MOBILE, Alabama -- There were nearly four times as many fish, shrimp and crabs in Alabama waters in the fall of 2011 as there were before the BP's Gulf of Mexico oil spill, according to scientific data collected by the Dauphin Island Sea Lab.
Scientists believe the months-long fishing closure caused by the spill helps explain the dramatic increase, which first became apparent in 2010, months after engineers capped the Deepwater Horizon well. But other factors may be at play as well, researchers said.
“The increase certainly indicates that the waters in Alabama are in relatively good shape, at least the nearshore waters,” said John Valentine, director of the Sea Lab.
“It could also be that things are not good in the Louisiana area and the fish are just getting up and leaving the area around the well site and the heavily oiled marshes there,” Valentine said. “Alabama might be getting the benefit of the problems in other places.”
The lab has population records for Mobile Bay, the Mississippi Sound and Gulf waters out to five miles going back to 2000. The most recent surveys conducted in the fall of 2011 show an increase in both the weight of the catch and in the number of creatures caught.
No surveys were conducted this spring because funding for the long-term project dried up, Valentine said.
“This is a critical time for us to have this information,” Valentine said. “The money ran out. Unfortunately, it isn’t really glitzy enough science to attract much money. It’s just good, old-fashioned shrimp trawling. But it produced a lot of really useful data.”
Historical data show moderate annual increases prior to spill
The historical data show a small increase in aquatic populations that became apparent after Hurricane Katrina in 2005. That jump, Valentine said, likely stemmed from reduced fishing due to the loss of commercial vessels.
That moderate increase continued in the years before the BP spill, perhaps due to rising gasoline costs for the commercial fleet, Valentine speculated.
Then, in April 2010, came the spill.
Trawl surveys conducted in fall 2010 after the capping of the BP well showed a nearly threefold increase in the biomass in Alabama’s coastal waters.
Some shark populations also increased the year of the spill, roughly by a factor of three.
While shark populations had returned to pre-spill levels according to the 2011 sampling conducted by Sean Powers with the Sea Lab, the increases widened in terms of the fish, shrimp and crab populations.
“You can see in the 10 years running up to the accident, the numbers were much lower than they are now,” Valentine said, discussing the data. “Certainly the effects are strongest in the years after the Deepwater Horizon, and they do seem to be building. The interesting part is it’s really not related to fishes people target. It’s a mix of all kinds of fish, and shrimp and crabs. They all increase in abundance.”
One of the most profound lessons, he said, “is that it shows what happens when you prohibit fishing in all of the Gulf.”
Powers said the increase in population numbers will make it more difficult to detect oil-related impacts. He noted that some declines in sea creature populations in Alaska after the Exxon Valdez spill took years to materialize.
“The take-home message for me, is we need to monitor the 2010 and 2011 year classes in a detailed manner across multiple species to determine the effects of the spill and response activities,” Powers said.
Valentine said the opportunity to keep tabs on the fish populations in Alabama is slipping away. For lack of money, the lab was unable to conduct the traditional sampling in the spring of this year.
If funding could be found, he said, the Sea Lab could resume its research right away.