scholarly journals Delphinid spatial distribution and abundance estimates over the shelf of the Bay of Biscay

2008 ◽  
Vol 65 (4) ◽  
pp. 656-666 ◽  
Author(s):  
G. Certain ◽  
V. Ridoux ◽  
O. van Canneyt ◽  
V. Bretagnolle
Keyword(s):  
Spatial Distribution ◽  
Large Scale ◽  
Bottlenose Dolphins ◽  
Shelf Break ◽  
Bay Of Biscay ◽  
Stenella Coeruleoalba ◽  
Abundance Estimate ◽  
Abundance Estimates ◽  
Common Dolphins ◽  
Strip Transect

Abstract Certain, G., Ridoux, V., van Canneyt, O., and Bretagnolle, V. 2008. Delphinid spatial distribution and abundance estimates over the shelf of the Bay of Biscay. – ICES Journal of Marine Science, 65: 656–666. The small delphinid community (bottlenose Tursiops truncatus, common Delphinus delphis, and striped Stenella coeruleoalba dolphins) of the Bay of Biscay (100 000 km2 of continental shelf along the French Atlantic coast) has been studied here by combining strip-transect aerial surveys conducted between 2001 and 2004 and ship-based surveys conducted between 2003 and 2006. Distribution was modelled spatially in relation to several large-scale descriptors of the environment. Highest densities of small delphinids were associated with the shelf break, in particular in two hotspots located in the north and the south of the bay. Using ship-based data, we found strong spatial segregation between common and bottlenose dolphins in spring, with common dolphins associated with coastal areas (and especially river plumes) and bottlenose dolphins on the outer shelf and the shelf break. Assuming a detection probability of 1, a strip-transect abundance estimate for the small delphinid community was obtained in August 2002 with 56 500 (95% CI 29 100–90 400), but relative abundance varied across months.

scholarly journals Determinants of lungworm specificity in five cetacean species in the western Mediterranean

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Rachel Pool ◽  
Clara Romero-Rubira ◽  
Juan Antonio Raga ◽  
Mercedes Fernández ◽  
Francisco Javier Aznar
Keyword(s):  
Bottlenose Dolphins ◽  
Parasite Burden ◽  
Western Mediterranean ◽  
Host Size ◽  
Cetacean Species ◽  
Stenella Coeruleoalba ◽  
Species Similarity ◽  
Pilot Whales ◽  
Common Dolphins ◽  
Prey Overlap

Abstract Background Current data about Pseudaliidae show contrasting patterns of host specificity between congeneric species. We investigated how both contact and compatibility between hosts and parasites contributed to the patterns of lungworm infection observed in a community of five species of cetaceans in the western Mediterranean. Methods The lungs of 119 striped dolphins Stenella coeruleoalba, 18 bottlenose dolphins Tursiops truncatus, 7 Risso’s dolphins Grampus griseus, 7 long-finned pilot whales Globicephala melas, and 6 common dolphins Delphinus delphis were analysed for lungworms. Parasites were identified by morphology and analysis of ITS2 sequences using both maximum likelihood and Bayesian inference methods. Body length was used as a proxy for lungworm species fitness in different hosts and compared with Kruskal-Wallis tests. Infection parameters were compared between cetacean species using Fisher’s exact tests and Kruskal-Wallis tests. Phylogenetic specificity was explored by collating the overall lungworm species prevalence values in hosts from previous surveys in various localities. To explore the relative importance of vertical and horizontal transmission, Spearman’s rank correlation was used to look for an association between host size and lungworm burden. A Mantel test was used to explore the association between lungworm species similarity and prey overlap using dietary data. Results Halocercus delphini had higher infection levels in striped dolphins and common dolphins; Stenurus ovatus had higher infection levels in bottlenose dolphins; and Stenurus globicephalae had higher infection levels in long-finned pilot whales. These results are congruent with findings on a global scale. Morphometric comparison showed that the larger nematodes were found in the same host species that had the highest parasite burden. Lungworms were found in neonatal striped dolphins and a Risso’s dolphin, and there was a weak but significant correlation between host size and parasite burden in striped dolphins and bottlenose dolphins. There was also a weak but significant association between prey overlap and lungworm species similarity. Conclusions Data indicate that phylogenetic specificity has an important role in governing host–parasite associations, as indicated by the higher infection levels and larger nematode size in certain hosts. However, diet can also influence infection patterns in these preferred hosts and contribute to less severe infections in other hosts.

