Region GB + Depth >70m >70m <70m <70m >70m >70m >70m >70m Mortality rate 0.585 0.030 0.801 0.066 0.255 0.135 0.376 0.384 Z -0.881 -0.031 -1.613 -0.068 -0.294 -0.145 -0.471 -0.485
Tab. 2.1.20. The total amount of the eggs spawned by sprat in the Gotland Basin from 55°30’N to 58°N (ICES subdivisions 26/1, 28/3,4, and the southern halves of 28/1,2) during 1999, and the calculation of its spawning stock biomass in this basin in 1999.
Period Egg
production Egg production
during Mean individual
fecundity Number of
spawning Spawning
sprat Mean Total weight of
stock of sprat,
*1000 t.
Tab. 2.1.21. Mean relative error in abundance estimates (mean), standard deviation (STDV) and maximum error (max) resulting from spatial sampling resolution for the May 1988 and August 1991 model runs.
Calculations are based on the standard 45 stations grid. Ex.1-5=Experiments 1-5 (see Fig. 2a-c);
SL=Sprat larvae; SE=Sprat eggs; CL=Cod larvae; CE=Cod eggs.
May 1988 August 1991
Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 SLmean 5.3 10.4 3.9 10.6 10.0 11.9 9.7 24.7 17.9 14.3 SLSTDV 6.0 4.7 4.3 5.2 6.1 8.9 6.1 11.4 12.6 7.5 SLmax 20.3 18.1 18.8 18.1 29.0 40.7 39.0 43.2 70.6 41.3 SEmean 5.3 11.3 5.6 8.5 15.5 11.7 23.7 8.9 17.4 24.7 SESTDV 5.4 5.5 4.1 4.5 9.0 9.7 11.1 3.4 13.4 16.1 SEmax 20.5 20.2 17.6 19.1 35.7 28.8 41.5 18.4 45.0 55.3 CLmean 6.5 13.3 4.2 6.5 17.4 13.4 21.1 9.5 21.3 25.9 CLSTDV 4.7 8.1 4.7 4.4 12.2 8.1 11.8 5.1 16.0 18.9 CLmax 20.7 26.2 17.9 17.5 41.7 28.3 41.9 18.2 61.9 65.0 CEmean 9.3 1.6 15.4 10.4 5.3 5.5 6.1 18.3 14.2 5.3 CESTDV 4.2 1.8 3.4 10.1 3.4 4.6 3.4 8.3 5.4 6.4 CEmax 20.5 6.9 23.5 34.8 13.9 22.5 13.2 35.1 23.7 22.3
Tab. 2.1.22. Summary output of the multiple linear regression.
Intercept 7.1951576 0.690 10.43 0.0000005 5.68 8.71 5.68 8.71 Julian Day of the
survey -0.0038047 0.005 -0.77 0.46 -0.01 0.01 -0.01 0.01 Water density at the
depth of isooxygen 2ml/l
0.2014555 0.074 2.71 0.02 0.04 0.36 0.04 0.36
Water temperature at
10 m depth -0.0974754 0.033 -2.92 0.01 -0.17 -0.02 -0.17 -0.02
Tab. 2.1.23. The generalized vertical distribution of sprat eggs in the Gotland Basin and the Gdansk Deep in all month of the spawning season. 0 corresponds to the mean specific gravity of sprat eggs in the specific observation.
Water layer with density diapason, Relative abundance of
sprat eggs, % 0.1 0.6 2.8 7.3 14.7 25.5 22.1 15.1 6.9 2.9 1.4 0.4 0.1
Tab. 2.1.24. Ichthyoplankton surveys in 1999- 2000 used in the calculation of the spawning-stock biomass of sprat in the Gotland Basin.
Year Date Vessel Number of stations in the Gotland Basin 1999 20 - 22 April Alkor 15
Tab. 2.1.25. Mortality of sprat eggs in the different regions of the Gotland Basin in the different months of 1999. GB is the central part of the Gotland Basin, SGB is the southern part of it. Z = Instantaneous mortality coefficient (per day): Z = 1/t*ln(Nj,m/Ni,n), where N is daily abundance of eggs at stage.
