Multiple research efforts are on-going to study the potential impact(s) on dolphins of the Deepwater Horizon oil spill, which occurred during April – July 2010, .

Bottlenose dolphins are the most common cetacean in inshore waters in the southeastern United States, but little is known about how an oil spill impacts these dolphins.

Dolphins may be impacted by direct contact, ingestion, or by inhaling oil or associated chemicals in the air.

The food chain may also be impacted, which affects dolphins as a top predator.

Efforts are underway to learn more about the spill effects throughout the northern Gulf of Mexico, and the long term research of the SDRP, more than 80 miles from the closest approach of oil from the spill, is important as a benchmark for comparison with areas closer.

Nicks_n_Notches (pdf), the yearly SDRP newsletter reports on a number of research projects related to the Deepwater Horizon oil spill. Articles include:

 Deepwater Horizon Oil Spill: 2010-2011 Efforts to respond to threats to dolphins along the central west coast of Florida

Deepwater Horizon Oil Spill: 2010-2011 Natural Resource Damage Assessment (NRDA) of the St. Joseph Bay bottlenose dolphin community

Deepwater Horizon Oil Spill: 2010-2011 Biopsy sampling of estuarine dolphins in the western Florida Panhandle potentially exposed to contaminants from the spill

2011: Assessing the potential sublethal and chronic health effects of dolphins from an area oiled by the Deepwater Horizon Oil Spill

Deepwater Horizon Oil Spill: 2011 Bottlenose dolphin tracking in Barataria Bay, Louisiana

West Florida Shelf bottlenose dolphins: Population structure, health, and oil spill impacts

Research efforts to learn more about spill effects have been funded by the Morris Animal Foundation’s Betty White Wildlife Rapid Response Fund, NOAA, Disney Worldwide Conservation Fund, Florida Institute of Oceanography, and BP.

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If so, please donate to the SDRP.    Your contribution will help make our work possible.

In 2011, operating at the request of Federal authorities, staff from the SDRP led or participated in 3 rescue attempts involving entangled dolphins.

Most often, a dolphin requiring a rescue is entangled, and its swimming movements are restricted.

Often, lines cut deeply into the animals creating visible wounds that may become infected.

Synthetic fishing lines, especially some of the newer stronger designs  are surprisingly sharp and dangerous when they come into contact with a dolphin’s soft skin.

An article summarizing dolphin rescue attempts from 2006-2011 is included in the recently published Nicks_n_Notches   newsletter (pdf).

While the need for a rescue attempt is often caused by fishing lines or rope, which is cutting through the skin, but in the case of Scrappy, it was a Speedo swim suit that caused life-threatening wounds.

The goal of a rescue is to free the dolphin from the threat, and each case is different.

Occasionally, as in the case of FB28, the line can be cut with a long handled tool from a boat, without requiring capture.

If capture is needed, however, the ideal solution is to briefly capture the dolphin, free it from the threatening condition(s), and release it after examination by a marine mammal veterinarian. If necessary, the rescue team must be prepared to transport the dolphin to Mote Marine Laboratory’s Dolphin Hospital for rehabilitation, and hopefully eventual release.

As you might imagine, putting a dolphin rescue together is quite a task. Multiple boats, a dolphin catcher (using a 500 meter long net), and 25 or more staff and experienced volunteers must be gathered on short notice.

Sometimes the rescue crews will spend fruitless days on the water searching for the threatened dolphin, while very occasionally everything comes together and a successful rescue can be accomplished in a matter of hours.

Some dolphins, such as FB28, Scrappy, and Nellie are sighted for years after the rescue, but as detailed in the link above, the outcome is not always so positive.

Partial funding for past rescue operations has been provided by support from NOAA, but these funds are no longer available. Funding for future rescues will have to be obtained through individual donations.

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Want to help? If so, please support the SDRP. Become a member or donate to the SDRP.

You can read about them by downloading a pdf of our annual newsletter Nicks n Notches.

It contains articles written by SDRP staff, students, visiting scientists, and current and former interns.

We’ll be highlighting some of the research in upcoming posts to this website.

Annie surfacing with her third calf, less than two months old at the time. This calf is the great-great-grand-calf of Cathy (age 45), who is still alive and observed in Sarasota Bay year round. Can you imagine being a great-great-grand parent at only 45 years old?