Stomach contents of English Channel cetaceans stranded on the coast of Normandy

2005 ◽  
Vol 85 (6) ◽  
pp. 1539-1546 ◽  
Author(s):  
J.F. De Pierrepont ◽  
B. Dubois ◽  
S. Desormonts ◽  
M.B. Santos ◽  
J.P. Robin
Keyword(s):  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Stomach Contents ◽  
Important Species ◽  
Stenella Coeruleoalba ◽  
Delphinus Delphis ◽  
Common Squid ◽  
Pilot Whales ◽  
The University ◽  
Common Dolphins

During 1998–2003 stomach contents of 47 marine mammals stranded on the coast of Normandy were analysed. The animals were first examined by a veterinary network and stomach contents were analysed at the University of Caen. The sample comprised: 26 common dolphins (Delphinus delphis), four bottlenose dolphins (Tursiops truncatus), seven harbour porpoises (Phocoena phoecoena), five grey seals (Halichoerus grypus), two long-finned pilot whales (Globicephala melas), one white beaked dolphin (Lagenorhynchus albirostris), one minke whale (Balaenoptera acurostrata) and one striped dolphin (Stenella coeruleoalba). The identification of food items was done using hard parts (i.e. fish otoliths and cephalopod beaks). Diet indices were computed including prey frequency and percentage by number. Common dolphins ate mainly gadoid fish (Trisopterus sp.), gobies and mackerel (Scomber scombrus). Cephalopods occurred in small numbers in the diet and commercially important species (cuttlefish and common squid) were scarce.

scholarly journals An ecosystem approach for the assessment of fisheries impacts on marine top predators: the Bay of Biscay case study

2012 ◽  
Vol 69 (6) ◽  
pp. 925-938 ◽  
Author(s):  
Géraldine Lassalle ◽  
Didier Gascuel ◽  
François Le Loc'h ◽  
Jérémy Lobry ◽  
Graham John Pierce ◽  
...  
Keyword(s):  
Bottlenose Dolphins ◽  
Resource Depletion ◽  
Ecosystem Approach ◽  
Bay Of Biscay ◽  
Biological Interactions ◽  
Ecosystem Models ◽  
Top Predators ◽  
And Function ◽  
Common Dolphins

Abstract Lassalle, G., Gascuel, D., Le Loc'h, F., Lobry, J., Pierce, G. J., Ridoux, V., Santos, M. B., Spitz, J., and Niquil, N. 2012. An ecosystem approach for the assessment of fisheries impacts on marine top predators: the Bay of Biscay case study. – ICES Journal of Marine Science, 69: 925–938. A number of marine mammal populations is currently threatened by their interactions with fisheries. The present study aimed to provide insights into the severity of potential impacts of operational and biological interactions between top predators and fisheries, in the Bay of Biscay region. Our approach was to modify an Ecopath with Ecosim (EwE) model describing the overall structure and function of the ecosystem by including landings and discards of exploited stocks and estimations of the bycatch of non-target compartments. Second, a set of ecological indices and a trophic level (TL)-based model (EcoTroph, ET) were derived from the EwE model. ET was used to simulate the effects of increasing fishing pressure on the ecosystem and, more particularly, on top predators. The Bay of Biscay was demonstrated to be not far from overexploitation at the current fishing rate, this phenomenon being particularly noticeable for the highest TLs. Within the toothed cetacean community, bottlenose dolphins appeared the most sensitive to resource depletion, whereas common dolphins and harbour porpoises were most impacted by their incidental captures in fishing gears. This study provides a methodological framework to assess the impacts of fisheries on ecosystems for which EwE, or other ecosystem models, already exist.

