Cod

Fig 1. Historical spawning areas for cod in the Baltic Sea. From Bagge, O., Thurow, F., Steffensen, E., Bay, J. 1994. The Baltic Cod. Dana Vol. 10:1-28, modified by Aro, E. 2000. The spatial and temporal distribution patterns of cod (Gadus morhua callarias) in the Baltic Sea and their dependence on environmental variability – implications for fishery management. Academic dissertation. University of Helsinki and Finnish Game and Fisheries Research Institute, Helsinki 2000, ISBN-951-776-271-2, 75 pp.

Cod is relatively scarce in the Gulf of Bothnia and the Gulf of Finland, except after major influxes of saline and oxygen-rich water from the North Sea. At those times cod may also spawn further north than usually. The general decline of cod in the Baltic during the 1980s and 1990s is at least partly due to the lack of any major influx of saline water from the North Sea and possible competition from other species such as sprat. In some areas the only waters saline enough for cod eggs now lie at depths where there is little or no oxygen. The subsequent decrease in reproductive volume of cod since the 1980s together with too high fishing pressure has resulted in weak cod year classes since the early 1990s. 

Cod catches, management and recovery plan

Cod is the most important commercial fish species in the Baltic Sea. In 1963-1973 cod catches were on the level of 133 000 - 202 000 tons. In the period of 1980-85 the cod stocks were at an extremely high level of 344 000 - 442 000 tons and cod fishery expanded also to the northern waters of the Baltic Sea. From 2000 to 2007 Baltic cod catches have been on the lowest levels (105 000 – 63 000 tons) since the recording of catches started in 1950s.

Baltic cod is managed by two management units: the eastern stock (ICES subdivisions 25–32) and the western part of the stock (ICES 22-24). The adopted TAC (total allowable catches) in 2008 for the eastern stock was 45 000 tons and for the western stock 15 500 tons. The recent ICES advice (report/2008/Baltic Sea) for cod fisheries in 2009 for eastern Baltic cod is that landings should not exceed 48 600 tons. Landings of the western cod unit (ICES 22–24) should not exceed 13 700 tons.

Click here to see ICES sub-divisions for the Baltic Sea. 

The current level of cod fishing is unsustainable and EU has adopted 2007 the multiannual plan for the Baltic Sea cod for the recovery of the Baltic cod stocks (Council Regulation (EC) No 1098/2007). During 2008 ICES is going to analyze whether the EC recovery plan is in accordance with the precautionary approach.

Figure 2. Spawning stock biomass (SSB, in thousand tons), total stock biomass (TSB, in thousand tons), fishing mortality (F, ages 4–7) and recruitment (age 2, millions) of cod in ICES SDs 25–32 and separately for SD 25 and SDs 26 and 28 from the mid-1940s. The left axis refers to the separate SDs, the right to the entire stock (Eero et al. 2007).

Time-series of reproductive volume for cod spawning site (MacKenzie et al. 2000).

Source: http://ec.europa.eu/fisheries/press_corner/press_releases/com07_57_graphs_en.pdf

Reference:

Eero, M., Koster, F.W., Plikshs, M. and Thurow, F. 2007. Eastern Baltic cod (Gadus morhua callarias) stock dynamics: extending the analytical assessment back to the mid-1940s. ICES Journal of Marine Science, 64: 1257–1271.

MacKenzie, B. R., Hinrichsen, H.-H., Plikshs, M., Wieland, K., Zezera, A. 2000. Quantifying environmental heterogeneity: estimating the size of habitat for successful cod Gadus morhua egg develop­ment in the Baltic Sea. Marine Ecology Progress Series 193: 143-156. With updates by Maris Plikshs (Pers. Comm.).

ICES 2006. Report of the ICES Advisory Committee on Fisheries Management, Advisory Committee on the Marine Environment and Advisory Committee on Ecosystems, 2006. ICES Advice. Book 8, 119 pp.

Last updated: 3 December 2008