A brief overview of key research in seadragon population monitoring
A variety of innovative research projects have worked over the years toward building a knowledge base for seadragon populations. Pioneering projects have utilized radio-tracking devices, fluorescent marking, and individual pattern identification to monitor seadragons across different locations and time periods. This research has paved the way for current seadragon projects, including SeadragonSearch.
In 2002, Dr. Rod Connolly of Griffith University in Queensland and his colleagues published their research tracking leafy seadragons in South Australia, revealing new information about their movements and preferred habitats. Connolly and his team were able to identify and monitor individual seadragons using ultrasonic telemetry, meaning they carefully attached a small transmitter to the bony plates on the body of each fish studied, and used that transmitter to gather data. They also photographed the seadragons in their study, and noted that adult seadragons could be recognized by the unique patterns on their faces over the course of almost a year. This observation suggested that facial markings could be a stable, useful tool for identifying individual seadragons going forward. Ultimately, Connolly’s tracking of leafies demonstrated that they tended to stay within a small home range (for the sites studied), and concluded that even localized protected areas could benefit future conservation efforts for these fish. He added that further studies at other sites would be needed to confirm that these movement patterns were characteristic of other seadragon populations, and that looking more closely at how components like gender and life stage might affect movements would also be important.
A couple of years later, between 2004 and 2006, another research team based in Sydney added to this foundational data with new knowledge about seadragon populations in New South Wales and Tasmania. Dr. Jaime Sanchez-Camara and colleagues of the University of Technology Sydney studied the demographics and distributions of weedy or common seadragons using a combination of visual implant fluorescent elastomer (VIFE) tags as well as observations of unique markings and patterns on each seadragon. VIFE tags allowed scientists to carefully inject a small amount of colored liquid under the skin of each fish, which then remained visible through the tissue. Their study covered a seven year period and confirmed that, like the leafies in South Australia, these common seadragons had very limited home ranges and tended to remain in the same small area over time. The research also showed some differences between populations at different latitudes, including differences in growth rates and reproduction, highlighting the need for locally-informed protections and further study. Some populations declined over the course of the study, and the researchers pointed out that it would be important to determine whether these declines were natural or related to human impacts on the environment.
Both Connolly and Sanchez-Camara had noted the utility of using individual seadragon markings to support identification and monitoring efforts, and in 2011 Keith Martin-Smith, then at the University of Tasmania, expanded on this idea with a study fully focused on identifying weedy or common seadragons through photographs and pattern-matching. Martin-Smith studied adult common seadragons around southern Tasmania, using images to identify individual seadragons by the markings on their bodies. He found that these markings were indeed unique to each seadragon and did not change over the course of a year and a half. He was able to gather new data on population dynamics, including reproductive events and longevity estimates. Martin-Smith’s work suggested that identification based on individual patterns obtained from photographs could be an effective way to monitor seadragon populations going forward, particularly if combined with technology to improve the efficiency of the matching process.
While scientists in South Australia, New South Wales, and Tasmania were honing different techniques for physically tracking seadragons, a team of researchers based in Western Australia and California were investigating the genetic relationships between different populations of seadragons. This work would provide valuable information about connections between seadragons living in different areas, and how resilient different populations might be to challenges in their environments. Dr. Nerida Wilson from the Western Australian Museum (WAM) and Dr. Greg Rouse and Dr. Josefin Stiller from Scripps Institution of Oceanography at UC San Diego (SIO) sampled both weedy/common and leafy seadragon populations across all Australian states where seadragons occur, scuba diving to locate seadragons and carefully clip small pieces of tissue from their appendages. To ensure that the same seadragon was only sampled once, the researchers also took photographs of their faces, using the pattern-matching technique to differentiate individuals. DNA was extracted from the tissue samples, and then genes were sequenced so that they could be compared to one another. The team found that genetic diversity is low and connectivity limited in the majority of known seadragon populations, which could result in less resilience to environmental stressors. This new knowledge affirmed the importance of proper monitoring and conservation measures for seadragons across the southern coast of Australia, which would require broad-scale and long-term data collection efforts.
As a reminder of how much we have yet to learn, Stiller, Wilson, and Rouse made an unexpected discovery in the course of their work on common and leafy seadragons: a third, deeper-living species, the ruby seadragon. The team confirmed the uniqueness of the new species using samples provided by WAM, and then successfully captured video footage of live ruby seadragons off the coast of Western Australia in April 2016. They had searched for the ruby for several days using a remotely operated vehicle (ruby seadragons live deeper than recreational scuba depths), and were rewarded with observations of two wild rubies swimming and feeding. The team emphasized the event as symbolic of how much diversity and discovery lives and waits beneath the waters off of Australia’s southern coast.
SeadragonSearch aims to build upon this legacy of seadragon research and contribute to the efforts of current projects by monitoring seadragons across their distribution for at least a decade. Our project will use innovative new technology and collaborate with local projects and communities to work toward a healthier future for seadragons and their habitats.