Let's start with the big question: how many marine species are there in the world's seas? The answer is a little tricky... but in 2012, the Census of Marine Life estimated there were 2.2 million species in the world’s oceans (give or take a few hundred thousand).

For the marine world, this estimate means that 91% of marine species are yet to be discovered or described (Mora et al, 2011).  The World Register of Marine species lists over 459,000 currently described marine species worldwide. So only a 1.5 million to go... Another reason we need more marine biologists!

Some other global fish facts

- Orange roughy (Hoplostethus atlanticus) are among the longest-living marine fish and can get to ~150 years old!

- Males of Photocorynus spiniceps, a species of anglerfish, are one of the world's smallest fish and grow to only 6mm long. The males are parasitic and spend their life attached to the much larger female, which is nearly ten times longer at 50mm!

- The whale shark (Rhincodon typus) is the largest fish in the sea and grows up to 14m long.

- Blue whales (Balaenoptera musculus) are the largest sea creature – over 30m &180 tons!

- The longest lived animal on earth is black coral! In 2009, scientists studying deep-sea corals discovered specimens of Leiopathes to be among the oldest continuously living organisms on the planet: approx 4,265 years old! With some members found in Australia (see: Atlas of Living Australia)

Closer to home, Australian marine statistics:

- Australia has 4000+ marine fish species (~2000 on the Great Barrier Reef alone!)

- 45 species of cetaceans (whales, dolphins, porpoises) live in or migrate through our waters

- 19 albatross species (of a total of 24 throughout the world)

- 166 species of shark

- Marine reptiles: over 30 species of sea snakes, 6 species of marine turtles (7 worldwide), and 1 species of saltwater crocodile inhabit Australian waters

- Marine invertebrates: 1000+ species of echinoderms (e.g. urchins and sea stars), 200+ species of sea spiders and 1500+ species of jellyfish, sea anemone and corals.