Old Friends in New Places: Cetacean Research in the Western Pacific
Last month, we returned to the Mariana Islands for our ninth year, looking for whales and dolphins off the islands of Saipan, Tinian, Aguijan, and Guam. This long-term
Pantropical Spotted Dolphin
Pantropical Spotted Dolphin
Stenella attenuata
Protected Status
CITES Appendix II
Throughout Its Range
SPAW Annex II
Throughout the Wider Caribbean Region
MMPA Protected
Throughout Its Range
MMPA Depleted
Pacific northeastern offshore stock
Quick Facts
Weight
250 pounds
Lifespan
46 years
Length
6 to 7 feet
Threats
Entanglement in fishing gear,
Illegal feeding and harassment
Location
New England/Mid-Atlantic,
Pacific Islands,
Southeast
Pantropical Spotted Dolphin
Pantropical Spotted Dolphin
About the Species
Pantropical spotted dolphins are found in all tropical and subtropical waters worldwide. These relatively small dolphins are quite social and often school with other dolphin species, including the rough-toothed dolphin, short-finned pilot whale, and spinner dolphin.
The tuna purse-seine fishery depleted the pantropical spotted dolphin population in the eastern tropical Pacific, and the northeastern offshore stock in the eastern tropical Pacific is considered depleted under the Marine Mammal Protection Act. All pantropical spotted dolphins are protected under the MMPA.
NOAA Fisheries is committed to conserving and protecting pantropical spotted dolphins. Our scientists and partners use a variety of innovative techniques to study, learn more about, and protect this species.
Status
NOAA Fisheries estimates population size for each stock of pantropical spotted dolphin in its stock assessment reports. The Pacific northeastern offshore stock is considered depleted under the MMPA.
Protected Status
CITES Appendix II
- Throughout Its Range
SPAW Annex II
- Throughout the Wider Caribbean Region
MMPA Protected
- Throughout Its Range
MMPA Depleted
- Pacific northeastern offshore stock
Appearance
Pantropical spotted dolphins are relatively small, reaching lengths of 6 to 7 feet and weighing approximately 250 pounds at adulthood. They have long, slender snouts or beaks. Like the Atlantic spotted dolphin, pantropical spotted dolphins do not have spots at birth, but accumulate them as they age until they are almost completely covered with overlapping patterns. They are also distinguished by a dark cape or coloration on their backs—stretching from their head to almost midway between the dorsal fin and the tail flukes—and by a white-tipped beak.
Behavior and Diet
Pantropical spotted dolphins usually occur in groups of several hundred to 1,000 animals. They are considered quite social, often schooling with other dolphin species. Although their specific migratory patterns have not been clearly described, they seem to move inshore in the fall and winter months and offshore in the spring.
Pantropical spotted dolphins spend most of their day in shallower water between 300 and 1,000 feet deep. At night, they dive into deeper waters to search for prey. They feed primarily on mesopelagic cephalopods and fishes.
Where They Live
Pantropical spotted dolphins can be found in all tropical and subtropical oceans worldwide. The depleted northeastern stock inhabits the eastern tropical Pacific Ocean, far at sea. Coastal spotted dolphins are found within 100 miles of the coast. In addition, a Hawaiian stock occurs throughout the Hawaiian Islands.
In the Hawaiian archipelago, there are genetically distinct populations of pantropical spotted dolphins found between Hawaii Island, Maui Nui, Oahu, and offshore. Animals from each population can travel 120 to 300 miles offshore, but they are generally found closer to the islands.
Lifespan & Reproduction
The maximum lifespan for pantropical spotted dolphins is 46 years. Mating and calving occurs year-round, with gestation lasting around 11 months. Lactation usually lasts 2 years, but it can also last for only 1 year. At 3 to 6 months old, however, calves will begin taking solid food. Calving intervals depend on the population, but they range from 2.5 to 4 years. Maturity occurs around age 11.
Threats
Entanglement in Fishing Gear
One of the main threats to pantropical spotted dolphins is becoming entangled or captured in commercial fishing gear. Entanglement is particularly threatening for the northeastern offshore stock in the eastern tropical Pacific Ocean. Some species of tuna are known to aggregate beneath schools of northeastern offshore spotted dolphin stocks in the eastern tropical Pacific. This close association led to the fishing practice of encircling a spotted dolphin school to capture the tuna concentrated below.
Illegal Feeding and Harassment
Because pantropical spotted dolphins are common and abundant throughout the Hawaiian archipelago (where they are the second most frequently sighted species during nearshore surveys), interactions with tourists are a growing issue for the Hawaiian stock.
Hunting
Pantropical spotted dolphins are hunted for food in Asia, Indonesia, the Philippines, and parts of the Pacific.
Scientific Classification
| Kingdom | Animalia | Phylum | Chordata | Class | Mammalia | Order | Cetacea | Family | Delphinidae | Genus | Stenella | Species | attenuata |
|---|
What We Do
Conservation & Management
All pantropical spotted dolphins are protected under the MMPA, with the Eastern Pacific stock listed as depleted. Our work protects and conserves pantropical spotted dolphins by:
- Reducing interactions with commercial and recreational fishing gear.
- Minimizing harassment and illegal feeding.
- Responding to dead, injured, or entangled dolphins.
- Encouraging responsible viewing of wild dolphins.
- Minimizing the effects of vessel disturbance, noise, and other types of human impacts.
Science
Our research projects have helped us better understand pantropical spotted dolphins and the challenges they face. Our work includes:
- Undertaking stock assessments to determine the status of populations and/or sub-populations.
