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Accepted Article Accepted ArticleThis article is protected by copyright. All rights reserved. By including a quantitative modelling approach, our study explicitly took evolutionary processes into account for informing the conservatio… Show more
1. Protecting species often involves the designation of protected areas, wherein suitable management strategies are applied either at the taxon or ecosystem level. Special Areas of Conservation (SACs) have been created in European waters under the Habitats Directive to protect bottlenose dolphins, Tursiops truncatus, which forms two ecotypes, pelagic and coastal.
1. Protecting species often involves the designation of protected areas, wherein suitable management strategies are applied either at the taxon or ecosystem level. Special Areas of Conservation (SACs) have been created in European waters under the Habitats Directive to protect bottlenose dolphins, Tursiops truncatus, which forms two ecotypes, pelagic and coastal.
“…Allen et al . 29 , however, illustrated that the dolphins interacting with the PTF are a different species and genetically isolated from the coastal Indo-Pacific bottlenose dolphin populations and this study shows that the number of common bottlenose dolphins ( T. truncatus ) interacting with the PTF is relatively small. Determinations such as “Given the area of distribution and expected population size of these protected species, the impact of the trawl on the stocks of these protected species is probably minimal”; that up to 75 dolphin mortalities year −1 is an “acceptable” limit; and that mortalities from bycatch pose “negligible risk” to the dolphin population 32, 35, 51 have been made in the absence of fundamental data on mortality rates and abundance, and appear to be overly optimistic.…”
Section: Discussionmentioning
confidence: 58%
“…Samples should be gathered from common bottlenose dolphins in adjacent areas to assess levels of gene flow, or the degree of isolation of the fishery-impacted community 29 , and to better-define population boundaries and/or establish management or conservation units 62 .…”
Section: Discussionmentioning
confidence: 99%
“…Small tissue samples were collected, stored and analysed as described in Allen et al . 29 . The software microsatellite toolkit 77 was used to determine identical genotypes among all sampled individuals.…”
Section: Methodsmentioning
confidence: 99%
“…Common bottlenose dolphins ( Tursiops truncatus , ‘bottlenose dolphins’ hereafter) are well known globally 28 , but considered ‘data deficient’ around Australia, where they tend to occur in pelagic habitats, more distant from the coast and human population centres than the closely related Indo-Pacific bottlenose dolphins ( T. aduncus ) 22, 29 . No population estimates for T. truncatus exist in Australian waters, and our limited knowledge from north-western Australia is a result of relatively recent research due to their bycatch in the Pilbara Fish Trawl Interim Managed Fishery (‘Pilbara Trawl Fishery’, or ‘PTF’, hereafter - Fig.…”
The incidental capture of wildlife in fishing gear presents a global conservation challenge. As a baseline to inform assessments of the impact of bycatch on bottlenose dolphins (Tursiops truncatus) interacting with an Australian trawl fishery, we conducted an aerial survey to estimate dolphin abundance across the fishery. Concurrently, we carried out boat-based dolphin photo-identification to assess short-term fidelity to foraging around trawlers, and used photographic and genetic data to infer longer-term fidelity to the fishery. We estimated abundance at ≈ 2,300 dolphins (95% CI = 1,247–4,214) over the ≈ 25,880-km2 fishery. Mark-recapture estimates yielded 226 (SE = 38.5) dolphins associating with one trawler and some individuals photographed up to seven times over 12 capture periods. Moreover, photographic and genetic re-sampling over three years confirmed that some individuals show long-term fidelity to trawler-associated foraging. Our study presents the first abundance estimate for any Australian pelagic dolphin community and documents individuals associating with trawlers over days, months and years. Without trend data or correction factors for dolphin availability, the impact of bycatch on this dolphin population’s conservation status remains unknown. These results should be taken into account by management agencies assessing the impact of fisheries-related mortality on this protected species.
The functioning of marine protected areas (MPAs) designated for marine megafauna has been criticized due to the high mobility and dispersal potential of these taxa. However, dispersal within a network of small MPAs can be beneficial as connectivity can result in increased effective population size, maintain genetic diversity, and increase robustness to ecological and environmental changes making populations less susceptible to stochastic genetic and demographic effects (i.e., Allee effect). Here, we use both genetic and photo‐identification methods to quantify gene flow and demographic dispersal between MPAs of a highly mobile marine mammal, the bottlenose dolphin Tursiops truncatus. We identify three populations in the waters of western Ireland, two of which have largely nonoverlapping core coastal home ranges and are each strongly spatially associated with specific MPAs. We find high site fidelity of individuals within each of these two coastal populations to their respective MPA. We also find low levels of demographic dispersal between the populations, but it remains unclear whether any new gametes are exchanged between populations through these migrants (genetic dispersal). The population sampled in the Shannon Estuary has a low estimated effective population size and appears to be genetically isolated. The second coastal population, sampled outside of the Shannon, may be demographically and genetically connected to other coastal subpopulations around the coastal waters of the UK. We therefore recommend that the methods applied here should be used on a broader geographically sampled dataset to better assess this connectivity.
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