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Mackerel icefish (icefish) have long slim bodies with a large elongated head. Mackerel icefish are white-blooded as they lack haemoglobin. They are known as the 'anti-freeze' fish as chemicals in their blood prevent the build-up of ice crystals. They are found exclusively in the Antarctic Southern Ocean. As icefish mature they more into deeper waters and become increasingly benthic, thus juvenile icefish can be classified as mesopelagics and adults as benthopelagics. Icefish Important prey species for larger fish, as well as penguins and seals. Icefish were over-exploited but are now managed by CCAMLR. Fished areas in include Subarea 48.3 (South Georgia) and Division 58.5.2 (Heard and McDonald Islands).
Images: Thomas Desvignes |
Summary role in ecosystem
Central role in Southern Ocean foodwebs as consumers of zooplankton and a prey source to higher predators. Icefish migrate vertically in the water column and may be important in linking benthic and pelagic environments.
Short lived, fast growing species, sexually mature between 3-4 years. Inhabiting depths up to 700 m can school at or near the sea floor or mid-water (Bray, 2019).
Parameters | Juvenile | Adult |
|---|---|---|
Maximum age | 4-5 years Icefish generally do not survive past 5 years of age, although there are exceptions in the South Atlantic area. Even in the absence of significant fishing pressure, abundance of cohorts aged 4 years or greater declines rapidly and dramatically. The cause of this high mortality is not known. Note that in Kock 1992 it states that C. gunnari attains ages of 12-15 years at South Georgia. (Kock 1992, Williams 2004) | |
Average adult size | max. 44 cm | |
Age at maturity | Juveniles obtain sexual maturity around 2 yrs, move to adult benthic phase | |
Size at maturity | Juveniles are 240mm SL at 2 years of age >350mm at 5 yrs (Williams 2004) | |
Spawning/breeding area | Spawning occurs in inshore waters (confirmed for S. Georgia & Kerguelen, strong circumstantial evidence at Heard). (Williams 2004) | |
Spawning/breeding season | Spawning season generally autumn/winter (March-September) but highly variable between locations. It has been noted that 15-25% of the population around South Georgia, and an unknown proportion of the other populations in the Atlantic Ocean sector do not spawn each year (Kock 1990 cited in Kock 1992; Williams 2004, Kock, 2005) | |
Larval/gestation period | 90 day pelagic larval period; Incubation lasts about 3 months, as does the pelagic larval period (11mm to 24mm approx) in inshore waters. At S. Georgia, larvae occur over an extended time, suggesting an extended hatching period. Larvae present from August-December, depending on location. | |
Location of recruits | After the larval stage, C. gunnari spread over pelagic waters on the shelf in the first two years of their life, still segregated into age classes. | |
Size of recruits | 11-24 mm pelagic larval recruits, present for three months | |
| Overall natural mortality rate | ||
Non-predation natural mortality rates | Highly variable juvenile population, which is a result of variable spawning success and juvenile survival | 0.35-0.45 Mortality probably relatively low in 2 & 3 year olds, then rising abruptly in 4 year olds. Few fish remain after 5 years. It has been estimated to attain max ages of 13-15 yrs, but it is likely that longevity does not exceed 10-12 years, which would correspond to a natural mortality of 0.35-0.45 (Kock 1992, Williams 2004) |
Juvenile icefish migrate to deeper water at around 2 yrs old (Williams 2004).
During the adult phase they tend to aggregate near the bottom during daytime, rising into the water column at night, presumably to feed. The extent and timing of this diurnal vertical migration is variable. Williams (2004)
Around South Georgia, males and females move inshore for spawning (males earlier than females) (Kock 1992)
Larval and small juvenile icefish feed on various stages of krill from furcilia larvae to juvenile individuals; Icefish larvae were able to switch prey from krill to Thysanoessa macrura when E. superba larvae were sparse (Kellermann, 1996).
In the South Atlantic area, the principal food item is Euphausia superba (Antarctic Krill). On the Kerguelen Plateau, where E. superba does not exist, the principal diet component is Euphausia vallentini with Themisto gaudichaudi being a secondary component and occasional occurrences of other hyperiid amphipods (Williams 2004).
When investigated at South Georgia the proportion of Antarctic krill and T. gaudichaudii in the diet varies across years, whereas the proportion of mysids in the diet remained fairly constant. Krill appears to be the preferred food and in years of krill shortage, (e.g. 1991) krill is replaced by T. gaudichaudii (Kock et al. 1994).
