Marine Autonomous Recording Units, or MARUs, used to record sound on the ocean floor. Photo courtesy of NOAA Fisheries/NEFSC.
HYANNIS – The noise of vessels in Northeast waters may be reducing the communication distances for Atlantic cod and haddock at spawning sites, according to NOAA scientists.
A study recently published in Nature Scientific Reports indicates that daily behavior, feeding, mating and socializing may be altered during critical periods for the fish species.
Three months of monitoring was conducted at two sites within Stellwagen Bank National Marine Sanctuary and one south of Cape Ann by researchers at the Northeast Fisheries Science Center laboratory in Woods Hole and sanctuary offices in Scituate.
Sounds such as Atlantic cod grunts and haddock knocks were recorded by instruments at each site during spawning in winter and spring.
“We looked at the hourly variation in ambient sound pressure levels and then estimated effective vocalization ranges at all three sites known to support spawning activity for Gulf of Maine cod and haddock stocks,” said Jenni Stanley, a marine research scientist in the passive acoustics group at the NEFSC and SBNMS and lead author of the study.
“Both fluctuated dramatically during the study. The sound levels appear to be largely driven by large vessel activity, and we found a signification positive correlation with the number of Automatic Identification System (AIS) tracked vessels at two of the three sites.”
AIS is an automatic tracking system, used on ships that provides information on a vessel, such as its unique identification number, position, course and speed.
Ambient sounds include animals vocalizing, physical sounds such as wind and water movement or geological activity, and human-produced sound from ships and marine construction.
Many marine animals use ambient sound to navigate, to choose where to settle, or to modify their daily behaviors including breeding, feeding and socializing.
Cod grunts were present for 100 percent of the spring days and 83 percent of the winter days. Haddock knocks were present for 62 percent of the winter days within the three-month sampling period.
However, ambient sound levels differed widely at the three sites, both on an hourly and daily time scale.
The Atlantic cod winter spawning site, nearest the Boston shipping lanes, had the highest sound levels, while the Atlantic cod spring spawning site inshore south of Gloucester had the lowest.
Sound levels in the haddock winter spawning site, further offshore in the sanctuary, were in the middle of the range detected in the study.
Data was also used to calculate the estimated distance a fish vocalization would be heard at each of the spawning sites. The effective radius ranged widely, from 4 to 70 feet, and was largely dependent on the number of tracked vessels within a 10 nautical mile radius of the recording sites.
Chronic exposure at a low level to increased ambient sound from human activities is one of the most widespread, yet poorly understood, factors that could be changing fish behavior.
If they cannot hear as well as they need to, then sound signals from other fish can be lost, compromised, or misinterpreted in ways that can cause a change in behavior.
“Anthropogenic sound in certain ocean regions has increased considerably in recent decades due to various human activities such as global shipping, construction, sonar, and recreational boating,” Stanley said.
“As ocean sound increases, so does the concern for its effects on populations of acoustic signalers, which range from invertebrates to marine mammals. We don’t know if or to what extent specific species can adapt or adjust their acoustic signals to compete in this environment.”
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