Research
Ontogeny of Diving and Foraging Behaviors of the Immature California Sea Lion (Zalophus californianus californianus)
Collaborators: A Orr (graduate student), R DeLong (National Marine Mammal Laboratory [NMML], Alaska Fisheries Science Center, NOAA Fisheries)
Support: NMML
The bioaccumulation of pollutants in species that occupy high trophic levels has been implicated in several population-level effects, including reproductive and developmental retardation, hormonal alterations, skeletal malformations, and immunotoxicity. Although it is difficult to directly measure the risks associated with exposure of wildlife to chemicals released into the environment, marine mammals can serve as sentinels of the health of the marine ecosystem.
The California sea lion (Zalophus californianus californianus) is an ideal species to examine the relationship between the ecology of marine mammals and the consequences of bioaccumulating pollutants. The foraging ecology and distribution of sea lions, which differ among age classes and between sexes, exposes them to a variety of pollutants that accrue in their tissues. As part of a multidisciplinary study to examine some of the ecosystem factors that influence diseases in California sea lions, we propose to investigate the little known ontogeny of diving and foraging behaviors of juvenile sea lions.
California sea lions are marine mammals that lead an amphibious existence; during their ontogeny they live through a purely terrestrial phase after birth relying on their mother’s milk and with age they gradually forage independently in the aquatic environment. During this transition, the animal is able to store more oxygen in its lungs, blood, and muscles as it grows, which allows it to dive to greater depths and longer distances and forage on a greater variety of prey. We plan to examine immature sea lion movements and diving behaviors (e.g. distance from haulout, time spent in water, dive duration, depth, and bottom time) as it relates to oceanographic features (e.g. current flow, bathymetry, chlorophyll concentrations, sea surface temperature and height) and other environmental factors that delineate and influence prey distributions. These factors will be examined using a Geographical Information System and Remote Sensing tools in conjunction with satellite telemetry. Satellite transmitters (Sirtrack KiwiSat Platform Transmitter Terminal, Havelock North, New Zealand) will be attached to immature (pup, yearling, 2 and 3 year old) sea lions at the Channel Islands, CA to determine if movements and diving behaviors differ spatially or temporally among ages or between sexes. In addition to obtaining a better understanding of the movement and foraging maturation of juvenile sea lions, we hope to gain insight on what and where these individuals are feeding that might expose them to pollutants in the environment, which in turn may predispose them to diseases adversely affecting their health.
Humpback Whales (Megaptera novaeangliae) as Bioindicators of Ocean Health: a Study of Persistent Organic Pollutants in the North Pacific Ocean
Collaborators: C Elfes (graduate student), M. Krahn (Northwest Fisheries Science Center, NOAA Fisheries), P. Wade (National Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA Fisheries)
Support: NOAA Fisheries
Flame retardants, such as polybrominated diphenyl ethers (PBDEs), are a relatively new class of persistent organic pollutants (POPs), present in high concentrations in many consumer products such as plastics, electronic equipment, and textiles. With estimated worldwide consumption of 40,000 tons/year, these substances can now be detected virtually everywhere, from human breast milk to the blubber of whales. Although there is limited knowledge of their toxicology, PBDEs have been shown to act as developmental neurotoxicants and endocrine disrupters. PBDEs, like polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT), are lipophilic, persistent in the environment and can therefore bioaccumulate easily. These pollutants can enter aquatic food webs through atmospheric dispersion and are cause for increasing concern due to their potential to compromise ecological integrity and human health. Although PBDEs have been well studied and even banned in many European countries, there is urgent need for a large-scale study of PBDE contamination in the North Pacific.
