Fishing is the most likely reason a large dead porbeagle shark washed up on Mohaka beach, DoC says. Photo / Kali Wyllie
Did you know that dead sharks usually sink to the bottom of the sea?
So the sudden emergence of one on Mohaka Beach in Hawke’s Bay has left a local whānau scratching their heads, and experts forced to answer the question of whether it’s safe to go back in the water.
The region has seen a significant amount of dead marine life wash upon its shore in recent times, but the porbeagle shark, a common offshore species and close relative of mako and great white sharks, appeared well-fed, unlike a spate of starving seals found on Ocean Beach further south.
Mohaka locals Kali Wyllie, partner Tyrone Thornton and their two children were going for a walk for a fish on the bar when they spotted it.
“It was freshly washed up,” Wyllie said. “It was just under two metres and was really fat.”
DoC technical adviser marine Clinton Duffy said the shark was not a dangerous one and people should be safe to swim.
He said there have been no unprovoked attacks by porbeagles reported from New Zealand, and that attacks by the species were extremely rare globally.
“Porbeagles are primarily fish and squid eaters and seldom come into direct contact with humans due to their offshore habitat,” he said.
“That said, large [1.8m or more] potentially dangerous sharks can be encountered anywhere around the New Zealand coastline at any time of the year.
“Places where extra care should be taken are anywhere in or around deep channels, places with concentrations of potential prey such as large schools of fish or seal colonies, or anywhere someone is fishing or cleaning fish.”
Duffy said sharks were occasionally found dead on beaches around NZ. The most common reason was that either recreational or commercial fishers had discarded them.
“Recreational fishers often discard sharks and rays caught from shore on the beach rather than returning them alive to the water. This may be because they consider them pests, or because they are concerned about being bitten or stung.
“Commercial fishers usually discard unwanted sharks alive or dead at sea. Those that are discarded alive but weakened or disoriented sometimes swim inshore and end up getting stranded.”
He said most sharks are negatively buoyant, so dead sharks don’t usually wash up if they have been discarded any distance offshore.
The relevant information for the shark on Mohaka Beach was passed on to the Minsitry for Primary Industries (MPI.)
MPI New Zealand fisheries acting director fisheries management Rob Gear said in the Hawke’s Bay region, porbeagle sharks falls under the finfish daily combined bag limit for recreational fishers, which is 20.
He said sharks could appear dead on beaches for a number of reasons but people should not always assume it was a result of commercial fishing.
“Shark species that are targeted for commercial fishing are predominately rig and school sharks. There are no commercial fisheries that specifically target porbeagle sharks in New Zealand,” he said.
“It’s not correct to assume that sharks that wash up on beaches are attributed to commercial fishing, as this can result from recreational fishing or other causes. It is legal for recreational fishers to return unwanted shark catch to the sea, and live release is encouraged.”
Duffy said besides fishing, toxic algal blooms have sometimes resulted in strandings of sharks after they had been poisoned, although this was a rare occurrence.
He encouraged people to report sightings, strandings or captures of any species of shark or ray to the DoC Sharks Mailbox (sharks@doc.govt.nz).
The shark sighting wasn’t the first time Wyllie had seen washed-up wildlife along the beach. She said she had also seen seals, both alive and dead, turn up at the shoreline this year.
It was reported last week that 23 dead seals of “varying age and decomposition” had been found washed up on Ocean Beach near Waimarama since September 3.
DoC science adviser marine Laura Boren said initial results indicated starvation as the cause of death for those seals.
Mitchell Hageman joined Hawke’s Bay Today in late January. From his Napier base, he writes regularly on social issues, arts and culture, and the community.