Isotopic niche width differentiation between common bottlenose dolphin ecotypes and sperm whales in the Gulf of California

2017 ◽  
Vol 34 (2) ◽  
pp. 440-457 ◽  
Author(s):  
Raúl E. Díaz-Gamboa ◽  
Diane Gendron ◽  
Geraldine Busquets-Vass
Keyword(s):  
Bottlenose Dolphin ◽  
Gulf Of California ◽  
Niche Width ◽  
Isotopic Niche ◽  
Sperm Whales ◽  
Common Bottlenose Dolphin ◽  
Isotopic Niche Width

scholarly journals Observations of cetaceans off southern Sri Lanka, April 2007–2013

2019 ◽  
Vol 20 (1) ◽  
pp. 13-25
Author(s):  
R. C. Anderson ◽  
A. Alagiyawadu
Keyword(s):  
Sri Lanka ◽  
Bottlenose Dolphin ◽  
Sperm Whale ◽  
Abundant Species ◽  
Sperm Whales ◽  
Spotted Dolphin ◽  
Common Bottlenose Dolphin ◽  
Westward Movement ◽  
Number Of Individuals ◽  
Blue Whales

Cetaceans were observed off the South coast of Sri Lanka in the month of April, every year over a seven-year period, 2007–13. During 48 days atsea a total of 290 cetacean sightings were recorded. Blue whales were abundant, accounting for 61% (n = 177) of all sightings. This concentrationof blue whales was predicted and discovered based on a migration hypothesis and there was evidence of the expected net westward movement inApril. Nevertheless, most blue whales seen were not obviously on passage and many appeared to be feeding. Mothers with calves and likelyreproductive behaviour (breaching and rushing) were also observed. There were five sightings of Bryde’s-type whales (B. brydei/edeni); four wereidentified as B. brydei, one was identified as B. edeni. Sperm whales were sighted 16 times within a narrow band centred just outside the 1,000misobath. Modal group size was 10–12; based on size most individuals appeared to be mature females or immatures. Spinner dolphin (n = 35 sightings)was the most abundant species, accounting for 67% of all cetaceans seen by number of individuals. They were frequently associated with tuna andseabirds. Risso’s dolphin was only seen once, despite being reported as common around Sri Lanka in the early 1980s. They were taken in largenumbers by local fisheries, which may have reduced local abundance. Other species recorded were: dwarf sperm whale (n = 3 sightings); shortfinnedpilot whale (n = 3); common bottlenose dolphin (n = 9); Indo-Pacific bottlenose dolphin (n = 3); pantropical spotted dolphin (n = 4); andstriped dolphin (n = 4). Since the discovery of blue whales off southern Sri Lanka, commercial whale watching centred on the fishing port of Mirissahas developed rapidly, bringing new revenue to the region but also the potential for disturbance to the whales.

Size‐based differences in isotopic niche width (δ 13 C and δ 15 N) of green turtles ( Chelonia mydas ) nesting on Príncipe Island, Gulf of Guinea

2021 ◽  
Vol 42 (1) ◽  
Author(s):  
Rogério L. Ferreira ◽  
Filipe R. Ceia ◽  
Teresa C. Borges ◽  
Jaime A. Ramos ◽  
Alan B. Bolten
Keyword(s):  
Chelonia Mydas ◽  
Niche Width ◽  
Isotopic Niche ◽  
Gulf Of Guinea ◽  
Green Turtles ◽  
Isotopic Niche Width

The effects of spatial scale and isoscape on consumer isotopic niche width

2018 ◽  
Vol 32 (4) ◽  
pp. 904-915 ◽  
Author(s):  
Carl J. Reddin ◽  
John H. Bothwell ◽  
Nessa E. O'Connor ◽  
Chris Harrod
Keyword(s):  
Spatial Scale ◽  
Niche Width ◽  
Isotopic Niche ◽  
Isotopic Niche Width

scholarly journals Resource use and the impacts of fisheries on two sympatric sea snake species on the West Coast of India.

