The Eastern Tropical Pacific (ETP) Research Program was created in the 1970s to investigate the status of dolphin populations incidentally caught by the purse-seine fishery for yellowfin tuna in the region (see “The Tuna-Dolphin Issue”). Our research, which is mandated by the Marine Mammal Protection Act, Section 304, is focused on ETP dolphin populations, impacts of the fishery on these dolphins, and the ecosystem that supports them (including physical and biological aspects of the environment).
An important function of the ETP Research Program is also to provide scientific expertise to the US delegations to the two regional fishery management organizations: the Inter-American Tropical Tuna Commission and the Agreement on the International Dolphin Conservation Program. These international management bodies are responsible for managing ETP tuna fisheries and promoting dolphin conservation. The estimates of abundance for ETP dolphins, as well as other studies conducted by this program, provide these international management bodies with information that is critical to assessing the effectiveness of fishery management and conservation measures. In addition, these dolphin abundance estimates are the basis for calculation of annual, stock-specific mortality limits.
Due to the vast oceanic area encompassed by the ETP (some 20 million square kilometers of water), the assessment of dolphin populations affected by the fishery has required the use of large-scale research cruises spanning decades, and the ETP Research Program has maximized its use of this platform by simultaneously collecting oceanographic and biological data to understand the ecosystem supporting these dolphin populations. The studies on these ship-based surveys are conducted by scientists from many different groups within the Marine Mammal and Turtle Division, including: ETP Cetacean Assessment, Ecosystem Studies, Cetacean Health & Life History, Marine Mammal Genetics, EEZ Mammals and Acoustics, Marine Turtle Research, and Science Implementation, Planning & Policy.
II. Research Questions
With rich datasets from this remote open ocean system, the ETP Research Program is uniquely positioned to answer remaining questions about ETP dolphin populations, as well as develop ecosystem approaches to management for application in other areas. Currently, our research is focused on addressing the following questions:
- How does the purse-seine fishery for yellowfin tuna affect depleted dolphin stocks beyond observed kills, and to what degree are these effects responsible for the failure of these stocks to recover?
- Goal: Determine the effects (for example, on pregnancy, calf abundance and distribution, stress hormone level, and evasive behavior) of exposure to the fishery and the relationship with population growth rate
- What analytical tools can we develop or refine to better assess whether ETP dolphin stocks are recovering?
- Goal: Improve the resolution of stock structure for spotted, spinner, common, and coastal spotted dolphins (through application of species-habitat relationships, genetics, morphology, acoustics, and stable isotopes)
- Are ecosystem shifts, whether caused by the fishery or other factors, responsible for the delayed recovery of depleted dolphin stocks?
- Goal: Improve our understanding of critical linkages between ecosystem components and resilience measures, with a view toward investigating thresholds, tipping points, and alternative stable states for the ETP ecosystem
- How can the decades-long time series of ecosystem data collected in the ETP advance NOAA’s mission and further development of ecosystem approaches to management?
- Goal: Apply the concepts of Ecosystem-Based Management to the ETP by quantifying ecosystem services, users and impacts, and ecosystem linkages, to develop an explicit framework documenting trade-offs among ecosystem services and anthropogenic activities
III. Recent Publications Resulting from ETP Research
The large-scale, long-term nature of these studies has enabled the ETP Research Program to lead the development of cutting edge research that advances the science of conservation and management in the ETP and elsewhere. Examples of these advances include:
- Design and implementation of line-transect surveys for cetaceans in open ocean ecosystems and development of analytical methods and models for estimating abundance and trends. (View publications)
- Development of advanced sampling technologies and novel laboratory and analytical methods to clarify cetacean population structure (stocks, sub-species, species). (View publications)
- Collection of data and development of methods to assess cetacean life history, condition, and health. (View publications)
- Quantification of indirect and unobserved effects of anthropogenic perturbations. (View publications)
- Development of passive acoustics field and analytical methods to improve abundance estimation, identification of species and stocks, and understanding of distribution and ecology of cetaceans. (View publications)
- Use of ecosystem data to improve understanding of cetacean ecology, ecosystem structure and function, and variation in space and time. (View publications)