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“Don’t do a PhD research project on live marlin,” they said. “It will never work.”

I responded, “Why not?”

They said, “It’s far too hard, marlin are highly migratory, incredibly elusive, they dwell in the outer reaches of most oceans, and in most cases they are solitary. And, finally, you’re trying to work out the very early stages of their life.”

They were making some good points.

“We know next to nothing about their reproduction and behavior,” they said. “Please do another project like reef-fish, or tide pool shellfish. It’ll be easier on everyone.”

I may have heeded their words if it wasn’t for two factors: One, I was moving back to Kailua Kona, Hawaii, where I had lived as a teenager and knew something of the waters. Two, I had a great supervisor, Dr Julian Pepperel, one of the world’s experts on billfish.

So, after visiting the Australian museum larval fish collection to get an idea of what a larval billfish looked like, I headed to Kona.

As I stepped onto his boat as a shiny new PhD student, the charter skipper looked me up and down. “What the hell do you know about marlin, Sonny?” he asked.

Clearly I needed to earn my respect in this legendary fishing town. You see, larval marlin are around 3mm in length when they hatch (about the width of a match) and most commonly found in the neuston layer of the ocean from 1-to-4 weeks after a marlin-spawning event. The neuston layer is the thin (2-to-3 feet) layer of the ocean’s surface where most of the phytoplankton can be found. It is a place where there is a ready source of food for these voracious little buggers.

So funds being low, I constructed some larval marlin capture nets out of mosquito mesh, old carpet and PVC pipe. Armed with this high-tech research equipment my wife Jane and I headed out into the blue to test these ghetto nets. I needed Jane there for moral support and to continually pump air back into our leaky Zodiac inflatable boat.

I threw the nets over the side, with my ears still echoing the words of some of my biologist friends. “Andrew, we don’t know for sure that they spawn in Hawaii, don’t waste your time.” We were only 300 yards out of the Honokohou harbor when the Coast Guard ordered us back in. Dejected after our brief larval tow we headed for shore, and examined the contents of our catch bucket to find three larval marlin!  We were absolutely ecstatic, peering at those incredibly beautiful cobalt-blue mini marlin darting around our bucket.

We were on the right track!  And the quest had begun. That was ten years ago.

A year later I was invited to be a part of a scientific cruise with some top marine scientists looking for billfish larvae. I won’t forget the interesting looks I received when I threw my homemade nets on the deck of the ship. Why would we bring nets when they had a 60-foot-long plankton net that ran down half the length of the ship?

I just asked them to put me in the dinghy and let me do my thing. On that cruise my little nets had a higher capture rate then the huge net on the ship. Not surprisingly. I was invited back every year after but they would always end the invitation with, “Can you bring those nets with you?”

The crazy marine biologist became a commonplace site in the waters off Kona, as charters fished past me looking intently over the side of the boat, head down, with his bum in the air. Now I was able to spot larval half-inch marlin from up to 20 feet away. Once spotted, the larval marlin were quickly dip-netted, placed into a bucket, and soon returned to the water followed by a video camera and instruments recording swimming speeds. For me, swimming alone miles out to sea following larval billfish was almost a daily event. This was sometimes punctuated with panic swimming as the breeze would pick up and I had to chase the unattended boat. (Of course, I never informed the wife of those details.)

These tiny marlin still amaze me. On more than one occasion I have extended my hand toward half-inch marlin, and elicited a response that shocked me. They would stop swimming, turn around to face me, raise their dorsal fins as a menacing gesture, and eventually rush in, nipping at my fingers! Their whole demeanor screamed, “You want a piece of me buddy?”

In ten years of research, we’ve learned volumes. The most relevant are the following:

  • Short billed spearfish spawn all year off Kona Hawaii, with a peak in spawning late winter
  • Blue marlin spawn all year off Kona with a peak in late summer
  • Swordfish spawn in Hawaii July to August
  • Billfish larvae grow amazingly fast, and there is very little they are scared of
  • Their diet consists firstly of crustacean larvae, then fish larvae
  • Their favorite diet is mahi mahi larvae, flying fish larvae, and each other
  • I once removed a 9mm marlin from the stomach of a 13mm marlin

We’ve now established that the Kona Coast is a major spawning ground for blue marlin. There are a few locations around the world, such as the Gulf of Mexico, where we can seasonally find recently hatched blue marlin, but nothing like Kona. There is no wonder why Kona is one of the world’s premier fishing locations for large marlin. This is where they come for love (well, spawning anyway). I believe it is not only a hot spot for human honeymooners and romantic vacationers, but also a site where pacific blue marlin get busy. Gravid (egg laden) blue marlin females are attracted to the calm, clear, food rich waters that Kona provides.

One of the main facts that we know about blue marlin reproduction is that all the big marlin are females. Males only grow to 300 pounds. What is the upper limit to blue marlin size? We can only guess, but my estimation is somewhere over 3,000 pounds. Female marlin get big because they are essentially large egg factories.
The general rule with fish reproduction is egg production is exponential to fish size. That is, if you double the size of the fish, you may more than quadruple the amount of eggs it produces.  The blue fin trevally (Caranx melampygus) is a great example. The number of eggs produced by a two-foot-long female is 86 times the number produced by a one-foot-long female. Not only do larger fish produce more eggs, but the eggs are of better quality. Having larger oil globules (energy reserves), the emerging larva are in much better condition, and less starvation resistant.