We have followed up last summer’s 17 new babies with a very respectable eight newborns in 2011.

It has been a decade since so many calves have been born into the population over only two years.

2011 moms included three first time mothers (F165, Holly, and F199) as well as three well experienced mothers. FB25, Moonfin Look-a-like, and Tramp gave birth to their 8th, 7th, and 5th calves, respectively. In addition, Annie gave birth to her third calf this year, another in one of the two lineages we have studied across five generations. Is this calf a girl, who seven years from now will give birth to the great-great-great-grand-calf of Cathy? Only time will tell.

While it is too soon to know the long-term fates of these little guys and gals, we are happy to report that 21 of the 25 have survived to date.

Nicklo (age 61, background) and Black Tip Double Dip (age 58, foreground) surface together as they head through Big Pass, probably on their way to feed in the seagrass meadow behind Mote Marine Laboratory.

The 2010 calves of FB55 and Trisha, as well as the 2011 first calf of F199 (Wanda’s 2002 calf) have not been observed with their mothers for some time and are assumed gone.

Before Trisha’s calf disappeared, it was seen with fishing line on its right tail fluke. We were successful in removing some of it with a long-handled cutting tool; the small amount of line remaining likely did not play a significant role in the calf’s disappearance. Unfortunately, the 2010 calf of FB79 (C797) was entangled much more severely in fishing line from at least five different entanglements. In spite of our disentanglement efforts, he did not survive.

The majority of our elderly animals have survived another year, with the exception of FB36 who died this fall at age 39.

Number of identifiable dolphins using Sarasota Bay on a regular basis; 96% of dolphins seen in the bay are identifiable.

The oldest male observed this year was FB28 (age 46), but he is a youngster compared to female Nicklo, who remains our oldest resident at 61 years young. She is often accompanied by Black Tip Double Dip (age 58), and the two are frequently seen just behind Mote Lab’s docks chasing fish over the seagrass meadow before whacking them out of the water with their tail flukes.

They are occasionally joined by another of the oldest females, Squiggy (age 55). In combination, the large number of successful calves and the small number of mortalities has the resident Sarasota Bay dolphin community at about 160 individuals, on a positive trajectory, moving in the direction of abundance levels reached at the turn of the century.

We have been able to continue our year-round monthly monitoring of the Sarasota bottlenose dolphin community thanks largely to support from the Batchelor Foundation, the Disney Worldwide Conservation Fund, and private donations, as well as the continued dedication of our core volunteers and undergraduate interns.

Thanks to these efforts, this community remains one of the most thoroughly studied free-ranging dolphin populations in the world.

They are large predators near the top of their food web and they are long-lived.

Top predators are useful indicators of marine ecosystem health because they depend on linkages throughout the food web.

Nitrogen isotope values from teeth of bottlenose dolphins resident to Sarasota Bay highlighting the incorporation of nitrogen pollution into the Sarasota Bay food web prior to 1989.

In addition, some bottlenose dolphins in Sarasota Bay can live well over 50 years. During its lifetime a 50 year old Sarasota Bay dolphin would have experienced numerous alterations to their habitat including dredge and fill habitat alteration, human population growth, the 1995 net fishing ban, and severe red tides.

This ecological history of Sarasota Bay is recorded in the tissues of bottlenose dolphins. Using stable isotope analysis, we can learn how dolphins responded to disturbances that changed their ecosystem for over six decades.

Stable isotopes are unique forms of the same element which differ only in mass. For instance, in nature the most abundant form of nitrogen is 14N or “nitrogen 14” meaning that it has an atomic mass of 14 derived from 7 protons and 7 neutrons. Less abundant is 15N, which is like 14N but has one additional neutron.

The ratio of the abundance of 15N to the abundance of 14N is an indicator of an animal’s place in their food web also known as trophic level. This is because animals preferentially excrete more 14N than 15N and, thus, the ratio of 15N to 14N of an organism will be higher than that of their diet. Nitrogen isotope ratios are unit-less but are commonly expressed as isotope values which are denoted with a per mil (‰) sign. One trophic level results in a 3.2‰ difference between diet and consumer.

