During the Friends of the Environment’s Abaco Science Alliance Conference on January 8, Diane Claridge of Bahamas Marine Mammal Research Organization (BMMRO) spoke of concerns of declining population numbers of the Atlantic Bottlenose Porpoise in the Abaco area.
The research, which has taken place over the past almost several decades in both the Sea of Abaco area as well as around the southern end of Abaco, focused on the coastal eco-type of the dolphin. In their research it was noted that there are coastal and oceanic eco-types of this dolphin with some distinct differences, include body and dorsal fin sizes.
The oceanic type spend their time in deeper waters and only once in her research has one ever been spotted swimming with a group of coastal type dolphins.
She said it is important to note that these two have been divergent for over 100,000 years so if there is a decline in population of the coastal type the oceanic will not replenish their numbers.
Ms. Claridge said that the dolphin are a top predator (not an apex predator) and only have a few species of shark to be mindful of. They also play an important role in maintaining a healthy marine environment around the reefs, sea grass beds and mangroves.
She said that they serve as sentinels – “if there is something wrong with the dolphins we should pay attention to it, because it could mean there is something wrong with our environment; they eat some of the same fish we do.”
In their surveys and research it was noted that the dolphin groups in each area tended to stay in their area and not travel outside their areas much. The average group is three to four together.
She said it was found in the research that dolphin populations in the Sea of Abaco area were facing declining numbers when compared with those closer to the southern end of Abaco.
The reasons for the difference can be attributed to human impacts as the Sea of Abaco sees much more activity from boats, shoreline construction and other activities.
She said that there is some good news as the population in the southern Abaco region has stayed stable over the study period of over twenty years where the number observed is around 29, however, that is not a lot of dolphins.
According to research it was noted that while mortality is about the same as in the southern Abaco area as in the Sea of Abaco the rate of reproduction is not.
Hurricanes over the last 15 years have had an impact, but the impact of development in the sea of Abaco area has likely led to a destabilizing of the structure of the marine environment adding pressure to the dolphin populations of the area.
Plastics and other pollution breaking down in the water has also led to a less healthy fish population and has likely had a notable effect on populations.
Dolphin abundance in the Sea of Abaco continues to be relatively low compared to estimates in the 1990s, but the discovery of four new calves since last year is encouraging, she said.
Future monitoring will investigate if these calves survive and grow to boost population numbers.