Ecology Summary - Gadus morhua

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Main Ref.	Cohen, D.M., T. Inada, T. Iwamoto and N. Scialabba, 1990
Remarks	Opportunistic predator that forages mainly at dawn and dusk (Refs. 1371, 46189). Larvae feed mainly on zooplankton while juveniles prey predominantly on benthic crustaceans; adults feed mainly on zoobenthos and fish (Refs. 5743, 9604, 26813) including juvenile cod. Fish prey becomes more common in the diet with increasing body size (Refs. 1371, 89387). Adults may cover large distances during the feeding period (Ref. 89387). Young cod are also preyed upon by different fish species and octopus. Adult cod are prey items of top predators like sharks, rays, whales, dolphins, seals, and sea birds (Refs. 9023, 9581, 26954, 43651, 45735). In the Baltic it grows up to 5 kg weight in 7-8 years; in the North Sea it reaches 8 kg in the same time span . Natural mortality for adults of both stocks is assumed to be around M=0.2, resulting in a mean adult life expectancy and mean duration of the reproductive phase of 5 years (Ref. 88171). Parasites of the species include protozoans (trypanosome), myxosporidians, monogeneid, trematodes, cestodes, nematodes, acanthocephalan, hirudinid and copepods (Ref. 5951).

Main Ref.

Cohen, D.M., T. Inada, T. Iwamoto and N. Scialabba, 1990

Remarks

Opportunistic predator that forages mainly at dawn and dusk (Refs. 1371, 46189). Larvae feed mainly on zooplankton while juveniles prey predominantly on benthic crustaceans; adults feed mainly on zoobenthos and fish (Refs. 5743, 9604, 26813) including juvenile cod. Fish prey becomes more common in the diet with increasing body size (Refs. 1371, 89387). Adults may cover large distances during the feeding period (Ref. 89387). Young cod are also preyed upon by different fish species and octopus. Adult cod are prey items of top predators like sharks, rays, whales, dolphins, seals, and sea birds (Refs. 9023, 9581, 26954, 43651, 45735). In the Baltic it grows up to 5 kg weight in 7-8 years; in the North Sea it reaches 8 kg in the same time span . Natural mortality for adults of both stocks is assumed to be around M=0.2, resulting in a mean adult life expectancy and mean duration of the reproductive phase of 5 years (Ref. 88171). Parasites of the species include protozoans (trypanosome), myxosporidians, monogeneid, trematodes, cestodes, nematodes, acanthocephalan, hirudinid and copepods (Ref. 5951).

Aquatic zones / Water bodies

	Marine - Neritic	Marine - Oceanic	Brackishwater	Freshwater
Marine zones / Brackish and freshwater bodies	supra-littoral zone littoral zone sublittoral zone	epipelagic mesopelagic epipelagic abyssopelagic hadopelagic	estuaries/lagoons/brackish seas mangroves marshes/swamps	rivers/streams lakes/ponds caves exclusively in caves

Highighted items on the list are where Gadus morhua may be found.

Habitat

Substrate	Soft Bottom Hard Bottom: rocky;
Substrate Ref.
Special habitats	Beds: sea grass;
Special habitats Ref.

Associations

Ref.
Associations	schooling;
Associated with
Association remarks	Generally considered a demersal fish although its habitat may become pelagic under certain hydrographic conditions when feeding or spawning. There is some evidence that cod leave the bottom and school pelagically to spawn in preferred temperatures when bottom tempetatures are unsuitable. Gregarious during the day, forming compact schools that swim between 30-80 m above the bottom, and scatter at night (Ref. 1371). Schooling behavior may be adaptive for feeding. Reproductive behavior during spawning involves the circling of a female often by only one male per spawning bout (Ref. 86779).
Parasitism

Feeding

Feeding type	mainly animals (troph. 2.8 and up)
Feeding type Ref.	Nordeide, J.T. and J.H. Fosså, 1992
Feeding habit	hunting macrofauna (predator)
Feeding habit Ref.	Nordeide, J.T. and J.H. Fosså, 1992

Trophic Level(s)

Estimation method	Original sample		Unfished population		Remark
Estimation method	Troph	s.e.	Troph	s.e.	Remark
From diet composition	4.09	0.18	4.34	0.72	Troph of adults from 7 studies.
From individual food items	4.29	1.00			Trophic level estimated from a number of food items using a randomized resampling routine.
Ref.	dos Santos, J. and S. Falk-Petersen, 1989

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