Research Projects



Current:

White-capped albatross habitat use and association with fishing activities, New Zealand (NIWA)

Buller's albatross habitat use and association with fishing activities, New Zealand (NIWA)

Habitat modeling of New Zealand's threatened marine megafauna, New Zealand (NIWA)

Previous:

Top predator distribution and foraging ecology in Florida Bay, Florida, PhD thesis, Duke University

Pilot whale interactions with the pelagic long-line fishery, North Carolina, USA (Duke University)

Structure of Populations, Levels of Abundance, and Status of Humpbacks (SPLASH), Central America (Cascadia Research Collective)

Stock structure of bottlenose dolphins in winter off North Carolina, USA (Duke University)

Mark-recapture abundance surveys of bottlenose dolphins, North Carolina, USA (Duke University)

Sea ice variation along east coast of Canada and implications on seal pupping

Seasonal distribution of bottlenose dolphins in US mid-Atlantic (University of North Carolina, Wilmington)

Right whale aerial surveys, US mid-Atlantic coast (University of North Carolina, Wilmington)

Bottlenose dolphin distribution off the US east coast, Master's thesis, Duke University



White-capped albatross habitat use and association with fishing activities, New Zealand (NIWA)



White capped albatross In my current post-doc at the National Institute of Water and Atmospheric Research, Ltd (NIWA), I am researching the distribution patterns of seabirds relative to environmental variability and fishing activity. Using comparative spatial analysis of tracking data together with environmental variables and fishing effort data we have been able to discern habitat use patterns and rates of overlap and interaction with fishing vessels.

The white-capped albatross (Thalassarche steadi) breeds primarily in the Auckland Islands archipelago in the New Zealand sub-Antarctic and is the second most commonly killed seabird species by New Zealand fisheries. With colleagues at NIWA, we have tagged and tracked white-capped albatrosses during different phases of their breeding cycle with 3 types of tracking gear: GPS tags, satellite tags, and geolocator tags. Our goals are to (1) quantify and describe overlap between individual white-capped albatrosses and commercial fishing activity, and (2) characterize changes in white-capped albatross behavioral and habitat selection patterns when associating with fishing vessels.

From 25 GPS tracks of foraging trips during the guard stage, we determined that 75% of the foraging trips by white-capped albatrosses overlapped with fishing vessels during some point in their trip. However, 6 out of 19 tracked birds (32%) never overlapped with fishing vessels. Furthermore, this analysis revealed that white-capped albatrosses alter their behavior patterns when associating with fishing vessels (slower speeds and less sinuous tracks). These results indicate that fishing activity may be influencing the ecology and biology of this seabird population. Yet, it is also evident that many individual white-capped albatrosses choose not to associate with fishing activity at all. While overlap between seabirds and fishing activity has been identified on a coarse scale in previous studies, this study is the first to quantify interaction rates between individual seabirds and individual fishing vessels at fine spatial and temporal scales.

This work has been submitted for publication to Ecological Applications: Torres, L.G., D.R. Thompson, S. Bearhop, S. Votier, G.A. Taylor, P.M. Sagar, and B.C. Robertson. Submitted. White-capped albatross alter fine-scale foraging behavior patterns when associated with fishing vessels. Ecological Applications.
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Buller's albatross habitat use and association with fishing activities, New Zealand (NIWA)



Similar to my work with white-capped albatrosses, we are interested in the habitat use patterns, foraging ecology, and association rates with fishing activities of Buller’s albatrosses (Diomedea bulleri). With colleagues at NIWA, we temporarily attached GPS tags on Buller’s albatrosses breeding at the Snares islands in New Zealand during the chick guard stage in April of 2008 and 2009. Two colonies of Buller’s albatrosses at the Snares are long-term study sites (> 20 years), providing valuable demographic data such as gender and age on individual birds, which is used to decipher distribution and ecological trends. This research project is in progress, but preliminary results already show divergent distribution patterns between male and female Buller’s albatrosses during foraging trips from the colony.
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Habitat modeling of New Zealand’s threatened marine megafauna, New Zealand (NIWA)



I am a co-Principal Investigator on a large project funded by New Zealand’s Foundation for Research, Science and Technology (FRST) to model the habitat use patterns of threatened Great White sharks, Hector’s dolphins, and three seabird species that breed on Campbell Island. The aim of this multi-disciplinary project is to maximize the protection of New Zealand’s unique marine megafauna while minimizing the regulatory burdens and economic costs to human resource users. Considering fluctuating threat intensities relative to species distributions, this project will allow responsive management, leading to effective mitigation options.

