Fig 1.
Time series of spatial distribution of Eastern Baltic cod in comparison with stock biomass.
(A) Proportion of the commercial cod landings taken in ICES Subdivisions 27–32 (bars), i.e. in the northernmost edge of distribution range of the stock in the Baltic Sea, is considered as a proxy for stock distribution. The biomass shown is for commercial sized cod, i.e. > = 35 cm in length [24] (B) A map illustrating the location of ICES Subdivisions in the Baltic Sea.
Fig 2.
Time series of body condition of Eastern Baltic cod.
(A) Developments in average LeCren’s K condition index, by quarter (Q), but combined for all SDs and data sources (commercial and survey). The bars indicate standard error of the mean. The line shows smoothed year effects from GAM analyses including data source, Q and SD as categorical variables. (B) Variability in LeCren’s K condition indices (Q1 and Q2 combined) in selected time periods representing peaks and troughs in the average condition: 1948–1955 (Period 1), 1970–1975 (Period2), 1978–1983 (Period 3); 1989–1993 (Period 4) and 2015–2021 (Period 5).
Fig 3.
Time series of hepatosomatic index of Eastern Baltic cod.
The average index (HSI) is shown for female cod at 40–60 cm in length, by quarter. The bars indicate standard error of the mean.
Fig 4.
Time series of length at maturity and sex ratio of Eastern Baltic cod.
(A) Length at maturity is the length at which 50% of the cod are mature (L50) with the bars indicating standard error of the estimate. (B) Proportion of female (F) and male (M) cod in the stock is shown for fish > 40 cm and > 50 cm in length. The lines in A and B illustrate smoothed trends over time.
Fig 5.
Liver worm (C. osculatum) infection loads in Eastern Baltic cod in comparison with trends in grey seal abundance in the Baltic Sea.
C. osculatum load is represented by prevalence (percentage of infected fish; open circles) and intensity of infection (mean number of parasites in infected individuals; filled circles). Grey seal abundance shown in the figure is for the entire Baltic Sea, while liver worm infection loads are from the southern and central Baltic Sea.
Fig 6.
Time series of length structure of Eastern Baltic cod stock in comparison with trends in fishing mortality.
L95 is length at 95th percentile of the length distribution, based on data from commercial catches. The error bars show standard error of L95 for years where several length distribution datasets were available. The line illustrates smoothed trends in L95 over time. Fishing mortality (F) is average for ages 4–6, including 90% confidence intervals [12, 38].
Fig 7.
Long-term relative changes in health indicators of Eastern Baltic cod.
The colors represent 20th percentiles of the range of smoothed average values observed in the time series, with the blue representing the best and red the worst state. These are overlaid with trends in biomass of commercial sized cod (> = 35 cm; black line) and smoothed time series of recruitment per spawning stock biomass (white broken line), estimated from stock assessment.