Tying policy to system: Does the Ross Sea region marine reserve protect transport pathways connecting the life history of Antarctic toothfish?

ABSTRACTRecent analyses of anthropogenic impacts on marine systems have shown that the Ross Sea is the least affected stretch of ocean on Earth, although historical effects were not included in those studies. Herein the literature is reviewed in order to quantify the extent of extraction of biological resources from the Ross Sea continental shelf and slope from the start of the 20th century. There was none before that time. An intense extraction of Weddell seals Leptonychotes weddellii by the expeditions of the ‘heroic’ period and then by New Zealand to feed sled dogs in the 1950–1980s caused the McMurdo Sound population to decrease permanently. Otherwise no other sealing occurred. Blue whales Balaenoptera musculus intermedia were extirpated from waters of the shelf break front during the 1920s, and have not reappeared. Minke whales B. bonaerensis probably expanded into the blue whale vacated habitat, but were then hunted during the 1970–1980s; their population has since recovered. Some minke whales are now taken in ‘scientific whaling’, twice more from the slope compared to the shelf. Other hunted cetaceans never occurred over the shelf and very few ever occurred in slope waters, and therefore their demise from whaling does not apply to the Ross Sea. No industrial fishing occurred in the Ross Sea until the 1996–1997 summer, when a fishery for Antarctic toothfish Dissostichus mawsoni was initiated, especially along the slope. This fishery has grown since then with effects on the ecosystem recently becoming evident. There is probably no other ocean area where the details of biological exploitation can be so elucidated. It appears that the Ross Sea continental shelf remains the least affected of any on the globe. However the same cannot be said of the slope.

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Physical–biological interactions influencing large toothfish over the Ross Sea shelf

Antarctic Science ◽

10.1017/s0954102017000359 ◽

2017 ◽

Vol 29 (6) ◽

pp. 487-494 ◽

Cited By ~ 3

Author(s):

Julian Ashford ◽

Michael Dinniman ◽

Cassandra Brooks

Keyword(s):

Life History ◽

Recent Literature ◽

Ross Sea ◽

Physical Structure ◽

Biological Interactions ◽

Research Groups ◽

Antarctic Toothfish ◽

Shelf Circulation ◽

Dissostichus Mawsoni ◽

Competing Hypotheses

AbstractWe add comments to a recent series of publications in peer-reviewed journals concerning the distribution of large Antarctic toothfish (Dissostichus mawsoni) found over the inner shelf of the Ross Sea. We note that earlier fish ecologists advanced innovative hypotheses invoking physical–biological interactions with life history, and that these, far from being disproved, have been relegated by more immediately pressing management concerns. We argue that, despite the considerable advances achieved by research groups working onD. mawsoni, an understanding of distribution and abundance is incomplete without reference to the physical structure that supports their life history. We briefly consider hypotheses highlighted by the recent literature in the context of major features of the shelf circulation in the Ross Sea, in particular intrusions of modified Circumpolar Deep Water along trough systems. We suggest physical–biological interactions that may be involved and call for improvements in the monitoring programme that can help test between the competing hypotheses.

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A multidisciplinary approach to understanding the population structure of an exploited Southern Ocean top predator, the Antarctic toothfish, to improve sustainability and marine spatial planning

10.5194/egusphere-egu2020-894 ◽

2020 ◽

Author(s):

Jilda Caccavo ◽

Camila Mazzoni ◽

Thomas Brey

Keyword(s):