Parameters | |
|---|---|
| Ingestion rate | Insert values and short citations here |
| Metabolism | "low" as an adaptation to compensate for lacking respiratory pigments (Kock 2005). |
Fecundity | Absolute fecundity ranges from 1294 to 31045. Eggs are small by channichthyid standards and are probably benthic, as no eggs have been recovered from plankton tows. Yolk deposition probably takes less than one year. Fecundity decreases with higher latitudes (Kock 1992, Williams 2004) |
Length-weight relationships | CCAMLR WG-FSA has used the following length to mass relationships for C. gunnari: (Williams 2004) |
Growth rate | Most fish do not live beyond 5 years of age, during which time they attain approx 35cm total length. Growth is therefore relatively fast for notothenioid fish. Ageing by otoliths or other hard parts has not yet been developed to a reliable stage; most age estimates are based on length frequency analysis, which is straightforward for ages up to 3+, but is only possible for later ages by the use of mixture analysis and tracing strong cohorts from earlier years (Williams 2004). |
Size at age | 240mm at approx 2 yrs, >350mm at 5 yrs (Williams 2004) |
| Population Productivity (average life time) |
This species is found mainly around the Heard and McDonald Islands, Îles Kerguelen and island in the south Atlantic such as South Georgia (AAD, 2012).
Oceanic - benthopelagic as adults, mesopelagic as juveniles. They become more demersal when reaching age class 3 and tend to congregate in specific feeding grounds.
Pelagic in near-shore waters 0 - 150m. Gradually spreads over inner plateau in pelagic zone and occupies lower position in water column (Williams 2004).
Oceanic - benthopelagic as adults, mesopelagic as juveniles. They become more demersal when reaching age class 3 and tend to congregate in specific feeding grounds. Bentho-pelagic in shelf waters to about 350m depth. Optimum temperature for icefish appears to be within the range -0.5 to 1.5°C, and their upper limit may be at about 5°C. Williams (2004)
Bentho-pelagic in shelf waters to about 350m depth. Optimum temperature for icefish appears to be within the range -0.5 to 1.5°C, and their upper limit may be at about 5°C. Williams (2004)
Icefish have a prolonged recovery following stress compared to red-blooded Antarctic fish, this may reflect the limitations of their aerobic metabolism as a result of their lack of haemoglobin (Kock, 2005).
Here we ask that you endeavour to characterise the relationships of the taxon with the habitat as a function relationship, i.e. the response of the taxon (life stage)(y-axis) relative to the magnitude of the habitat (x-axis). We provide icons below to paste into the table. If possible, add the values of the parameters of the relationship and detail the uncertainty around them.
| Variable | Taxon size/stage impacted | Functional response (icon) | Parameters and uncertainties | Risk areas/regions impacted | Notes |
|---|---|---|---|---|---|
Temperature | C. gunnari |
| Upper incipient lethal temperature 4-5oC | Kock, 2005 | |
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Abundance is highly variable at any location, and fluctuations are not synchronised between areas. Year class strength of prominent year classes at South Georgia was 10 – 20 times that of year classes small in size (Kock, 1991). A good year class which supported a fishery was produced every three years at Kerguelen (Duhamel, 1991, 1995; Duhamel and Agnew, 1990). A similar situation occurs at Heard Island, where the population at any one time is dominated by one strong year class. There are a number of clear differences between the South Atlantic and Kerguelen Plateau fish, which, taken with the long distance separating these areas, suggests that fish from these two areas belong to different populations. These criteria include morphological and meristic characters, spawning season and maximum length attained (600mm S. Atlantic, 450mm Kerguelen). Within the South Atlantic area, there are differences in the age structure in different areas of the Scotia Arc. In the S. Orkney & S. Shetland Islands large fish of 40-50cm, which are at least age 7-10, have been observed. Fish of this age are typically found only in low numbers at S. Georgia and further to the north (SC-CAMLR-XX, p473). Records of episodic declines in the abundance of icefish at South Georgia base on bottom trawl surveys appear to coincide with year when krill are known to have been sarce on the South Georgia Shelf. Fur seals may also play an important role icefish abundance. Periodic shifts in prey availability and predation activity may explain episodic declines in icefish in the absence of fishing (Everson et al. 1999).
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Predation pressure affects all age-classes of C. gunnari alothough some species target certain size classes, for example gentoo penguins take individuals < 20cm (Kock, 2005). Predators include larger fish (Chaenocephalus aceratus (blackfin icefish), Pseudochaenichthys georgianus (Crocodile icefish) and Dissostichus eleginoides (Patagonian toothfish) see refs in Kock (2005)), albatross, fur seals and gentoo penguins.
Form Kock (2005) "No estimate of the level of mortality through natural predation exists for any single year. However, the number of C. gunnari taken by predators seemed to have increased in the last decade when the availability of krill appeared to have decreased around the island (Reid and Croxall 2001)."
Collins et al. (2004) estimated an annual consumption of 131, 161 tonnes of C. gunnari by fur seals and 35, 547 tonnes by gentoo penguins over a 14 year period.
Other krill eating species. This may be enhanced/apaprent in years of low krill production.
