Effects of fish size on spawning time in Norwegian spring-spawning herring

During October-January in a northern Norwegian fjord system and in February -March at the main western Norway spawning grounds, an index I-G of gonad w eight of spring-spawning herring Clupea harengus in percentage of expected gonad weight at full maturity for a given total length L-T, tended to incre ase with L-T in the range 27-31 cm as the proportion of recruit spawners de creased. Insignificant differences in I-G were found between L-T groups in the range 32-37 cm (repeat spawners). This is contrary to that suggested in other studies and signifies that generally the stock spawns in only two wa ves, repeat spawners first and the recruit spawners second. I-G also increa sed with somatic and total condition factor, which signifies that spawning time may be influenced by summer feeding conditions. (C) 2000 The Fisheries Society of the British Isles.