The project contains three research objectives: (1) Use of state-of the-art electronic tags to record distribution data of species at different life stages. Our methodology will identify foraging areas, breeding grounds and any migration corridors regularly used by these species. (2) Utilize geographic information systems (GIS) and advanced modeling techniques to generate spatio-temporal habitat use models of the study species based on the tracking data. Unlike typical static maps of species distribution, these predictive models will be dynamic, mirroring the reality of marine megafauna distribution relative to ever-changing habitat characteristics and demographic patterns. (3) Incorporate these habitat use models with layers of risk assessment, based on various anthropogenic threats (i.e. fishing activity, shipping traffic, or run-off), to produce predictive and dynamic maps identifying critical habitats requiring protection.

Through this project, we will provide management agencies with the tools necessary to develop effective and targeted mitigation measures that reduce mortality of threatened marine megafauna species, while also minimizing the financial and social costs for users of the marine environment.
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Top predator distribution and foraging ecology in Florida Bay, Florida, PhD thesis, Duke University



My dissertation explored the distribution and foraging ecology of top predators in Florida Bay, Florida. I led four field seasons of data collection in Florida Bay during which I conducted line transect surveys for bottlenose dolphins (Tursiops truncatus) and piscivorous seabirds (osprey, pelicans, cormorants, frigates and terns). Focal animal follows were also conducted on individual dolphins to track their fine-scale movement patterns relative to environmental variation and behavior state. Additionally, extensive fish sampling (using trawls and gillnets) was conducted and environmental variability was monitored throughout the fieldwork. I used these large datasets to examine the distribution ecology of dolphins, sharks and seabirds relative to environmental variability, prey distribution, and effects of competition and predation. I also recorded and examined the foraging tactics employed by top predators to exploit particular prey items within specific habitat types. By understanding the behavioral ecology of these animals and the biological environment of the heterogeneous Florida Bay ecosystem, my goal was to establish species-specific habitat use patterns and to determine spatial and habitat overlap between these potential competitors for prey resources. I employed GIS and multiple spatial analysis techniques (i.e. generalized additive models, classification and regression trees, Mantel’s tests, Ripley’s K, ordinations) to investigate these ecological interactions in Florida Bay (PDF of L. Torres dissertation). I secured funding for my research through a grant from the office of Coastal Ocean Research in the National Oceanographic and Atmospheric Administration and The Dolphin Ecology Project.

From this research, I have published five manuscripts in peer-reviewed journals:
Through my dissertation and studies at Duke University I became very familiar with the literature, both theoretical and empirical, related to species distribution modeling including model evaluation, detection probabilities, incorporation of rare sightings data and generation of pseudo-absences. I also developed a thorough understanding of line-transect survey methodology. This complimentary background enables me to understand limitations and nuances within datasets, allowing me to develop and apply appropriate analysis techniques to provide accurate spatial habitat models.
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Pilot whale interactions with the pelagic long-line fishery, North Carolina, USA (Duke University)



During September 2006 and May 2007 I was an observer, data recorder, and photo-id specialist in a fisheries by-catch mitigation study between pilot whales (Globicephala spp.) and long-line fishing gear. Off Cape Hatteras North Carolina, pilot whales are known to depredate (take target fish off hooks of fishing gear) the commercial NE Atlantic tuna long-line fishery. This interaction leads to by-catch of pilot whales and the loss of valuable catch and gear for the fishermen. This is a challenging problem and one that is becoming more prevalent throughout our oceans. The goal of this project was to characterize the behavior and distribution patterns of pilot whales and to investigate the factors associated with these harmful interactions. Pilot whales were detected using visual and acoustic monitoring, site-fidelity and individual interaction patterns were assessed by conducting photo-id, and the species of pilot whale (long-finned or short-finned) was determined through collection of biopsy skin samples. We also teamed with fishermen to investigate the timing of interactions using acoustic recording equipment. Through two years of fieldwork, we established spatial and habitat overlap patterns between pilot whales and the long-line fleet.