Unlike mammals, most fish do not senesce (slow reproduction in old age) when they get big. Rather, fish have more of their body reserves to dedicate to reproduction. Also a very important factor is when they get big they are less likely to get eaten by other fish. So, in essence, they have already run the gauntlet of predators and natural attrition, they have graduated, and now their only job is to eat and make lots of babies. The bottom line is that the larger the female, the far more valuable she is to the fish population.

Hawaii is still one of the only places in the developed world where you can legally kill as many marlin as you want. To date there has not been any management restrictions or quotas applied to marlin fishing. This is not to say that fishermen in Hawaii are mindless fish killers, in fact most feel a strong connection with the “aina” (environment). Rather, many fishermen or tourists are new comers to the islands and relish the new freedom of no restrictions.

A debate has raged for decades now as to who is really to blame for dwindling marlin stocks in the Pacific. There is a lot of finger pointing between the marlin charter sports-fishermen and the long-line fleet. The facts are actually surprising. The sports-fishermen do catch considerably less animals than the long-liners but the fish they catch are generally larger and hence more valuable ecologically
Over the last 10 years I have seen a move away from open season on marlin to more of a conservation mindset, where fishermen are realizing that they may be sitting on the branch they are sawing. In fact, now, two thirds of marlin fishermen in Kona practice tag and release only. I have also been delighted recently to hear a cry for marlin management by the charter fleet captains; half of them recently signed a petition wanting management that protects the marlin population.

A small group of captains have been meeting together discussing a ban on the commercial sale of blue marlin meat in Hawaii. This solution would have to be adopted by both charter fishers and the long-liners. To me this makes great sense. This would mean that local fishermen can keep a fish to feed his family, but he could not to sell it.

I applaud this effort, as it would favor the big female marlin, for only the smaller fish are ever kept for eating. Larger fish are harder to sell anyway, as they are too coarse and may contain high levels of mercury. This solution removes the impetus for fishermen to keep large marlin that are sometimes kept only for the sole purpose to pay for the ice in their coolers.

What about the tournaments?
Kona is the home to many great marlin-fishing tournaments attracting anglers from all around the world.  During summer there is a tournament underway almost every weekend. Some conscientious tournament directors have upped the minimum size to 500 pounds.  However, while feeling good about this decision, they are still targeting the most valuable breeding females.
Perhaps it’s because I’ve lived in Australia for so long, and possibly still see things upside down, but isn’t this all a bit backwards?  Instead of releasing the little guys and killing the big gals, we should be releasing all the big gals keeping a few small ones?

From what I am aware there are very few tag and release tournaments in existence. The only two that I know of are the Marlin Masters in Mauritius, and Curacao’s Marlin Release Tournament. I was surprised to read that one of the tag and release tournaments has a line class of 30-to-80 pounds. As a marlin biologist this alarms me. In one of our recent studies we tagged 50 blue marlin with PSAT satellite tracking tags in order to get some hard answers on post-release survival rates. Most fish were caught in tournament conditions with the only criteria being that “the fish has a heart-beat”. Some very iffy looking fish were tagged and sank from sight upside down. To our surprise they later reported as having survived. The purpose of our research was to determine stress levels through biochemical indicators, and the survival rates of captured and released fish.  I was expecting about a 50 percent post-release survival rate. The results shocked me, as 97 percent of all fish survived! This is not to say that the ordeal of being captured and released is not stressful to the fish, it is, but as long as the fight times are kept down to a minimum (under 30 minutes if possible) and the fish has no major damage, it has a great chance of surviving.

After working as deck hand on many of the charter boats in Kona, I am amazed at the skills of these skippers. If the fish isn’t in within 30 minutes, usually something is wrong, and it’s usually the guy in the fighting chair cranking the reel. To get a blue or a black marlin in quickly and increase its chance of surviving, 130-pound line is recommended.
I have a love-hate relationship with tournaments, I love anything based around marlin species and tournaments are one of the few portals we have to get close to marlin, get samples, and learn about their behavior. However, I hate seeing large majestic marlin hanging dead for the sake of some tournament points. Let’s face it; it is time to restructure the tournaments.

We live in the video entertainment age. Digital cameras already abound on charter boats.

I would suggest a marlin-fishing tournament in Hawaii that is tag and release only, with every team having a designated video operator who films all the action. The video is then viewed at the end of the day before a panel of judges (and spectators) who assign points for three different criterion:

  • Estimated size of fish
  • The coordination of the boat team
  • The length of time it takes to tag fish

Judging only by the size of carcass you can hang on the pier is outdated and should be changed. Spectators would love to be entertained by videos of the fight, the live fish and the action. Currently they just wait around to see a dead fish weighed.

How about a Guy Harvey Hawaiian tag and release tournament with funds going towards billfish research?  It is a new era for sports-fishing and we need to make changes to help save the majestic billfish we all admire.


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