SARASOTA COUNTY, Fla. (WFLA) – A record 22 babies were born to mother dolphins in Sarasota Bay this year, surpassing the previous record set in 2017, and researchers believe it may be due to red tide.
The Chicago Zoological Society’s Sarasota Dolphin Research Program documented the births throughout the year. The program studies 170 dolphins that researchers see on a regular basis in Sarasota Bay. The dolphins have been studied since the 1970s. Through their studies, researchers know the dolphins in Sarasota Bay are long-term residents who have lived there across decades and generations.
According to the Sarasota Dolphin Research Program, the dolphins are “the focus of the world’s longest-running study of a wild dolphin population.”
“We can recognize them from patterns of nicks and notches on their dorsal fin, on the fin on their back, and we’ve been able to track them through as many as five concurrent generations, and up to six generations for some of the lineages in the area,” said Dr. Randy Wells, vice president of Marine Mammal Conservation and Director of the Chicago Zoological Society’s Sarasota Dolphin Research Program.
This year’s baby boom comes after a difficult time for the dolphins of the bay due to strong and long-lasting red tide that came into the Sarasota area in the summer of 2018. Dr. Wells said dolphins died due to both the brevotoxins of red tide directly, as well to ecological effects of red tide, like loss of fish.
Dr. Wells said that more than 75% of the dolphins’ prey fish were gone as result of red tide.
The red tide existed in the bay through the winter of 2018 and in to 2019. Returning predators became an issue when it waned. One hypothesis that researchers have leads to sharks and their prey of stingrays.
“The dolphins stayed in the area and the sharks came back to the area. The rays did not come back in the same numbers that they had been before. Previously, when we’ve seen declines in stingray abundance through the fishing studies that we do to monitor the available fish in Sarasota Bay, when we see a decline in rays, we see it increasing the number of shark bites,” Dr. Wells said. “This time we saw a record number of shark bites on our dolphins during 2019 and 2020 following this red tide.”
Dr. Wells explained that, in those years, they saw a decline in baby dolphins, possibly related to the decline in the stingray population.
“So it’s hard to prove a negative, but these little babies are bite-sized morsels for some of the larger sharks like bull sharks and we wouldn’t expect them to necessarily show a scar that is healing. They would just be gone,” he said.
While the baby dolphin population declined due to these issues, it led to the “baby boom” of 2021.
Dolphins who lost their calves were able to become pregnant again. According to the Sarasota Dolphin Research Program, Sarasota dolphins typically rear their young for around four years.
Dr. Wells said red tide issues in 2020 did not have any major effects on the dolphins in Sarasota Bay. Pregnant dolphins were able to carry their babies for 12.5 months, giving birth this year.
The fish populations have bounced back quickly from red tide blooms in 2021, according to Dr. Wells.
“We learned long ago that studying the dolphins in a vacuum doesn’t get you very far. You really need to understand the dolphins relative to the drivers that determine what their behavior is going to be,” he said. “So ecology is important. We monitor the fish and we found that the fish populations came back within a few months to near record levels.”
The new year also looks to be shaping up well for Sarasota Bay’s 22 babies and other resident dolphins, as Dr. Wells said the fish population is doing well and researchers are not seeing any indications of health issues among the dolphins.
He does ask that residents and dolphin lovers do their part to keep waterways clean and the animals safe.
“[The dolphins don’t] get to just choose which threat they’re going to face. [They] can’t say, ‘oh this month we’re going to face red tide,'” he said. “They have to face a variety of threats at any given time and we need to give them the freedom to do that by creating as good quality of an ecosystem and a home as we possibly can.”