scholarly journals Acoustic surveys for juvenile anchovy in the Bay of Biscay: abundance estimate as an indicator of the next year's recruitment and spatial distribution patterns

2013 ◽  
Vol 70 (7) ◽  
pp. 1354-1368 ◽  
Author(s):  
G. Boyra ◽  
U. Martínez ◽  
U. Cotano ◽  
M. Santos ◽  
X. Irigoien ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Distribution Patterns ◽  
Horizontal Distribution ◽  
Bay Of Biscay ◽  
Spatial Distribution Patterns ◽  
Abundance Estimate ◽  
Juvenile Abundance ◽  
Wide Range ◽  
Acoustic Surveys ◽  
Management Advice

Abstract Boyra, G., Martínez, U., Cotano, U., Santos, M., Irigoien, X., and Uriarte, A. 2013. Acoustic surveys for juvenile anchovy in the Bay of Biscay: abundance estimate as an indicator of the next year's recruitment and spatial distribution patterns. – ICES Journal of Marine Science, 70: . A series of acoustic surveys (JUVENA) began in 2003 targeting juvenile anchovy (Engraulis encrasicolus) in the Bay of Biscay. A specific methodology was designed for mapping and estimating juvenile abundance annually, four months after the spawning season. After eight years of the survey, a consistent picture of the spatial pattern of the juvenile anchovy has emerged. Juveniles show a vertical and horizontal distribution pattern that depends on size. The younger individuals are found isolated from other species in waters closer to the surface, mainly off the shelf within the mid-southern region of the bay. The largest juveniles are usually found deeper and closer to the shore in the company of adult anchovy and other pelagic species. In these eight years, the survey has covered a wide range of juvenile abundances, and the estimates show a significant positive relationship between the juvenile biomasses and the one-year-old recruits of the following year. This demonstrates that the JUVENA index provides an early indication of the strength of next year's recruitment to the fishery and can therefore be used to improve the management advice for the fishery of this short-lived species.

A robust baseline for bottlenose dolphin abundance in coastal Moreton Bay: a large carnivore living in a region of escalating anthropogenic impacts

2008 ◽  
Vol 35 (7) ◽  
pp. 593 ◽  
Author(s):  
Vimoksalehi Lukoschek ◽  
B. Louise Chilvers
Keyword(s):  
Bottlenose Dolphin ◽  
Anthropogenic Impacts ◽  
Bottlenose Dolphins ◽  
Estimation Methods ◽  
Line Transect ◽  
Mark Recapture ◽  
Abundance Estimate ◽  
Photo Identification ◽  
Moreton Bay ◽  
Abundance Estimates

Marine megafauna populations in coastal waters are increasingly threatened by anthropogenic impacts. Moreton Bay, a large embayment in south-east Queensland, lies adjacent to one of the fastest growing regions in Australia and has a resident population of bottlenose dolphins, Tursiops aduncus. Evaluation of the effectiveness of any proposed management strategy requires robust population abundance estimates. We estimated abundances of bottlenose dolphins in central eastern Moreton Bay (350 km2) using two commonly used abundance estimation methods for cetaceans: photo-identification mark–recapture and line-transect surveys. Mark–recapture data were analysed in CAPTURE using a model that allowed capture probabilities to vary between sampling events and between individuals. Based on an estimated 76% of the population identifiable photographically, total abundance estimates were 673 ± 130 s.e. (1997) and 818 ± 152 s.e. (1998). Line-transect data, analysed using DISTANCE, gave an abundance estimate of 407 ± 113.5 s.e. (2000). These abundance estimates are large compared with many other coastal bottlenose dolphin populations. The line-transect surveys comprised a pilot study, and the lower line-transect abundance estimate is probably best attributable to methodological issues. In particular, smaller mean group size was estimated for the line-transects surveys (2.85 ± 0.29 s.e.) than the mark–recapture surveys (4.87 ± 0.39 s.e., 1997; 5.78 ± 0.73 s.e., 1998), and line-transect group sizes were probably underestimated. In addition, the line-transect detection probability (g(o)) was assumed to be one but was almost certainly less than one. However, the possibility of an actual decline in population size cannot be ruled out. Coefficients of variation (CV) were lower for mark–recapture than for line-transect surveys, however, CVs of line-transect estimates could be lowered through improved survey design. We evaluated the power of these surveys to detect trends in potential population declines for bottlenose dolphins in Moreton Bay and make recommendations for ongoing monitoring strategies.

