High pollutant exposure level of the largest European community of bottlenose dolphins in the English Channel

Abstract The objective of this study was to assess the levels of persistent organic pollutants (POPs) and mercury (T-Hg) in the blubber and skin, respectively, of the free-ranging bottlenose dolphins, Tursiops truncatus, from the Normanno-Breton Gulf, one of the largest identified coastal population in Europe. Among all the POPs analysed in this study, the ∑NDL-PCBs were the most abundant compounds found in the blubber (mean: 1.33 × 105–0.65 × 105 ng.g−1 lipid weight (lw) for males and females respectively), followed by ∑DDX (1.11 × 104–4.67 × 103 ng.g−1 lw) > ∑DL-PCBs (8.06 × 103–2.62 × 103ng.g−1 lw) > ∑PBDEs (1.95 × 103–0.64 × 103ng.g−1 lw) > dieldrin (1.86 × 103–0.18 × 103 ng.g−1 lw) > ∑endosulfan (405–62 ng.g−1 lw) > HCB (86–52 ng.g−1 lw) > ∑HCHs (47–60 ng.g−1 lw) > ∑chlordane (24–0.97 ng.g−1 lw) > ∑PCDFs (0.3–0.1 ng.g−1 lw) > ∑PCDDs (0.06–0.05 ng.g−1 lw). The T-Hg concentrations were highly variable between individuals (2.45 × 103 ng.g−1 to 21.3 × 103 ng.g−1 dry weight, dw). The reported concentrations are among the highest reported for cetaceans. We strongly recommend that the Normanno-Breton Gulf be a special area of conservation (cSAC) candidate because it contains the last large European population of bottlenose dolphins (rare or threatened within a European context) designated under the EC Habitats Directive.

Download Full-text

Foraging Behavior of Bottlenose Dolphins in the Shannon Estuary, Ireland as Determined through Static Acoustic Monitoring

Journal of Marine Science and Engineering ◽

10.3390/jmse9030275 ◽

2021 ◽

Vol 9 (3) ◽

pp. 275

Author(s):

Mathijs Carmen ◽

Simon D. Berrow ◽

Joanne M. O’Brien

Keyword(s):

Foraging Behavior ◽

Bottlenose Dolphins ◽

Industrial Area ◽

Acoustic Monitoring ◽

Habitats Directive ◽

Foraging Area ◽

Special Area ◽

High Conservation ◽

Eu Habitats Directive ◽

The Eu

The Shannon Estuary in Ireland is home to a resident population of bottlenose dolphins (Tursiops truncatus) and is designated as a Special Area of Conservation under the EU Habitats Directive. It is an important industrial area, with numerous deep-water berths for shipping. Despite its high conservation value, there are few published studies on habitat use or foraging behavior of the Shannon dolphins throughout the year. The present study assessed the year-round presence and foraging activity of bottlenose dolphins at different locations in the middle and inner estuary using static acoustic monitoring. Dolphin presence was found to decrease with increased distance from the estuary mouth, i.e., where the estuary meets the Atlantic Ocean, while at the same time, foraging was found to be considerably higher in the upriver areas, suggesting the inner estuary was an important foraging area. Model predictions for seasonal, tidal and diel foraging were highly variable across locations, indicating that changes in dolphin behavior occurred over relatively small geographical scales. These results indicate that conservation efforts should consider the Shannon Estuary as a dynamic aggregation of habitats and future development initiatives should attempt to mitigate disturbance to the dolphins during important foraging periods on seasonal and diel scales.

Download Full-text

Behaviourally specific preferred associations in bottlenose dolphins, Tursiops spp.

Canadian Journal of Zoology ◽

10.1139/z05-155 ◽

2005 ◽

Vol 83 (12) ◽

pp. 1566-1573 ◽

Cited By ~ 57

Author(s):

S Gero ◽

L Bejder ◽

H Whitehead ◽

J Mann ◽

R C Connor

Keyword(s):

Social Relationships ◽

Bottlenose Dolphins ◽

Adult Males ◽

Short Term ◽

Shark Bay ◽

Behavioural State ◽

The Social ◽

Association Group ◽

Males And Females ◽

Free Ranging

We investigated association patterns of 52 photographically identified, free-ranging bottlenose dolphins (Tursiops spp. Gervais, 1855) across four behavioural states (rest, travel, social, and foraging/feeding) to investigate how behavioural state influences patterns of association. Group composition and behavioural data were extracted from 2178 encounter surveys collected over 3 years. Analyses revealed three general types of association: (1) affiliates, which consistently demonstrate preferred associations across all behavioural states; (2) acquaintances, which never form preferred associations but still associate in at least one behavioural state; and (3) behavioural associates, which form preferred associations in at least one, but not all behavioural states. The majority of associations in Shark Bay, Australia, are acquaintance type (38.2%), with affiliates (5.7%, principally between adult males) and behavioural associates (28.9%, principally between juveniles) being relatively rarer. Permutation tests identified behaviourally specific preferred associations during all behavioural states. Although behaviourally specific preferred associations appear to exist within the Shark Bay social structure, it seems that the social organization and mating system constrain the social relationships for the majority of males and females in differing ways which prevent them from having behavioural associates, leaving juveniles free to associate based on short-term expediency and behavioural specific needs.

Download Full-text