Ar Research Station Gotland University. In the centre of the Baltic Sea!

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1 Ar Research Station Gotland University In the centre of the Baltic Sea!

2 Ar Research Station The station is situated on the land-strip between the lake Bäste träsk (to the right) and the Baltic Sea (to the left)

3 A part of the small village Ar and the lake Bäste träsk (you can drink the water!)

4 Ponds for experiments can be provided with either fresh or brackish water The station offices etc (to the right) and the experimental hall (to the left)

5 The experimental hall Both fresh- and brackish water available Provided with an aeration-system Eight 2x2m basins and twenty 1x1 m basins

6 Two laboratories Rooms with temperature-control system for small-scale experiments Brackish- and freshwater & aeration

7 The office section Four offices, two sleeping-rooms (8 beds)

8 a room for meetings, kitchen and a place for coffee-breaks OPEN FOR GUESTS!

9 Fieldof interest Sustainable development Biodiversity Basic research! Baltic Sea Applied Research!

10 Flounder in the Baltic Sea Coastal spawning demersal eggs Two populations Genetically distinct Different life-history Separated during spawning Share the same feeding areas Offshore spawning pelagic eggs

11 A gotlandic species Landings Flundra on Gotland Stable catches until the 1980s High population density Potential target species Fish in poor condition/slow growth Landningar (ton)

12 Life-cycle of flatfishes egg-larvae-metamorphosis-juvenile-adult Eggs: Survival according to salinity, oxygen, temperature Buoyancy (at what depths do eggs develop) Larvae: Not very much so far Juveniles: Habitat preferences Feeding (preferred food items) Growth (temperature, food availability) Predation (mortality risk) Mortality during early stages determine the year-class strength! Adults: Mortality Growth & condition Egg production Egg quality Habitat utilization during the year

13 The flounder project Experimental work in the laboratory (eggs, larvae & juveniles) Field sampling at nursery areas (juveniles) Monitoring fishing (adults) Basic & applied research

14 Brackish water & stratified water column Increase in salinity decrease in oxygen with depth Decreasing salinity (3-8 ) Halocline at 50-70m (10-20 ) Salinity & oxygen condition affects the reproductive success & the year-class strength Governed by saline water inflows

15 Major inflows during the last century frequency and magnitude vary Strong inflows during the 1970s Long stagnation period up to 1993 Inflows in 2003 and 2005; 2013? very strong strong moderate weak

16 Effects of salinity on Spermatozoa activity & fertilization Egg development Egg specific gravity ability to keep buoyant Inflow events & stagnation periods affects the reproductive success and the year-class strength - stock abundance & distribution

17 Flounder with pelagic eggs efter inflow inflöde event Salthalt (promille) Salinity(%) 0 10 Egg buoyancy(%) 10 Skrubbskädda stagnation utan period inflöde Andel ägg med flytförmåga (%) Reproduction layer thickness (m)

18 Flounder with demersal eggs following an inflow Andel utvecklade ägg (%) Egg development (%) Befruktning Salthalt (promille) Salinity(psu) during stagnation = Reproduction areas, >6psu salinity in the bottom layer = Areas with <2 ml O 2 /l in the bottom layer

19 Egg production & growth - allocation of energy To grow or to produce eggs? Numb ber of eggs (x1000) Egg production Coastal- & Offshore-spawners Somatic weight (g) CSSA CSNG Coastal spawners produce more eggs Offshore spawners grow faster and reach a higher final size Adaptation to spawning strategy!? CSEG OSBB OSGB Larger fish in the south vs. in the north 22

20 Development of a sustainable gotlandic flounder fishery Questions: Fishing -when and at what depths Contribution of the respective population The reason/s for fish being in poor condition Measurements in the field and sampling in the lab EUROPEISKA UNIONEN Europeiska fiskerifonden - en satsning på hållbart fiske

21 Preliminary results depth distribution share of catch (%) at 3, 10, 20, 50 and 80 m along two transects January Antal SO Antal NO n=51 April n=1562 Antal SO Antal NO Andel (%) Djup (m) Andel (%) Djup (m) June n=1575 July n=935 Antal SO Antal NO Antal SO Andel (%) Andel (%) Djup (m) Djup (m)

22 Preliminary results fish condition Fulton s condition factor at spawning & feeding season Fishing (females) at 20 m depth in August and early September Condition males Condition females 1,1 1,1 1,05 1 0,95 0,9 0,85 0,8 0,75 0,7 0,65 0,6 April Juni Juli Augusti September 1, , ,9 0, ,8 0,75 80 godkänd 0,7 0,65 0,6 April Juni Juli Augusti September Depth (m) godkänd Preferred condition

23 Welcome to visit the Ar Research Station!