Population Structure ◽

Life History ◽

Southern Ocean ◽

Ross Sea ◽

Critical Role ◽

Weddell Sea ◽

Passive Transport ◽

Antarctic Toothfish ◽

Fishing Vessels ◽

The Antarctic

The Antarctic toothfish (Dissostichus mawsoni), commonly known as Chilean Sea Bass, has a critical role in Southern ecosystems as a top fish predator. Simultaneously, it represents the most lucrative Antarctic fishery.Its fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which introduced the world&#8217;s largest Marine Protected Area (MPA) in the Ross Sea region of the Southern Ocean in 2016.Since 2013, scientists at the Alfred Wegener Institute in Germany have been proposing the creation of an even more expansive MPA in the Weddell Sea region of the Southern Ocean, in order to protect unique ecosystems in this region, which has largely escaped the exploitation seen in the Ross Sea, due to its historic inaccessibility. However, CCAMLR, whose 25-member country composition functions by consensus, has failed to arrive at unanimous support for the various forms of a Weddell Sea MPA (WSMPA) proposed over recent years.A remaining impediment to the design and acceptance of a WSMPA, is a near total lack of knowledge of the life history and population structure of Antarctica toothfish in the Weddell Sea. Much of the data regarding connectivity and ontogenic movement of Antarctic toothfish derive from the Ross Sea, given the presence of an active fishery there since 1997. Based on the hypotheses that have arisen from the Ross Sea (which remain contentious), a possible life cycle of Antarctic toothfish comprises juvenile development on nutrient rich continental shelf areas, followed by passive transport via gyre systems to offshore sea mounts, where spawning occurs, prior to completion of the cycle as fish are passively transported back towards the coast.The combination of population genetics and otolith chemistry, methodologies which define population structure via metrics of relatedness and provenance respectively, offers the possibility to fill many of the existing knowledge gaps with regards to Antarctic toothfish life history connectivity in the Weddell Sea region of the Southern Ocean. The integration of hydrographic data on water mass movement which informs both the passive transport of Antarctic toothfish at various life stages, as well as the location of important prey sources, is an integral third point of consideration, completing the development of life history connectivity hypotheses testable via the aforementioned metrics.Tissue samples from the present study derive from otoliths (fish ear bones), which are a standard tissue extract by CCAMLR observers on Antarctic fishing vessels, historically collected for age determination. Otoliths provide both a source of DNA for genetics work, via tissue traces dried on the otolith exterior, as well as a source for chemistry analysis, via trace element analysis of otolith ring layers from the nucleus (earliest) to edge (latest) elemental depositions.The aim of the present study is to utilize this readily available tissue source (otoliths) in order to apply both aforementioned methodologies, with the ultimate aim to test between hypotheses of single or multiple populations within the Weddell Sea, while also contextualizing those Weddell Sea population(s) within the greater Southern Ocean distribution of Antarctic toothfish.

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Comments on “The Antarctic toothfish (Dissostichus mawsoni): biology, ecology, and life history in the Ross Sea region,” by S. Hanchet et al.

Hydrobiologia ◽

10.1007/s10750-015-2607-4 ◽

2016 ◽

Vol 771 (1) ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

David G. Ainley ◽

Joseph T. Eastman ◽

Cassandra M. Brooks

Keyword(s):

Life History ◽

Ross Sea ◽

Antarctic Toothfish ◽

Dissostichus Mawsoni ◽

The Antarctic

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Does large-scale ocean circulation structure life history connectivity in Antarctic toothfish (Dissostichus mawsoni)?

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f2012-111 ◽

2012 ◽

Vol 69 (12) ◽

pp. 1903-1919 ◽

Cited By ~ 25

Author(s):

Julian Ashford ◽

Michael Dinniman ◽

Cassandra Brooks ◽

Allen H. Andrews ◽

Eileen Hofmann ◽

...

Keyword(s):

Life History ◽

Ocean Circulation ◽

Early Life ◽

Large Scale ◽

Ross Sea ◽

Life Stages ◽

Lagrangian Particle ◽

Antarctic Toothfish ◽

Dissostichus Mawsoni ◽

Particle Simulations

A multidisciplinary approach incorporating otolith chemistry, age data, and numerical Lagrangian particle simulations indicated a single, self-recruiting population of Antarctic toothfish (Dissostichus mawsoni) in the Southeast Pacific Basin (SPB) and Ross Sea, with a life history structured by the large-scale circulation. Chemistry deposited prior to capture along otolith edges demonstrated strong environmental heterogeneity, yet the chemistry in otolith nuclei, deposited during early life, showed no differences. Age data showed only adult fish in catches on the Pacific–Antarctic Ridge in the SPB and structuring of life stages consistent with transport pathways from the northern Ross Sea. Lagrangian particle simulations predicted that early life stages following the flow in the SPB would be transported to areas in the Ross Sea where juveniles are caught, whereas the circulation would facilitate adult movement along the shelf slope and back into the SPB where spawning adults are caught. These results suggest that successfully spawning fish spend only a part of their adult life history in the Ross Sea, areas in the eastern Ross Sea contribute disproportionately to the spawning population, and areas in the southwestern Ross Sea may supply fisheries in the southern Indian Ocean.

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