e. the continuous seaward increase in depth, was confirmed in only

5 profiles (12, 13, 14, 15 and 16). The relief in the majority of profiles was more complex: the average slopes for 100 m profiles (Table 3) indicate that towards the shore eastward slopes prevailed over westward ones, contradicting the natural tendency for depth to decrease close to the shore. In the seaward direction (west) over a distance buy Bleomycin of 100 m the majority of detected spawning locations shared a significant depth gradient (mean value 2.4 ± 1.1 m), and there was at least one 10 m segment with a relatively steep westward slope (mean value – 4.8 ± 1.8) (Table 3, Figure 5). The spawning locations plotted on the multibeam bathymetry map seems to correspond to local bottom elevations (Figure 6), and three relatively large spawning beds, extending for several hundred metres, can be distinguished (Table 4). Although these areas are geomorphologically similar, they differ biologically: two of them are dominated by the red alga F. lumbricalis, whereas the third is dominated by red alga P. fucoides, suggesting that for Baltic herring choosing spawning beds, bottom geomorphology plays a more important role than biology (e.g. spawning substrate). Besides those bigger spawning beds, eggs were found on several smaller-scale local elevations ( Figure 6). The Lithuanian coast does not have any sheltered areas, preferred by other

populations AZD9291 cost of the Baltic herring during spawning (e.g. Aneer et al. 1983, Kääriä et al. 1997, Krasovskaya 2002, Rajasilta et al. 2006), which probably explains why in our area Baltic herrings spawn at greater depths (4–8 m) than the 0.5–4 m typical of sheltered areas (Aneer et al. 1983). Despite the different average spawning depth, the spawning

onset temperature (ca 6°C) remains in agreement with the overall trend in the Baltic (Klinkhardt 1996, Krasovskaya 2002). With increasing Thiamine-diphosphate kinase spawning depth, Baltic herring have limited access to algal beds, because only two red algae species (F. lumbricalis and P. fucoides) form sufficiently dense cover suitable for successful egg development. Although in this study eggs were also found on unvegetated substrates, this was recorded at only one location (of 31 unvegetated locations sampled) and during a repeat survey, no eggs were not found on such a substrate, signifying the importance of vegetation cover. The spawning locations remained constant from season to season: we believe that the most probable reason for such consistency is the local geomorphology – a combination of slopes and depth gradients. The latter are relatively stable over time compared to the hydrological conditions. Other authors reported that the spawning locations were often close to deeper areas (Kääriä et al. 1988, 1997, Rajasilta et al. 1993), which is in good agreement with our findings.