leadGOOD bottom shed, also known as lead shed, is important to keep the cleaner fish away from the bottom of the pen and lead it back to the salmon by the main shed. The bottom shed will also increase the survival of wrasse during winter. The wrasse will usually seek deeper waters when the temperature drops. Without a shed at the bottom of the pen, it will have no place to hide and hibernate. The bottom shed also keeps the wrasse away from the mort collector system, preventing live wrasse from following the lures when retrieving morts.