid-soluble (nondetrital) fraction, and they generally decrease with depth. Nondetrital Cu, Pb, and Zn likely derive from those metals held in ion exchange positions, certain carbonates, and from easily soluble amorphous compounds of Mn and perhaps those of Fe. Diagenetic processes involving Mn and to a lesser extent, Fe compounds, as well as the vertical changes in the oxidizing/reducing boundaries, appear to be the most important factors controlling the behavior of the metals in these cores. Organic matter and the aluminosilicate minerals, however, appear to be less important carriers of the metals studied.  相似文献   

12.
Since the heterogeneity of oceanographic conditions drives abundance, distribution, and availability of prey, it is essential to understand how foraging predators interact with their dynamic environment at various spatial and temporal scales. We examined the spatio-temporal relationships between oceanographic features and abundance of fin whales (Balaenoptera physalus), the largest free-ranging predator in the Western Mediterranean Sea (WM), through two independent approaches. First, spatial modeling was used to estimate whale density, using waiting distance (the distance between detections) for fin whales along ferry routes across the WM, in relation to remotely sensed oceanographic parameters. At a large scale (basin and year), fin whales exhibited fidelity to the northern WM with a summer-aggregated and winter-dispersed pattern. At mesoscale (20–100 km), whales were found in colder, saltier (from an on-board system) and dynamic areas defined by steep altimetric and temperature gradients. Second, using an independent fin whale satellite tracking dataset, we showed that tracked whales were effectively preferentially located in favorable habitats, i.e. in areas of high predicted densities as identified by our previous model using oceanographic data contemporaneous to the tracking period. We suggest that the large-scale fidelity corresponds to temporally and spatially predictable habitat of whale favorite prey, the northern krill (Meganyctiphanes norvegica), while mesoscale relationships are likely to identify areas of high prey concentration and availability.  相似文献   

13.
Whale depredation occurs when whales steal fish, damage fish or damage fishing gear. In Alaska, killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) primarily depredate on demersal sablefish (Anoplopoma fimbria) and Pacific halibut (Hippoglossus stenolepis) longline fisheries. Quantitative data on whale depredation in Alaska is limited due to low fishery observer coverage and minimal depredation evidence left on longline fishing gear. This study utilized semidirected interviews (n=70) and written questionnaires (n=95) with longline fishermen to examine: (1) perceptions and experiences of whale–fishery interactions in Alaska, (2) effects of depredation on fishing practices, and (3) potential depredation mitigation measures. Eighty-seven percent of fishermen surveyed agreed that whale depredation became worse between 1990 and 2010. Respondents reported changing their fishing practices in response to depredating whales in several ways, including: traveling up to 50 nautical miles and ceasing hauling operations up to 24 h until the whales left the fishing grounds. Respondents fishing in western Alaska, primarily encountering killer whales, were forced to wait longer and travel greater distances than fishermen operating in central and southeast Alaska, regions more affected by sperm whales. Deterrent research, gear modifications and real-time tracking of depredating whales were solutions favored by study participants. Survey respondent answers varied based on areas fished, quota owned, years involved in the fishery and vessel size. This study presents the first statewide evaluation of fishermen's perception and knowledge of whale interactions with the Alaskan longline fleet and is a critical step toward developing baseline data and feasible depredation mitigation strategies.  相似文献   