We plan to analyze concentrations and congener profiles of PBDEs and other lipophilic contaminants in the blubber of humpback whales (Megaptera novaeangliae) collected with biopsy darts from 11 feeding areas throughout the North Pacific. The life history characteristics of humpback whales, in particular their seasonal feeding behavior and high fidelity to feeding areas make these animals ideal biological indicators of regional contamination. The results of this study will provide information about the distribution and concentrations of PBDEs and other POPs throughout the North Pacific basin. Although several studies have determined contaminant levels in top predators such as killer whales (Orcinus orca), less is known about the degree of bioaccumulation in mid-trophic level organisms, and no previous research has determined PBDE contamination in the endangered humpback whale. The results of this work will establish a baseline level of POP concentrations, including that of PBDEs in humpbacks in the North Pacific, which will be a critical tool for future studies monitoring the health of these populations.
Does Fatty Acid Composition of Beluga Blubber Vary with Blubber Depth and/or Body Location?
Collaborators: H Smith (graduate student), R Suydam (graduate student, Department of Wildlife Management of the North Slope Borough [NSB], Alaska, and Alaska Beluga Whale Committee [ABWC]), K Frost (University of Alaska Fairbanks, and ABWC), ABWC, Village of Pt. Lay, Alaska
Support: Biological Resources Division of the U.S. Geological Survey, NSB, NOAA Fisheries, Alaska Fisheries Science Center, National Marine Mammal Laboratory
Fatty acid composition of blubber is increasingly used as a tool for examining diet in marine mammals. In order to make dietary inferences on the basis of blubber fatty acid composition, it is necessary to consider factors other than diet that may influence what fatty acids are present. Blubber samples are typically collected from free-ranging live animals by biopsy darting. It follows that there is a need to understand how fatty acid profiles are affected by variation in sample collection location due to differences in location and depth of dart penetration on the target animal's body.
There is current interest in using fatty acid methods to examine dietary patterns in populations of belugas (Delphinapterus leucas [Pallas, 1776]) in Alaska. Four of five Alaskan beluga stocks are healthy, and all are traditionally important for subsistence for Alaska Natives. Quantitative characterization and perhaps protection of important prey resources may contribute to informed and effective management of beluga populations in Alaska and elsewhere.
Blubber samples were collected from 10 female and 10 male belugas taken by Native harvest near Pt. Lay, Alaska (USA) in early July 2002. Full depth blubber samples were collected immediately post-harvest at six dorsal or lateral locations on each animal, in our opinion spanning the portion of the body that would most probably be remotely sampled in free-ranging wild animals via biopsy dart. Blubber was sub-sampled by dividing full depth samples into inner (adjacent to muscle), middle and outer (adjacent to skin) layers. Fatty acid composition will be determined for each sub-sample, and compared among sub-samples with respect to blubber depth, body location, and individual animal.
Use of Quantitative Methods to Estimate Density and Population Size of Cetaceans
Collaborators: A Zerbini (graduate student), D DeMaster (NOAA Fisheries, Alaska Fisheries Science Center), P Wade, J Laake (NOAA Fisheries, Alaska Fisheries Science Center, National Marine Mammal Laboratory [NMML])
Support: Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazil), NMML
Population size and density are key parameters in wildlife research, assessment, and management. They are often used to monitor trends across time, as input parameter values in population and ecosystem modeling and to investigate habitat changes. Several sampling techniques are currently used to estimate population size of marine animals. The objective of our project is to apply some of these methods, particularly distance sampling and capture-recapture techniques, to estimate density and population size of cetaceans. Work will focus on several whale species, including humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), minke (B. acutorostrata) and killer whales (Orcinus orca) in western Alaska and the eastern and central Aleutian Islands through a series of three shipboard surveys. Results will be significant with regard to several management issues. For example, recent studies have raised the hypothesis that mammal eater killer whales have been responsible for the decline of several sea otter, sea lion and seal populations due to a shift in diet from pre-whaling to recent years. For this reason, accurate estimates of abundance of cetaceans are required in order to evaluate density and abundance of killer whales relative to the habitat and density of their potential prey. Closed population mark-recapture models will be used to estimate abundance of killer whales in the study area. Multiple covariate distance sampling will be used to obtain estimates of population size for both killer whales and large whales. For killer whales, a comparison between mark-recapture and line transect estimates will be made and discussed in regards to survey design. We will also investigate the performance of line transect variance estimators in a theoretical context using simulation. Finally, line transect data from the Alaska and Aleutian Island surveys will be integrated with the US Southwest Fisheries Science Center and the International Whaling Commission sighting datasets to improve the estimation of the detection probability of killer whales in Alaska. This will possibly be obtained by incorporating data from other surveys with a larger sample of killer whale sightings.
