Cooperative Fish and Wildlife Research Units Program: Hawaii
Education, Research and Technical Assistance for Managing Our Natural Resources

Electronic data storage tags (DSTs) were implanted into Atlantic cod captured in Icelandic waters during 2002-2007 and the depth profiles recovered from these tags (females: n=31, males: n=27) were used to identify patterns consistent with published descriptions of cod courtship and spawning behavior. The individual periods of time males spent exhibiting behavior consistent with being present in a spawning aggregation, i.e., periods consisting of a clear tidal signature in the DST depth profile associated with an individual remaining on or near the substrate, were longer than those of females. Over the course of a spawning season, male cod spent approximately twice the amount time in spawning aggregations than females. Despite spending less time in spawning aggregations per season than males, female cod visited more aggregations per unit time. On average, males participated in approximately 57% more putative spawning events, i.e., vertical ascents potentially corresponding to gamete release, than did females. However, males less than 85 cm total length participated in the same number of putative spawning events as females of comparable size. In both sexes, larger individuals and/or individuals that spent a longer period of time within an aggregation participated in a larger number of putative spawning events. Although further validation and refinement is necessary, particularly in the identification of putative spawning events, the ability to quantify cod spawning behavior offered by DSTs has the potential to aid in the development of management and conservation plans.