Larisa Avens

Larisa Avens
National Oceanic and Atmospheric Administration | NOAA · Southeast Fisheries Science Center

PhD

About

84
Publications
32,441
Reads
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1,939
Citations
Citations since 2016
46 Research Items
1254 Citations
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
Introduction
Larisa Avens currently works with the National Oceanic and Atmospheric Administration's National Marine Fisheries Service at the Southeast Fisheries Science Center and her research focuses on sea turtle biology and ecology.
Additional affiliations
September 1995 - May 1998
University of North Carolina at Chapel Hill
Position
  • Research Assistant
Description
  • Teaching assistant for undergraduate Cell and Developmental Biology and Anatomy and Physiology courses.
Education
September 1995 - January 2003
September 1991 - May 1995

Publications

Publications (84)
Article
Full-text available
In the eastern Pacific Ocean, hawksbill sea turtles ( Eretmochelys imbricata ) are adapted to use coastal habitats and ecosystems uncharacteristic of most other sea turtles. Once considered extirpated from this region, hawksbills had sought refuge in estuaries, nesting on muddy banks among the tangles of mangrove roots. This population is at high r...
Article
Full-text available
To address a major knowledge gap for flatback sea turtles ( Natator depressus ), a species endemic to Australia and considered ‘Data Deficient’ for IUCN Red List assessment, we present the first-ever skeletochronology-derived age and growth rate estimates for this species. Using a rare collection of bone samples gathered from across northern Austra...
Article
Quantifying demographic parameters and variable vital rates, such as somatic growth rates, time to maturity, and reproductive longevity, is important for effective management of threatened and endangered populations such as sea turtles (Cheloniidae). To address these knowledge gaps, we applied skeletochronology to analyze and compare somatic growth...
Article
Full-text available
Sea turtles exhibit complex life histories, encompassing intermittent use of multiple spatially separated habitats throughout long lifespans. This broad scope presents challenges for collecting comprehensive biological and ecological data, yet absence of such information complicates evaluation of management strategies for populations at risk of ext...
Article
For species of conservation concern, somatic growth and age at maturation are key parameters in models used to evaluate population dynamics, as spatial and temporal variability in growth rates may be particularly important for predicting population recovery. Following an oceanic juvenile developmental stage, endangered Kemp’s ridley sea turtles Lep...
Article
Full-text available
Many environmental processes influence animal somatic growth rates. However, elucidating specific drivers of somatic growth variation has been challenging for marine megafauna. Using a 20+ year dataset of somatic growth generated through skeletochronology, we evaluated the relationship between multiple region-wide environmental factors-the Deepwate...
Article
Full-text available
Reptile growth is influenced by many ecological processes that can cumulatively give rise to divergent somatic growth rates within spatially structured populations. As somatic growth variation can strongly influence a species’ population dynamics, identifying proximate drivers can be critical to the conservation and management of protected species....
Article
Discerning the foraging habitat requirements of wildlife is key to providing for their conservation and management, especially with rare species. Sea turtles are slow-growing, late-maturing species that undertake wide-ranging migrations, making them especially susceptible to changes and disruptions in their environment. To protect and successfully...
Article
For stochastic growth processes, integrated mixed-effects (IME) models of capture-recapture data and size-at-age data from calcified structures such as otoliths can reduce bias in model parameters. Researchers have not fully explored the performance of IME models for simultaneously estimating the unknown ages, growth model parameters, and derived v...
Article
Full-text available
Data characterizing somatic growth patterns and the ages and sizes at which organisms mature are fundamental to understanding population dynamics. However, obtaining this information for endangered leatherback sea turtles (Dermochelys coriacea) is particularly challenging due to unusual physiology and prevalence of remote oceanic habitat use, which...
Book
Full-text available
SWOT Report XIV features an up-to-date, comprehensive map of sea turtle distribution in the Mediterranean, a picture of loggerhead movements in the Atlantic, and expert answers to the most frequently asked questions about sea turtles. Other articles explore the effects of red tides on turtles, best practices for transporting stranded turtles, and...
Article
Full-text available
Despite observations extending back several centuries, the presence of hard-shelled sea turtles in the eastern North Atlantic is often considered anomalous, as these species more typically inhabit lower latitudes. However, in recent years the occurrence of small juvenile loggerhead Caretta caretta, Kemp's ridley Lepidochelys kempii, and green sea t...
Article
Full-text available
Sea turtle research has received substantial focus worldwide. However, research on the immature life stages of sea turtles is still relatively limited. The latter is of particular importance, given that a large proportion of sea turtle populations comprises immature individuals. We set out to identify knowledge gaps in immature sea turtle research,...