Host specificity ofOschmarinella rochebruniandBrachycladium atlanticum(Digenea: Brachycladiidae) in five cetacean species from western Mediterranean waters

2010 ◽  
Vol 85 (1) ◽  
pp. 12-19 ◽  
Author(s):  
P. Mateu ◽  
J.A. Raga ◽  
F.J. Aznar
Keyword(s):  
Host Species ◽  
Bottlenose Dolphins ◽  
Western Mediterranean ◽  
Its2 Region ◽  
Single Individual ◽  
Common Dolphin ◽  
Cetacean Species ◽  
Stenella Coeruleoalba ◽  
Pilot Whales ◽  
Common Dolphins

AbstractWe investigated patterns of specificity of liver flukes (fam. Brachycladiidae) in a community of cetaceans from the western Mediterranean. The liver and pancreas of 103 striped dolphins,Stenella coeruleoalba, 18 Risso's dolphins,Grampus griseus, 14 bottlenose dolphins,Tursiops truncatus, 8 common dolphins,Delphinus delphis, and 5 long-finned pilot whales,Globicephala melas, were analysed for brachycladiid species. Two species were found:Oschmarinella rochebruniin striped dolphins (prevalence (P): 61.2%; mean intensity (MI) (95% CI): 34.2 (25.7–45.6)), andBrachycladium atlanticumin striped dolphins (P: 39.8%; MI: 7.1 (4.8–13.1)) and a single individual of common dolphin (P: 12.5%; intensity: 19), which represents a new host record. A molecular analysis using the internal transcribed spacer 2 (ITS2) region of the rDNA gene confirmed that specimens ofB. atlanticumwere conspecific regardless of host species. Available dietary data suggest that Risso's dolphins, bottlenose dolphins and long-finned pilot whales would contact rarely, if at all, the infective stages ofO. rochebruniandB. atlanticum. Neither the prevalence nor the mean abundance ofB. atlanticumdiffered significantly between striped and common dolphins, but a principal component analysis using seven morphometric variables indicated that specimens collected from the common dolphin were stunted. These worms also had fewer eggs compared with specimens typically found in striped dolphins, although the size of the eggs was similar in both host species. Dwarfism and low fecundity have typically been found in helminths infecting unusual host species, and might reflect the lower compatibility ofB. atlanticumfor common dolphins. In summary, bothO. rochebruniandB. atlanticumappear to exhibit a narrow specificity for striped dolphins in the western Mediterranean.

Cetacean stranding and diet analyses in the North Aegean Sea (Greece)

2017 ◽  
Vol 98 (5) ◽  
pp. 1011-1028 ◽  
Author(s):  
C.B. Milani ◽  
A. Vella ◽  
P. Vidoris ◽  
A. Christidis ◽  
E. Koutrakis ◽  
...  
Keyword(s):  
Bottlenose Dolphins ◽  
Aegean Sea ◽  
Cetacean Species ◽  
Stenella Coeruleoalba ◽  
The North ◽  
Aegean Islands ◽  
North Aegean ◽  
Diet Analyses ◽  
North Aegean Sea ◽  
Common Dolphins

