Monteiro S.S.,University of Minho |
Monteiro S.S.,University of Aveiro |
Mendez-Fernandez P.,CNRS Coastal and Marine Environment Laboratory |
Mendez-Fernandez P.,University of Sao Paulo |
And 13 more authors.
Marine Ecology Progress Series
Integration of ecological and genetic approaches is a particularly powerful strategy to identify natural population diversity and structure over different timescales. To investigate the potential occurrence of population differentiation in long-finned pilot whales Globicephala melas in the North Atlantic, both biogeochemical (fatty acids and stable isotopes) and genetic (mito - chondrial DNA) markers were analyzed in animals from 4 regions within the North Atlantic: the northwestern Iberian Peninsula, the United Kingdom, the Faroe Islands and the United States of America. Genetic data revealed strong regional levels of divergence, although analysis of molecular variance revealed no differentiation between the northeastern and northwestern Atlantic. Results from biogeochemical tracers supported previous dietary studies, revealing geographic and ontogenetic dietary variation in pilot whales. Fatty acids revealed ecological differentiation between all regions analyzed, while stable isotopes showed an overlap between some sampling regions. These results suggest that both ecological and genetic factors may drive the levels of pilot whale differentiation in the North Atlantic. The ecological differentiation observed may be related to the exploitation of different foraging niches (e.g. oceanic vs. coastal), which can be highly influenced by prey distributions or oceanographic phenomena. Genetic differentiation may result from historical or contemporary processes or even limited dispersal mediated through the social structure displayed by this species and potential foraging specialization. These results highlight some problems when assessing population structure across multiple markers and the ecological vs. evolutionary timescales over which differences may accumulate. Notwithstanding, the data provide preliminary information about pilot whale diversity and stocks in the North Atlantic, giving essential baseline information for conservation plans. Copyright © 2015 Inter-Research. Source
Johnston D.W.,Duke University |
Frungillo J.,Duke University |
Smith A.,Duke University |
Moore K.,Marine Mammal Rescue and Research Program |
And 3 more authors.
Harbor seals and gray seals are sympatric phocid pinnipeds found in coastal waters of the temperate and sub-Arctic North Atlantic. In the Northwest Atlantic, both species were depleted through a combination of subsistence hunts and government supported bounties, and are now re-occupying substantial portions of their original ranges. While both species appear to have recovered during the past 2 decades, our understanding of their population dynamics in US waters is incomplete. Here we describe trends in stranding and bycatch rates of harbor and gray seals in the North East United States (NEUS) over the past 16 years through an exploratory curve-fitting exercise and structural break-point analysis. Variability in gray seal strandings in Southern New England and bycatch in the Northeast Sink Gillnet Fishery were best described by fitting positive exponential and linear models, and exhibited rates of increase as high as 22%. In contrast, neither linear nor exponential models fit the oscillation of harbor seal strandings and bycatch over the study period. However, a breakpoint Chow test revealed that harbor seal strandings in the Cape Cod, Massachusetts region and harbor seal bycatch in the Northeast Sink Gillnet Fishery increased in the 1990s and then started declining in the early to mid-2000s. Our analysis indicates that ongoing variation in natural and anthropogenic mortality rates of harbor and gray seals in the NEUS is not synchronous, and likely represents diverging trends in abundance of these species as they assume new roles in the marine ecosystems of the region. Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Source