- Examining population structure, abundance, and dynamics using a variety of research techniques, including photo-identification and genetics.
- Conducting research to better understand how fishery interactions impact pantropical spotted dolphins.
How You Can Help
Keep Your Distance
Be responsible when viewing marine life in the wild.
Observe all dolphins and porpoises from a safe distance of at least 50 yards and limit your time spent observing to 30 minutes or less.
Don't Feed Wild Dolphins
Dolphins fed by humans lose their natural wariness and learn to associate people with food, causing them to beg for handouts and take bait and catch directly from fishing gear. This puts them at risk from vessel strikes and becoming entangled in or ingesting fishing gear. Dolphins may teach these behaviors to their young, thereby putting them at risk.
Report Marine Life in Distress
Report a sick, injured, entangled, stranded, or dead animal to make sure professional responders and scientists know about it and can take appropriate action. Numerous organizations around the country are trained and ready to respond.
Learn who you should contact when you encounter a stranded or injured marine animal >
Report a Violation
Call the NOAA Fisheries Enforcement Hotline at (800) 853-1964 to report a federal marine resource violation. This hotline is available 24 hours a day, 7 days week for anyone in the United States.
You may also contact your closest NOAA Office of Law Enforcement field office during regular business hours.
Management Overview
Like all marine mammals, the pantropical spotted dolphin is protected under the Marine Mammal Protection Act. The Pacific northeastern offshore stock is listed as depleted under the MMPA. NOAA Fisheries is working to conserve this species to ensure populations remain stable.
Pantropical spotted dolphins observed during the 2017 Hawaiian Islands Cetacean and Ecosystem Assessment Survey. Photo: NOAA Pacific Islands Fisheries Science Center/Amanda L. Bradford.
Conservation Efforts
Reducing Interactions with Fishing Gear
Pantropical spotted dolphins are caught as bycatch in fishing gear, leading to deaths and serious injuries, especially in the eastern tropical Pacific. NOAA Fisheries works with fishermen, industry, nongovernment organizations, and academia to find approaches and strategies for reducing bycatch in U.S. fisheries.
Learn more about bycatch and fisheries interactions
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes identify strandings due to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Learn more about the Marine Mammal Health and Stranding Response Program
Minimizing Harassment and Illegal Feeding
As human interactions with wild dolphins increase, so does the risk of disturbing or injuring these animals. The Hawaiian stock of pantropical spotted dolphins is especially vulnerable to disturbance and harassment from tourists. NOAA Fisheries provides guidance on how to safely and responsibly view dolphins, including the following initiatives:
Learn more about the rules regarding feeding and harassing marine mammals in the wild
Implementing the Dolphin-Safe/Tuna Tracking and Verification Program
Pantropical spotted dolphins, like other marine mammals, may become bycatch in fisheries. Some species of tuna are known to aggregate beneath schools of northeastern offshore spotted dolphin stocks in the ETP. This close association led to the fishing practice of encircling a spotted dolphin school to capture the tuna concentrated below. The Dolphin Protection Consumer Information Act established a national tuna tracking program to ensure that tuna imported into the United States meets certain requirements. The program helps ensure the safety of dolphins—such as the northeastern offshore spotted stock—during tuna fishing operations.
Learn more about the Dolphin-Safe/Tuna Tracking and Verification Program
Regulatory History
Pantropical spotted dolphins are protected under the MMPA. In 1993, NOAA Fisheries listed the northeastern offshore stock as depleted.
In 1999, the United States signed on as a Party to the Agreement on the International Dolphin Conservation Program. In addition to other requirements, the AIDCP mandates the establishment of an international tuna tracking program for tuna caught in the ETP. The program helps minimize dolphin deaths during fishing for tuna destined for canning.
The International Dolphin Conservation Program Act (PDF, 19 pages) amended the MMPA to make the objectives and requirements of the AIDCP legally effective in the United States.
Science
NOAA Fisheries and its partners are committed to research to help us better understand pantropical spotted dolphins and the challenges they face.
A pantropical spotted dolphin in Mariana Islands, Guam. Photo: NOAA Pacific Islands Fisheries Science Center/Adam Ü.
Stock Assessments
Determining the size of pantropical spotted dolphin populations helps resource managers determine the success of NOAA Fisheries’ conservation measures. Our scientists collect and present these data in annual stock assessment reports.
Shipboard Studies
NOAA’s Southwest Fisheries Science Center has conducted over 10 cetacean and ecosystem assessment surveys to collect information on pantropical spotted dolphins in the eastern tropical Pacific Ocean. The primary objective of these surveys is to investigate trends in population size of those dolphin stocks most affected by the tuna purse-seine fishery. The project takes a multidisciplinary approach. The SWFSC collects data on cetacean distribution, school size, and school composition to determine dolphin abundance. We also collect data on dolphin behavior to determine how that behavior influences our ability to detect dolphin schools and how dolphins respond to research vessels. Oceanographic data are collected to characterize habitat and its variation over time. Data on the distribution and abundance of prey, fishes and squids, seabirds, and marine turtles further characterize the ecosystem in which these dolphins live. Skin biopsies provide a database for investigations of stock structure, phylogenetic relationships, and the reproductive potential of female dolphins. Acoustic recordings supplement visual survey data and provide information for ongoing studies of cetacean vocalizations.
NOAA Fisheries also implemented an observer program in the early 1970s that has collected thousands of biological samples to study ETP stock structure and to quantify life history characteristics of the population. NOAA Fisheries can use information from the assessment surveys and the observer program to improve conservation and management plans for this species.