2021 ◽  
Author(s):  
Shawn Dsouza ◽  
Chetan Rao ◽  
Muralidharan Manoharakrishnan ◽  
Kartik Shanker
Keyword(s):  
Food Webs ◽  
Resource Use ◽  
West Coast ◽  
Niche Width ◽  
Isotopic Niche ◽  
The West ◽  
Sea Snake ◽  
Snake Species ◽  
West Coast Of India ◽  
Isotopic Niche Width

Abstract Species interactions are central to community assembly and ecosystem functioning. Sea snakes play an important role as mesopredators and as intermediate links in coastal marine food webs. However, they are impacted by anthropogenic pressures such as fisheries throughout their range. We investigated differences in resource use between two sympatric sea snake species from the west coast of India, Hydrophis curtus and H. schistosus, and described the impacts of fishing on the interactions of these species. We compared habitat use, diet, and isotopic niche width between species to determine resource overlap. We then compared trophic overlap of each species with the fisheries in the region and tested the effect of fishing intensity on their isotopic niche width. We found that H. curtus used deeper habitats than H. schistosus, resulting in increased spatial overlap with fisheries. The two species also had distinct trophic niches and H. curtus prey formed a larger proportion of fishery catch on average than H. schistosus. This greater overlap could make H. curtus more vulnerable to the effects of fisheries. Both species exhibited expansion in short-term and long-term isotopic niche width along a gradient of fishing intensity which may indicate behavioural changes associated with the presence of fisheries. Hydrophis curtus is a trophic generalist, competes with syntopic species and is dominant in most assemblages. However, H. schistosus exhibits higher plasticity in resource use and may have an advantage over H. curtus. Thus, fishing could alter the relative abundance of these mesopredators with cascading effects through coastal food webs.

Can variations in the spatial distribution at sea and isotopic niche width be associated with consistency in the isotopic niche of a pelagic seabird species?

2014 ◽  
Vol 161 (8) ◽  
pp. 1861-1872 ◽  
Author(s):  
Filipe R. Ceia ◽  
Vitor H. Paiva ◽  
Stefan Garthe ◽  
João C. Marques ◽  
Jaime A. Ramos
Keyword(s):  
Spatial Distribution ◽  
Niche Width ◽  
Isotopic Niche ◽  
Seabird Species ◽  
Pelagic Seabird ◽  
Isotopic Niche Width

First Leucistic Bottlenose Dolphin (Tursiops truncatus) Sighting Registered in the Gulf of California, Mexico

2019 ◽  
Vol 45 (5) ◽  
pp. 507-512
Author(s):  
Héctor Pérez-Puig ◽  
Gisela Heckel ◽  
Lorayne Meltzer
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Gulf Of California

scholarly journals Long-term monitoring for the surveillance of the conservation status of Tursiops truncatus in an EU Natura2000 site in the Mediterranean Sea. A pilot study in the Tuscan Archipelago

2021 ◽  
Author(s):  
ANTONELLA ARCANGELI ◽  
ROBERTO CROSTI ◽  
ILARIA CAMPANA ◽  
LARA CAROSSO ◽  
MARTINA GREGORIETTI ◽  
...  
Keyword(s):  
Pilot Study ◽  
Mediterranean Sea ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Conservation Status ◽  
Natura 2000 ◽  
Research Network ◽  
Habitats Directive ◽  
Common Bottlenose Dolphin ◽  
The Mediterranean

A pilot study, using the dataset from the research network ‘FLT Med Net’, which regularly monitors transborder regions in the Mediterranean Sea using ferries as platform for systematic surveys, was undertaken to assess common bottlenose dolphin range and population trends within the Natura 2000 EU marine site “Tutela del Tursiops truncatus”. The site was recently designated by the Tuscany Region (Italy) within the requirement of the EU Habitats Directive. In order to evaluate the conservation status of bottlenose dolphin according to the surveillance scheme of the Directive, two six-year periods (2007-2012; 2013-2018) were compared to assess trends in distribution-occurrence (range); Sightings Per Unit of Effort and Density (population). In total, 18146 NM were surveyed along two fixed transects, recording 90 sightings of Tursiops truncatus and a total of 268 specimens. Between the two periods, slight but not statistically significant differences were assessed, with decreasing trend in range and population  of the species; no variation was detected in mean group sizes. Travelling was the most common behaviour, and juveniles were present in 20% of the sightings, concentrated during spring and summer. The consistent FLT Med Net dataset was found to be appropriate to evaluate important parameters for the assessment of trends in the conservation status of Tursiops truncatus at the Natura2000 site scale. 

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