Figure 1
Map presenting the sampling sites in the southern Baltic Sea (Arkona Basin: GA1 and GA2, GB, BB23 and IBY5 in the Bornholm Basin, RS – Slupsk Furrow, GG – Gotland Deep, GGd and Krynica in the Gdansk Basin)
Table 1
Characteristics of the sampling sites in the southern Baltic Sea in 2015
| Site | Coordinates | Date | Depth layer [m] | Bottom depth [m] |
|---|---|---|---|---|
| Arkona Deep 1 | 55°0ʹ0.36ʹʹN 13°10ʹ29.279ʹʹE | 07.06.2015 | 2–0 25–0 46–0 | 46.10 |
| Arkona Deep 2 | 55°9ʹ15.48ʹʹN 14°19ʹ36.48ʹʹE | 08.06.2015 | 2–0 25–0 46–0 | 46.90 |
| Bornholm Deep | 55°10ʹ13.08ʹʹN 15°30ʹ0.719ʹʹE | 09.06.2015 | 2–0 27–0 94–0 | 96.10 |
| BB23 | 55°17ʹ31.2ʹʹN 15°45ʹ0ʹʹE | 22.06.2015 | 2.5–87.5* | 94.00 |
| IBY5 | 55°14ʹ509ʹʹN 15°59ʹ037ʹʹE | 29.05.2015 | 55–0 82–55 | 86.00 |
| Slupsk Furrow | 55°7ʹ49.08ʹʹN 17°2ʹ30.839ʹʹE | 09.06.2015 | 2–0 65–0 94–0 | 93.00 |
| Gotland Deep | 55°28ʹ41.88ʹʹN 18°20ʹ0.6ʹʹE | 10.06.2015 | 2–0 60–0 103–0 | 109.00 |
| Gdansk Deep | 54°30ʹ24.48ʹʹN 19°10ʹ28.92ʹʹE | 10.06.2015 | 2–0 53–0 110–0 | 108.58 |
| Krynica | 54°14ʹ0.6ʹʹN 19°11ʹ51.36ʹʹE | 10.06.2015 | 2–0 20–0 | 22.20 |
[i] *stratified samples collected every 5 meters
Figure 2
Water temperature and salinity in the southern Baltic Sea in June 2015
Table 2
Abundance of fish species (n m–3) recorded in the southern Baltic Sea in May and June 2015
| species | life stages of fish | sites | |||||||
|---|---|---|---|---|---|---|---|---|---|
| GA1 | GA2 | GB | IBY5 May | RS | GG | GGd | Krynica | ||
| Sprattus sprattus | eggs | 5.45 | 4.28 | 7.58 | 15.51 | 3.62 | 1.13 | 7.17 | 0.00 |
| larvae | 1.26 | 2.24 | 0.52 | 0.68 | 1.45 | 0.39 | 1.50 | 0.00 | |
| Clupea harengus | larvae | 0.19 | 0.19 | 0.09 | 0.00 | 0.24 | 0.04 | 0.20 | 0.00 |
| Gadus morhua | eggs | 0.00 | 0.00 | 2.57 | 1.18 | 1.95 | 0.00 | 0.00 | 0.00 |
| Enchelyopus cimbrius | eggs | 0.00 | 0.00 | 0.00 | 0.00 | 2.15 | 0.00 | 0.04 | 0.00 |
| larvae | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.04 | 0.00 | |
| Platichthys flesus | eggs | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.08 | 0.00 |
| larvae | 0.00 | 0.00 | 0.00 | 0.00 | 0.05 | 0.00 | 0.00 | 0.00 | |
| Pomatoschistus minutus | larvae | 0.00 | 0.19 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.56 |
| Hyperoplus lanceolatus | larvae | 0.09 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Taurulus bubalis | larvae | 0.09 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Nerophis ophidion | larvae | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.07 | 0.00 | 0.00 |
Table 3
The number of sprat early developmental stages (n m–3) at four of the examined sites where the largest number of the early stages of development occurred
| site | development stage | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| I | II | III | IV | V | yolk-sac stage | pre-flexion | flexion | post-flexion | |
| GB | 4.29 | 2.15 | 0.81 | 0.33 | 0.00 | 0.52 | 0.00 | 0.00 | 0.00 |
| IBY5 May | 11.41 | 2.73 | 1.37 | 0.00 | 0.00 | 0.68 | 0.00 | 0.00 | 0.00 |
| RS | 2.60 | 0.44 | 0.48 | 0.05 | 0.05 | 0.98 | 0.10 | 0.24 | 0.13 |
| GGd | 4.40 | 0.53 | 1.91 | 0.29 | 0.04 | 1.34 | 0.16 | 0.00 | 0.00 |
Table 4
The size of sprat eggs in stage I at different sites and depth layers
| site | haul | number of eggs | mean [mm] | min. [mm] | max [mm] |
|---|---|---|---|---|---|
| GA1 | 0–2 | 2 | 1.48 | 1.4 | 1.55 |
| 0–25 | 12 | 1.39 | 1.3 | 1.55 | |
| 0–46 | 14 | 1.4 | 1.2 | 1.55 | |
| GA2 | 0–2 | 10 | 1.45 | 1.3 | 1.55 |
| 0–25 | 11 | 1.45 | 1.25 | 1.6 | |
| 0–46 | 6 | 1.31 | 1.25 | 1.35 | |
| GB | 0–2 | no data | |||
| 0–27 | no data | ||||
| 0–94 | 20 | 1.36 | 1.25 | 1.45 | |
| RS | 0–65 | 17 | 1.36 | 1.3 | 1.5 |
| 0–91.5 | 20 | 1.45 | 1.3 | 1.55 | |
| GG | 0–60 | 8 | 1.44 | 1.4 | 1.5 |
| 0–103 | 15 | 1.39 | 1.3 | 1.5 | |
| GGd | 0–2 | no data | |||
| 0–53 | 14 | 1.38 | 1.2 | 1.45 | |
| 0–110 | 7 | 1.33 | 1.2 | 1.45 |
Figure 3
Average diameter of sprat eggs in stage I (solid line), standard deviation range (blue field), minimum and maximum size of eggs (dotted lines) and salinity (red line) in different depth strata at the BB23 site