Mackerel icefish, *Champsocephalus gunnari* Lönnberg, 1905.

Mackerel icefish, Champsocephalus gunnari Lönnberg, 1905.


Distribution of reported catch

Distribution of reported catch of *Champsocephalus gunnari* at the ASD scale. (Source: C1 data).

Distribution of reported catch of Champsocephalus gunnari at the ASD scale. (Source: C1 data).


Life-history

Champsocephalus gunnari (Mackerel icefish), belong to the notothenioid family Channichthyidae (ice fish, white-blooded fish). Antarctic fish in general have a lower erythrocyte number and haemoglobin concentration than fish from temperate and tropical waters. Icefish are an extreme case and lack haemoglobin completely, lack myoglobin in five species, and have a vestigial number of erythrocytes or erythrocyte-like cells only. Mackerel icefish are endemic to the Southern Ocean and confined to the island shelves of the sub-Antarctic and the Antarctic Peninsula.

Spawning takes place in shallow water, with eggs laid on the seafloor. Larvae are pelagic and may be caught in coastal areas during late winter. Mackerel icefish is considered a semi-pelagic species; young (0+ and 1+) fish are found strictly in the pelagic zone, while adult fish move more towards the demersal zone. Icefish predators include Antarctic fur seals (Arctocephalus gazella) and gentoo penguins (Pygoscelis papua). Fisheries for Mackerel icefish take place in Subarea 48.3 and Division 58.5.2.

In Subarea 48.3, C. gunnari is restricted to the shelf area, generally shallower than 350m, all around South Georgia and Shag Rocks, forming large aggregations. Differences in length distribution have been noted between Shag Rocks and South Georgia, although these differences are not thought to represent separate stocks for stock assessment purposes.

In Division 58.5.2, C. gunnari is most abundant at depths of less than 350m in the waters surrounding Heard Island. In this area they grow to a maximum length of around 45cm and a maximum age of 6 years. Size at first maturity for females is 26.5cm and for males is 28.5cm total length. High abundances have also been observed in a non-contiguous area at Shell Bank to the northeast of the islands. The Heard Plateau and Shell Bank populations have different size structures and recruitment patterns.

Parameter estimates

In Subarea 48.3

In 2021 the growth and mortality parameters used in the assessment were those used by CCAMLR in previous years. Length to weight parameters were updated according to the 2021 survey results (Table 1).

Table 1: Biological parameters assumed for Champsocephalus gunnari in Subarea 48.3.
Component Parameter Value Unit
Natural mortality M 0.71000 /y
VBGF K 0.17000 /y
t0 -0.58000 y
L_inf 55.70000 cm
Length to weight A 0.00163 g/cm
B 3.40600
Maturity (0 to 1) 1.00000


In Division 58.5.2

The length-weight parameters were re-estimated using the fish sampled during the 2020-2021 surveys (Table 2). Growth parameters were re-evaluated in 2017 using survey data between 2010 and 2017 and used in the assessment. Natural mortality was assumed to be 0.4 (de la Mare, 1998) (Table 2).

Table 2: Biological parameters assumed for Champsocephalus gunnari in Division 58.5.2.
Component Parameter Value Unit
Natural mortality M 0.4 /y
VBGF K 0.368 /y
t0 0.067 y
L_inf 490 mm
Length to weight A 1.285 x 10-9 kg/mm
B 3.257


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
Mesh size for Champsocephalus gunnari Champsocephalus gunnari All Areas CM 22-03
Limits on the fishery for Champsocephalus gunnari in Statistical Subarea 48.3 in the 2021/22 and 2022/23 seasons Champsocephalus gunnari Subarea 48.3 CM 42-01
Limits on the fishery for Champsocephalus gunnari in Statistical Division 58.5.2 in the 2021/22 and 2022/23 seasons Champsocephalus gunnari Division 58.5.2 CM 42-02

Additional Resources