For example, if a dolphin fed exclusively on a single prey species which had a nitrogen isotope value of 4‰, the dolphin in question would likely possess an isotope value of 7.2‰. The tips of bottlenose dolphin teeth record an animal’s diet prior to 1 year of age and remain inert for the rest of the dolphin’s life. Thus, by sampling a tooth from a dolphin which died in 1994 and was 50 years old, we can assess the diet of the dolphin from 1944. We analyzed stable nitrogen isotopes from the tips of teeth from 69 dolphins from the Sarasota Bay population to assess how their trophic position may have changed in response to ecosystem disturbances occurring between 1944 and 2007.

The most striking feature of our data was a 3‰ increase in average nitrogen isotope value of dolphins from 1944 to 1989.

Traditionally, this would indicate the increase of one whole trophic level. However, such an increase is highly unlikely for this time period in which fishing pressure increased, the human population in the area quintupled and there was wide spread habitat destruction.

Nitrogen isotope values increased as human population grew in the Sarasota Bay area.

We determined that the increase in nitrogen isotope value was not caused by an increase in trophic level but rather probably the incorporation of human produced wastewater, high in 15N, into the Sarasota Bay food web.

Since 1989 the amount of human-produced nitrogen entering Sarasota Bay has been greatly reduced predominately through advances in wastewater treatment. Nitrogen isotope values show no trend after 1989, indicating improved wastewater treatment was successful in reducing the amount of human produced nitrogen entering not only Sarasota Bay but its food web as well.

In this capacity the dolphins of Sarasota Bay serve as historians of ecological change, allowing us to reconstruct disturbances that occurred more than 60 years ago.

This work was conducted as part of Sam Rossman’s dissertation at Michigan State University and is being funded though a National Science Foundation Graduate Research Fellowship.

One important effect is the influence that predatory pressures exact upon the abundance and distribution of prey species.

The prey sampling team, including project leader Elizabeth Berens McCabe and local volunteer Jeff Hollway, completes a purse seine set.

Conversely, individual predators such as bottlenose dolphins can be affected by changes in prey density by consuming more of a particular type of prey, or the dolphin population as a whole may respond by changing density within certain areas.

In 2004 the Sarasota Dolphin Research Program initiated an ongoing seasonal multi-species fish survey in Sarasota Bay to investigate the distribution and abundance of prey fish available to resident bottlenose dolphins.

This work has allowed us to look at fine-scale habitat and prey selection in bottlenose dolphins, as well as the ecological effects of Karenia brevis red tide events on the nearshore fish community upon which the resident dolphins depend.

Each field year consists of a winter fishing season, January-March, and a summer season, June-September, during which we catch, measure, count and release fish from the R/V Flip using a 183 m-long purse seine.

In the summer of 2010 we completed 40 seine sets in seagrass habitats, catching a total of 35,787 fish of 66 different species.

From the 30 seine sets performed during our 2011 winter season we caught a total of 3,820 fish of 59 different species in seagrass habitat.

Mean catch-per-unit-effort (CPUE), or the number of fish caught at each sampling station, was 624 fish per set for summer 2010, and for winter 2011 it was 127 fish per set. This seasonal variation is seen each year.

To look at potential annual trends in fish abundance, we compared the mean CPUE across years and found that summer 2010 was not significantly different than any previous years with the exception of 2005, the year of a severe red tide, which was lower.

The long and protracted K. brevis red tide event in 2005 corresponded with sharp decreases in the CPUE of nearshore estuarine fishes and changes in fish community structure. There were no significant differences in CPUE between this past 2011 winter season and previous winter seasons. Excluding the 2005 severe K. brevis bloom event, fish abundance in the seagrass habitats of Sarasota Bay appears to be fairly stable within each season.

Species-specific trends in abundance were investigated for nine select dolphin prey species: ladyfish, pinfish, pigfish, spot, spotted seatrout, Gulf toadfish, striped mullet, scaled sardines, and Atlantic threadfin herring. While we did not find any consistent annual trends from 2004-2011, CPUE’s of seven out of nine select dolphin prey species were not significantly different than any other year in summer 2010 and winter 2011.

Many factors can contribute to changes in overall and species-specific fish abundances such as natural mortality, immigration, emigration, prey availability, recruitment, and differential habitat use. Changes can occur quickly or over long periods of time and can have a profound impact on higher level predators like the bottlenose dolphin. Long-term multi-species fisheries-independent monitoring surveys, such as ours, are crucial for documenting ecosystem changes, including changes in fish abundance, and for evaluating the effects of disturbance on a system. With the help of Harbor Branch Oceanographic Institution’s Protect Wild Dolphins Program, we plan to continue monitoring fish abundance and species composition in Sarasota Bay.

