Charles Sturt University (CSU) PhD student Mr Keller Kopf likes to travel, which is lucky for him as so does the subject of his research, the Striped Marlin.
 
Living in inland NSW, Australia, he travels at least four hours by car to the sea or flies to Sydney just to start to find his deep sea subjects.
 
“The Striped Marlin is highly migratory so I travel a lot,” Mr Kopf said. “It just means a little more travel for me. The School of Animal and Veterinary Sciences at CSU in Wagga Wagga has good facilities for handling large animals such as horses so this has translated quite well to my research on marlin. I’m also the first person to do marlin research out of Wagga!”
 
Originally from Nebraska, USA, Mr Kopf did his undergraduate degree in fisheries and wildlife management at the University of Nebraska before commencing research in the Missouri and Platte rivers on the endangered Pallid Sturgeon and the Sturgeon Chub, a small native fish found in America’s Mid-West.
 
In 2004, Mr Kopf moved to New Zealand to complete his Masters degree with Professor Peter Davie working on Striped Marlin. When Professor Davie joined CSU in 2006, Kopf moved to Wagga Wagga to complete his PhD under the supervision of Professor Davie and Associate Professor Robyn Watts from the University’s Institute for Land, Water and Society, as well as Mr Julian Pepperell, a private consultant in marine science.

The Striped Marlin is the main marlin species targeted by game fishers in NSW. Mr Kopf studied the age, growth and reproductive biology of Striped Marlin in the south west Pacific Ocean, which borders NSW. For the research, which Mr Kopf completed last year as part of his PhD, he collected samples from commercial long-line fishing vessels and recreational game fishing tournaments in south eastern Australia, from Mooloolaba in Queensland in the north to Eden in far south NSW, and across to New Zealand.
 
“In summer Striped Marlin migrate south down the Australian east coast. As the weather cools in winter they migrate north to the tropics, so we also took samples from fish caught around New Caledonia and Fiji,” Mr Kopf said.
 
While the commercial long-line fishing primarily targets tuna, they also catch Striped Marlin which is exported, mainly to Japan, for sushi and sashimi.
 
“In Japan it is considered a delicacy, but it is also sold in Australia, similar to tuna but not as popular.”
 
Mr Kopf’s research was funded in Australia by the Fisheries and Research Development Corporation, the Australian Fisheries Management Authority and the NSW Recreational Fisheries Trusts.  He also received collaboration and in-kind support to collect samples from New Zealand, New Caledonia, Fiji and Polynesia. 

“This project has provided the first base-line biological information ever collected on the Striped Marlin, which is vital for effective fisheries management,” says Mr Kopf, whose research results were presented last year to the Western and Central Pacific Fisheries Commission.
 
“Fisheries scientists use complex statistical models to predict how many fish are out there, and how many you can catch before fish stocks ‘crash’.”
 
Mr Kopf collected samples from over 500 Striped Marlin. They included smaller, whole fish samples which were taken back to CSU’s laboratories in Wagga Wagga, as well as fin spines and otoliths, or ear bones, which were used to determine the fish’s age.

The study, the first scientific ageing study for the species, provided some interesting results.
 
“Striped Marlin grow a lot faster than we thought,” he said. “In the first year of life, they grow from an egg one millimetre in diameter to well over a metre long. Their strategy for living in the open ocean is to get big fast or be eaten.” The maximum age of the sample fish was 10 years.
 
The study also found that the fish spawn in the Coral Sea off the Queensland coast, mainly in November and December. Females release over 900 000 small eggs many times each season. The eggs float in the ocean and are fertilised as the males swim past.
 
“Most of the young die, and the lucky one or two make it to one or two years of age and fewer make it beyond that,” says Mr Kopf, who explains that the official status of Striped Marlin is uncertain because, up until this study was done, so little was known about them.

“Catches of Striped Marlin by commercial and recreational fishermen were unusually high in the 1990s, but since then the number caught has declined, which has lead to some concern,” Mr Kopf said.
 
Today over 90 per cent of Striped Marlin caught by recreational fishers are tagged and released.
 
“Being a fast growing species, Striped Marlin should be resilient to high fishing pressure but that doesn’t mean they can’t be over-exploited,” Mr Kopf said.
 
“In terms of commercial fishing, Striped Marlin is in the Eastern Tuna and Billfish Fishery, which is inside Australia’s 200 nautical mile economic zone off its east coast.  This fishery mainly targets Yellowfin Tuna, Big Eye Tuna, Swordfish, and Albacore Tuna for markets across the world.
 
“Striped Marlin is the fifth most commercially important species caught by long-line fishermen.
 
With so many people and organisations interested and involved in the research, Mr Kopf felt good knowing his research findings will be used to help determine future fisheries management policy.

A highlight for Mr Kopf’s research was the field work.
 
“It was amazing to be out in the open ocean and see everything that was out there,” he says. “Commercial and recreational fishermen were really helpful. It wouldn’t have been possible to do the research without their cooperation.”
 
The average trip out with the commercial fishermen was five days, “which was long enough to be in close quarters with five other guys who haven’t showered for a few days who have been elbow deep in fish guts”.
 
Mr Kopf is looking to continue his affair with the sea, continuing research on open ocean fish such as tuna or marlin.
 
“There is a surprising amount that isn’t known which is particularly of concern because we rely on these fish species for food,” he says.
 
“Fisheries are the largest source of food from wild animal populations. The rest - the animals that live on land - are all domestic. Imagine culling hundreds of tonnes of kangaroos and not knowing anything about their breeding behaviour, how fast they grow, and how they respond to the culling? People would be shocked. But because these fish live in the ocean they are easy to forget.”

Perhaps this research will make us a little more aware of what we catch and eat out of the vast ocean.

Source: CSU News