Establishing the Connectivity Between Nearshore Juvenile Nursery and Adult Habitats for Hogfish in the Dry Tortugas using Biochemical Analysis and Acoustic Telemetry

  • An acoustic receiver station that will record when a tagged hogfish is swimming nearby.

  • A photo of a hogfish swimming among corals and other natural habitat.

  • A hogfish swimming amongst soft corals.

  • A pair of hogfish swimming among natural habitat.

Hogfish (Lachnolaimus maximus) has long been a popular fish among anglers in the warm, turquoise waters of the Florida Keys and Dry Tortugas. While hogfish is a popular commercial and recreational species, very few studies have examined their movement and they were only small in scope. This study, conducted in a no-take marine reserve, will help answer questions about home range extent, habitat use, and connectivity of this species over multiple years. Maintaining connectivity allows hogfish to shift habitats to adjacent areas if populations experience loss of habitat. The study will also determine if there is a difference in movement between males and females.

By working in a no-take marine reserve, fishing pressure will not influence the study animals’ behavior, thus providing a better understanding of the movement and connectivity of hogfish throughout various life stages. In addition, this study will provide a more detailed spatial and temporal description of the reproduction behavior of hoghfish. This species forms harems and has socially mediated sex change. Questions researchers will be asking include: Does a male hold a territory all year long, or only during breeding season. Do the same females stay with the same male season after season? Do the females leave the area after the breeding season or do they remain in the male’s territory? How does hogfish movement change throughout the life of the animal?  

Scientists will use multiple techniques to assess movement. Acoustic telemetry (tagging the fish with an active transmitter) will allow for examination of the spatial needs of the fish for two years. Examining otolith (ear bones) microchemistry with stable isotope analysis will define connectivity between different habitats for this species. Stable isotope analysis will reveal when the hogfish moved from nursery habitat to adult habitat and demonstrate how their place in the food web may change over time.

Scientists and researchers from FWRI’s Marine Fisheries Research group are still in the initial phase of the project and are planning a trip to the Dry Tortugas in winter 2020 to set up an acoustic monitoring array and begin tagging hogfish. The purpose of the initial phase of the study is to determine optimal density/spacing of receivers to ensure that the tagged fish will be “heard” over the noise of all the other animals in this healthy reef. Researchers have already gone to the Research Area of the Dry Tortugas and selected an appropriate site for the acoustic telemetry array. This particular site has high noise levels (a sign of a healthy reef ecosystem) and therefore, to determine the spacing of the array, a range test was conducted. This range test determined how well an acoustic receiver ‘hears’ a transmitter in the site. The results of the range test will tell scientists how closely they need to place their receivers to ensure good coverage of the area for detecting the transmitting tags. Once the acoustic receiver array is deployed and the fish are tagged, focus will shift to downloading receiver data every four months and collecting hogfish otoliths from the surrounding areas. 

The FWRI researchers involved with this project are Alejandro Acosta, Paul Barbera, Mareike Duffing-Romero, Jennifer Herbig, Colin Howe (formerly FWRI), Jessica Keller, Danielle Morley, Jesse Secord, and Ariel Tobin.   

Once complete, this research will benefit managers and will be used to determine if current management changes for the species are appropriate. Resource managers will be able to look at the fine-scale movement information from the acoustic telemetry and use that information to inform spatial management decisions in areas that are fished. Information from the otolith microchemistry will demonstrate the nursery habitat of these fish and the age at which they transition to adult habitat. Again, this information can prove valuable to natural resource managers as they ensure this fishery is used in a sustainable and healthy manner. This project is funded through a grant from Dry Tortugas National Park.