14.
90Sr,106Ru, natural strontium and major elements were studied in 12 samples of beach deposits from Togi, Fukuura and Shiga, and in 26 samples of shallow water sediments from sea off Fukuura, Noto Peninsula, Ishikawa Pref., Japan.The average contents of natural strontium and90Sr in the beach deposits were 488 ppm ranging from 247 to 1,550 ppm and 45±9 pCi kg–1-dry mud ranging from 18 to 72 pCi kg–1-dry mud, respectively. While the average contents of natural strontium,90Sr and106Ru in the sediments were 234 ppm ranging from 136 to 415 ppm, 22±6 pCi kg–1-dry sand ranging from 7 to 48 pCi kg–1-dry sand and 0.6 ±0.2 nCi kg–1-dry ranging from 0.3 to 1.2 nCi kg–1-dry, respectively.The average contents of each natural strontium and90Sr in the beach deposits were about two times higher than those in the shallow water sediments. But no obvious relation of natural strontium to90Sr was found in all the samples. The enrichment of90Sr and108Ru in the beach deposits or tthe sediments were as high as 150320 and of 2,0003,000 compared with average contents of90Sr and106Ru in a liter of surface water from the Japan Sea. It is to be noticed that the average106Ru to90Sr ratio of 27 for the shallow water sediments is much higher than the average of 1.0 for surface sea water of the Japan Sea.As to major elements of the samples, the beach deposits are rich in silicon (Av. 70.89 ±0.92% SiO2), but poor in iron (Av. 2.99±0.32% Fe2O3). Whereas the shallow water sediments are poor in silicon (Av. 52.96±10.33% SiO2) and rich in iron (Av. 5.50±1.90% Fe2O3), calcium (Av. 9.64±9.22% CaO) and magnesium (Av. 2.83±1.58% MgO).  相似文献   

15.
The activity concentrations of dissolved137Cs have been determined in the water column and137Cs and134Cs in the sediments and the sediment porewaters of the southern Baltic Sea. The mean activity concentration of dissolved137Cs in the Gdansk Deep declined from 109 Bq m−3in June 1986 to 61 Bq m−3in 1999. In sediments, the activity concentrations of137Cs (33-231 Bq kg−1) were highest in muds and the activity concentrations of134Cs were about 6% of the total Cs activity. The Chernobyl contribution to137Cs activity was between 43% and 77%. The porewater activity concentrations of137Cs in muddy sediments were in the range 71 to 3900 Bq m−3and were higher than those in the overlying seawater. The diffusive flux of dissolved137Cs from the muddy sediments was estimated in the range 5 to 480 Bq m−2year−1. The flux of137Cs from sediment porewaters of the southern Baltic Sea was about 45% of the total, including fluxes of137Cs from wet and dry atmospheric deposition and the fluvial inputs. The results were used to elucidate the rate of recovery of the sediments and the waters of the southern Baltic from Chernobyl-derived137Cs.  相似文献   

16.
In September 1993 (M26) and June/July 1996 (M36), a total of 239 surface samples (7 m depth) were collected on two transects across the open Atlantic Ocean (224 samples) and northwest European shelf edge area. We present an overview of the horizontal variability of dissolved Cd, Co, Zn, and Pb in between the northwest and northeast Atlantic Ocean in relation to salinity and the nutrients. Our data show a preferential incorporation of Cd relative to P in the particulate material of the surface ocean when related to previously published parallel measurements on suspended particulate matter from the same cruise. There is a good agreement with results recently estimated from a model by Elderfield and Rickaby (Nature 405 (2000) 305), who predict for the North Atlantic Ocean a best fit for αCd/P=[Cd/P]POM/[Cd/P]SW of 2.5, whereas the approach of our transect shows a αCd/P value of 2.6. The Co concentrations of our transects varied from <5 to 131 pmol kg−1, with the lowest values in the subtropical gyre. There were pronounced elevations in the low-salinity ranges of the northwest Atlantic and towards the European shelf. The Co data are decoupled from the Mn distribution and support the hypothesis of marginal inputs as the dominant source. Zinc varied from a minimum of <0.07 nmol kg−1 to a maximum of 1.2 and 4.8 nmol kg−1 in regions influenced by Labrador shelf or European coastal waters, respectively. In subtropical and northeast Atlantic waters, the average Zn concentration was 0.16 nmol kg−1. Zinc concentrations at nearly three quarters of the stations between 40°N and 60°N were <0.1 nmol kg−1. This suggests that biological factors control Zn concentrations in large areas of the North Atlantic surface waters. The Pb data indicated that significant differences in concentration between the northwest and northeast Atlantic surface waters presently (1996) do not exist for this metal. The transects in 1993 and 1996 exhibited Pb concentrations in the northeast Atlantic surface waters of 30 to 40 pmol kg−1, about a fifth to a quarter of the concentrations observed in 1981. This decline is supported by our particle flux measurements in deep waters of the same region.  相似文献   

