Invasion ecology of the round goby in the Baltic Sea Henn Ojaveer - - PowerPoint PPT Presentation

Invasion ecology of the round goby in the Baltic Sea

Henn Ojaveer Kristiina Nurkse

Jonne Kotta

Distribution

Kotta et al. 2016

Driving forces

Probability of occurrence explained:  66% by coastline morphology  18% by distance to port

Kotta et al. 2016

Density estimation

• 1. Spring-summer-autumn

2015 and 2016: 18 locations in 3 areas

• 2. Once in 2016: 33 locations

Diving locations

Underwater data collection protocol development:

Densities

Nurkse et al. unpubl.

Initial probability of round goby occurrence map

Next step: Modeling densities using different environmental factors Observations:

• Environmental

factors, like exposure, are more important than prey or habitat availability

• Fishermen data is

unreliable

Movement

• Acoustic signal receivers set up in a grid in the sea bottom
• Record signals from fish (each with timestamp and ID)

Small tags (V7) are operated into fish abdominal cavity

• Fish are positioned in every 10 minute based on signals

received by stationary receivers

Movement

Nurkse et al. unpubl.

Currently analyzing:

• How much do they move?
• What causes movement (e.g.

environmental conditions; suitable habitat availability)

• How large is their home

range? Is it habitat specific? First results:

• 1. Adults move MUCH

MORE than suggested in literature (5m2);

• 2. Lower prey availability

results is larger home range.

Predation: experimental

Laboratory experiments

(1 m2 of benthic prey consumed in 10 days)

Field experiments

(1 m2 of bivalves consumed in 30 days) 1m

Predation: results

 The round goby is a generalist feeder;  The round goby has no preference towards prey species;  Prey consumption rates substantially higher than the secondary production of benthic invertebrates;  Substantial impacts on communities, with 100% mussel removal in 30 days.

Nurkse et al. 2016

Stomach content analysis

• Three areas, spring-summer-autumn, 2015 and 2016
• NTOTAL=1728; data under analysis

Nurkse et al. unpubl.

Invertebrate prey consumption % out of total consumed (first draft)

Fisrt observations:

• 1. Consumes important

bivalves or amphipods if available;

• 2. Consumes even

barnacles in prey shortage.

Round goby as prey

Three areas, spring-summer-autumn, 2015 and 2016

Nurkse et al. unpubl.

PERCH

PIKEPERCH

PIKE

ROUND GOBY

First observations:

• 1. Important prey for all

dominant piscivorous fish;

• 2. Main prey for perch;
• 3. Appears in stomachs of

fish in areas where not yet

• bserved by divers;
• 4. Since goby population is

still expanding in all areas, current densities of piscivorous fish insufficient to control round goby.

ROUND GOBY ROUND GOBY

Management

Management

• Establishment of a coordinated pan-Baltic monitoring

programme and associated data storage and exchange, as well as recording landing statistics;

• Eradication is unrealistic;
• Population control that leads to minimising the risk of

transfer to yet uncolonised areas in the Baltic Sea and adjacent water bodies is feasible;

• Landing obligation;
• Management of ships’ ballast water and sediments, and

hull fouling of inland and sea-going vessels, and recreational boats.

Ojaveer et al. 2015

International cooperation (I)

International cooperation (II)

THANK YOUR FOR YOUR ATTENTION!