From CCAMLR....https://www.ccamlr.org/en/fisheries/icefish-fisheries
"This species was heavily exploited in the 1970s and 1980s. Concern over the levels of exploitation in these fisheries, and the high annual variability in catches, led to the closure of the fisheries in the early 1990s. Nowadays, fisheries on mackerel icefish may only occur within two years of a survey, if sufficient stock is assessed to be available.
Mackerel icefish (Champsocephalus gunnari) is targeted by licensed fisheries in the Southern Ocean using midwater trawls at South Georgia in Subarea 48.3, and using both bottom and midwater trawls at Heard and McDonald Islands in Division 58.5.2. These established fisheries are reviewed annually by CCAMLR’s Working Group on Fish Stock Assessment (WG-FSA) and the Scientific Committee. See annual Fishery Reports. The Commission’s agreed limits for the current fishing season are defined in the Conservation measures."
None of these species has been assessed for the Red List.
A list of references referred to on this page.
Please use Ecology style, for more information and examples see:
https://besjournals.onlinelibrary.wiley.com/hub/journal/13652745/author-guidelines
AAD, (2012). http://www.antarctica.gov.au/about-antarctica/wildlife/animals/fish
Bray, D.J. (2019). Champsocephalus gunnari in Fishes of Australia (Online) Available at: http://fishesofaustralia.net.au/home/species/4878. Accessed 16 Jul 2019,
Collins, M., Xavier, J., Reid, K., Belchier, M., Goss, C., Agnew, D. (2004). Does the current South Georgia ground fish survey accurately estimate the standing stock of mackerel icefish? WG-FSASAM- 04/20. Hobart, Australia: CCAMLR.
Duhamel, G., (1991). The biological and demographic peculiarities of the icefish Champsocephalus gunnari Lönnberg, 1905 from the Kerguelen plateau. In G. Di Prisco G. et al. (Eds.) Biology of Antarctic Fishes (pp. 40-53). Heidelberg, Germany: Springer Verlag. doi: 10.1007/978-3-642-76217-8_3
Duhamel, G. (1995). New data on spawning, hatching and growth of Champsocephalus gunnari on the shelf of the Kerguelen Islands. CCAMLR Science 2, 21-34.
Duhamel, G. & Agnew, D. (1990). A re-analysis of the Kerguelen shelf and Skiff bank stocks of Champsocephalus gunnari. CCAMLR WG-FSA-90/17. Hobart, Australia: CCAMLR.
Duhamel, G., Hulley, P-A., Causse, R., Koubbi, P., Vacchi, M., Pruvost, P., ... Van de Putte A. P. (2014). Part 7 Biogeographic Patterns of Fish. In C. De Broyer & P. Koubbi (Eds.) The SCAR Biogeographic Atlas of the Southern Ocean (pp. 328-362). Cambridge, UK: Scientific Committee for Antarctic Research.
Everson, I., Parkes, G., Kock, K.H. & Boyd, I.L. (1999). Variation in standing stock of the mackerel icefish Champsocephalus gunnari at South Georgia. Journal of Applied Ecology, 36(4), 591-603. doi: 10.1046/j.1365-2664.1999.00425.x
Kellermann, A. (1996). Midwater fish ecology. In R.W., Ross, Hofmann, E. & Quetin, L.B. (eds.) Foundation for Antarctic Research west of the Antarctic Peninsula (pp. 231-256), Antarctic Research Series Vol. 70. American Geophysical Union.
Kock, K.H. (1991). The state of exploited fish stocks in the Southern Ocean—a review. Arch FischWiss 41, 1–66. doi: 10.1007/978-3-642-84074-6_35
Kock, K.H. (1992). Antarctic fish and fisheries. Studies in Polar Research. Cambridge, UK. Cambridge University Press.
Kock, K.H., (2005). Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part I. Polar Biology, 28(11), 862-895. doi: 10.1007/s00300-005-0019-z
Kock, K.H., Wilhelms, S., Everson, I. & Groger, J. (1994). Variations in the diet composition and feeding intensity of mackerel icefish Champsocephalus gunnari at South Georgia (Antarctic). Marine Ecology Progress Series, 108(1), 43-58. doi: 10.3354/meps108043
Reid, K. & Croxall, J.P. (2001). Environmental responses of upper trophic-level predators reveals a system change in an Antarctic marine ecosystem. Proceedings of the Royal Society, London B, 268, 377–384. doi: 10.1098/rspb.2000.1371
Williams, R. (2004). Conceptual model of Antarctic epi- and mesopelagic fish. WG-EMM-04-58.
| Name | Affiliation |
|---|---|
| Cath Frampton | |
| Madeleine Brasier | ACE CRC/IMAS |
Version number | Date of creation * | Expert reviewers | Peer reviewers | Date of completion* |
|---|---|---|---|---|
| 1.0 | 2019.04.30 | |||
* Date format is YYYY.MM.DD
