Species Description 2022:
Dissostichus mawsoni
CCAMLR Secretariat
17 April 2023
Antarctic toothfish Dissostichus mawsoni Norman, 1937.
Distribution of reported catch
Distribution of cumulative reported catch of Dissostichus mawsoni at the ASD scale. (Source: C2 data).
Life-history
Dissostichus mawsoni (Antarctic toothfish) is characterised by slow growth, low fecundity and late maturity. It has a circumpolar distribution, typically south of 60\(^{\circ}\)S, although it occurs further north, associated with colder, typically deeper, water, in Subareas 48.6 and 88.1. Analyses of the genetic diversity for D. mawsoni has found generally weak genetic variation between the areas 48, 58 and 88. D. mawsoni appears to have protracted spawning periods, taking place mainly in winter, but which may start as early as late autumn and extend into spring. However, as this is the period least accessible to fishing, and thus the collection of biological data, knowledge of specific life-history traits for this species is limited. Depending on the exact location of spawning, eggs and larvae become entrained by the gyres with juvenile fish being found on the continental slope and shelf. As these juveniles grow in size they move out into deeper water feeding in the slope region in depths of 1,000-1,500m, where they gain condition before spawning. Fish may remain in the northern area for up to two or three years, although this pattern may be different for males versus females. They may then move southwards back onto the shelf and slope where productivity is higher and food is more plentiful and where they regain condition before spawning.
The 2018 CCAMLR Workshop for the Development of a D. mawsoni Population Hypothesis for Area 48, suggested that in defining the spatial boundaries for a stock, it was important that such an area included all of the required habitat types for different life stages of D. mawsoni. Accordingly, the converse suggests that an area that does not contain that range of habitats would not be considered a stock, for example the collection of sea mounts in the north of Subarea 48.6, in which there are no shelf habitats would not be considered to constitute a stock.
Biological parameters estimates
In Subarea 48.4
Estimates of natural mortality, length-mass, and tagging parameters for D. mawsoni in Subarea 48.4 are given in Table 1.
| Component | Parameter | Value | Unit |
|---|---|---|---|
| Natural mortality | M | 0.13 | /y |
| tag-induced mortality | t | 0.1 | /y |
| tag failure | f | 0.0064 | |
| Length to mass | a | 1.246 x 10-5 | kg/cm |
| b | 2.967569 |
In Subarea 88.1
Estimates of natural mortality, length-mass, growth and maturity parameters for D. mawsoni in Subarea 88.1 are given in Table 2.
| Relationship | Parameter | Male | Female |
|---|---|---|---|
| Natural mortality | M (/y) | 0.13 | 0.13 |
| Von Bertalanffy | t0 (y) | -0.292 | -0.712 |
| k (/y) | 0.101 | 0.082 | |
| L_inf (cm) | 164.06 | 180.49 | |
| c.v. | 0.101 | 0.101 | |
| Length-weight | a (t/cm) | 1.247 x 10-8 | 7.361 x 10-9 |
| b | 2.99 | 3.105 | |
| Age at maturity (y) | A50 | 11.99 | 16.92 |
| Stock recruit steepness (Beverton-Holt) | h | 0.75 | |
| Recruitment variability | sigmaR | 0.6 | |
| Ageing error (CV) | cv | 0.1 | |
| Initial tagging mortality | 10% | ||
| Initial tag loss (per tag) | 3.30% | ||
| Instantaneous tag loss rate (per tag) | 0.062/y | ||
| Tag detection rate | 99.30% | ||
| Tag related growth retardation | 0.5 y |
Relevant Conservation Measures
In addition to Conservation Measures that apply to all Areas and all Species, the following Conservation Measures apply:
| Description | Species | Area | Conservation Measure |
|---|---|---|---|
| Limits on the exploratory fishery for Dissostichus mawsoni in Statistical Subarea 48.6 in the 2022/23 season | Dissostichus mawsoni | Subarea 48.6 | CM 41-04 |
| Limits on the exploratory fishery for Dissostichus mawsoni in Statistical Division 58.4.2 in the 2022/23 season | Dissostichus mawsoni | Division 58.4.2 | CM 41-05 |
| Limits on the exploratory fishery for Dissostichus mawsoni on BANZARE Bank (Statistical Division 58.4.3b) outside areas of national jurisdiction in the 2022/23 season | Dissostichus mawsoni | Division 58.4.3b | CM 41-07 |
| Limits on the exploratory fishery for Dissostichus mawsoni in Statistical Subarea 88.1 in the 2022/23 season | Dissostichus mawsoni | Subarea 88.1 | CM 41-09 |
| Limits on the exploratory fishery for Dissostichus mawsoni in Statistical Subarea 88.2 in the 2022/23 season | Dissostichus mawsoni | Subarea 88.2 | CM 41-10 |
| Limits on the exploratory fishery for Dissostichus mawsoni in Statistical Division 58.4.1 in the 2022/23 season | Dissostichus mawsoni | Division 58.4.1 | CM 41-11 |
| Catch Documentation Scheme for Dissostichus spp. | Dissostichus spp. | All Areas | CM 10-05 |
| Prohibition on fishing for Dissostichus spp. in depths shallower than 550 m in exploratory fisheries | Dissostichus spp. | All Areas | CM 22-08 |
| Prohibition of directed fishing for Dissostichus spp. except in accordance with specific conservation measures in the 2022/23 season | Dissostichus spp. | Subarea 48.5 | CM 32-09 |
| General measures for exploratory fisheries for Dissostichus spp. in the Convention Area in the 2022/23 season | Dissostichus spp. | All Areas | CM 41-01 |
| Limits on the fishery for Dissostichus spp. in Statistical Subarea 48.4 in the 2022/23 season | Dissostichus spp. | Subarea 48.4 | CM 41-03 |