In our Research Highlights blog series, we debut newly published fisheries research by our women of fisheries colleagues. If you have research you would like to highlight and share with our readers, submit a nomination form here!
Lindelien, S., D.C. Parkyn, C.C. Anderson, J.H. O’Connor, A.C. Dutterer, and P. Schueller. 2024. Use of fin rays and fin spines in nonlethal age estimation of Florida Bass. Journal of Fish and Wildlife Management 15:203–215.
Black bass—a name that refers to fishes in the genus Micropterus—comprises the most popular freshwater sport fishes in North America. People spend a lot of time, energy, and money searching for that elusive “big one.” The world record, a Florida Bass Micropterus salmoides, stands at 22.25 lb (10.12 kg), but a worthy trophy fish is anything reaching 8 lb (3.6 kg) or over. Catching a trophy fish is a memorable experience, one that warrants sharing pictures with friends, on social media, and to broader audiences through programs like Florida’s TrophyCatch.
It’s a prize catch for good reason. These large fish are the oldest and rarest Florida Bass in the water. Florida Bass can live up to 16 years of age, but according to biologists, a Florida Bass can reach trophy size in as little as 4 years and as long as 14 years. That’s a big growth difference!
Growth is an important aspect of a fish population. It can help biologists gauge the health of the population and determine what kind of actions would be best to achieve their management goals. To get a good handle on growth, biologists need to know how big and how old the fish are. It’s easy to weigh and measure the length of a fish, but what about aging them?
Aging fish is not always easy, and many times, it requires killing the fish. “Even the big ones?” you may wonder. Yes, even the big ones.
That’s because to date, the most reliable method for aging Florida Bass uses otoliths, or ear bones, which can only be extracted after killing the fish. The annuli or annual rings of these structures are then counted to get an age for the fish. However, these rings are not just found in otoliths. Other structures, from fin rays and spines to scales to eye lenses, also have rings and have been used to age fish in a similar way.
Researchers like Summer Lindelien, a Research Associate with the Florida Fish and Wildlife Conservation Commission, are looking into new non-lethal aging alternatives for Florida Bass. Summer began this study as a graduate student at the University of Florida because of her interest and previous work history with fish aging. “During my time as an undergraduate student and while interning with the Minnesota DNR, I worked on ageing techniques (lethal and nonlethal) for Yellow Perch, Walleye, Bluegill, Largemouth Bass, Tiger Muskellunge, and Round Goby. I applied for the assistantship because I thought I could apply some of my previous knowledge to aging fish in Florida.” She hasn’t looked back since.
In all, Summer and her research team looked at seven different alternative structures from the anal, pelvic, pectoral and dorsal fins. They were interested in comparing the age estimates from these structures with age estimates from otoliths and evaluating whether these structures were reliable. From this work, the person aging the fish, referred to as the reader, was found to be really important, even more so than the structure itself. This is due to the readers’ different levels of experience, skill, and interpretation of these structures. With some adjustments and considerations, researchers concluded that aging fish using these alternative structures is a valid non-lethal technique that can provide information about Florida Bass populations.
Photo Credit: Summer Lindelien
Researchers had a favorite, though—dorsal spines. Not because they were better for aging, but rather for more practical reasons. They were easier to collect, clean, and section for the aging process.
If this is something you would like to consider in your work, Summer shares a reference guide (under other resources below) and the following recommendations:
- Remove the middle fin ray or spine within the fin to avoid damaged ones
- Cut as close to the fish’s body as possible when removing the fin ray or spine
- Take multiple cross-sections of the fin structure near the base for best view of annuli
- Experiment with the thickness of the cross-section, typically between 0.5 and 1.0 mm
- Validate that one annulus is being deposited per year, and document when that occurs
- Make a reference set specific to your water body and train on it using fish of known ages
- Focus the first stages of training on the youngest fish, so you can identify where the first annulus is located
- Later training should focus on differentiating true from false annuli
Summer’s work won’t end here. Additional studies on nonlethal aging of Florida Bass are underway. Preliminary results from a recent simulation study indicate that estimates of mortality and mean length by age of Florida Bass are relatively unaffected by the absence of large fish or alternatively whether dorsal spines or otoliths were used for aging. Other efforts are looking at the use of genetic techniques to age fish that will remove reading error altogether.
One thing is for certain. As we look beyond otoliths, the future of aging trophy Florida Bass—and Florida Bass in general—is sure to be a life saver.
The full manuscript can be found and downloaded here (open access):
doi.org/10.3996/JFWM-22-067
Other resources:
Florida TrophyCatch
Dorsal Spine Processing and Ageing Guide
I have always been into fishing as a hobby. So, the idea of understanding more about the fish I catch amazed me right away. When I caught my first 6 lb. bass, I caught the big bass bug. Since then, I have broken my personal best bass twice in Florida (an 8 lbs. and 8.75 lbs.). Along my path to become a fish biologist I worked in sales for an outdoor retailer, did promotional work for several companies in the fishing industry, did research on plants, monitored Great Lakes streams and aquatic communities, and conducted research on age and growth of numerous fish species. I enjoy being on the water just as much as I enjoy being in the lab looking at what I have collected. My current job is the most rewarding job I have ever worked. I get to work with the trophy bass angling community (TrophyCatch) as well as conduct my own research. It is a win-win.
(Photo Credit: Chris Anderson)