This work is on-going and conducted through the Duke University Marine Lab. This research is supported by the North Carolina Sea Grant Fishery Resource Grant Program and NEAq Consortium for Wildlife By-catch Reduction.

Please read here for more information: http://www.ml.duke.edu/faculty/read/pilot_whale.htm
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Structure of Populations, Levels of Abundance, and Status of Humpbacks (SPLASH), Central America (Cascadia Research Collective)



This multi-national effort was designed to determine the abundance, trends, movements, and population structure of humpback whales (Megaptera novaeangliae) throughout the North Pacific. Field efforts were conducted in all known winter breeding regions of humpback whales in the North Pacific during three seasons (2004, 2005, 2006) and all known summer feeding areas during two seasons (2004, 2005). Photo-identification was conducted to estimate abundance and distribution, and biopsy tissue samples were also collected for genetic studies of population structure.

Between February and April 2005 my husband, Todd Chandler, and I led a field team aboard our 60ft wooden schooner, Russamee, to conduct the Mexican and Latin American field component of the SPLASH census. Together we organized, facilitated and managed all logistical aspects of the survey effort and actively participated in surveys, small boat operations, photo-id work, and biopsy sampling.

Please read here for more information: http://www.cascadiaresearch.org/SPLASH/splash.htm
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Stock structure of bottlenose dolphins in winter off North Carolina, USA (Duke University)



During the winter months between November 2004 and April 2006, I assisted with surveys of bottlenose dolphins (Tursiops truncatus) off the coast of North Carolina, USA. The purpose of this study was to determine the stock structure of bottlenose dolphins present off the North Carolina coast in the winter months, the degree of mixing among these multiple stocks, and the patterns of association among dolphins from particular stocks.

I was a boat driver and observer during these surveys that covered both the waters close to shore (less than 1 km from the beach) and, weather permitting, out to the 6 km stock boundary defined by NMFS. Photo-id was conducted at all sightings and dorsal fin images are used to examine distribution and association rates of individuals.

This research is in progress and conducted through the Duke University Marine Lab. The study is supported by the North Carolina Sea Grant Fishery Resource Grant Program.

Please read here for more information: http://www.ml.duke.edu/faculty/read/winter_stock.htm
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Mark-recapture abundance surveys of bottlenose dolphins, North Carolina, USA (Duke University)



I assisted with mark-recapture surveys of bottlenose dolphins (Tursiops truncatus) in the estuarine and coastal waters of North Carolina during July 2000 and July 2006 using photographic identification techniques. The objective was to estimate the abundance of bottlenose dolphins in the bays, sounds and estuaries of North Carolina. I was a photographer and observer during the 2000 mark-recapture work, and the boat driver and an observer during the 2006 field season.

In 2000, it was estimated that 1,033 dolphins were present in the estuaries of North Carolina (Read et al. 2003). This information provided the first abundance estimate for bottlenose dolphins in the inshore waters of North Carolina and was used in the stock assessment process. This abundance estimate will be updated based on the nearly 11,000 digital images taken during our surveys in 2006. Using mark-recapture statistical techniques (see Read et al. 2003) abundance will be estimated from the proportion of dolphins photographed in the second sample that were also observed in the first sample.

This research was conducted through the Duke University Marine Lab and was supported by the North Carolina Sea Grant Fishery Resource Grant Program.

