A new study has, for the first time, put a dollar value on the contribution of Australia’s coastal ecosystems as breeding grounds for fish.
Researchers from Deakin University’s Blue Carbon Lab calculated that a single hectare of seagrass supports 55,000 more fish a year compared to seabed without vegetation.
This represents a commercial value of fish of up to $21,200 per hectare per year.
Healthy beds of sea grass, mangrove swamps and tidal marshes sustain larger populations of fish than unhealthy or degraded areas.
The most abundant fish across all three ecosystems were small, non-commercial species (e.g. gobies and glassfish), but the highest biomass production and economic value originated from larger, longer-lived fish that are regularly targeted by fisheries (e.g. tharwine, breams and mullets).
Lead researcher, PhD candidate Holger Jänes, said understanding the value of coastal ecosystems was critically important as these areas face a range of threats from climate change, coastal development, invasive species and nutrient run-off from farms and other sources.
“To better conserve, protect, restore and rehabilitate ecosystems degraded by human impact we must know its associated values to human well-being,” Mr Jänes said.
“Over the past decades, we have lost more than 180 km2 of seagrass in Victoria alone and this is a potential loss of fish production of millions of dollars.”
Mr Jänes said mangroves and tidal marshes supported 19,000 and 1,700 of fish per hectare per year.
“These are smaller numbers than for seagrass and include less commercially valuable fish, but these areas are still important ecosystems because they represent important breeding grounds for certain fish species,” Mr Jänes said.
“Across Australia more than 117 individual fish species use seagrass as a nursery area, 23 species use mangroves and eight species use tidal marshes as nursery areas.”
Mr Jänes said the higher value of seagrass as a fish nursery, compared to mangroves and tidal marsh, was likely related to the ease of access for fish through the softer grasses that generally remain under water.
“Mangroves are intertidal with complex root systems and tidal marshes in Australia are even less frequently inundated than mangroves.”
Mr Jänes’ research, Quantifying fisheries enhancement from coastal vegetated ecosystems, published in Ecosystem Services is an output of The Nature Conservancy’s Great Southern Seascapes programme.
The research was supported by The Thomas Foundation, HSBC Australia, the Ian Potter Foundation, and Victorian and New South Wales governments including Parks Victoria, Department of Environment, Land, Water and Planning, Victorian Fisheries Authority, New South Wales Office of Environment and Heritage, and New South Wales Department of Primary Industries.
