New insights into the recent collapse of Eastern Baltic cod from historical data on stock health.

The Eastern Baltic cod (Gadus morhua) stock is currently in a very poor state, with low biomass and adverse trends in several life history and demographic parameters. This raises concern over whether and to what level recovery is possible. Here, we look for new insights from a historical perspective, extending the time series of various stock health indicators back to the 1940s, i.

Seeking the true time: Exploring otolith chemistry as an age-determination tool.

Fish otoliths' chronometric properties make them useful for age and growth rate estimation in fisheries management. For the Eastern Baltic Sea cod stock (Gadus morhua), unclear seasonal growth zones in otoliths have resulted in unreliable age and growth information. Here, a new age estimation method based on seasonal patterns in trace elemental otolith incorporation was tested for the first time and compared with the traditional method of visually counting growth zones, using otoliths from the Baltic and North seas.

Effects of freezing on length and mass measurements of Atlantic cod Gadus morhua in the Baltic Sea.

An aggregated sample of 925 Atlantic cod Gadus morhua collected by four countries in different regions of the Baltic Sea during different seasons were measured (total length, L = 161-890 mm and weighed (mass, M = 45-6900 g) both before freezing and after defrosting. The cod were found to decrease significantly in both L and M following death and frozen storage. There was an average (±SD) change in L of -2.

Marine litter on the seafloor of the southern Baltic.

Marine litter occurrence and composition were investigated during routine bottom trawl fish surveys type BITS performed in the Polish Maritime Areas (the southern Baltic Sea). Sampling covered a distance of 325km and an area of 16km at a depth range of 19-110m. Litter densities varying between 0 items/ha (34% of tows) and 2.

Inter-tissue distribution and evaluation of potential toxicity of PCBs in Baltic cod (Gadus morhua L.).

PCBs measured in the muscle, liver, and gonads of cod collected from two locations in the southern Baltic were evaluated as total (summation operator PCBs), indicator (summation operator PCB(7)), and dioxin-like (summation operator DL-PCBs) concentrations. Gender, tissue lipid content, and collection site were important determinants of PCB levels. Irrespective of collection site, lipid-normalized summation operator PCBs, summation operator PCB(7), and summation operator DL-PCBs in females were the lowest in the muscle, and of similar levels in liver and gonads.