Spring 2019

Hook, Line & Science

J Hooks, Warming Waters, and Favorite Reefs

May 22, 2019 6-min. read

The award-winning series curated by Scott Baker and Sara Mirabilio, fisheries specialists with North Carolina Sea Grant

Can Circle Hooks Compete with J Hooks?

One Hook Clearly Wins in the N.C. Offshore Dead-Bait Troll Fishery

Almost one-half of North Carolina’s 11 million pounds of marine recreational landings in 2017 came from three species: yellowfin tuna, dolphinfish and wahoo. Clearly, the act of hooking — and then successfully bringing the catch aboard — is important to saltwater anglers!

Research Need

At the time of this study, fisheries managers were unsure whether to require the use of circle hooks in offshore dead-bait troll fisheries. Some studies had found that circle hooks maintained catch rates but reduced rates of deep hooking for billfishes, compared with J hooks. If circle hooks were required, what impact would it have on catch rates in these troll fisheries? Members of North Carolina’s charter boat industry were eager to find out.

What did they study?

Fisheries scientists partnered with charter and recreational fishermen to compare catch rates for circle hooks and J hooks for three common fish species in the N.C. offshore, dead-bait troll fishery: dolphinfish, yellowfin tuna and wahoo. Prior to testing, scientists and expert fishermen met at a planning workshop to determine the hooks and gears to be tested “side-by-side” on 75 trips. It was important for everyone to come to agree on the parameters, including selecting specific circle hooks that are comparable to the J hooks used in this fishery. The scientists then ran computer models to better understand how such factors as hook type, leader type, species, trip type, and wave height affected catch rates.

What did the results show?

Generally, more fish were caught on J hooks than circle hooks. In fact, computer modelling suggests that fishermen can expect 65 percent greater catches of the three species with J hooks. The results confirm the general observation of the charter boat industry that J hooks perform better than circle hooks in this fishery.

What else did they find?

While king mackerel were not a large proportion of the total catch in this study, the research team found that J hooks also were more effective than circle hooks in catching this species.

Anything else?

As tackle manufacturers continue to introduce new hooks and terminal tackle, will these results hold? They certainly could. The planning workshop for the study generated many novel rigging and fishing techniques with circle hooks, but only the most promising were tested.

Reading

For specific hook descriptions, fishing techniques and more: Rudershausen, Paul J., Jeffrey A. Buckel, Greg E. Bolton, Randy W. Gregory, Tyler W. Averett, and Paul B. Conn. 2012. A comparison between circle hook and J hook performance in the dolphinfish, yellowfin tuna and wahoo troll fishery off North Carolina. Fishery Bulletin 110 (2):156–175.

From Coastwatch: “Hooks in the Gulf Stream: Captains and Scientists Reel in Data”

Summary compiled by Scott Baker

Above photo courtesy of Paul Rudershausen (NCSU)

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Will Fish Move as the Atlantic Warms?

Warming Could Lead to Distribution Shifts for Popular Species

Sometimes it’s difficult to see differences in fisheries populations when we look at data from season to season or year to year, because often differences are variable or small. Generally, the best insights come from examination of long-term data sets. Here is a great example of the utility of looking at data trends over a longer period.

Research Need

The waters around the U.S. Northeast Continental Shelf have warmed considerably faster than the world’s oceans as a whole, and this increase is expected to continue. Warming of ocean temperatures may ultimately change the distributions of many popular fish species, impacting both local fishing communities and possibly even major fishing ports. Having a better understanding of where fish might move as the ocean warms can help fishermen plan for the future.

What did they study?

Scientists used a high-resolution global climate model and historical observations of species distribution from trawl surveys to estimate changes in thermal habitats. This study is important, because different fish prefer different habitats — and their preferences also are linked to a suitable water temperature at those habitats. The research focus was the U.S. Northeast Continental Shelf from the ports of Wanchese, North Carolina, to Portland, Maine.

What did the results show?

At the end of the 80-year model simulation period (or year 2093), ocean temperatures in the southern portion of the study area (nearest North Carolina) are forecast to increase by a projected 7.4^oF (4.1 °C) on the surface and 9.0^oF (5.0 °C) on the seafloor along the Shelf. This will result in a probable northward shift for the majority of species’ thermal habitats.

What else did they find?

The anticipated increase in water temperature will impact some species more than others. For example, projections suggest that butterfish and black sea bass will suffer moderate losses in preferred thermal habitat, whereas such species as summer flounder, striped bass and Atlantic croaker will experience significant increases.

Anything else?

The Atlantic croaker and smooth dogfish also showed strong northern shifts under future warming predictions. All things being equal, North Carolina fishermen targeting these species in the future will have to travel farther to reach them.

Reading

Kleisner, K., Fogarty, M., McGee, S., Hare, J., Moret, S., Perretti, C. and Saba, V. (2017). Marine species distribution shifts on the U.S. Northeast Continental Shelf under continued ocean warming. Progress in Oceanography, 153, pp.24-36.

Summary compiled by Caitlin Cunningham and Scott Baker

Above photo: smooth dogfish, by Chuck Bangley

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Do Anglers Prefer Artificial Reefs?

Patterns along the Gulf Coast Suggest Anglers Favor One Type of Reef

Have you ever been to one of your favorite fishing spots and found you were the only one in sight? Did you think either no one was fishing that day or few people knew about your spot? Or maybe, you pondered whether you were missing “the bite” somewhere else? What if there was a way to see how much boat traffic occurred at various fishing locations without actually being there in person to observe it?

Research Need

Knowing whether anglers prefer one reef type more than another can help to assess the value of reefs for fishing and enjoyment, as well as characterize the economic impact of natural and man-made fish habitats.

What did they study?

To better understand where anglers prefer to fish, researchers studied four pairs of artificial and natural reefs in the eastern Gulf of Mexico off western Florida, where a lot of artificial and natural reefs are in close proximity. Scientists calculated boat visitation rates for these reefs using underwater acoustic recorders, collecting digital sound files over almost two years.

They then developed a computer program to automatically identify boat noise and to separate that sound from any others present at the reef locations. Once the boat engine sounds were isolated from all other background noises, the scientists developed a procedure to count individual boats at each reef site for each day of the study. With this information in hand, they compared visitation rates between natural reefs and nearby artificial reefs. They looked at two inshore and two offshore reef pairs.

What did the results show?

In all four artificial-natural reef pairs, visitation rates were much higher at the artificial reef than at the natural reef. At the inshore locations, visitation rates at the artificial reefs were approximately 10 times higher than those at natural reefs. The difference in visitation rates between paired offshore locations was not as dramatic: only two times higher for the artificial reef in one pair and eight times higher for the artificial reef in the other pair.

During the study, visitation patterns were a bit sporadic for inshore locations, with peaks occurring in the warmer months, but fairly consistent across seasons for offshore locations.

What else did they find?

The researchers felt that the increase in boat visitation patterns at artificial reefs was likely due to (1) actual or perceived increased quality of fishing and diving at these locations, and (2) lack of knowledge of the presence or location of nearby natural reefs.

Anything else?

The research team documented that the background noise collected with the recorders was highly variable and made the automated detection process of boat noise difficult. Fine-tuning the detection process to better eliminate background noise or to better identify boat noise could make this type of study easier to replicate in other locations.