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Grabowski TB, KM Boswell, BJ McAdam, RJD Wells & G Marteinsdóttir. 2012. Characterization of Atlantic cod spawning habitat and behavior in Icelandic coastal waters. PLOS One 7(12):e51321-e51331. doi:10.1371/journal.pone.0051321

Images of Atlantic cod captured by a dual-frequency identification sonar (DIDSON) deployed approximately 1.0 km off the coast of Iceland at Knarrarós on 15 April 2009. In panels a-d, the DIDSON is positioned approximately 10 m off the bottom and is oriented at a 30° angle off perpendicular to the substrate. The Atlantic cod shown in these panels (a-d) are swimming up into the water column. The DIDSON is the same distance above the substrate in panels e-h, but oriented at approximately a 60°-angle to it. These cod seem to have reached the depth that the fish in panels a-d were ascending to and are swimming parallel to the substrate. Arrows indicate two individuals that may be coupling and engaged in a spawning event.

Abstract

The physical habitat used during spawning may potentially be an important factor affecting reproductive output of broadcast spawning marine fishes, particularly for species with com-plex, substrate-oriented mating systems and behaviors, such as Atlantic cod Gadus morhua. We characterized the habitat use and behavior of spawning Atlantic cod at two locations off the coast of southwestern Iceland during a 2-d research cruise (15-16 April 2009). We simul-taneously operated two different active hydroacoustic gear types, a split beam echosounder and a dual frequency imaging sonar (DIDSON), as well as a remotely operated underwater vehicle (ROV). A total of five fish species were identified through ROV surveys: including cusk Brosme brosme, Atlantic cod, haddock Melanogrammus aeglefinus, lemon sole Microstomus kitt, and Atlantic redfish Sebastes spp. Of the three habitats identified in the acoustic surveys, the transitional habitat between boulder/lava field and sand habitats was characterized by greater fish density and acoustic target strength compared to that of sand or boulder/lava field habitats independently. Atlantic cod were observed behaving in a manner consistent with published descriptions of spawning. Individuals were observed ascending 1-5 m into the water column from the bottom at an average vertical swimming speed of 0.20-0.25 m s-1 and maintained an average spacing of 1.0-1.4 m between individuals. Our results sug-gest that cod do not choose spawning locations indiscriminately despite the fact that it is a broadcast spawning fish with planktonic eggs that are released well above the seafloor.

 

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Status

Published
December 2012

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Unit Authors

Texas Cooperative Fish and Wildlife Research Unit Cooperators

  1. Texas Parks and Wildlife
  2. Texas Tech University
  3. U.S. Fish and Wildlife Service
  4. U.S. Geological Survey
  5. Wildlife Management Institute