Growth histories derived from otolith microstructure of three Norwegian cod stocks co-reared in mesocosms; effect of initial size and prey size changes
Specific growth rates and survival were not significantly different among the pelagic juveniles of three electrophoretically distinguishable stocks of Norwegian cod ( Gadus morhua ), co-reared in four replicate 5.2 m3 mesocosms, from hatch to day 38 or day 43 post-hatch. Arcto-Norwegian cod (AC, the...
| Published in: | ICES Journal of Marine Science |
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| Main Authors: | , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
1999
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| Subjects: | |
| Online Access: | http://icesjms.oxfordjournals.org/cgi/content/short/56/5/658 https://doi.org/10.1006/jmsc.1999.0474 |
| Summary: | Specific growth rates and survival were not significantly different among the pelagic juveniles of three electrophoretically distinguishable stocks of Norwegian cod ( Gadus morhua ), co-reared in four replicate 5.2 m3 mesocosms, from hatch to day 38 or day 43 post-hatch. Arcto-Norwegian cod (AC, the main commercial cod stock which spawn in Lofoten and are distributed in the Barents Sea, mostly north of 70°N), were compared with a nearby coastal stock (Balsfjord cod, BC – from a fjord near Tromsø at 69°30′N), and a more southern coastal cod stock (CC, from near Bergen at 60°N). The increment width series of the lapillus – otolith growth history – and the relative daily growth rate were not significantly different among stocks within any mesocosm. Although AC larvae were larger, being derived from larger brood stock, they did not exhibit consistently greater otolith growth during the experiment. Larger size at harvest was correlated with growth during the latter part of rearing (>fourth week), which is when most differences in size at age are generated. Decreases in daily increment widths occurred in all stocks within 1–2 days, when the zooplankton food supply was changed from nauplii and copepodites to adult copepods, and when the average AC cod began to exhibit greater daily growth. Increment widths of reared AC cod at 37 days post hatch (>8 μm) were 2–3 times greater, and ontogenetically more variable than those of similar sized cod previously sampled from the Barents Sea (3–4 μm). Average otolith growth histories of pelagic juvenile cod reveal a substantial range in growth potential that is not apparent from more conservative comparisons of weight, and reveal a temporal sensitivity useful for the assessment of environmental fluctuations in the rearing process. |
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