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Fish Tales

 

Mako For Mañana

 

One of Southern California's leading shark fishermen, Keith Poe shares with us his thoughts on mako fishing and conservation ...


Background

I began fishing for shortfin makos (Isurus oxyrinchus) in 1994 and after learning about their reproductive biology, I decided that the responsible thing to do was to give back to the resource rather than to take from it. As my interest in makos grew I learned about the Department of Fish and Game's (DFG) volunteer shark tagging program. The program's objectives are to use the data obtained from the tag and release of pelagic sharks to estimate the local distribution and abundance, and to track the shark's long-term migrations within and beyond the southern California Bight. My involvement in the tag and release program has grown considerably, as a result of which during the past four years I have tagged and released over 1,000 sharks (over 50% makos).

In addition to simply implanting the spaghetti tags on sharks, we must acquire data on sex and length if we are to increase our understanding of the local shark population structure. However, if you have ever tried to handle an explosive small mako at the side of your boat, you will know that obtaining accurate length and sex data is not an easy task. Inaccurate sexing may arise from the fact that the reproductive organs of male juvenile makos are not yet fully developed and consequently are very small. There is also some variation between the common visual guestimation of length and a more precise direct measurement (see Tagging section). Striving to come up with a better way to collect this and other biological information, I designed and created a shark sling. The original sling was made of plastic ABS pipes and an old canvas boat cover, however, the sharks teeth proved more powerful than expected and the canvas was replaced by thick rubber. The sling was suspended by an engine hoist, salvaged from the garage, and bolted through the deck of the 24' Skipjack, "The Shark Tagger". Finally, to complete my new contraption, I attached a load cell between the engine hoist and the shark sling. This allowed for a precise measurement of live weight before the shark was released.

The first day of weighing sharks off Redondo Beach with Mike Jones (a professional photographer from Canada) and David Lopez (a.k.a. "Jaw Man") was very exciting. The first fish brought to the boat that day was a 6ft. mako, a very respectable mako for these waters, and a formidable adversary. After a quick battle we pulled the mako into the sling and slowly raised the sling out of the water. We anxiously looked at the digital scale readout as it leveled at 127 pounds, what an incredible moment. Next, we implanted the tag at the base of the dorsal fin and collected the makos total length and sex. Finally we released the hook and lowered the sling into the water. The mako instantly disappeared from sight and left us with a vigorous splash.

The idea of weighing the sharks was adopted by John Ugoretz, from the DFG, and was put to use during their annual long-lining research cruise off the Southern California Bight. I was fortunate enough to able to participate in this four-day research cruise and assisted in many ways. During my many talks with the investigators aboard the research vessel, I realized the importance of the bilateral flow of information between scientists and sport fishermen. For example, to achieve a clean jaw hook set as opposed to a gill hook set or deeper stomach set, I showed them my baiting techniques. In turn the scientists taught me how fragile the sharks really are, especially the gills where only a paper-thin layer of tissue separates the water from the bloodstream. This prompted me to use smaller hooks, and to pay close attention that if when releasing the fish there was a possibility of damaging the gills it is better to cut the leader and leave the hook, rather than taking the chance of deeply wounding the shark.

During the research cruise I met Diego Bernal, a scientist on the cruise who was collecting tissue samples for shark biochemical research. Since then, we have been working together on various projects. Diego is a graduate student at the Scripps Institution of Oceanography and is conducting his Ph.D. research on mako shark physiology. Diego's research focuses on mako shark swimming energetics, and the use muscle biochemical capacities as an index of swimming performance. Another focus on his mako project is to understand how the relative proportion of swimming muscles, gill surface area and heart mass change with size, and how these animals utilize their ability to retain metabolically produced heat to warm certain muscles and improve sustained locomotor activity. The combined efforts of my fishing expertise provide Diego's research with specific tissues, that will in turn offer a better understanding of mako biology and may ultimately assist the fishery management in insuring a brighter future for this very important resource.

