Spatial distribution of annual stock mixing proportions in SD 24.

Mixing proportions of WBC (blue) and EBC (red) are based on cod samples (N = 6597) from trawl surveys between 2010 and 2019, grouped by ICES rectangles (see Fig 1 for statistical rectangles). Rectangles are arranged according to their relative position within SD 24 from west to east and from north to south (Fig 1). Absolute numbers of otoliths used in the shape analysis are given on the right side of each year. Years without bars = no data available. (TIF)</p

Spatial distribution of stock mixing proportions in SD 24.

Mixing proportions of WBC and EBC are based on cod samples from German commercial catches between 2010 and 2019. Samples from active and passive gear fisheries are marked with black and green outlines, respectively. Only fishing hauls with ≥50 individuals are shown (Ntotal = 10 631 otoliths from 62 sampled hauls).</p

Seasonal proportions of WBC in SD 24.

Mixing proportions are based on cod samples from German commercial catches between 2010 and 2019 (selected years, NOtoliths = 10 924). Active and passive gear samples are pooled. Absolute numbers of otoliths used in the shape analysis are given on the top of each bar. Quarters without bars = no data available. (TIF)</p

Sampling locations of Baltic cod in SD 24 separated by sampling decade.

Cod samples originate from bottom-trawl survey catches between 1977 and 2019. (TIF)</p

Proportion of WBC in SD 24.

Mixing proportions are based on cod samples from 1st and 4th quarter trawl surveys between 1995 and 2016 (selected years, NOtoliths = 7532). Absolute numbers of otoliths used in the shape analysis are given on the top of each bar. (TIF)</p

GLMs containing stock mixing proportions of survey and commercial data as Gaussian response variable and mean depth, longitude, latitude and capture year of fishing hauls as predictors.

GLMs containing stock mixing proportions of survey and commercial data as Gaussian response variable and mean depth, longitude, latitude and capture year of fishing hauls as predictors.</p

Sampling locations of Baltic cod in SD 24.

Cod samples originate from bottom-trawl survey catches (1977 to 2019) and commercial (= com) catches (2010 to 2019) using active (= a) and passive (= p) fishing gears. Inset is a map of the larger Baltic Sea region, indicating ICES subdivisions 22 (Belt Sea), 23 (Øresund), 24 (Arkona Sea) and 25 (Bornholm Basin). Grid within SD 24 represents ICES statistical rectangles. Source of elevation data from [41].</p

Mixing proportions and spawning stock biomass of Baltic cod stocks.

a) Annual mixing proportions of EBC in SD 24 based on cod otoliths (N = 20 302) from trawl surveys between 1977 and 2019 (black bars) and annual proportions of spawning stock biomass (SSB) of EBC on total cod SSB (i.e. SSBEBC+SSBWBC) in the Baltic Sea (red line). b) Correlation analysis of proportion of EBC in SD 24 and proportion of SSB of EBC in the Baltic Sea. WBC = Western Baltic Cod, R = Pearson correlation coefficient. (TIF)</p

Proportion of genetically identified WBC in SD 24.

Mixing proportions are based on genetically validated baseline samples (N = 348) from [29]. Mixing data were grouped by capture depth and used type of fishing gear (active = trawl, passive = mainly gillnet). Absolute numbers of cod samples used for genetic analysis (in bold) and total numbers of fishing hauls used in the stock mixing analysis (in brackets) are given on the top of each bar. Depths without bars = no data available. (TIF)</p

Fishing gear-specific proportions of WBC in SD 24.

Mixing proportions are based on cod samples (N = 10 924) from German commercial catches between 2010 and 2019, using different types of fishing gears (active = trawl, passive = mainly gill net). Mixing data were grouped by a) capture depth and b) sampling year. Absolute numbers of otoliths used in the shape analysis (in bold) and total numbers of fishing hauls used in the stock mixing analysis (in brackets) are given on the top of each bar. Depths without bars = no data available.</p