A Seascape of Barrens
Dr Jen Thompson remembers diving through beautiful kelp forest looking for Weedy Seadragons at Barunguba/Montague Island.
That was over 30 years ago.
Now so much of that incredible biodiversity has been lost as Long spined Sea Urchins have eaten the kelp, leaving urchin barrens. Dr Thompson, a member of Nature Coast Marine Group (NCMG), is passionate about protecting one of the few predators of these urchins - the Eastern Blue Groper.
“These fish need time to be effective predators. Research has found that sea urchins occur in the gut content of 70% of large blue gropers, but in only 30% of the smaller ones,” she said
These fish live for decades and need time to grow large, breed productively and not be caught.
Labradors of the sea
Blue Groper & Diver, Baranguba
”Blue gropers are friendly and they come up to say hello,” Dr Thompson said. “Back in the 1950s blue gropers were around 40% of the reported catch of spearfishers, but this fell to 4% by the late 1960s.”
The fish became fully protected in NSW in 1969 but lobbying by fishers overturned that in 1974. Two by line can still be caught. The fish is fully protected in Victoria and Tasmania and is listed as ‘near threatened’ by the International Union for the Conservation of Nature.
“You don’t see big ones here anymore and there is a strong case to restore full protection for this magnificent fish which is the Marine Emblem for NSW,” Dr Thompson said. “Data from NSW Fisheries shows thousands of blue gropers are caught each year.”
Sanctuary lost
Sanctuary zones around Barunguba/Montague Island were among those lost in December 2019 when the NSW government announced a fishing amnesty. The amnesty allows recreational fishing without being prosecuted. “If you stop the amnesty, at least you will protect blue gropers in those areas,” Dr Thompson said.“We need long-term sanctuaries for these territorial and decades-lived fish.”
Marine heatwave
Dr Jane Elek, a scientist and ex-president of NCMG, said warming ocean temperatures are compounding kelp loss. “It is two-fold - our local kelp doesn’t like warm water while the urchins do, breeding faster, ” Dr Elek said. “Ädded to this, we are losing urchin predators to fishing – blue gropers, big snappers and large crayfish.”
Urchin Barrens, Baranguba
She said fishing is also causing the general fish populations to become smaller in body length and breed earlier, meaning less eggs are laid. Dr Elek said if sanctuary zones are restored in Australia’s marine parks, the damage to fish populations may be reversible just like humpback whale numbers have recovered.