I have set my personal standards for responsible mako fishing. The resource cannot stand the pressure that has been placed upon it. In the past I have only kept four sharks, all males over 6 feet in length weighing more than 100 pounds. The last one, in April of 1998, was 9 feet and weighed over 400 pounds (the largest male mako recorded). If you are going to take a fish it is best to keep a larger male, leaving the females to reproduce. A larger male provides more table faire, as opposed to several pups.

In order to understand the importance of tagging and releasing makos it is important to review what is known about their size at first sexual maturity and growth rate. Scientists have shown that male and female makos sexually mature at different total lengths, with males maturing at 6ft and females at between 8 and 9ft. Moreover, the time it takes makos to reach sexual maturity has not yet been clearly resolved. For example, some workers have estimated that males take 3 to 4 years to reach sexual maturity and may live up to 20 years, while others estimate sexual maturity at 7 to 8 years and a longevity of 45 years. This is where the data collected from tagging and recapture become an extremely important tool for age and growth determinations of the eastern Pacific makos. In addition, by increasing the number of tagged makos we augment the probability of recapturing the fish and thus provide a better perspective on the distribution and abundance of the regional shark population.

All sharks fertilize their eggs inside the female and after an estimated 1 year gestation time, newborn mako pups are born alive and ready to fend for themselves. The average mako litter has 14 pups, which measure about 2 1/2ft. total length. It is important for us as sportfishers to understand that in difference to bony fish which can produce millions of larvae every year, makos (and sharks in general) have a very limited reproductive output. Such a great difference in the number and frequency of newborns produced by makos (average of 14/litter), puts them at a substantially greater degree of danger for overfishing. Moreover, since the average mako captured in southern California Bight is usually smaller than 4ft., and large sexually mature makos are a rare find, the Bight may serve as a nursery ground in which the pups feed and grow on the abundant prey, such as mackerel and sardines. In addition, the Bight may offer a safe place for small makos to avoid becoming prey of larger sharks.

Hunting

Most shark fisherman in Southern California run up to banks and throw out a bucket of chum, while sitting and hoping for the best. However, unlike rock cod, pelagic sharks do not sit and wait for a meal, they spend their entire life in continuous movement in search of prey. These highly mobile predators are not going to waste their energy by hunting in places where water conditions are not adequate. Pelagic sharks, especially makos, are usually found in a specific temperature range and in areas where there is an ample food supply. Even though there are some hypothesis about some shark species orientating their horizontal movements with the ocean floor's magnetic anomalies, conclusive evidence that makos follow such patterns remain unresolved. In addition, the eastern Pacific makos seem to spend the greatest percentage of time at depths that are above the thermocline, with only a limited number of deeper dives. It is important to reiterate that the large amount of data collected for the northwestern Atlantic makos may not directly apply to their west coast counterparts, as the thermocline depth and general bathimetry are widely different between the east and west coasts. For example, a mako sonic tracking study off Florida may lead us to conclude that makos follow the isolume (depth at which there is no considerable change in light level) and hence that makos are found in shallow waters during the night. However, studies of eastern Pacific mako vertical movements show that they rarely make excursions below the shallow eastern Pacific thermocline, thus, this mako population may be limited to an overall shallower depth. In contrast, the east coast is a completely different situation, as the thermocline is present at a greater depth allowing for a potential greater range of vertical movement.

One of the most important reasons why makos are commonly found around banks and canyons is that there is generally some associated nutrient rich deep-water upwelling. The influx of nutrient rich water sparks an increase primary production, which is the cornerstone of the marine food chain. Bait schools seek these conditions, and inherently makos and other apex predators follow. In summary, we are talking about a specific suite of oceanographic conditions. These conditions are what you must actively look for, so don't just sit and wait at any shallow spot for a hookup. Nevertheless, under the right conditions, I have found makos in 80 feet of water with no apparently relevant floor structure. ! Remember that you will never become a good fisherman until you become a great hunter!

