Otolith growth rates of the early life stages of herring Clupea harengus (n ¼ 472) and smelt Osmerus eperlanus (n ¼ 348) collected in the Vistula Lagoon (Baltic Sea) during 1997-1999 were analysed. The larvae and early juveniles were not only collected in the same geographical area they were also of the same size (range 15-43 mm standard length, L S ), similar ages and were collected during the same seasons (May to July). Although the two clupeid species experienced very similar environmental conditions, there were significant discrepancies in the analysed relationships. The otolith growth of larval and juvenile smelt was very strongly related to somatic growth while temperature had a minor effect. In herring, the effect of somatic growth, although clearly visible and statistically highly significant, was of less importance than temperature. Furthermore, variation in the otolith size and L S relationship was affected by temperature and somatic growth in both species, but the variance of otolith size at L S was higher for herring than for smelt. Although growth backcalculation from otoliths can presently be recommended as an appropriate method for use with both smelt and herring (despite possibly lower precision and accuracy with the latter), other methods referring directly to short-term increment width changes (e.g. marginal increment analysis) are recommended for smelt but not for herring.

The ages of 8 to 23·5 cm total length (L(T)) round goby Neogobius melanostomus collected monthly during 2006 and 2007 in the Gulf of Gdańsk (Baltic Sea) ranged from 2 to 6 years, with age class 4+ years dominant. Males were larger at age than females. The fastest growth occurred in the first 2 years of life in both sexes. Females were heavier at a given L(T) than males, but only for fish > c. 15 cm. A strong relationship between N. melanostomus otolith size and fish size was found, with no difference between males and females, and a significant relationship between fish growth rate and otolith growth rate, which enabled backcalculation of growth rates. Marginal increment width analysis confirmed the periodicity of annual ring formation in otoliths and showed that the most intense opaque zone formation occurs in July to August, while hyaline zone formation starts as early as September to October. It was concluded that the N. melanostomus that have colonized the southern Baltic Sea exhibit the largest size and longest life span ever recorded for this species.

Growth and migrations of Arctic charr from a Norwegian Arctic lake system were examined using structural and chemical characteristics of their otoliths as indicators of physiological and habitat characteristics. Measurements of otolith strontium/calcium concentration ratios by wavelength dispersive electron microprobe clearly revealed salinity migrations and provided a life history profile for individual fish. There was wide range in the age at first seaward migration (4 to 13 yr; mean 6.7 yr). Sr/Ca concentration data were also used to determine that a few migratory charr occasionally abstained from seasonal migrations Microchemical techniques are an innovative approach to life history analysis when used in combination with structural analyses of otoliths from migratory flsh

Transverse sections of otoliths from Atlantic cod Gadus morhua from the Baltic Sea revealed narrow growth increments. The widths of these increments corresponded to daily increments from fish with known otolith growth rates and were therefore assumed to be daily increments. They exhibited a distinct pattern with increasing distance from the primary primordium. A series of zones with clearly distinguishable increments, first with increasing then with decreasing widths in a dome-shaped pattern, were separated by zones where no regular increment structure was visible. Increment width seemed to be tightly coupled to the annual cycle in environmental temperature at a depth of 30-60 m, where G. morhua predominantly reside. Between 135 and 200 increments occurred within the different zones, with a non-significant trend towards lower increment numbers and widths with distance from the primary primordium of the otolith. Increment formation apparently ceased at temperatures < 5-6 degrees C, but growth during the cold months corresponded closely with estimated growth rates. The increment patterns seemed to reflect annual cycles in environmental temperature, and the count of the increment cycles may thus be a promising tool for the determination of the true age of Baltic G. morhua.

Larval and juvenile herring Clupea harengus collected in the Polish part of the Vistula Lagoon in May-July 1997 had hatched between 17 April and 9 June and originated from three cohorts. The spawning season began on 1 March at 3·8 C and was completed on 3 June at 12·7 C. Mortality among larvae was high in the first 2 weeks of April, probably associated with significant temperature decrease at the beginning of the spawning season. The growth of 10-48 mm L S herring was linear, highest for larvae and juveniles from the first cohort (0·58 mm mm 1 day 1 ), slower for the second cohort (0·55 mm mm 1 day 1 ) and the slowest for the third cohort (0·45 mm mm day 1 ). Temperature effects on the growth were inconclusive and potentially unfavourable feeding conditions in June might have been responsible for the relatively slow growth of third cohort larvae and juveniles.Relationships between otolith size (perimeter, length, width, area, and weight) and fish size (L S ) differed among the three cohorts, related mostly to the positive temperature effect on otolith growth, individuals growing in warmer water had larger otoliths. Although a negative growth rate effect was observed as well, it was less significant. 2001 The Fisheries Society of the British Isles