Cetacean stranding reports in the North Aegean Sea were recorded since 1998 from Strimonikos Gulf in Chalkidiki up to Alexandroupoli on the Turkish border and in a few northern Aegean islands. On site, the specimens were examined to identify species, gender, approximate age and, when possible, cause for stranding. A total of 26 filled stomachs of five cetacean species collected since 2002 were analysed: bottlenose dolphinsTursiops truncatus(N = 8), common dolphinsDelphinus delphis(N = 8), harbour porpoisesPhocoena phocoena(N = 5), striped dolphinsStenella coeruleoalba(N = 4) and Risso's dolphinsGrampus griseus(N = 1). From the analysed stomachs it was found that the bottlenose dolphins fed mainly on snake blennyOphidion barbatum(34%), bogueBoops boops(22%) and round sardinellaSardinella aurita(13%); common dolphins on round sardinella (17%), picarelsSpicaraspp. (10%) and Cocco's lantern fishLobianchia gemellaris(9%); harbour porpoises on Gobidae (four-spotted gobyDeltentosteus quadrimaculatus41% and black gobyGobius niger37%) and round sardinella (7%); striped dolphins on Myctophydae (Madeira lantern fishCeratoscopelus maderensis51%), and on Pfeffer's enople squidAbraliopsis morisii(10%) and bogue (8%); and Risso's dolphin exclusively on Teuthidae (31%), the umbrella squidHistioteuthis bonellii(30%) and the reverse jewel squidH. reversa(14%). The present work represents the first attempt to investigate the diet up to species level for several cetaceans in Greek waters and for harbour porpoises stranded in the Mediterranean Sea.

Large-scale mapping of the catenas vegetation in Subarctic tundra

1995 ◽  
pp. 3-21
Author(s):  
S. S. Kholod
Keyword(s):  
Spatial Distribution ◽  
Vegetation Cover ◽  
Large Scale ◽  
Block Diagram ◽  
Abiotic Factors ◽  
Ecological Factors ◽  
Spatial Arrangement ◽  
Geological Time ◽  
Ecological Barriers ◽  
Functional Zones

One of the most difficult tasks in large-scale vegetation mapping is the clarification of mechanisms of the internal integration of vegetation cover territorial units. Traditional way of searching such mechanisms is the study of ecological factors controlling the space heterogeneity of vegetation cover. In essence, this is autecological analysis of vegetation. We propose another way of searching the mechanisms of territorial integration of vegetation. It is connected with intracoenotic interrelation, in particular, with the changing role of edificator synusium in a community along the altitudinal gradient. This way of searching is illustrated in the model-plot in subarctic tundra of Central Chukotka. Our further suggestion concerns the way of depicting these mechanisms on large-scale vegetation map. As a model object we chose the catena, that is the landscape formation including all geomorphjc positions of a slope, joint by the process of moving the material down the slope. The process of peneplanation of a mountain system for a long geological time favours to the levelling the lower (accumulative) parts of slopes. The colonization of these parts of the slope by the vegetation variants, corresponding to the lowest part of catena is the result of peneplanation. Vegetation of this part of catena makes a certain biogeocoenotic work which is the levelling of the small infralandscape limits and of the boundaries in vegetation cover. This process we name as the continualization on catena. In this process the variants of vegetation in the lower part of catena are being broken into separate synusiums. This is the process of decumbation of layers described by V. B. Sochava. Up to the slope the edificator power of the shrub synusiums sharply decreases. Moss and herb synusium have "to seek" the habitats similar to those under the shrub canopy. The competition between the synusium arises resulting in arrangement of a certain spatial assemblage of vegetation cover elements. In such assemblage the position of each element is determined by both biotic (interrelation with other coenotic elements) and abiotic (presence of appropriate habitats) factors. Taking into account the biogeocoenotic character of the process of continualization on catena we name such spatial assemblage an exolutionary-biogeocoenotic series. The space within each evolutionary-biogeocoenotic series is divided by ecological barriers into some functional zones. In each of the such zones the struggle between synusiums has its individual expression and direction. In the start zone of catena (extensive pediment) the interrelations of synusiums and layers control the mutual spatial arrangement of these elements at the largest extent. Here, as a rule, there predominate edificator synusiums of low and dwarfshrubs. In the first order limit zone (the bend of pediment to the above part of the slope) one-species herb and moss synusiums, oftenly substituting each other in similar habitats, get prevalence. In the zone of active colonization of slope (denudation slope) the coenotic factor has the least role in the spatial distribution of the vegetation cover elements. In particular, phytocoenotic interactions take place only within separate microcoenoses of herbs, mosses and lichens. In the zone of the attenuation of continualization process (the upper most parts of slope, crests) phytocoenotic interactions are almost absent and the spatial distribution of vegetation cover elements depends exclusively on the abiotic factors. The principal scheme of the distribution of vegetation cover elements and the disposition of functional zones on catena are shown on block-diagram (fig. 1).