If you are planning to specifically target makos you must spend countless hours reading fish reports and analyzing sea-surface temperature maps, which in conjunction provide the best way to select the appropriate water conditions. These optimum conditions have proven to be: 70BAF surface water, lots of bait (preferably mackerel), and a good strong drift approximately 1-3 knots (best if parallel to the shelf). To increase the chances of catching a mako, you should preselect at least 4 different spots that meet you water condition criteria. Upon reaching the first spot it is important to use your fish-finder to locate a school of baitfish, in addition, look for signs of birds and jumpers. Next, determine the direction and strength of the drift and reposition yourself BC to BD mile updrift (a greater distance may be necessary if the drift is very fast). The objective is to lay a good chum slick that will pass directly over the preselected spot. The best chum slick is created using 2 square 4 BD gallon buckets of New Fishall Chum and dumping them into 5 gallon round buckets with 40 1" drilled holes. I have baptized this as "choke chumming". I have found New Fishall Chum to be the best bait mix available. When I start my drift and am trolling the buckets, I drop over a Top Gun Deep Diver made by Ballyhood Big Game International Trolling Lures. The Ballyhood has a 2lb mackerel inserted in it. When trolling, I usually use a Penn International 80 STW spooled with 130 LB Dacron with the drag set to 38lbs. It is important to keep the mackerel at the thermocline depth. Using this method I can attribute about half of my catch to the Ballyhood and have found that usually the bigger makos hit it first! To give your chum slick that "special quality", have a one gallon dispenser of Menhaden Fish Oil from Bordner Offshore Products, dispensing oil in the fully open position. It has proven extremely effective to continuously submerge a Mako Magnet over the side of the boat. Since your slick only distributes its smell along your drift path, the Mako Magnet expands you effective range of fish attraction by projecting a 360BA low frequency sound up to a distance of 1 mile. Scientists have long taken advantage of the shark's incredibly sensitive hearing and pressure wave perception and used low frequency sounds to attract them. If there is no activity for about an hour at the first preselected spot around move to the next one. Remember that this is the reason you have 4 preselected spots.

Tagging

Fishing alone over 90% of the time has obligated me to devise some unique techniques for safely capturing and tagging sharks. I use a Penn International 50SW reel spooled with 100 LB Dacron, and attach a wind on leader made of Burns Saltwater Outfitter's Soft Steel monofilament. Practical experience has taught me that Dacron is far superior to monofilament because it does not stretch and you can get a higher test line with the same capacity of line on the reel. One of the advantages of using the Soft Steel wind on leader is that you only need to attach a maximum of 5ft of 360lb single strand stainless steel leader. To estimate the length of the leader that will best work for you, place the rod into the rod-holder and let the leader hang over the side of the boat until it touches the surface of the water, measure this distance and then subtract 12 inches. I have found that following this procedure allows the bend of the rod to assist in an effective hook release. The 300 LB Soft Steel that I have setup enables me to max out the drag so that I can easily drop the rod in the rod-holder. This is the best and safest way to handle sharks at the side of the boat.

Releasing the sharks is as important as catching them. To release the sharks and minimize the damage to the their soft tissues, I use the Burns Saltwater Outfitters release stick. I have found that Burns has the best design available as it does not have any sharp edges, and has a smaller head which is easier to work with. Slide the release stick down the leader until you reach the arch of the hook, then patiently wait for the fish to position itself correctly, this will considerably reduce the chance of post-catch mortality. The predetermined length of the steel leader (see previous paragraph) bends the rod and creates the perfect spring action to help release the hook. Neonatal makos (under 3ft in length) are very fragile, in a sense like newborn babies, so I will not force a release stick into their mouth as the gills lie dangerously close. To decrease the damage done to small makos by the releasing process, I have found that if the hook is not clearly visible in the jaw, it best to cut the leader as close to the hook as possible. It is very important to avoid letting the sharks run with the bait as they can easily swallow the hook and become injured during the fight. To avoid such an outcome, I do not put the line more than 100 feet off of the back of the boat and I set the hook immediately to insure a proper jaw hook set. Remember that if you are going to go out and catch makos, there is no room for error and the job should be done right the first time.

