The Antarctic toothfish (Dissostichus mawsoni, TOA) is a commercially valuable circum-Antarctic fish that undertakes ontogenetic movements on the cont

Otolith chemistry reveals the ontogenetic movement of the Antarctic toothfish (Dissostichus mawsoni)

ANTARCTICA
Friday, May 24, 2024, 07:00 (GMT + 9)

Highlights

•Ontogenetic movement of Dissostichus mawsoni in the polynya is investigated for the first time.

•D. mawsoni moves ontogenetically from east to west along ice shelf in the Amundsen Sea polynya.

•Mature D. mawsoni prefers to staying in the deep waters > 1000 m.

Photo: Evolution of the dynamics, area, and ice production of the Amundsen Sea Polynya, Antarctica

Abstract

The Amundsen Sea polynya is one of the richest areas of primary productivity in Antarctica. The Antarctic toothfish (Dissostichus mawsoni, TOA) is a commercially valuable circum-Antarctic fish that undertakes ontogenetic movements on the continental shelf. However, the movement and distribution of this species remain unclear in the polynya, especially in the data-poor Amundsen Sea polynya. Along with hydrological and fishery survey data in the Amundsen Sea polynya, the otolith chemistry of TOA from three areas along the ice shelf of the Dotson–Getz Trough was analyzed to explore the movement pattern of this species. The elemental composition deposited during early life in the otolith core did not show significant differences, indicating that TOA in the Amundsen Sea polynya probably experienced a similar hydrological environment at the early life stage or might originate from the same spawning ground. However, the elemental composition deposited at the otolith edge showed that SrCa−1 and LiCa−1 differ in otolith chemistry between areas along the Amundsen Sea coast. In conjunction with additional data from the fish sampled in these areas, this study reveals that TOA shows an ontogenetic movement from westward along the ice shelf in the Amundsen Sea polynya. A deeper area (with a depth of over 1000 m) in the west box provides a fish pool for TOA, which needs to be conserved in the fishery management of toothfish populations.

Sample collection

All the fish were collected from the licensed Ukrainian longline vessel Simeiz targeting TOA from December 31, 2018, to January 23, 2019. All fish were captured in three boxes (Fig. 1) in the polynya along the Getz Ice Shelf of the western Dotson–Getz Trough (73°–74°S, 116°–119°W). Immediately after capture, standard length (cm) and wet weight (WW, kg) of fish were measured, and sex was identified using the Scheme of International Scientific Observation Scientific Observer’s Manual (Finfish

Hydrography

The depths of the three boxes were all more than 800 m and showed similar hydrological conditions (Fig. 3). At the sea surface, the temperature of the three boxes was ∽1°C, and the salinity was approximately 33. The EB is located further north and is slightly less affected by summer sea ice melt. Its sea surface temperature is lower, but its salinity is higher. The mixing phenomenon of seawater in the three boxes was not obvious at a depth of 100 m. Generally, the salinity and density gradually 

Photo: Scientific catch-and-release of toothfish in Antarctica/YouTube

Discussion

The TOA movement patterns in the Ross Sea, have been described based on larval drift simulations, tagging data and spatial patterns in size distributions (Hanchet et al., 2003, Hanchet et al., 2015, Parker et al., 2019, Ashford et al., 2012, Ashford et al., 2022). After the pelagic phase moves with the oceanic gyre, juveniles likely recruit to demersal habitats on the continental shelf of the Amundsen Sea. As they grow, they move west toward the Ross Sea shelf with the Antarctic coastal

Photo: Scientific catch-and-release of toothfish in Antarctica/YouTube

Conclusion

The polynya provides abundant nutrients, sufficient air-sea exchange, and direct sunlight to create high-productivity areas. It has a high biomass of phytoplankton and a rich biological network accumulating large numbers of ice krill (E. crystallorophias) under the ice edge and ice shelves (La et al., 2015).

This study provides evidence of the westward ontogenetic movement of TOA during immature to mature stages using otolith chemistry combined with fishery survey data. [continues....]

Authors/Source: Zhen Zhao, Illia Slypko, Kostiantyn Demianenko, and Guoping Zhu / ELSEVIER Science Direct

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