The Significance of Stranding Responses and Their Contributions to Research
Our planets' ecosystems are diverse and complex. Despite extensive research we are only beginning to comprehend the delicate balance of life. Our thinking and reasoning abilities give us a unique position in our environment, which include responsibility and stewardship. Many species have suffered the consequences of human ignorance. Taking responsibility means studying our environment and learning from our mistakes. The marine environment is not only home to abundant varieties of life, it is also one of the most significant food sources for people worldwide. It is in our best interest to ensure the health of this environment as well as its inhabitants.
Why Respond to Strandings of Marine Mammals?
As the top of the food chain in their ecosystem, marine mammals are indicator species for the condition of the seas. Observing these animals tells us about pollution, the effects of man-made and natural occurring toxins on the mammalian body systems, disease processes, changes in the ocean environment, and the status of species important to fisheries.1,2
Disease processes. While stranded carcasses are of great value to the scientific community, there are many things that cannot be studied from dead animals. Information regarding the processes of diseases and infectious agents requires live animals.
Indicators of ocean health. Changes in the marine environment have consequences on the well being of marine mammals. The presence of toxins and pollutants as well as diseases can weaken these animals to the degree that they strand.
Food sources contaminated by the algal toxin Saxitoxins are suspected to have been involved in the mortality event of 100 Mediterranean Monk Seals in May and June of 1997 in Mauritania, West Africa. About 70% of the local population, approximately one third of the world population of this species, were destroyed.2,4
Implications for human health. Studying the effects and consequences that infectious agents, diseases, pollutants and toxins have on marine mammals produces important implications for human health. A warning against human consumption of local anchovies was issued after a mass stranding of 70 California sea lions along the California coast in May and June of 1998 due to Domoic Acid poisoning. Consuming contaminated prey resulted in the death of more than 80% of the stranded animals.2,4,5
Consequences of human actions. Numerous human activities have detrimental consequences for marine mammals. Oil spills not only kill many marine mammals, but also have many short-and long-term affects on their health, destroy or severely alter their habitats and pollute their food sources.4 Organochlorines have been suggested to impair reproduction and possibly increase susceptibility to disease.7 Many animals are injured or die due to entanglement. Increasing boat traffic has caused physical trauma, permanent scarring, injuries or even death to many marine mammals.3
Contributions to Research and Science
Critical data necessary for the study of marine mammals and their environment are collected during stranding response including Level A and level B data supplied to National Marine Fisheries Service and US Fish and Wildlife Service regional stranding programs, the study of disease processes during the rehabilitation process, the collection of tissue samples from dead animals as well as the information gathered by monitoring rehabilitated animals.
The Alaska SeaLife Center, is one of many facilities in the US that provide rescue and rehabilitation of live stranded marine mammals. Since the center opened its doors in 1998, 104 marine mammals have been admitted to the Rehabilitation program. Note that the number of animals and the variety of species have increased over the years (Tables 1-3).
Successfully rehabilitated marine mammals are flipper tagged and, when possible, equipped with a SDR satellite tag. This device allows us to track the location of the animal and to monitor its survival in the wild. Depending on the satellite tag chosen, additional data such as the number, duration and depth of dives, water and air temperature, heart rate, location of and time spent on haul out sites, and distances traveled can be obtained. This information aids scientists in studying the animals' movement and migration patterns, its behavior and environment. Satellite telemetry permits the long-term study of marine mammals in their natural habitat without disturbing them and allows us to follow them into otherwise inaccessible territories in their environment.
Complete necropsy is performed on animals that die during rehabilitation or that are already dead on arrival to determine the cause of death. In this process, tissue samples are collected for diagnostics as well as for a variety of studies and research projects. The following list names some of the projects that are currently utilizing necropsy samples acquired from rehab animals from the ASLC:
Alaska Marine Mammal Tissue Archival Program (AMMTAP)
Alaska Native Heritage Museum--Seal Bladder Display
Alaska Veterinary Pathology Service--Disease studies
Alaska SeaLife Center--Diet Studies, Biotelemetry Attachment, Contaminant Load, Aging
Alaska Department of Fish and Game--Physiology
National Oceanic and Atmospheric Administration / National Marine Fisheries Service--Genetics, Parasites, Biotoxin monitoring
University of Alaska, Fairbanks (Museum)--Tissue Archive Program
University of California, Davis--Disease studies
University of Minnesota, Dept OB/Gyn--Reproductive Studies
US Fish and Wildlife--Sea Otter Biosampling Program
Improving our understanding of marine mammals is crucial to their battle for survival. As stewards, it is our responsibility to help maintain the balance of life, and to try to save those that may not survive on their own as the result of human interference with their populations and habitats. Rehabilitation of stranded marine mammals may not necessarily make a noticeable contribution to many wild populations, but it is a unique opportunity for education and raising public awareness and interest by bringing attention to these animals and the threats to their habitats and their survival.
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Table 1. Marine mammals collected by the Alaska SeaLife Center Rehabilitation Program. 1998-2004.
Table 2. Outcome for the 104 animals collected during the time frame of 1998-2004.
Table 3. Marine mammals collected by the Alaska SeaLife Center Rehabilitation Program by species. 1998-2004.
The species in the table are the most common species admitted to the Rehabilitation Department of the ASLC. A few individuals of other species have been represented throughout the years:
1998: 1 Northern fur seal (transferred)
1999: 1 Northern elephant seal (rehabilitated and released)
2001: 1 Humpback whale (disentangled and released)
2002: 1 Bearded seal (died in rehab); 1 California sea lion (DOA)
2003: 1 Gray Whale (DOA, Necropsy on beach)
2004: 1 Northern elephant seal (observed and left at site); 2 Steineger's beaked whales (DOA); 1 Humpback Whale (DOA, Necropsy on beach)
I would like to thank Pam Tuomi, Carol Stephens, Shawn Johnson, Lynne Gudes, Tim Lebling and the rehabilitation department for their assistance with this project.
1. Aguirre AA, Tabor GM. 2004. Ecosystem Health and Sentinel Species: Adding an Ecological Element to the Proverbial "Canary in the Mineshaft". EcoHealth 1, 226-228.
2. Aguirre AA, Wilcox BA. 2004. One Ocean, One Health. EcoHealth 1, 211-212.
3. Beck CA, Lefebvre LW, O'Shea TJ. 2001. Florida Manatees: Perspectives on Populations, Pain, and Protection. In Leslie A. Dierauf and Frances M.D. Gulland [eds.] CRC Handbook of Marine Mammal Medicine, 2nd ed. CRC Press, Boca Raton. Pp. 31-41.
4. Bossart GD, Fournier M, O'Shea TJ, Vos JG. [eds.] 2003. Toxicology of marine mammals. Taylor & Francis, London and New York. Pp. 4-5 & 249-256.
5. Dierauf LA, Gulland FMD, Reddy ML. 2001. Marine Mammals as Sentinels of Ocean Health. In Leslie A. Dierauf and Frances M.D. Gulland [eds.] CRC Handbook of Marine Mammal Medicine, 2nd ed. CRC Press, Boca Raton. Pp. 6-7.
6. Dierauf LA, Gulland FMD, Rowles TK. 2001. Marine Mammal Stranding Networks. In L.A. Dierauf and F.M.D. Gulland [eds.] Handbook of Marine Mammal Medicine, 2nd ed. CRC Press, Boca Raton. Pp. 45-46.
7. Reynolds JE, Rommel SA. [eds.]1999. Biology of marine mammals. Smithsonian Institution Press, Washington and London. Pp. 499-503.