Even though it is tempting to use big hooks so that the big one does not get away, I have found that 9/0 Mustad hooks are more than adequate. These small hooks are inexpensive and reduce the risk of damage to the fish. Not long ago, I tagged and released a 7ft. mako that was over 200 lbs, an 8ft 2inch mako over 300 lbs, and many pups on the same Mustad hook without any evidence of material stress. Shark skin and mandibular cartilage is very tough, so the hooks need to be razor sharp and it is wise to use a dremel tool as a sharpening instrument.

As far as tagging, I have found that the Aftco tag stick is the best. The best time to take a shot at the fish with the tag stick is when he is positioned dorsal up. Find the correct spot at the base of the dorsal fin, stare exactly at point where you intend to insert the tag and give it a shot. Tagging the fish while it is rolling on its side increases the chance of lacerating the great lateral vessels, which may result in death. The National Marine Fishery Service and the California Department of Fish and Game have successfully adapted a spear gun to insert the tags. This innovative device allows the tagger to accurately place the tag at the base of the dorsal fin while minimizing the fish handling time. It would be very wise to make this device available to all the taggers, and thus minimize post-catch mortality associated with bad tag insertion.

It is very important to obtain reliable length measurements, and here are some of the methods commonly employed by taggers:

a. marks on the side of the boat that have a known distance between them
b. marks on your tag and release stick that have known distance between them
c. different colored ribbons attached to the release stick that have a known distance between them
d. a stiff tape measure

Measuring techniques will vary depending on the size of shark that you are dealing with and the relative state of stress that the shark demonstrates. If the captured mako is under 5ft., has a clean jaw set hook, and it is not thrashing like mad at the surface, I like to gently hold the fish by the tail and roll it ventral side up. I immediately extend the tape measure next to it while checking its sex. If the mako is very small and I conclude that a visual determination of sex will not be accurate, I hold the leader with one hand and feel underneath the shark looking to find claspers if it is a male.

To minimize the shock associated with capture I like to beat the fish on heavy tackle, measure, sex, tag and release it as quickly as possible (usually less than 2 minutes). Occasionally I have recaptured a mako that I had tagged earlier that day, and I have also recaptured the same fish the next day. After all the time that I have spent fishing for makos, I have gotten better at minimizing capture related stress and I usually give the makos a few pets before sending them on their way.

Importance of tagging

Recent fishery studies conducted by the National Marine Fisheries Services (NMFS) off the western Atlantic and the Gulf of Mexico have concluded that the depletion of up to eighty five percent of the regional shark resource is attributed to overfishing. The eastern Pacific is by no means exempt from such poor management, and we must therefore learn from the East Coast example and prevent such devastating decreases in local shark populations. It is important to understand that the research conducted by scientists on East Coast makos, does not necessarily apply to the fishery in Southern California Bight. The ecology of eastern Pacific makos appears to be very different from their east coast counterparts, for example, they differ in food source, diving patterns, average depths (see Hunting sections for more details), temporal and spatial migrations, and overall length. So when it comes time to apply a management plan for the eastern Pacific mako population, decision makers should take caution in only using the information available from the east coast studies to infer a west coast management plan.

