The MARU recorded continuously for 75 days during the spring spawning season, with the acoustic sounds confirmed as cod grunts. Cod were also captured in the vicinity of the MARU as part of a tagging study being conducted concurrenty at that time by the Massachusetts Division of Marine Fisheries (DMF) confirming that cod were present.
Male cod grunts were recorded on 98 percent of the recording days. The grunts, were most often heard during daylight hours, and were most common in late May and early June. The MARU was deployed from April 14 through June 27
"We acoustically captured the start of the 2011 spawning period but not the end," said Van Parijs. "Future deployments of multiple MARUs over larger areas and in conjunction with tagging studies could help determine movement patterns of cod in the spring, and give a better picture of how cod are distributed within the spawning protection area. In addition, underwater cameras could provide insight into the structure of the spawning aggregation."
Atlantic cod are known to gather in high concentrations in very small areas to spawn, sometimes forming vertical columns or "haystacks". They often return to the same location to spawn, a behavior known as spawning site fidelity.
In the spring of 2012, the researchers deployed an array of nine MARUs in the same area as the 2011 pilot study to record cod acoustics through an entire spawning season and over a larger area.
Lead study author Keith Hernandez, formerly a researcher in Van Parijs' group at NEFSC and now a graduate student at Moss Landing Marine Laboratories in California, says human-produced sounds might mask cod grunts in coastal areas with high human activity, an issue of concern since grunts and other sounds can be used to advertise for females and warn off competitors.
The next steps for passive acoustic monit
|Contact: Shelley Dawicki|
NOAA Fisheries Northeast Fisheries Science Center