Region GB SGB GB SGB GB SGB
Date 21 April 20 April End of May End of May 20 June 20 June Stages St. I-II St. I-II St. I-II St. I-II St. I-II St. I-II Mortality rate per day [1-EXP(-Z)]: 0.176 0.147 0.349 0.344 0.359 0.320
Z 0.194 0.159 0.429 0.422 0.445 0.386 Period of time between the midpoints
of 2 stages (ti-j), in days 3.035 3.115 3.55 3.55 3.426 3.426 Ambient water temperature 4.56 4.46 4.00 4.00 4.12 4.12
Tab. 2.1.26. Mortality of sprat eggs in the different regions of the Gotland Basin in the different months of 2000. GB is the central part of the Gotland Basin, NGB and SGB are the northern and southern parts of it. Z= Instantaneous mortality coefficient (per day): Z = 1/t*ln(Nj,m/Ni,n), where N is daily abundance of eggs at stage.
Region NGB GB SGB NGB GB SGB GB SGB
Date 3 May 3 May 3 May 4 June 4 June 4 June 16 June 16 June Stages St. I-II St. I-II St. I-II St. I-II St. I-II St. I-II St. I-II St. I-II Mortality rate per day 0.302 0.260 0.179 0.312 0.297 0.400 0.280 0.267
Z 0.359 0.302 0.197 0.374 0.3520 0.511 0.328 0.310 Period of time
between the midpoints of 2 stages
(ti-j), in days
3.970 3.970 3.547 3.311 3.311 3.311 3.140 3.299
Ambient water
temperature 3.64 3.64 4.00 4.50 4.50 4.50 4.43 4.25
Tab. 2.1.27. The calculation of the total amount of the eggs spawned by sprat in the Gotland Basin (ICES subdivisions 26/3, 26/4, 28/1-4) during 1999 and the calculation of its spawning stock biomass in this basin in 1999.
Period Date of
ichthyoplankton survey
Egg production
per day, n*109 Egg production during the whole period, n*109
10 April - 9 May 20 April 368 11040 (368*30 days) 10 May - 10 June 28 May-2 June 3107 96317 (3107*31) 11 June - 12 July 20 June 5349 171168 (5349*32) 13 July - 2 August 01 August 20 420 (20*21) The whole spawning season 278945
Mean individual fecundity per spawning
season
Total weight of spawning stock of sprat, *1000 t
11738 23.76 47.53 8.7 413
Hydroacoustic survey 49.21
Tab. 2.1.28. The calculation of the total amount of the eggs spawned by sprat in the Gotland Basin (ICES subdivisions 26/3, 26/4, 28/1-4) during 2000 and the calculation of its spawning stock biomass in this basin in 2000.
Period Date of
ichthyoplankton survey
Egg production
per day, n*109 Egg production during the whole period, n*109
16.04-15.05 3 May 374 11220 (374*30 days) 16.05-10.06 3 June 5499 142974 (5499*26) 11.06-10.07 19 June 3358 100736 (3358*30) Second part of July
(precautious evaluation)
1000 20000 (1000*21)
The whole spawning season 274930
Mean individual fecundity per spawning
season
weight,g Total weight of spawning stock of sprat, *1000 t
12654 21.73 43.45 9.7 421
Hydroacoustic survey 41.48
Tab. 2.1.29. The calculation of the total amount of the eggs spawned by sprat in the Gotland Basin (ICES subdivisions 26/3, 26/4, 28/1-4) during 1999 and the calculation of its spawning stock biomass in this basin in 1999 with the assumption that the certain portion of eggs had sunk into the deep water layer with very unfavorable oxygen conditions (<1 ml/l) and died before sampling.
Period Date of
Amount of sprat eggs in the water layer with
O2<1ml/l, %
Corrected egg production per
day, n*109
Egg production during the whole
period, n*109
The whole spawning season 313068
Mean individual
weight, g Total weight of spawning stock of sprat, *1000 t
11738 26.67 53.34 8.7 463
Tab. 2.1.30. The calculation of the total amount of the eggs spawned by sprat in the Gotland Basin (ICES subdivisions 26/3, 26/4, 28/1-4) during 2000 and the calculation of its spawning stock biomass in this basin in 2000 with the assumption that the certain portion of eggs had sunk into the deep water layer with very unfavourable oxygen conditions (<1 ml/l) and died before sampling.
Period Date of ichthyoplankton Egg
production Amount of sprat eggs in
n*109 whole period, n*109
16.04-15.05 3 May 374 37 594 17810
16.05-10.06 3 June 5499 12 6249 162470 11.06-10.7 19 June 3358 10 3731 111928 Second part of July
(precautious evaluation)
- 1 - 1000 21000
The whole spawning season 313208
Mean individual
weight, g Total weight of spawning stock of sprat, *1000 t
12655 24.75 49.50 9.69 480
Tab. 2.1.31. Location depths (m) of 8 psu isohaline and the upper and lower 4 °C isotherms in the western and eastern parts of the Gdansk Deep