Historical Spawning Distribution And Origin Of Pelagic Juvenile Cod (Gadus Morhua) In Icelandic Waters

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Incongruity between the reconstructed spawning period of pelagic juvenile (0-group) cod (Gadus morhua) and the observed spawning period for adult cod on the main spawning grounds south of Iceland have indicated that large numbers of the surviving juvenile population may, in some years, originate from other smaller inshore spawning grounds located within fjords of the west, north and east coasts. We examine this hypothesis by using age/length and temperature/growth relationships, based on aging of 0-group cod from 1995 and 1997, to analyze historical demographic data from 0-group fish surveys (1970-1998) to determine the most likely spawning distribution and origin of pelagic juvenile cod. Data on life history characteristics m conjunction with temporal and spatial distribution of pelagic juvenile cod will be used to create new abundance indices representing the resident (inshore) vs. drifting (offshore) juvenile cod population components. Partitioning of the histoncal 0- group index into these population components at a finer geographic scale than has been used previously. and therr subsequent relationship with recruitment, will provide new information that can be used to estimate the relative contribution of the main spawning component vs. the smaller in-fjord spawning components towards variable recruitment levels in the Icelandic cod stock.