7 years after Deepwater Horizon oil spill, Louisiana dolphins struggle to reproduce

Oil spill-related compounds have led to reproductive, lung and hormone issues.

Pregnant dolphins showed an 80 percent reproductive failure rate, either because the fetuses were exposed to oil spill-related compounds or because the mothers' health suffered from the exposure, according to NOAA Fisheries.

According to a report by the National Wildlife Federation, bottlenose dolphins along the U.S. gulf coast from the Florida panhandle to the Texas-Louisiana border had twice the historic death rates in 2014, but even higher where oil concentration was elevated.

"Places that received less oil did not have particularly elevated numbers of dolphin deaths in 2014," the report said, "while dolphins in heavily oiled Louisiana were found dead at four times historic rates."

The report added that this is the longest period of above-average death rates in more than two decades and was not attributed to other common causes of death like viruses or red tide.

Further study is being funded by the Gulf of Mexico Research Initiative (GoMRI), which was established through a $500 million financial commitment from BP following the spill.

ABC News' Bianca Seidman contributed to this report.