VESSEL TRAFFIC SERVICE (VTS) For procedures and working details of the Den Helder Vessel Traffic Service, see Netherlands Coast Pilot HP 1 or Admiralty List of Radio Signals. CABLES AND PIPELINES Mariners are advised not to anchor or trawl in the vicinity of cables and pipelines. Pipelines are not always buried and their presence may effectively reduce the charted depth by up to 2 metres. They may also span seabed undulations and cause fishing gear to become irrecoverably snagged, putting a vessel in severe danger. See the Netherlands Coast Pilot (HP 1). TIDAL STREAMS Attention is drawn to the strong tidal streams in these waters. For tidal streams and tidal information see HP 33 Tidal heights and streams for coastal waters of the Netherlands and adjacent waters and HP 33D-NLTides published by the Netherlands Hydrographer. CENTRAL REPORTING POINT WADDENZEE For all reports and information. Telephone: +31 (0)88 79 74 599 VHF 4 (Safety and distress calls:VHF 16) MARINE FARMS Marine farms excist within the areas indicated. They may not al be shown individually and their positions may change frequently. Marine farms may be marked by lit or unlit buoys or beacons. Mariners are advised to avoid these structures and their associated moorings. DEPTHS AND AIDS TO NAVIGATION The channels and depths shown on this chart are subject to frequent change. The buoyage and other aids to navigation are adjusted accordingly. WINTER-BUOYAGE From ± December-March buoyage may be replaced by winter-buoyage. In severe winters buoyage is withdrawn. Buoyage will be replaced in order of importance. In spring it is possible that not all channels are already buoyed as charted. SUPPLEMENTARY MARKS In these waters supplementary marks for pleasure craft and special marks for watersports like waterskiing, kite surfing, jetskiing and fast motorboats and areas under the Nature Conservation Act are on station from ± April-October.