We thank the many interns and dedicated volunteers who have worked on this project. This work would not be possible without them. The Batchelor Foundation, Disney Worldwide Conservation Fund, NOAA’s Fisheries Service, Harbor Branch Oceanographic Institution’s Protect Wild Dolphins Program, and the Florida Fish and Wildlife Research Institute provided funding for this work.

The overarching goal of this collaborative project is to develop indicators and methods to quantify chronic stress in bottlenose dolphins.

Much research has focused on the stimuli which induce stress in marine mammals as well as the hormonal mediators of the stress response.

Stress may be induced by a variety factors, including noise, pollutant or toxin exposure, presence of predators, loss of prey, and/or habitat changes.

The stress response is complex and difficult to study, but has been well characterized in other laboratory mammal species, and studies of both captive and free-ranging individuals support the existence of these same stress response pathways in marine mammals.

Prolonged stimulation can overly burden the body’s regulatory systems and induce deleterious effects, including chronic immune suppression and inhibition of other energy expending hormonal systems, including disruption of reproductive function, all of which may cumulatively lead to decreased survival and/or inability to reproduce. For this reason, developing indicators and methods to quantify chronic stress in marine mammals is essential for understanding risks and long-term consequences for populations.

We are using the bottlenose dolphin as a model species and attempting to:1) determine correlation of hormone measures between blood and blubber, 2) develop a comprehensive understanding of factors that influence stress hormone levels and establish reference intervals for blood and blubber measurements, and 3) examine relationships among the various hormone measures and conduct preliminary screening analysis to examine potential relationships between the stress hormones and other health measures including immune function.

Samples are being obtained from dolphin health assessments and other sampling in the southeastern U.S., from Sarasota Bay and populations in heavily impacted coastal sites to gain an understanding of the effects of biological and chemical stressors on dolphin population health.

Capture-release studies have been conducted in the Florida Panhandle, where we are investigating the effects of chronic algal toxin exposure, and along the Georgia coast, where we are examining the impacts of high exposure to legacy chemical contaminants. In all of these capture-release projects, we have collected data on reproductive and thyroid hormones, as well as indicators of functional immunity, all measured simultaneously from the same individuals and processed by the same laboratories to ensure inter-study comparability.

We expect to better define the range of natural variability of stress hormones for bottlenose dolphins, as well as stress hormone responses to a variety of natural and anthropogenic stressors. By examining relationships between stress hormones in blood and blubber, we hope to enhance the utility of remote blubber biopsy sampling as a tool for measuring stress hormones and reduce the need for dolphin capture-release to obtain stress hormone measures. We will also examine potential relationships between stress hormone measures and longer-term dolphin health indicators in order to identify potential impacts of stress.

This project, funded by the Office of Naval Research, is a collaborative effort, in conjunction with Eric Zolman, NOAA/ National Ocean Service, Hollings Marine Laboratory, Dr. Nicholas Kellar, NOAA Fisheries, Southwest Fisheries Science Center, Dr. Patricia Rosel, NOAA Fisheries Southeast Fisheries Science Center, Dr. Stephanie Venn-Watson, National Marine Mammal Foundation, and Dr. Teresa Rowles, NOAA Fisheries, Office of Protected Resources.

Dorsal plane sonogram of healthy lung in an Atlantic bottlenose dolphin examined in Sarasota, May 2011. Image acquired with a GE Voluson i portable ultrasound unit and a 2-5MHz 3d/4d RAB transducer.

In order to accurately assess health and disease, there is a need to standardize ultrasound techniques.

The clinical team of the National Marine Mammal Foundation has collaborated with the Navy Marine Mammal Program and the Tufts Veterinary Diagnostic Imaging Service to standardize ultrasound examination of dolphins. This approach was applied during the dolphin health assessments conducted in Sarasota Bay this May of 2011.

Ultrasound was used to evaluate 14 bottlenose dolphins; one of the exams was shortened due to animal instability on the deck.

