A distinct marine community inhabits the water column above the seafloor. Unlike the air above land, the very medium of the marine environment supports a multitude of life. Surface waters teem with tiny plants (phytoplankton) and animals (zooplankton); some are the young larval stages of benthic animals or fish, others spend their entire lives in the plankton. The photosynthetic phytoplankton are very important to the ecology of the ocean, forming the basis of the marine food web.

In addition to the tiny plankton, the sea abounds with larger swimming animals, from shrimps and jellyfish to whales. Many of these animals migrate large distances. Whales arrive in Victoria from deep in the Southern Ocean. Eels migrate from Victoria’s rivers all the way to Torres Strait to spawn. Vertical migration is also common in the ocean, with animals ascending and descending during the day to feed or shelter.

Water is obviously a part of every marine environment, but pelagic communities are more complex in the deeper water off the open coast. Jellyfish, including comb jellies and salps, feed on phytoplankton and zooplankton carried in the currents. Jellyfish species include the By-The-Wind-Sailor and the Bluebottle. Molluscs include the Arrow Squid and the Paper Nautilus. Many species of fish inhabit Victorian waters; the most notable are Silver Trevally, Barracouta, Jack Mackerel, Pilchards and Anchovies.

Unlike reef animals whose colour usually matches that of their habitat for camouflage, most fish that live near the surface display counter-shading: a gradation of colour that camouflages them against the shadowy water when seen from above, and from the sunlit surface when seen from below.

A number of cetaceans travel through Victorian coastal waters. The most spectacular of all are the Southern Right Whales, which regularly calve off the coast of Warrnambool.

Others sighted include the Pilot, Killer, False Killer and Humpback Whales. Two dolphins regularly appear, the Bottlenose Dolphin and Common Dolphin. Fur-seals, sea-lions and true seals are often seen swimming in open waters, taking advantage of the abundance of small fish, squid and octopus. Some seals also take krill, seabirds, penguins, and even young seals. The Little Penguin, the star attraction of the Phillip Island ‘penguin parade’, also feeds on Pilchards and Anchovies in these waters.

The major challenges in managing our pelagic habitats concern fish harvesting and pollution. Commercial fishing practices need to be carefully managed to minimise the accidental capture of non-target species, or bycatch. Slow growing species with low fertility are particularly vulnerable. Inshore waters can become eutrophic from pollution, as decaying algal blooms deprive bottom waters of oxygen.