scholarly journals Modeling Spatiotemporal Population Changes by Integrating DMSP-OLS and NPP-VIIRS Nighttime Light Data in Chongqing, China

2021 ◽  
Vol 13 (2) ◽  
pp. 284
Author(s):  
Dan Lu ◽  
Yahui Wang ◽  
Qingyuan Yang ◽  
Kangchuan Su ◽  
Haozhe Zhang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Relative Error ◽  
Urban Areas ◽  
Large Scale ◽  
Population Distribution ◽  
Spatial Optimization ◽  
Distribution Data ◽  
Mountainous Areas ◽  
Mean Relative Error ◽  
Nighttime Light

The sustained growth of non-farm wages has led to large-scale migration of rural population to cities in China, especially in mountainous areas. It is of great significance to study the spatial and temporal pattern of population migration mentioned above for guiding population spatial optimization and the effective supply of public services in the mountainous areas. Here, we determined the spatiotemporal evolution of population in the Chongqing municipality of China from 2000–2018 by employing multi-period spatial distribution data, including nighttime light (NTL) data from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) and the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS). There was a power function relationship between the two datasets at the pixel scale, with a mean relative error of NTL integration of 8.19%, 4.78% less than achieved by a previous study at the provincial scale. The spatial simulations of population distribution achieved a mean relative error of 26.98%, improved the simulation accuracy for mountainous population by nearly 20% and confirmed the feasibility of this method in Chongqing. During the study period, the spatial distribution of Chongqing’s population has increased in the west and decreased in the east, while also increased in low-altitude areas and decreased in medium-high altitude areas. Population agglomeration was common in all of districts and counties and the population density of central urban areas and its surrounding areas significantly increased, while that of non-urban areas such as northeast Chongqing significantly decreased.

scholarly journals Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 275
Author(s):  
Daniela Silvia Pace ◽  
Chiara Di Marco ◽  
Giancarlo Giacomini ◽  
Sara Ferri ◽  
Margherita Silvestri ◽  
...  
Keyword(s):  
Population Size ◽  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
River Estuary ◽  
Suitable Habitat ◽  
Tyrrhenian Sea ◽  
Abundance Estimate ◽  
Photo Identification ◽  
Tiber River

Periodic assessments of population status and trends to detect natural influences and human effects on coastal dolphin are often limited by lack of baseline information. Here, we investigated for the first time the site-fidelity patterns and estimated the population size of bottlenose dolphins (Tursiops truncatus) at the Tiber River estuary (central Mediterranean, Tyrrhenian Sea, Rome, Italy) between 2017 and 2020. We used photo-identification data and site-fidelity metrics to study the tendency of dolphins to remain in, or return to, the study area, and capture–recapture models to estimate the population abundance. In all, 347 unique individuals were identified. The hierarchical cluster analysis highlighted 3 clusters, labeled resident (individuals encountered at least five times, in three different months, over three distinct years; n = 42), part-time (individuals encountered at least on two occasions in a month, in at least two different years; n = 73), and transient (individuals encountered on more than one occasion, in more than 1 month, none of them in more than 1 year; n = 232), each characterized by site-fidelity metrics. Open POPAN modeling estimated a population size of 529 individuals (95% CI: 456–614), showing that the Capitoline (Roman) coastal area and nearby regions surrounding the Tiber River estuary represent an important, suitable habitat for bottlenose dolphins, despite their proximity to one of the major urban centers in the world (the city of Rome). Given the high number of individuals in the area and the presence of resident individuals with strong site fidelity, we suggest that conservation plans should not be focused only close to the Tiber River mouths but extended to cover a broader scale of area.

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