Nutritional Significance of Ephemeral High-Quality Foraging Opportunities for Steller Sea Lions
Collaborators: L Hoberecht (graduate student), R Synovec, B Prazen (UW Department of Chemistry), M. Willson (University of Alaska Fairbanks), S Iverson (Dalhousie University)
Support: Steller Sea Lion Research Initiative, NOAA Fisheries, Alaska Regional Office
The two populations of Steller sea lions (Eumetopias jubatus) recognized in Alaska (eastern and western – divided at 144 degrees west) are undergoing different rates of change. The western population has been declining since the 1970’s while the eastern population remains stable. One of the primary hypotheses for the decline of the western animals is a change in the availability of prey species. Capelin (Mallotus villosus) and eulachon (Thaleichthys pacificus) are high quality prey species (high lipid and energy content) that may only be available to sea lions when the fish aggregate to spawn. Varying access to these prey species for the two populations of Steller sea lions could play a role in sea lion fitness. Fish species have unique fatty acid signatures that can be identified using gas chromatography. When pinnipeds ingest prey, most of the long chain fatty acids from the prey enter their blubber unmodified. Thus, if the signature of a prey species is known, it can be identified and potentially quantified, if present, in sea lion blubber.
Signatures will be determined for the two forage fish species listed and other potential prey items using two-dimensional gas chromatography. Investigations into the appearance, contribution, and retention of capelin and eulachon signatures in Steller sea lion blubber will be conducted via captive feeding trials and sampling of wild animals. To date a total of 1050 fish of 22 different species that Steller sea lions are known to feed upon have been collected. During springs and summers of 2002, 2003, and 2004 a remote biopsy system was used to collect blubber from 262 Steller sea lions, including 134 animals in southeastern Alaska, 95 animals in the Kodiak archipelago, and 33 animals in southwestern Alaska (Alaska Peninsula and Shumagin Islands). Project field work is complete, and effort is now focused entirely on laboratory analyses. Project completion is anticipated in summer 2006.
Long-Term Monitoring of Black Abalone (Haliotis cracherodii) Populations at San Nicolas Island, California
Support: USGS, NOAA Fisheries, COFS
Populations of abalone species have declined along the southern California mainland coast and offshore islands over the past half-century due to commercial and recreational fisheries, restoration of natural predators, and possibly diminished habitat quality. The emergence of the disease “Withering Syndrome” (WS), at Santa Cruz Island in 1985, has been followed by sharp declines of black abalone (Haliotis cracherodii) populations throughout their range in California. Black abalones have been monitored in permanent plots at nine sites on San Nicolas Island (SNI), California from 1981 to the present, to our knowledge the longest continuous time series of population data for abalones anywhere in the world. WS first appeared at SNI in 1992. Prior to the emergence of WS, SNI harbored black abalone populations of extraordinary abundance. SNI black abalone populations had declined to 1% of pre-disease numbers by 2001 because of WS. Recent data (2002 through 2006) indicate a significant recruitment event and a modest increase in abundance. The recruitment and apparent increase in abundance are the first such patterns at SNI since the onset of WS. These patterns may indicate both favorable oceanographic conditions for larval production, survival, and recruitment, and the presence of disease resistance in surviving adult black abalones at SNI. SNI thus offers the unique opportunity to characterize the recruitment dynamics of a population abruptly reduced to a small fraction of its previous size by disease, in a spatially isolated but largely pristine physical habitat.
The black abalone is now a candidate for listing pursuant to the Endangered Species Act of 1973 as amended. We will continue evaluation of population trends and size structure of black abalones in our permanent plots at SNI, providing information critical in guiding the definition and implementation of recovery options for black abalones. Our work will facilitate efforts by state and federal resource management authorities, in particular the California Department of Fish and Game and the National Marine Fisheries Service, in improving the effectiveness of conservation and recovery plans for black abalones, both with regard to protecting surviving wild populations and for identifying and implementing optimal proactive restoration strategies.
