Kim, E., Lam, C. H., Park, G. J., & Lee, J. H. (2024). Satellite tagging confirms long distance movement and fast dispersal of Patagonian toothfish (Dissostichus eleginoides) in the Southwest Atlantic. Frontiers in Marine Science, 11, 1334339. https://doi.org/10.3389/fmars.2024.1334339
Off the South American coast lives a fish monstrous in size (up to 2.3 m long and weighing over 200 kg) and impressive in resilience (with a life expectancy of 33-54 years). It is no surprise that, given the fish’s oil content and thick flesh, the Patagonian toothfish (Dissostichus eleginoides) is popular among fishermen, chefs, and foodies.
Despite its long life expectancy, the Patagonian toothfish faces two threats. First, it is often caught as bycatch by finfish and squid trawl fisheries. Additionally, in one location of particular importance to the species, Davis Bank, a high catch area just east of the Antarctic Polar Front, toothfish populations are isolated from one another geographically. This could potentially lead to speciation–the formation of a new species.
Prior tagging studies have found that Patagonian toothfish often stay within 50 km of their release locations even though they are capable of traveling over 5000 km, indicating site fidelity (the tendency of a species to return to previously occupied waters). However, it is known that the species also migrates to deeper waters in later life stages and other studies indicate that toothfish migrate between different locations throughout their lifetimes. So which is it – are toothfish a migratory species or a stationary one? And how do non-migratory toothfish remain connected to other members of the population?
Tracking Fish
In this study, researchers tagged toothfish with popup satellite archival tags (PSAT), which track fish movement and behavior. The tags used can withstand pressure of up to 2000 m and depths up to 1700 m.
Fish were tagged at the end of the fishing season in January 2019, with tags programmed to detach from the fish at various intervals over 16 months, after which their data would be transmitted to a satellite. Each tag provided data at 5 minute intervals in addition to daily summaries, which included temperature, depth, and location.
Figure 1. The physical and fisheries conditions surrounding Davis Bank, the study site.
What kind of toothfish are we talking about?
The average length of the toothfish tagged in the study was 114 cm, indicating that they were adults. All 44 PSATs indicated survival of the fish. 69 percent of the fish remained within 50 km of their release site and 10 percent of tags indicated toothfish trips of over 300 kms.
Fish that dispersed from the origin point at Davis Bank moved either north, west, or east, all to known fishing grounds and spawning locations. All long distance migrations were done within ten months by smaller toothfish. These long distance travels indicate a previously undetected capability of sustained swimming by toothfish, despite having unfavorable physiology. As a result, toothfish fishing grounds and populations are highly connected, potentially also leading to genetic connectivity.
The answer to the original question, then, is both! Toothfish exhibit migratory behavior and site fidelity. Most remain within 50 km of their release sites, but some may travel to further locations to find other populations and avoid fishing activities.
What next?
An important outcome of this study is its implication for cooperative research. The fishing industry played a significant role in carefully and humanely tagging the toothfish and the fishermen’s joint effort with researchers to conduct this study should set an example for future multi-industry collaboration. Another crucial implication is that fish move outside of their management areas, and policies that protect their migration paths and connected spawning grounds should also be prioritized.
While these findings provide new insight into toothfish movement patterns by contradicting the assumptions postulated in previous studies, it didn’t accomplish its goal of discovering how toothfish can travel such far distances. So now the mystery remains: how does this large, seemingly sedentary deep water fish move so far in such a short time?
Cover image: Patagonian Toothfish. Image credits: Biomedical Ephemera via Tumblr
I am an MPS student at the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Sciences pursuing a degree in Marine Biology and Ecology on the Tropical Marine Ecosystem Management Track. After graduating, I plan to use my education and experience to pursue a career in science writing or film production to help communicate the importance of the ocean to the general public.
