Atlantic cod (Gadus morhua L.) off Greenland over the past two decades

No abstracts are to be cited without prior reference to the author.

The present investigation deals with the ecological relationships between the observed variability in essential population parameters of the cod stock off Greenland including environmental conditions, i.e. the near bottom water temperature. The data were derived from an annual autumn survey series commenced in 1982. The survey estimates confirmed that the spawning stock biomass remained very low after the major stock collapse in the early 1970s. The estimated total stock abundance has undergone dramatic changes due to very high recruitment variability, fishing and emigration to Iceland. However, the year class 2003 is assessed as the second strongest year class since 1982 and is estimated to amount to 71 % of the strongest year class 1984 at age 1, which yielded about 170 000 t throughout its life. The variation of the mortality estimates indicates that the progressive depletion of the strong year classes 1984 and 1985 was mainly due to over-fishing. The very low mortality rates recently observed are possibly supported by increased availability due to increased stock size and/or improved environmental year effects. Interannual fluctuations in condition are positively correlated with water temperature and negatively with stock size. The recently improved condition of the cod off Greenland is indicated as enhanced from the continued warming and the low size of the stock. Furthermore, fish condition appears to affect the growth rates positively, with well conditioned fish growing faster than poorly conditioned fish. The observed changes to earlier maturation at age are correlated with water temperature, but they may have been caused by changes in growth too. Recent good recruitment, high condition and high growth rates as well as early maturation coincide with continued warm water temperatures. The significantly increased productivity potential implied by these changes in essential population parameters urgently requires a definite multi-annual management plan consistent with the precautionary approach in fisheries management.