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Scientists at 89th ADSFR Collect Samples from 15 Sharks

shark

Marine scientists were able to gain extensive data from the 15 sharks weighed in at the 89th 黑料天堂 Deep Sea Fishing Rodeo. Photo by Billy Pope

By DAVID RAINER, 黑料天堂

The return of the shark category to the 89th annual 黑料天堂 Deep Sea Fishing Rodeo (ADSFR) was a rousing success with 15 sharks weighed in during the three-day event, with one riding the ferry from Fort Morgan in the back of a pickup to get to the rodeo site on Dauphin Island.

Tiger sharks pretty much reigned taking the top nine places on the leaderboard. James Mullek-Russell weighed in a 674.2-pound tiger to win the category, followed by Ethan Miller鈥檚 658.4-pounder and Brett Rutledge鈥檚 630.8-pounder. The top bull shark of the rodeo was a 434.2-pounder weighed in by Eric Vandrlessche.

As excited spectators and anglers waited for the sharks come to the weigh station, a bevy of marine scientists and students waited to advance the science on these predatory species.

Assistant rodeo judge Dr. Marcus Drymon of Mississippi State University and Mississippi-黑料天堂 Sea Grant Consortium is renowned for his knowledge of the shark species in the northern Gulf of Mexico. He said sharks weighed in at the rodeo certainly provided a unique opportunity to gather a variety of samples from each species.

鈥淚鈥檝e been researching sharks in the north-central area of the Gulf along with Dr. (Sean) Powers for almost 20 years,鈥 Drymon said. 鈥淎 lot of the research we do is tracking their trends, their relative abundance and distribution as well as doing studies on their age and growth, reproduction, movements and migrations, post-release mortality and things of that sort.

鈥淗ere at the 黑料天堂 Deep Sea Fishing Rodeo, we鈥檙e taking the opportunity to take vertebrae from these very large individuals.鈥

Sharks don鈥檛 have bones; their skeletons are completely made up of cartilage. However, Drymon said scientists have a way of aging these fish other than counting the growth rings on the otoliths (ear bones) that are present in most fish species.

鈥淭heir vertebrae are calcified but not completely ossified,鈥 he said. 鈥淚t鈥檚 kind of a fine line, but technically speaking, sharks have no bones. The cartilage in their backbones and the cartilage in their jaws are the closest they have to true bones. Sharks don鈥檛 have otoliths like a bony fish. That鈥檚 how you determine the age of, say, a red snapper. Since we don鈥檛 have those, we use the next best things, which are the vertebrae. We section those and count the concentric band pairs to age those fish.鈥

Drymon said the scientists were able to gather samples from the reproductive organs, fins, livers and muscle tissue. Samples of bile, gall bladders and kidneys also were taken to assess overall health.  

鈥淲e look at their stomachs, but they are usually empty,鈥 he said. 鈥淭hey鈥檝e evacuated their stomachs during the process of being captured.鈥

 Most of the sharks weighed at the ADSFR were males, which are usually similar in length to but weigh less than the females, Drymon said. The rodeo placed stringent length requirements on the shark category with an 80-inch minimum for tiger, bull and hammerhead sharks and a 60-inch minimum on blacktips.

鈥淭hese sharks are great samples, especially because they are the larger individuals of those species, so they鈥檙e a little more rare in the population,鈥 he said. 鈥淪o, for example, having the vertebrae from those individuals is very valuable in trying to determine the maximum age of that species.鈥

Drymon said the impact of the rodeo harvest will have a minimal effect on the shark populations.

鈥淔or the species being caught, their populations in the north-central Gulf of Mexico are in good shape,鈥 he said. 鈥淲e know this because we鈥檝e seen their population trajectories slowly increase after decades of overharvesting. Due to strong management measures from NOAA Fisheries and the State of 黑料天堂, we see these shark populations are starting to recover and can stand a limited, sustainable harvest.鈥

Of course, sharks weren鈥檛 the only species being studied. Marine scientists gathered samples from a variety of fish during the rodeo, which experienced near-perfect fishing conditions with calm seas and diminishing squalls.