Article
Full-text available
Chronically debilitated loggerhead sea turtles (Caretta caretta) (DT) are characterized by emaciation, lethargy, and heavy barnacle coverage. Although histopathological findings associated with this condition have been reported, only limited data is available on health variables with clinical application. The objectives of this study were to 1) to...
Data
Photos of a debilitated loggerhead sea turtle. Photographs of a dead debilitated loggerhead sea turtle (Caretta caretta) with (A) emaciation, sunken eyes, epibiota on head and skin, and (B) severely sunken plastron, poor body condition, and generalized epibiota growth on plastron and skin. (TIF)
Data
Hematological data in debilitated sea turtles (DTs) stranded along the southeast U.S. compared to healthy control turtles. (DOC)
Data
Immune function measurements in debilitated sea turtles (DTs) stranded along the southeast U.S. compared to healthy control turtles. (DOC)
Data
Protocol for assessing deibilitated loggerhead sea turtles. Written protocol, datasheets, flowcharts. (PDF)
Data
Differences between different measures of plasma proteins in debilitated sea turtles (DTs). Mean and standard deviation of the difference between paired plasma samples from debilitated loggerhead turtles (DTs) for different measures of plasma proteins. PE = plasma electrophoresis; BG = bromocresol green. An asterisk indicates a significant differen...
Data
Morphometric data in debilitated sea turtles (DTs) stranded along the southeast U.S. compared to healthy control turtles. (DOC)
Data
Scatterplots of different measures of plasma proteins in debilitated loggerhead sea turtles (DTs). Linear trendlines and equations are shown for each comparison along with the Spearman correlation coefficient and p-value. (TIF)
Data
Plasma chemistry data in debilitated sea turtles (DTs) stranded along the southeast U.S. compared to healthy control turtles. (DOC)
Data
Prognostic indicators determined by correlations with severity indicator. Spearman correlations between the severity indicator in debilitated loggerhead turtles (DTs) and hematology, plasma chemistry and immune function variables. Values for the severity indicator decrease with worsening severity of debilitation. P-values in bold with * are signifi...
Article
Sex ratio is fundamental to the demography of animal populations. For sea turtles, the operational sex ratio (i.e., that of breeding adults) can be inferred from juvenile sex ratio. In this study, we characterize sex ratio of n = 1401 juvenile loggerhead sea turtles (Caretta caretta) sampled from foraging grounds in North Carolina, USA. For a subse...
Article
Full-text available
The use of satellite systems and manned aircraft surveys for remote data collection has been shown to be transformative for sea turtle conservation and research by enabling the collection of data on turtles and their habitats over larger areas than can be achieved by surveys on foot or by boat. Unmanned aerial vehicles (UAVs) or drones are increasi...
Poster
Incidental capture of sea turtles in certain fishing gear can have negative impacts to sea turtle populations, and time-area restrictions have been implemented to mitigate these captures. However, to make these restrictions most effective, knowledge of a sea turtle’s habitat preference, site fidelity, and spatial and temporal use of that habitat ne...
Article
Full-text available
The East Pacific green turtle Chelonia mydas population is gradually recovering, yet much remains unknown about their long-term demographics and habitat use due to their inaccessibility for study. We present the first detailed characterization of age-at-settlement (~3?5 yr), age-at-maturity (~17?30 yr), and long-term resource use patterns for these...
Article
Trace element analysis has emerged as a powerful tool to elucidate past movement and habitat use in aquatic animals, but has been underutilized in studies of non-fish species. When applied to sequentially deposited tissues (e.g. fish otoliths, sea turtle humerus bone), the technique can be used to infer aspects of an individual’s ecology through ti...
Article
Full-text available
Ontogenetic niche theory predicts that individuals may undergo one or more changes in habitat or diet throughout their lifetime to maintain optimal growth rates, or to optimize trade-offs between mortality risk and growth. We combine skeletochronological and stable nitrogen isotope (δ¹⁵N) analyses of sea turtle humeri (n = 61) to characterize the g...
Article
The green turtle (Chelonia mydas) has a circumtropical distribution and is globally endangered. This long-lived, migratory turtle has a spatially complex life cycle that encompasses initial development in oceanic habitat, with subsequent recruitment to neritic habitat. In the coastal waters of the western South Atlantic Ocean, juvenile green turtle...
Article
Full-text available
Effective management of protected sea turtle populations requires knowledge not only of mean values for demographic and life-history parameters, but also temporal and spatial trends, variability, and underlying causes. For endangered Kemp's ridley sea turtles (Lepi-dochelys kempii), the need for baseline information of this type has been emphasized...
Data
Summary of Generalized Additive Mixed Model (GAMM) statistical output for models incorporating back-calculated somatic growth data for all known-sex Gulf of Mexico Kemp’s ridley sea turtles (Lepidochelys kempii) <50 cm Straightline Carapace Length (SCL). Covariates include SCL or Age, Sex, and calendar year (Year). Boxes enclose statistical output...
Data
