An outbreak of red sores on whiting caught in the surf on Dauphin Island was most likely caused by small parasites, scientists said.
During an early January fishing trip, 14 of 21 fish caught by the Press-Register had lesions of some kind on their bodies, including red sores and fin rot. At the time, surf fishermen on Dauphin Island reported catching a lot of fish with the sores.
On subsequent fishing trips by the newspaper, fewer sick fish were caught, with no sick fish caught on a trip last week.
Scientists at the Dauphin Island Sea Lab said they were receiving fewer reports of fish with sores, possibly suggesting the January disease outbreak had tapered off.
State officials said they had not caught any fish with lesions during recent sampling, but had received a few phone calls from recreational anglers reporting sick fish.
Will Patterson, a Sea Lab scientist specializing in fish diseases and parasites, said the sores seen on the whiting and black drum were likely caused by small parasites, primarily isopods and smaller copepods commonly referred to as sea lice.
“These parasites are common in our waters,” said Patterson, who conducted research after the BP spill on red snapper and other fish that had bloody lesions on their bodies. He noted that in the fall and spring following the spill, fish were observed with unusually “heavy” parasite loads.
“None of the images I have seen to this point from fish collected around Dauphin Island over the past couple weeks have been of fish with large open lesions like we saw periodically from winter/spring until fall 2011” Patterson said.
He has been collecting samples of internal organs from the fish to investigate possible connections between the oil and increased susceptibility to parasites and disease.
“We are still working through fish liver and bile samples to get a sense of whether there might be a link between exposure to (oil) and parasite loads,” Patterson said.
In January, the newspaper sent a half-dozen whiting with visible sores to the Florida Fish and Wildlife Conservation Commission for analysis, but lab results are not yet available.
Marine parasite populations in the surf zone fluctuate dramatically from year to year and location to location, said Micah Bakenhaster, a research associate with the Florida commission. He said water quality, temperature and a host of other factors are at play when it comes to the abundance of sea lice and other creatures.
“Certainly a weakened immune system could be a factor that would explain an intense infection,” Bakenhaster said. “Could be a lot of hosts packed into a small area, could be temperature, it could just be a really good year for the parasites.”
Mississippi/Alabama SeaGrant director LaDon Swann caught a number of whiting with sores on them in January while fishing in the surf on Dauphin Island. While most of the fish he caught appeared healthy, he said he had never encountered so many sea lice.
“Everything I caught, the redness, the sores, they seemed to be caused by the sea lice,” Swann said. “You wouldn’t normally see that. A healthy fish shouldn’t have that many lice on them.”
Numerous sea lice were visible on fish caught by the newspaper, even on fish without apparent blemishes. The small, translucent creatures cling to fish bodies and scurry across their flesh.
Kevin Anson, with the Alabama Division of Marine Resources, said the red areas seen on the whiting could be caused by parasites, bacteria or injuries.
“Typically, water temperature fluctuations can weaken the immune response in fish, which may result in higher incidences of bacterial or viral infections and possibly parasites,” Anson said.
Water temperatures this year have been warmer than normal, and fluctuated significantly with warm weather around New Year’s Eve.
“The water temperatures have stabilized over the last couple of weeks and this might be the reason why you have seen fewer fish with lesions,” Anson said.