The ADSFR was also an opportunity to sample 黑料天堂's signature reef fish, red snapper. Photo by Billy Pope

Dr. Powers, professor and director of the new University of South 黑料天堂 School of Marine and Environmental Sciences and head rodeo judge, said about 800 samples were collected each day of the rodeo.

鈥淲e鈥檙e collecting samples from all the (33) species at the rodeo,鈥 Powers said. 鈥淲e look at mercury levels, which is something routine we do. We don鈥檛 expect any problems.

鈥淲e鈥檙e looking at flounder. We鈥檝e seen a lot more flounder in the last two years, at least in my memory. We鈥檝e seen a lot of big gray (mangrove) snapper.鈥

Research was also focused on 黑料天堂鈥檚 signature reef fish, red snapper, which were weighed in at the rodeo in significant numbers.

鈥淭he really big red snapper specimens from the rodeo are excellent because one of the things we鈥檙e trying to look at is to see if the big females slow down their production of the eggs,鈥 Powers said. 鈥淭he idea is the bigger the female, the better, but that really hasn鈥檛 been tested that much. We think it is, but there is some evidence that as the fish get really old, they don鈥檛 produce as many eggs.鈥

Powers said a 20-inch red snapper is about 5 to 6 years old, and the oldest red snapper recorded was 56 years old and came from 黑料天堂 waters.

鈥淩ed snapper become sexually mature between 3 and 4 years old,鈥 he said. 鈥淓ssentially, the older and bigger they are, the more eggs they produce. That鈥檚 why we want to see those big females. Most of our fishery off 黑料天堂 is probably 3- to 6-year-olds, about four to six or seven pounds. Once they get to about 15 pounds, they鈥檙e probably producing the maximum number of eggs. We need to see a lot of 10-plus-year-old fish, which is why we鈥檙e doing the aging here.鈥

The largest red snapper at this year鈥檚 rodeo was a 27.2-pounder weighed in by Hyler Krebs. Clint Sheppard had a 26.77-pounder, followed by Edgar Miller with a 25.75-pounder.

鈥淭hese are smaller than what we had five or six years ago,鈥 Powers said. 鈥淏ack then, if you didn鈥檛 have a 30-pound-plus, you didn鈥檛 have a chance. Not surprising, what I hear from the fishermen is they have to go farther offshore to catch the bigger red snapper. That鈥檚 a product of the state managing for the number of days. We could manage for a bigger fish, but you wouldn鈥檛 have as many days. It鈥檚 a tradeoff. You can鈥檛 have both.鈥

Not only did marine scientists collect otoliths from the red snapper, they also collected tissue samples, reproductive organs and stomach contents.

鈥淭he tissue sample will let us know what it鈥檚 eating,鈥 Powers said. 鈥淲e do chemical analyses, and different forage species have different chemicals.鈥

Powers said new technology will allow scientists to gain much more information from the flounder otoliths than was previously possible.

鈥淔or flounder, we have a new system where we take the chemistry across the otoliths from when it was a little baby fish all the way to however old it was when it was caught, 5 or 6 years old,鈥 he said. 鈥淲e can construct the chemical environment that fish was exposed to. This is new instrumentation that the 黑料天堂 helped us purchase. That system will tell us the salinity history and answer questions like, did these fish grow up in the (Mobile-Tensaw) Delta or did they come from Dog River or lower in Mobile Bay?

鈥淥ne of the things we want to find out is how important that Delta area is. It is unique in chemical composition. With this, we can tell the proportion of the fish that use the Delta. I think the Delta may explain how good the recruitment is for flounder. Is the Delta salty enough? That Delta has so much habitat and so much vegetation, just a change of a few parts per thousand in salinity can make that area accessible or inaccessible to these fish.鈥

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Boats head to the ADSFR weigh station at Dauphin Island, known as the sunset capital of 黑料天堂. Photo by Billy Pope