Well-Being of the Baltic Herring and Bycatch Fish Species from FAO Major Fishing Areas 27 According to Microplastic Pollution

Abstract

Condition factors are essential in fishery science. They provide insights into fish well-being according to the impact of environmental stressors. The Fulton condition factor (K) and hepatosomatic index (HSI), as well as two new indices (GILSI and GITI), were used to assess the well-being of herring and bycatch species (cod, flounder, sprat, long-spined bullhead, lumpfish) from the Baltic Sea. For Cyclopterus lumpus and Taurulus bubalis, K and HSI values were reported for the first time. Fish from different basins differed according to biometric measures (weight: 6.09-750.12 g; length: 8.6-41.8 mm) and condition indices (mean K: 1.19; HSI: 0.02; GITI: 0.04; GILSI: 0.03). Microplastics (MPs) were found in all species (21% (sprat)-79% (lumpfish)), averaging 3.1 items/fish. The organ-wise analysis revealed that 46% of the gills, 16% of the livers, and 38% of the gastrointestinal tracts were contaminated with MPs. The relationship between these indices and MPs abundance in the organs of herring was examined using PCA, revealing a negative impact of MPs on fish health. The morphometric features and the chemical composition of MPs were also detected. The dominant size ranges were 0.11-0.5 mm (30%) and 1.01-5 mm (28%). Blue fibers were the most common.

Keywords: Baltic cod; biometric features; flounder; long-spined bullhead; lumpfish; pollution with microplastics; principal component analysis; sprat; the Baltic Sea.

Figure 1

The sampling sites of fish collection in the southern BS, including fishing zones 103 (Władysławowskie), 105 (Ustecko-Łebskie), 108 (Słupsk Gutter), 129 (Gotlandic), and 135 (Kalmarskie), located within FAO fishing area 27.III.d.25 (the colors of frames surrounding fishing zones used have no meaning).

Figure 2

Relation between total length (l) and total mass (m) according to fish species (straight line—regression line; dashed ellipse—a two-dimensional area of normal data distribution at p = 0.05).

Figure 3

Normalized K factor values according to species based on an intensive literature survey and current data (numbers in shapes correspond to references: good condition; moderate condition; poor condition [109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147]; empty shapes correspond to the current study).

Figure 4

Relation between total length, total mass, and K factor (A); total mass, liver mass, and HSI values (HSI) (B); total mass, gills mass, and GILS index (GILSI) (C); and between total mass, gastrointestinal tract (GIT) mass, and GIT index (GITI) (D) according to fish species (bullets—particular specimens, ellipses—surround specimens of the given species).

Figure 5

Biplots of PC1 and PC2 loadings and scores with active variables and cases and additional variables (A) and principal component scores according to fishing zone (fz) and fishing date (B), respectively, computed for the Baltic herring data set.

Figure 6

Quantitative distribution of MPs items colors across different size classes, visualized as a Sankey diagram (the colors of size classes have no meaning).