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 T = 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 T and M following death and frozen storage. There was an average (±SD) change in L T of −2.91% (±0.05%) following freezing, independent of starting L T . Total M changed by −2.65% (±0.14%), independent of starting mass. Shrinkage of L T and M did not differ significantly between 1 and 4 months frozen storage, though L T shrinkage was significantly greater after 1 or 4 months in the freezer compared with after 5 days. There was significant variation in L T and M shrinkage between regions of capture. A significant negative relationship between condition of cod and L T or M change was also observed. Equations to back‐calculate fresh L T and M from thawed L T , M and standard length ( L S ), gutted L T , gutted L S and gutted M are provided.