Lv 1 ShellsAthens - Siebold's Cone
Alexandria, Mallorca - Keyhole Limpet
Mallorca - Trumpet Triton
Sicily - Mantle top
Beirut - Bull's-mouth Helmet
[/list:u]
Lv 2 ShellsAthens, Barcelona - Lettered Cone
Algiers [Fishing], Mallorca - Queen Tegula
Istanbul, Sicily, Genoa, Tripoli [Fishing] - Chambered Nautilus
Beirut, Tripoli [Fishing] - The Princely Cone
[/list:u]
Lv 3 ShellsMadeira - Imperial Delphinula
Seville [Fishing], Algiers [Fishing], Corsica- Tapestry Turban
Genoa, Las Palmas, Corsica, Santa Maria - Cone-shaped Top
Bordeaux, Amsterdam, Stockholm, Accra, Dakar - Pallid Carrier
[/list:u]
Lv 4 ShellsLondon, Reykjavik, Luanda, Cape Town, Santa Maria - Starry Carrier
Madeira, Santa Maria - Sunflower Starry Carrier
Luanda - Linneaus
Lisbon - Comercial Trochus
[/list:u]
Lv 5 ShellsMozambique [City/Fishing], Aden [Fishing], Hamburg [Fishing] - Natica tigrina
Sri Lanka, Bombay, Basra- Charonia tritonis
Tourane [Fishing], Semarang, Malacca - Cymantium pileare
Santa Maria - Great Green Turban
[/list:u]
Lv 6 ShellsQuanzhou [Fishing], Nagasaki - Chiragra-Spider-Conch
Edo [Fishing] - Tonna
Zhigu - Precious Wentletrap
Bordeaux [Fishing], Amsterdam, Stockholm - Banded Tun
Santa Maria - Cymatium pileare
[/list:u]
Lv 7 Shells??? - Ficus subintermedius
Suez, Aden, Mogadishu - Cymatium femorale
Mozambique [City/Fishing], Cape Town - Murex haustellum
Bombay, Basra, Muscat - Dwarf Horned Helmet
[/list:u]
Lv 8 ShellsNagasaki, Quanzhou [Fishing], Tourane [Fishing] - Flame Horned Helmet
??? - Ptrynotus aparii
[/list:u]
Lv 9 ShellsZhigu - Lachiniate-Conch
Edo [Fishing] - Rooster-tail-Conch
[/list:u]
Lv 10 Shells

Got the following info from a fishing guide posted on the Chinese official site and so I cannot guarantee accuracy. Thought I'd post, though, in case you find it helpful.

Lv 1 Shells
Beirut - Bull's-mouth Helmet [/list:u]
Lv 2 Shells
      Athens, Barcelona - Lettered Cone
      Istanbul, Genoa, Tripoli - Chambered Nautilus
      Beirut, Tripoli - The Princely Cone [/list:u]
Lv 3 Shells
      Genoa, Las Palmas  - Cone-shaped Top
      Bordeaux, Amsterdam, Stockholm, Accra, Dakar  - Pallid Carrier[/list:u]
Lv 4 Shells
      London, Reykjavik, Luanda, Cape Town - Starry Carrier
      Lisbon,  - Comercial (Commercial?) Trochus  [/list:u]
Lv 5 Shells
      Sri Lanka, Bombay, Basra- Charonia tritonis
      Tourane, Semarang, Malacca - Cymantium pileare [/list:u]
Lv 6 Shells
      Nagasaki - Chiragra-Spider-Conch
      Zhigu - Precious Wentletrap
      Bordeaux, Amsterdam, Stockholm - Banded Tun [/list:u]
Lv 7 Shells
      Suez, Aden, Mogadishu - Cymatium femorale
      Cape Town - Murex haustellum
      Bombay, Basra, Muscat - Dwarf Horned Helmet[/list:u]
Lv 8 Shells
      Nagasaki, Quanzhou, Tourane - Flame Horned Helmet[/list:u]
Lv 9 Shells