Marine mammal
Science - Marine mammals

Brief Outline
Our objective is to map the distribution of upper-trophic predators with respect to physical and biological gradients across the NC shelf. A team of observers will use standardized population sampling techniques, including line-transect and strip transect methods, to survey the distribution and abundance of marine mammals, birds and turtles. By repeatedly surveying the study area in conjunction with physical and biological measurements from in-situ and remote-sensing platforms, we will quantify how these predators respond to changes in the oceanography of this dynamic region over short time scales (days) and across seasons (summer - winter).

The cruise data will be included in the Spatial Ecological Analysis of Megavertebrate Populations (OBIS - SEAMAP) database, a publicly-available archive of marine mammal, bird and turtle distribution data for the Ocean Biogeographic Information System.

A thorough understanding of the patterns of marine biodiversity and species abundance are necessary foundations for effective management and conservation of marine systems. In particular, distribution and abundance information is needed for long-lived species, including marine turtles, seabirds, sharks and marine mammals, which are especially susceptible to over-exploitation and other indirect anthropogenic impacts (e.g., fisheries bycatch).

Marine scientists have long recognized that upper trophic-level predators are not distributed uniformly across the world's oceans. Instead, their ranges mirror large-scale ocean productivity patterns and the distributions of distinct oceanic regions termed water masses. Over smaller spatial scales, (1 - 10s km), these species frequently aggregate and migrate along bathymetric (e.g., shelf-slope) and hydrographic (e.g., frontal systems) gradients.

Nevertheless, relatively little is known about the mechanisms that restrict marine mammal, bird and turtle species to specific ocean domains, and the extent to which species distributions are influenced by variability in the location and strength of specific hydrographic gradients. This uncertainty hinders our ability to manage marine vertebrate populations, because we cannot discriminate demographic changes due to natural environmental variability from those caused by anthropogenic impacts. Thus, merging standardized time series of abundance and oceanographic parameters is a critical first step to interpret apparent population changes in highly migratory species.

Preliminary Results - August 2004
The following distribution plots are preliminary:

Birds Mammals

We anticipate encountering these species during the August 2004 cruise:
Atlantic Spotted Dolphin
Bottlenose Dolphin
Cuvier's Beaked Whale
Risso's Dolphin
Long-fined Pilot Whale
Short-fined Pilot Whale
Sperm Whale

We anticipate encountering these species during the January / February 2005 cruise:
Bottlenose Dolphin
Common Dolphin
Fin Whale
Harbor Porpoise
Humpback Whale
Risso's Dolphin
Sperm Whale

Marine Birds:
A large number of seabird species are sighted during pelagic trips off the NC shelf - slope and in offshore waters out to the Gulf Stream, both during winter and summer. Check out some photos of the most common seabird species we may encounter during our cruises.

Marine Turtles:
Observers will also record marine turtle sightings, due to their important conservation status. Several species of marine turtles enter Pamlico Sound and travel through the NC shelf during their seasonal migrations. We may potentially see five different species during these surveys, though we anticipate that most of the sightings will be of Loggerhead Sea Turtles, which occur off Cape Hatteras in both winter and summer.

The four other sea turtle species occur in this area largely during the warm water months of summer and fall:
and Kemp's Ridley

Observers will also record opportunistic sightings of large fish, visible at the surface, including Basking Sharks in winter and Ocean Sun Fish in summer. These species have been shown to aggregate at productive fronts, where they forage on weakly-swimming planktonic prey concentrated by convergence zones.