Summary of Generalized Additive Mixed Model (GAMM) graphical output for models incorporating back-calculated somatic growth data for known-sex Gulf of Mexico Kemp’s ridley sea turtles (Lepidochelys kempii) <50 cm Straightline Carapace Length (notch-tip; SCL). Covariates include SCL, Age (yr), and calendar year (Year). Plots for those covariates exh...
Data
Summary of Generalized Additive Mixed Model (GAMM) statistical output for models incorporating back-calculated somatic growth data for all known-sex Gulf of Mexico Kemp’s ridley sea turtles (Lepidochelys kempii) >50 cm Straightline Carapace Length (SCL). Covariates include SCL or Age, Sex, and calendar year (Year). Boxes enclose statistical output...
Data
Summary of Generalized Additive Mixed Model (GAMM) graphical output for models incorporating back-calculated somatic growth data for known-sex Gulf of Mexico Kemp’s ridley sea turtles (Lepidochelys kempii) >50 cm Straightline Carapace Length (notch-tip; SCL). Covariates include SCL or Age (yr), and calendar year (Year). Plots for those covariates e...
Data
Results of validation analysis involving humeri collected from tagged, stranded Kemp’s ridley sea turtles (Lepidochelys kempii) and comparison of Straightline Carapace Length (SCL) measured at tagging with SCL back-calculated for the Line of Arrested Growth (LAG) deposited in the humerus closest to the time of tagging, as well as back-calculated SC...
Data
Summary of Generalized Additive Mixed Model (GAMM) statistical output for models incorporating back-calculated annual somatic growth data for all known-sex Gulf of Mexico Kemp’s ridley sea turtles (Lepidochelys kempii). Covariates include straightline carapace length (SCL) or Age, Sex, and calendar year (Year). Boxes enclose statistical output for...
Article
Full-text available
Determining location and timing of ontogenetic shifts in the habitat use of highly migratory species, along with possible intrapopulation variation in these shifts, is essential for understanding mechanisms driving alternate life histories and assessing overall population trends. Measuring variations in multi-year habitat-use patterns is especially...
Article
Full-text available
Alterations have occurred and continue to manifest in the Earth’s biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decr...
Data
Summary of turtle testosterone level and sex determination. (DOCX)
Article
Age and growth are important parameters for better understanding of life history and population dynamics of animal species, as well as for formulating management strategies. However, these data are difficult to obtain for sea turtles because of overall slow growth, delayed maturation and highly migratory behaviour. The loggerhead sea turtle, Carett...
Article
Olive ridleys Lepidochelys olivacea are the most abundant sea turtles in the world, and their early life and adulthood offshore distributions make them less prone to anthropogenic coastal threats. However, primary use of oceanic habitat also results in olive ridley life history being the least studied of all sea turtle species. Here, age at maturat...
Article
Full-text available
Abstract Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis (SIA) has proven useful in addressing fundamental questions in ecology such as reconstructing trophic interactions, habitat connections, and climate regime shifts. The temporal scales over which SIA can be used to address ecological problems vary depending on the protein turnover ti...
Article
Full-text available
Ontogenetic changes in resource use often delimit transitions between life stages. Ecological and individual factors can cause variation in the timing and consistency of these transitions, ultimately affecting community and population dynamics through changes in growth and survival. Therefore, it is important to document and understand behavioral a...
Article
Full-text available
Individual variation in diet composition has important evolutionary, ecological, and conservation implications. However, few studies of marine turtles have examined long-term foraging behavior of individuals. Using stable carbon (13C) and nitrogen (?15N) isotope values from blood plasma, we examined long-term variation in resource use of 27 juvenil...
Article
Full-text available
Age at maturation data are integral to understanding dynamics of threatened and endangered sea turtle populations. However, full characterization of this parameter requires information regarding variability in growth rates and both size and age at maturation potentially resulting from diverse environmental and biological influences. To address the...
Article
Full-text available
The loggerhead sea turtle (Caretta caretta) is found throughout the waters of the Atlantic, Pacific, and Indian Oceans. It is a protected species throughout much of its range due to threats such as habitat loss, fisheries interactions, hatchling predation, and marine debris. Loggerheads that occur in the southeastern U.S. are listed as "threatened"...
Article
Full-text available
Stage durations are integral to wildlife population models that can inform management, as they influence age at maturation and stage-specific survival rates. To refine oceanic stage duration estimates for western North Atlantic loggerhead sea turtles Caretta caretta, skeletochronological analysis was conducted on humeri collected in the Azores isla...
Article
Full-text available
Characterization of a population of green turtles inhabiting the northeastern Gulf of Mexico was made possible by the mortality of a subset of >4500 sea turtles that stranded during a mass cold stunning event in Florida, USA, during January 2010. In total, 434 dead, stranded green turtles Chelonia mydas were evaluated through necropsy and skeletoch...