17.
Three-year investigations into sperm whale-fall ecosystems in Japan   总被引：2，自引：0，他引：2  
We report the first study of sperm whale‐fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2‐year period on replicate sperm‐whale carcasses implanted at depths of 219–254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis‐based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep‐water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep‐water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale‐fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls.  相似文献   

18.
Recent carbonate data collected in the North Pacific were combined with the data in the literature in order to understand more clearly the carbonate chemistry in the North Pacific. Our analyses show that inorganic CaCO3 dissolution contributes about 26% of the total inorganic CO2 increase of deep water, after leaving the Southern Ocean. The calcium and alkalinity data indicate a CaCO3 dissolution rate of 0.060±0.010 and 0.053±0.005 µ mol kg–1 yr–1 respectively, for waters deeper than 2,000 m in reference to the Weddell Sea Deep Water. The organic carbon decomposition rate is 0.107±0.012 µ mol kg–1 yr–1 while the oxygen consumption rate is 0.13±0.002 µ mol kg–1 yr–1. These results which are based on the direct comparison of two water masses agree well with other estimates which are based on methods such as the one-dimensional-diffusion-advection model. Comparison of data along the two sections at 165°E and 150°W shows no significant difference in the ratio of the CaCO3 dissolution rate and the organic carbon decomposition rate. The eastern section, however, has a higher TCO2 input than the western section because of the older age of the deep water along the eastern section.  相似文献   

19.
The sperm whale is one of the very few deep diving mammal species in the Mediterranean Sea. Following a rare mass stranding of male sperm whales in the Adriatic Sea in December 2009, photo-identification methods were used in order to investigate previous sightings of the stranded whales in the region. Fluke photos of the stranded whales were compared with those of 153 and 128 free-ranging individuals photographed in the western and eastern Mediterranean basins, respectively. Three out of the seven stranded whales had been previously photo-identified and some of them more than once. To reach the stranding place, two of these re-identified whales performed long-range inter-basin movements of about 1600-2100 km (in a straight line) either through the Strait of Sicily or the Strait of Messina. In addition, comparisons among all whales photographed in the two Mediterranean basins revealed that one more individual first photographed in the western basin (1991) was re-identified 13 years later in the eastern basin (2004). These three cases provide the first conclusive evidence of inter-basin movement of sperm whales in the Mediterranean Sea. Inter-basin gene flow is important for the survival of the small and endangered Mediterranean sperm whale population. Mitigating the disturbance created by human activities in the straits area is crucial for its conservation.  相似文献   

20.
Cetacean research, in terms of the number of papers, and areas for which data are available, has expanded considerably in the southern African subregion in the past decade, especially in the South-West Indian Ocean. We review cetacean research within this subregion from the 1800s to the present to provide an overview of findings, investigate trends and identify knowledge gaps. Data are presented separately for large whales (those subject to commercial whaling) and smaller cetaceans, and are separated by era and ocean basin. Over 550 peer-reviewed papers and books were identified relating to research on cetaceans within the subregion. More than half (284) have been produced since 1990 and 193 relate specifically to South African waters. The most-studied species are those that are most accessible due to their coastal distributions (southern right whale Eubalaena australis: 45 papers, humpback whale Megaptera novaeangliae: 31 papers, killer whales Orcinus orca: 27 papers, Indo-Pacific bottlenose dolphin Tursiops aduncus: 30 papers, Indo-Pacific humpback dolphin Sousa chinensis (plumbea form): 25 papers) and/or were hunted commercially (sperm whale Physeter macrocephalus: 25 papers). Identified conservation concerns vary throughout the subregion, but include bycatch and directed hunts, oil and gas development, ecotourism activities, shifts in prey resources, and noise and chemical pollution. The inshore stocks of Bryde's whales Balaenoptera edeni, the Indo-Pacific humpback dolphin and the Atlantic humpback dolphin S. teuszii were identified as the populations of highest conservation concern, although there are considerable knowledge gaps relating to deep-water species and almost no data (even on species occurrence) are available for several areas and countries.  相似文献   

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