An east-west profile MK-1775 supplier direction was chosen in accordance with western Baltic herring spawning migration patterns in Lithuanian waters (Fedotova 2010). The patchiness of the spawning beds was substantial. We therefore assumed that small-scale bottom geomorphological features were important factors shaping the distribution of spawning beds and could affect these within a 100 m radius around the detected spawning location. Therefore,

for each point where spawning was recorded, 200 m long bottom surface profiles were drawn eastwards and westwards using a IVS3D Fledermaus 7 profiling tool with the spawning location in the middle. As a result we obtained two 100 m bottom surface profiles for each spawning location: towards the coast (eastwards) and towards the open sea (westwards). The bottom slope was estimated from these profiles, since it is an important geomorphological descriptor describing surface

steepness and direction. The slope is calculated as the ratio of the vertical (elevation) difference to the horizontal range. In this study bottom slopes were derived in two ways: as an average along the whole 100 m profiles and as an average along 10 m segments in order to indicate more local effects. Because of Daporinad price the direction of the bottom profiles, negative slope values correspond to western slopes (from west to east) and positive values correspond to eastern slopes (from east to west). For many fish species spawning is triggered by water temperature. Owing to the variety of spawning strategies of the Baltic herring this temperature is different for different populations (Elmer 1983, Evtjukhova & Berzinsh 1983, Aneer 1989, Kornilovs 1994, Klinkhardt 1996, Krasovskaya 2002). Baltic herring spawning usually starts in March (sometimes in February) in the south-western

and southern areas of the Baltic Sea when the water temperature reaches 4°C (Klinkhardt 1996), continues till the middle of summer and finishes in the northern parts at water temperatures up to 15–16°C (Krasovskaya 2002). Generally, spawning temperatures tend to Silibinin increase with latitude, resulting in later spawning seasons for the northern populations (Jørgensen et al. 2005). Water surface temperature was measured daily by the Lithuanian Environmental Protection Agency, Marine Research Department (EPA-MRD) at the Palanga meteorological station, which is located close to the centre of the multibeam area (Figure 1). The first eggs were found when the surface water temperature was 5.9°C in 2009 and 6.4°C in 2010 (Figure 4); in our area, therefore, spawning most likely begins when the temperature reaches approximately 6°C. These values are in good agreement with the general trend of herring spawning temperatures along the Baltic Sea (Krasovskaya 2002, Jørgensen et al. 2005). Baltic herring eggs were found at 25 sites, 18 of them located within the multibeam area (Figure 1). The majority (80%) of eggs were found within a depth interval from 4 to 8 m, with a mean depth of 6.5 ± 1.