Department of Primary Industries

Thursday, 18 October 2007

SEAGRASS HABITATS CRUCIAL TO FISH PRODUCTION IN CORNER INLET

New research has found seagrasses and the filamentous algae growing on seagrass leaves
(epiphytes) are a vital source of nutrition for fish in Corner Inlet in south Gippsland and accounts for up to 90 per cent of the total nutrition of a number of species.

“Seagrasses and epiphytes are the foundation of the food webs – meaning these are plants eaten by small animals, which are then eaten by larger animals,” said Department of Primary Industries Project leader, Andy Longmore.

“For years we have watched fish activity around seagrasses, but the role of seagrass and other types of marine vegetation, like seaweeds or phytoplankton for producing food for fish in Corner Inlet is not well known.”

Using stable isotopes (forms of common chemical elements that do not degrade) researchers established profiles for each type of plant including seagrass, algae and phytoplankton.

The research identified seagrasses and filamentous algae as major nutritional sources for King George whiting, southern sea garfish and yellow eye mullet, dwelling in Corner Inlet waters, even though very few of these species feed directly on seagrass or epiphytes.

DPI research also showed mangroves and salt marshes did not contribute significantly to the staple diets of King George whiting, southern sea garfish or yellow-eye mullet in Corner Inlet.

Mr Longmore said during studies, researchers determined the proportional contribution of
seagrass-based nutrition to each species of seagrass and algal epiphytes.

“Three seagrass species Heterozostera, Halophilia and Posidonia contributed around 70 per cent of the seagrass-based nutrition for King George whiting, with seagrass epiphytes contributing the remaining 30 per cent,” Mr Longmore said.

“Our research indicates 60 per cent of seagrass-based nutrition for southern sea garfish and
yellow-eye mullet was obtained from algae epiphytes.

“Now we have identified which seagrass habitats are crucial to production, it will help us
confidently assess what impact any future changes in seagrass cover will have on Corner Inlet’s fisheries production.”

The research was carried out by Fisheries Victoria and the West Gippsland Catchment
Management Authority and also supported by funds provided through the Natural Heritage Trust.

For more information on DPI seagrass research in Corner Inlet contact Andy Longmore on
5258 0111.