In 1983 the Department of Fish and Game started the volunteer pelagic shark tagging program. Out of the 21,000 shortfin makos that have been tagged and released to date, there have only been 84 reported recaptures. Most of the recaptures have occurred within thirty days from the original date of capture, and within fifty miles of the initial site. It is extremely difficult for policy makers to rely on such a small data set to dictate future management decisions. Sportfishermen offer an important link between scientist and policy makers, as our combined fishing effort can provide an adequate number of tagged sharks which in turn will ensure a more comprehensive picture of the eastern Pacific mako population. There are currently only 52 active taggers on the West Coast and most of these taggers only tag a few sharks (5-10) per year. There is a desperate need for more fishermen to pick up the phone and call (562) 590-4801, to get their free tagging kit, the future of our resource depends on this.

I have personally concentrated my efforts and made it my goal to increase the number of taggers in our local program. Not only have I learned a great deal about sharks, but I have found some great avenues for teaching the general public about our decreasing shark population and how they can influence its future. Chuck Myers and I have been able to increase awareness through our television show the West Coast Sport Fishing Show by filming conservation minded shows, and focusing on the tagging program. Last May I started my own web site (www.sharktagger.com) with the assistance from my engineer and designer Jamie Wilkinson. It has been people like Jamie, who have helped increase awareness on this issue without expecting anything in return, that emphasize the good nature sportfishermen have. The web site provides a lot of exciting information for fishermen. We have a very active message board with Live Fish Reports and have focused in offering the public a number of scientific studies that will provide the visitor with an in depth review of some aspects of mako ecology and biology. In addition, the site provides all the information you need to know about the tagging program, and even has the capability of downloading an application form for tags. The site also has an impressive image gallery, which is constantly being updated with current photos. Through my website and in conjunction with Don and Mel from Allcoast (www.sport-fish-info.com), who have added a shark message board to their site, I have been able to expand my area of work and now have a much stronger voice that can reach out to many more fishermen.

Conclusion

Sport fishermen and commercial fishermen on the West Coast seem to be over fishing the local shark populations. Without adequate scientific studies, it is not possible to impose new laws to protect the shark fishery. I would like to see sport fishermen get together and set a standard of responsible fishing for the mako fishery. The guidelines that I feel we should follow are:

a. Set size limits (nothing taken under six feet).
b. No females taken.
c. One fish per angler per season.
d. All fisherman must tag.

If all sport fishermen tagged sharks, we would gather sufficient data to influence changes in the laws that would result in a regulation of the commercial fishery. In contrast to the 6500+ taggers that NMFS has in the East Coast, the West Coast only has 52 active taggers. If we collect enough tagging information, we will be able to make changes like the ones accomplished in the East Coast fishery, for example we could:

a. Impose size limits on commercial and sport fishermen.
b. Improve monitoring of recreational and commercial landings.
c. Prohibit finning of all cartilaginous fish in both state and federal waters.
d. Close the state waters to direct shark fishing during the pupping season.
e. Close some or all nursery areas to other fisheries that take large numbers of juvenile and adult sharks in their bycatch.
f. Prohibit the use of gear with high bycatch and or require the use of devices that cause such unnecessary mortality.
g. Require commercial fisherman to tag bycatch and undersized fish.
h. Develop tag and release training programs.

Although I have created a strong voice in conservation to increase further awareness and help develop future studies, I need to acquire more support and sponsorship. I am looking to large corporations, both marine and non-marine related, to expand awareness to all the fishing related public and the general public. To reach some of my goals, I need to have a larger, safer, and more dependable vessel in which more accurate data can be collected using the shark sling, and in which I can educate new taggers and collaborate with scientists. To continue my mission I need a boat sponsor, this will enable me to collect DNA samples from which scientists can build a spatio-temporal database of local shark populations, and will permit me to assist with the ongoing studies by scientists at Scripps Institution of Oceanography. In turn, I am able to provide my sponsors with advertising on my web site, television show, through media attention and via public speaking at seminars. If anyone is interested in learning more about tagging, information on sponsorship, or would like to go out fishing, please contact me at (310) 371-4401 or email me at sharktgr@gte.net, and please don't forget to check out the web site at www.sharktagger.com.


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