Cod reproduction

Oxygen dynamics in the deepwater of the central Baltic Sea is a key issue for the cod reproduction in the Baltic. The recruitment of cod depends on egg survival within the halocline, implying that hypoxia or anoxic condition can significantly decline the number of recruits. The ventilation of the deepwater below the halocline is associated with saltwater inflows, but oxygen consumption is mainly due to mineralization of detritus. 

There is a change with age in the ability of Atlantic cod to mobilize protein. This appears to be an attempt to compensate for the fact that, as the fish increase in length with age, the size of the gonads as a proportion of the body weight increases until the fish die through over-reproduction (Love, 1970). 

Ipatov, V.V. (1970). Dynamics of blood serum proteins in Baltic cod in relation to reproductive products, maturation and season (In Russian). Voprosy Ikhtiologii 10, 892-896. 

Ipatov, V.V. (1976). The dynamics of nucleic acids in Baltic cod during the reproductive period (In Russian). In Proceedings of the third All-Union Conference on Fish Ecological Physiology (V.D. Romanenko, ed.), p. 128. Naukova Dumka, Kiev. 

FIGURE 18.8 Interannual variability in reproductive volume (water with salinity >11 psu and oxygen concentration >2 ml/1) in the main cod spawning areas in the eastern Baltic Sea (Plikshs et al., 1993 ICES, 2004b). 

The cod stock has been driven down on the one hand by a rigorous fishery, with total allowable catches exceeding over many years the scientific recommendations, the reproduction on the other hand was hampered by the adverse hydrographic conditions. Under the prevailing conditions, with a continuous lack of inflow and a very high sprat stock a recovery... 

In this chapter, we review fishing history and climate effects on cod, sprat, and herring stocks considering effects of the fishery and physical environment on stock development and the reproductive success, recruitment, and growth. Finally, the potential for the recovery of the eastern Baltic cod stock and the benefits of a more balanced ecosystem are discussed. 

Vallin, L., Nissling, A., Westin, L., 1999. Potential factors influencing reproductive success of Baltic cod, Gadus morhua. a review. Ambio, 28, 92-99. 

Classification Aliphatic ether alcohol glycol ether Empirical C4H10O2 Formula CH3CH2OCH2CH2OH Properties Colorless liq. mild sweet ether odor misc. with hydrocarbons, alcohol, ether, acetone, liq. esters, water m.w. 90.14 dens. 0.9311 (20/20 C) vapor pressure 5.31 mm Hg m.p. -70 C b.p. 135.6 C flash pt. 48.9 C ref. index 1.4060 surf, tens. 28.2 dynes/cm dielec, const. 29.6 Toxicology ACGIH TLV/TWA 5 ppm (skin) LD50 (oral, rat) 3 g/kg, (IP, rat) 2800 mg/kg, (IV, rat) 2400 mg/kg, (skin, rabbit) 3300 mg/kg mod. toxic by ing., skin contact, IV, IP routes mildly toxic by inhaiation, subcut. routes mild eye/skin irritant experimental teratogen, reproductive effects TSCA listed Environmental VOC BODS 1.03 COD 1.92 ... 

Toxicology ACGIH TLV/TWA 100 ppm STEL 150 ppm LD50 (IP, mouse) 1739 mg/kg, (skin, rabbit) 14,100 mg/kg mod. toxic by IP mildly toxic by ing., skin contact, inh. severe skin irritant human systemic effects ing. of large amts, may cause CNS depression inh. may cause nose/throat irritation, CNS depression, headache, dizziness, nausea, vomiting experimental teratogen, reproductive effects common air contaminant TSCA listed Environmental VOC BODS 2.53 COD 2.62 ... 

BUTLER G L and ROWLAND s J (2009) Using underwater cameras to describe the reproductive behaviour of the endangered eastern freshwater cod Maccullochella ikei. Ecology of Freshwater Fish, 18, 337-349. 

ROWLAND s J (1998) Aspects of the reproductive biology of Murray cod, Maccullochella peelii peelii. Proceedings of the Linnean Society of NSW, 120,147-162. 

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