Understanding How Environmental Drivers Influence Spotted Seatrout Recruitment in Cedar Key
Written by: Samara Nehemiah, Master’s Student with UF/IFAS Fisheries and Aquatic Sciences
Spotted Seatrout, Cynoscion nebulosus, are one of the most sought-after sport fish in the state of Florida. This species can be found across the eastern United States in estuarine ecosystems from Texas to New York. Though Spotted Seatrout can utilize a wide variety of habitats, they can also be quite sensitive to change, and their recruitment can be influenced by changing habitat conditions. Understanding varying year classes – or the group of young produced by a population of fish in the same year or spawning season – of recreationally important fish such as Spotted Seatrout is essential for biologists to predict future adult population and evaluate how a population may respond to various management decisions or changes in their environment. However, the degree to which these factors have influenced Spotted Seatrout recruitment in Florida has received little attention thus far. I am looking to evaluate how some of these important environmental factors have influenced the recruitment of Spotted Seatrout within the last decade in Cedar Key.
What are we doing in Cedar Key?
In order to evaluate the impact of certain environmental drivers on recruitment, we are using age-and-growth to determine Spotted Seatrout year class strength. Fish grow faster in the summer and slower in the winter due to food availability and other factors such as temperature. These changes in growth are represented on their otolith, or ear bones, in which fish deposit opaque rings called annuli every year during periods of slow growth. To age bony fish, we can pull an individual’s otolith and count the opaque rings the same way we would count the rings on a tree. Compiled age data from our samples can then be used to determine strong and weak year classes for this species by looking at the total number of catches at each age.
We are lucky to have so many amazing charter captains here in Cedar Key who provide us with many seatrout samples (after they’ve been fileted for their clients, of course!). However, because carcasses from the local captains must be within the legal harvest slot of 15 to 20 inches, we also conduct our own sampling under a permit to target fish that are below the legal harvest limit in order to get a full understanding of the population here in Cedar Key.
Once we determine strong and weak years classes, we can look for correlations between year class strength and various environmental factors within that year. Spotted Seatrout recruitment is influenced by many environmental influences, but we plan to explore four main factors and their influence on the Cedar Key population. 1) How do yearly changes in seagrass abundance, caused from weather events or disturbances from boater recreation, influence recruitment? 2) How has the replacement of salt marshes by mangrove species that have been able to expand their range north as winters in Florida become less harsh, influenced Spotted Seatrout recruitment? 3) How do changes in salinity, due fluctuations in river flow from rain events, influence recruitment of Spotted Seatrout? And 4) How have major hurricanes and tropical storms, like Hurricane Hermine in 2016, affected recruitment of this species?
Still a lot of work to do!
Though we have started fish collections already, we are still in the early stages of this project. I plan to start aging my fish and building my population models this spring and continue through August 2020. We hope that by the completion of this project we will have a better understanding of how Spotted Seatrout may respond to changes in their environment. Check back for updates or visit our discovery days to learn about our progress!
This project is funded by the University of Florida and the Florida Fish and Wildlife Conservation Commission. Thank you to Captain Denny Voyles with Voyles Guide Service, Captain Carl Robinson, and Captains Jimbo, Steven, and Jim Keith with Saltwater Assassin Fishing Charters. All of these captains are providing numerous seatrout carcasses and leading our field sampling.