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Can the native shore crabs (Carcinus maenas) become a barrier to the invasion of the round goby (Neogobius melanostomus) in Öresund, southern Baltic Sea?

Papagiannopoulos, Nikolaos (2018) BION03 20172
Degree Projects in Biology
Abstract
The round goby (Neogobius melanostomus) is a non-indigenous species to the Baltic Sea that has drawn the attention of many researchers in the last decade due to its rapid spreading and its impact on the local fauna. With recent concerns about the dispersal of the round goby towards the North Sea, the aim of this study was to determine if the native shore crab could compete with the invaders and prevent their advance. The ash-free weight and the handling time of four blue mussel size classes (7mm, 12mm, 17mm, 22mm) was measured for both predators in order to calculate their feeding efficiency on each size class. Selectivity experiments were conducted, in aquariums, to determine which size class was preferred by each predator. The results... (More)
The round goby (Neogobius melanostomus) is a non-indigenous species to the Baltic Sea that has drawn the attention of many researchers in the last decade due to its rapid spreading and its impact on the local fauna. With recent concerns about the dispersal of the round goby towards the North Sea, the aim of this study was to determine if the native shore crab could compete with the invaders and prevent their advance. The ash-free weight and the handling time of four blue mussel size classes (7mm, 12mm, 17mm, 22mm) was measured for both predators in order to calculate their feeding efficiency on each size class. Selectivity experiments were conducted, in aquariums, to determine which size class was preferred by each predator. The results were in compliance with the optimal foraging theory; shore crabs consumed significantly more 17 and 22 mm mussels, while round gobies preferred significantly more 7 and 12 mm mussels. Competition experiments for a food source of ten mussels, with three treatments (goby vs. crab, goby vs. another goby, control), were also conducted. Round gobies were more dominant, consuming significantly more mussels than the crabs, indicating that the shore crab may not outcompete the invader in a limited prey situation. (Less)
Popular Abstract
Can shore crabs prevent a round goby invasion in the North Sea?

The round goby (Neogobius melanostomus) is a non-indigenous species to the Baltic Sea that has drawn the attention of many researchers in the last decade due to its rapid spreading and its impact on the local fauna. With recent concerns about the dispersal of the round goby towards the North Sea, the aim of this study was to determine if the native shore crab could compete with the invaders and prevent their advance.

Several experiments were conducted in order to test the hypothesis. The average energy content for four blue mussel size classes (7mm, 12mm, 17mm, 22mm) was measured. The average handling time, for those size classes, for both predator species (shore crabs &... (More)
Can shore crabs prevent a round goby invasion in the North Sea?

The round goby (Neogobius melanostomus) is a non-indigenous species to the Baltic Sea that has drawn the attention of many researchers in the last decade due to its rapid spreading and its impact on the local fauna. With recent concerns about the dispersal of the round goby towards the North Sea, the aim of this study was to determine if the native shore crab could compete with the invaders and prevent their advance.

Several experiments were conducted in order to test the hypothesis. The average energy content for four blue mussel size classes (7mm, 12mm, 17mm, 22mm) was measured. The average handling time, for those size classes, for both predator species (shore crabs & round gobies) was also measured and was used to determine the prey value; how profitable it would be to consume a certain size mussel. A 12 hour selectivity experiment was conducted to test if the predators preferred their optimal prey size, when offered all sizes in equal numbers. Finally, a competition experiment with a limited food source (blue mussels) was performed with three treatments: a) goby-crab, b) goby-goby, c) control.

The round goby proved to be a more efficient predator on average and dominated the limited food source in the competition experiments. Round gobies were significantly more efficient at consuming smaller mussels (<20mm) and equally efficient at consuming larger mussels (22mm) when compared to the shore crabs (Fig. 1). The results from the selectivity experiments were in agreement with each predator’s optimal prey size as estimated by the prey values. Shore crabs preferred larger mussels (>15mm), while the round gobies showed a clear preference for smaller mussels (<15mm). The round gobies also consumed significantly more blue mussels than the crabs when a limited food source was offered for a short period of time (60 minutes) (Fig. 2).
With the current dispersal rate of 30 km year-1, it is estimated that the round goby could reach the North Sea by 2019; meaning that preventative actions should be taken as soon as possible. Our findings contribute towards understanding the interactions between round gobies and marine species, which is vital when deciding what measures should be introduced.
Conclusions
Shore crabs may not prevent further round goby invasion towards the North Sea directly. But in combination with other factors, such as higher salinity and keystone predators including round gobies in their diet, shore crabs may contribute towards a more invasion-resilient ecosystem.

Master’s Degree Project in Biology 60 credits 2018
Department of Biology, Lund University

Advisor: Anders Persson
Department of Aquatic Ecology, Ecology Building, Lund University, SE-223 62 Lund, Sweden (Less)
Please use this url to cite or link to this publication:
author
Papagiannopoulos, Nikolaos
supervisor
organization
course
BION03 20172
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8950707
date added to LUP
2018-06-18 11:53:32
date last changed
2018-06-18 11:53:32
@misc{8950707,
  abstract     = {The round goby (Neogobius melanostomus) is a non-indigenous species to the Baltic Sea that has drawn the attention of many researchers in the last decade due to its rapid spreading and its impact on the local fauna. With recent concerns about the dispersal of the round goby towards the North Sea, the aim of this study was to determine if the native shore crab could compete with the invaders and prevent their advance. The ash-free weight and the handling time of four blue mussel size classes (7mm, 12mm, 17mm, 22mm) was measured for both predators in order to calculate their feeding efficiency on each size class. Selectivity experiments were conducted, in aquariums, to determine which size class was preferred by each predator. The results were in compliance with the optimal foraging theory; shore crabs consumed significantly more 17 and 22 mm mussels, while round gobies preferred significantly more 7 and 12 mm mussels. Competition experiments for a food source of ten mussels, with three treatments (goby vs. crab, goby vs. another goby, control), were also conducted. Round gobies were more dominant, consuming significantly more mussels than the crabs, indicating that the shore crab may not outcompete the invader in a limited prey situation.},
  author       = {Papagiannopoulos, Nikolaos},
  language     = {eng},
  note         = {Student Paper},
  title        = {Can the native shore crabs (Carcinus maenas) become a barrier to the invasion of the round goby (Neogobius melanostomus) in Öresund, southern Baltic Sea?},
  year         = {2018},
}