Please read here for more information: http://www.ml.duke.edu/faculty/read/dolphin_abundance.htm

Read, A. J., K. W. Urian, B. Wilson, and D. Waples. 2003. Abundance of bottlenose dolphins in the bays, sounds, and estuaries of Narth Carolina. Marine Mammal Science 19:59-73.
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Sea ice variation along the east coast of Canada and implications on seal pupping



Global climate change affects the amount and extent of sea ice cover along the east coast of Canada. This variability in sea ice cover impacts harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals which use the ice as an important pupping habitat. In this study, I examined the spatial variability of sea ice cover during February and March between 1969 and 2002. My colleagues and I illustrated high ice cover variability, identified spatially explicit areas of ice cover increase and decrease, and determined that ice cover in this region is correlated with the North Atlantic Oscillation (NAO). Light ice years and rapid reductions in ice cover threaten pagophilic (“ice-loving”) seals due to potential increases in neonatal mortality, changes in prey availability, and possible increased risk of epizootics due to crowding on limited ice cover space. This study highlights the importance of incorporating the effects of climate change into ecological research and conservation management.

The results of this study were published in the Journal of Climate Research: Johnston, D.W., A.S. Friedlaender, L.G. Torres, and D.M. Lavigne. 2005. Variation in ice cover on the east coast of Canada, 1969-2002: climate variability and implications for harp and hooded seals. Journal of Climate Research 29:209-222. (PDF)
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Seasonal distribution of bottlenose dolphins in US mid-Atlantic (University of North Carolina, Wilmington)



The stock structure of bottlenose dolphins (Tursiops truncatus) off the US mid-Atlantic coast is complex due to overlapping distributions of the coastal and offshore ecotypes. In this study I analyzed 2 years of aerial survey data from the US mid-Atlantic coast extending from the surf line to 35 nautical miles (64.8 km) offshore. Using spatial analysis and circular statistics, I determined the north/south and inshore/offshore distribution patterns of bottlenose dolphins within this region. Distinct patterns of seasonal distribution and relative abundance were identified: (1) significantly more dolphins were observed in winter, (2) during winter months significantly more dolphins were sighted in Raleigh Bay, and (3) in winter most dolphins were within 3 km of shore. These seasonal distribution patterns are likely correlated with water temperature gradients and prey availability.

The results of this study were published in the Journal of Cetacean Research and Management: Torres, L.G., W.A. McLellan, E.M. Meagher, and D.A. Pabst. 2005. Seasonal distribution and relative abundance of bottlenose dolphins, Tursiops truncatus, along the US mid-Atlantic Coast. Journal of Cetacean Research and Management 7(2). (PDF)
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Right whale aerial surveys, US mid-Atlantic coast (University of North Carolina, Wilmington)



Between January and April 2002, I was part of a right whale (Eubalaena glacialis) aerial survey team. We flew surveys along the US mid-Atlantic coast and identified new animals in this small and endangered population. Our work identified this region as critical right whale habitat needing increased protection and management. I was an observer and co-coordinator of these aerial surveys.


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Bottlenose dolphin distribution off the US east coast, Master’s thesis, Duke University



Two ecotypes of bottlenose dolphins (Tursiops truncatus), known as coastal and offshore, overlap in the Northwest Atlantic along the US east coast. These ecotypes are difficult to distinguish visually, making survey data challenging to interpret. I used sightings data and skin biopsy samples collected from ship board surveys throughout the region to identify the spatial distribution of ecotypes based on molecular analysis of mitochondrial DNA. Two distinct, and non-overlapping, areas of distribution by these two ecotypes were identified based on depth and distance from shore. This study is frequently used and sighted by management organizations to decipher the stock structure of these populations and develop effective management strategies. This work was funded by the Sussman Foundation and results were published in Marine Mammal Science in 2003.

Torres, L., P. Rosel, A. Read, and C. D’Agrosa. 2003. Improving management of overlapping bottlenose dolphin ecotypes through spatial analysis and genetics. Marine Mammal Science 19(3):502-514. (PDF)
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