Female exams began in the water with reproductive ultrasound evaluations to determine pregnancy status. If pregnant, a decision was made based on fetal age and animal stability whether or not it would be examined further on the boat.

Once animals were transferred to the boat deck, they were gently rolled onto their right side so that their left side could be scanned. Ultrasound times were kept to 10 minutes or less. The following organs were evaluated: lymph nodes, lung, pericardial space (area around the heart), liver, pancreas, stomach chambers, intestines, kidney, bladder, and reproductive tract (left ovary, uterus, mammary glands if female; testicles if male).

Ultrasound health assessments of these wild Sarasota dolphins were made based on clinical expertise gained while working with managed dolphins, as well as the published literature on cetacean health and disease.

Normal versus abnormal findings were documented on each organ. An example of a normal dolphin lung field can be seen in the image below. Although further standardization is needed of certain organs, we were able to make important assessments of animal health based on our findings. Ultrasound should be considered an important component of a comprehensive dolphin health evaluation based on the wealth of information gained in a short period of time.

Information is needed to define population units for management purposes; data on ranging patterns, genetics, and contaminant profiles can help to refine stock identification. Dolphins living in these offshore waters may have been impacted by oil from the 2010 Deepwater Horizon spill.

It is important that baseline information be collected on shelf dolphins to allow for future evaluation of changes that may be associated with long-term impacts from the spill.

With support from the Georgia Aquarium, Dolphin Quest, and Dolphin Connection, we will perform standard health assessments and sample collection for 6 bottlenose dolphins over the shelf, and we will tag them with satellite-linked transmitters that will provide data on movements and dive patterns for up to several months post-release. Remote tracking of the dolphins via satellite will allow evaluation of their movements, dive depths, duration of dives, and time spent at depth.

Dolphins riding at the bow of Mote Marine Laboratory’s R/V Eugenie Clark will be captured via standard hoop-net technique, brought aboard the Clark for a brief health assessment and tagging by an experienced team of researchers and veterinarians, and then released immediately onsite.

Sample collection will follow established NOAA protocols to facilitate comparisons with samples collected elsewhere in the Gulf of Mexico in association with oil spill research. Efforts to initiate this research in late October were thwarted by persistent high winds and rough seas; the project has been rescheduled for spring 2012.

In much of the Gulf, stock boundaries have been assigned arbitrarily based on geography rather than on dolphin biology.

Abundance estimates for putative stocks are out of date for most of the Gulf and are unusable for stock assessments. These problems have precluded assessment of the impacts of large scale environmental or mortality events, and inadequate baselines exist for accurately evaluating recovery.

Research Assistant Carolyn Cush performing photo-identification analyses.

With a pledge of 3-years of support from the Disney Worldwide Conservation Fund, we are developing a long-term, broad scale conservation tool to begin rectifying these issues and to meet the urgent need to monitor dolphins following the oil spill.

We are compiling a Gulf-wide photographic identification catalog involving contributing researchers from Texas to Key West. Photo-identification of individual dolphins allows for abundance estimation and provides opportunities to determine residency and transience. By accurately assigning specific individuals to specific areas, biologically based stocks can be defined, and exposures to threats can be evaluated. Had these kinds of efforts occurred before the oil spill and UMEs, it might have been possible to evaluate which specific stocks were impacted, to what extent, and to focus resources for monitoring recovery.

In response to the oil spill, increased bottlenose dolphin photographic identification efforts are underway along much of the northern Gulf of Mexico coastline (including and in addition to the efforts described elsewhere in this newsletter).

While it is too late to develop pre-spill baselines, it is worthwhile to establish current patterns of residency and abundance and to begin to look for movements of individuals outside of the oil-impacted area as ecological effects of the spill may begin to occur.

To detect larger-scale individual movements between the study areas of different investigators, a central clearinghouse for identification photographs and associated meta-data will be helpful.

In addition to developing and maintaining a Gulf-wide bottlenose dolphin photographic identification catalog, we will implement an updated and standardized database system for dolphin sighting data and identification images to facilitate data sharing. This database will be based on the Finbase system developed and currently maintained by NOAA.

Photographic identification leads to the compilation of individual animal histories. As another goal of the project, we plan to apply the histories of “real dolphins” to develop “dolphin stories” that can exemplify aspects of their biology and conservation issues and to disseminate these stories to elementary schools and the general public.