Foraging Ecology of Juvenile Steller Sea Lions (Eumetopias jubatus)
Collaborators: M Lander (graduate student), T Loughlin (NOAA Fisheries, Alaska Fisheries Science Center, National Marine Mammal Laboratory [NMML])
Support: NMML
The western stock of Steller sea lions (Eumetopias jubatus) has declined by 70% over the past three decades. Although many factors have been implicated as causes of the decline, the proximate cause appears to be chronically reduced juvenile survival, which may be attributed to nutritional stress, the synergistic effects of fisheries, or environmental perturbations, or changes in the foraging behavior of top-level carnivores. A combination of oceanographic data, positional data, and diving behavior is necessary for examining how sea lions alter or optimize their foraging strategies in response to seasonal or annual changes of oceanographic features, which ultimately affect the distribution of prey. The objective of this study, therefore, is to discern and quantify the ecological processes or mechanisms that are influencing the foraging ecology and habitat use of juvenile sea lions. More specifically, we plan to assess the factors that are affecting the foraging ecology of Steller sea lions by examining their movements and diving behaviors (i.e., depth, duration, and shape of dives, and a time allocation at depth index) with respect to environmental covariates (i.e., bathymetry, temperature at depth, sea surface temperature, chlorophyll concentrations, and ocean color) at various scales using remote sensing techniques coupled with a GIS. Satellite relayed data loggers (Sea Mammal Research Unit, University of St. Andrews, Scotland) will be attached to the dorsum of juvenile Steller sea lions to monitor spatially explicit patterns of diving behavior within areas of the eastern Aleutian Islands and Gulf of Alaska (i.e., Kodiak archipelago). Additionally, four years (2000 to 2003) of telemetry data collected in these regions by the National Marine Mammal Laboratory, National Marine Fisheries Service, will also be examined, allowing for temporal and spatial replication across heterogeneous conditions. An understanding of natural variation and the critical habitat of this species will be fundamental for formulating models that can be used to predict behavioral response as habitat quality or composition changes in the future.
Studies Toward Improved Management of Steller Sea Lions in Alaska
Collaborators: D Kinzey, L Hoberecht, M Lander, J London (graduate students), A Punt (faculty), M Hershman (School of Marine Affairs), D DeMaster (NOAA Fisheries, Alaska Fisheries Science Center [AFSC])
Support: AFSC
The western population of Steller sea lions (Eumetopias jubatus [Schreber]) is in decline while the eastern population is increasing, based on counts of animals at rookeries. At present the western population is listed as "endangered," and the eastern population "threatened," pursuant to the U.S. Endangered Species Act of 1973 as amended. There are two primary categories of hypotheses for explanation of the observed declines in the western population. The first is nutritional shortfalls, driven either by competition with fisheries for primary prey or by basin-scale oceanographic fluctuations. The second is increasing importance of direct predation on Steller sea lions by top-level predators. The two categories of hypothesis are not necessarily mutually exclusive. In this project several coordinated studies will be employed to improve the understanding of trophic ecology and fishery interactions of Steller sea lions, and to clarify the role of agencies in policy implementation regarding sea lion and fishery management. The related projects jointly will contribute to improved conservation and management of Steller sea lions in Alaska.
The project includes the following interrelated, coordinated components. First, we will develop a dynamic food web model capable of representing those species that interact substantially with Steller sea lions. Second, we will evaluate application of two-dimensional gas chromatography as a method for determining sea lion diet from analyses of dietary fatty acid concentrations in the blubber layer. Third, we will evaluate genetic analyses of microsatellite DNA patterns as a method for confirming the scats, collected on haulouts and used for dietary studies, are from Steller sea lions and not from related species. Finally, we will conduct research on optimal methods for agency compliance with federal regulations pertaining to fishery and marine mammal management, in the context of the Steller sea lion’s current status.