Caption: Round gobies and many other species of fish observed using baited remote underwater video (BRUV).
Photo: Leon Green

Predators and biodiversity as biocontrol of the invasive round goby

Research project
Active research
Project size
3 600 000
Project period
2021 - 2023
Project owner
Department of Biological and Environmental Sciencepartment of Biological and Environmental Sciences

Short description

The non-native invasive fish called round goby (Neogobius melanostomus, sv: svartmunand smörbult) is currently expanding on the Swedish west-coast. The species is already very abundant in the Baltic Sea, but the spread of the species is occurring differently in these two differtent regions. These regional differences calls for local understanding of the ecological processes that limit or allow the spread of the round goby, as well as the effects on the local ecosystem. This project aims to further this understanding by studying two important ecological processes: [1] top-down control from predation; and [2] competition for nische space due to high biodiversity. We use the round goby and the closely associated benthic fish community as models to increase the regional and global knowledge of invasion dynamics in marine environments.

A non-native invasive fish is spreading on the Swedish west-coast

Populations of the invasive round goby (sv: svartmunnad smörbult, Neogobius melanostomus) are expanding on the Swedish west-coast. Unfortunately, there is not a single success story of eradictation of invasive species in the marine environment, globally. This is true for fish as well as algae. This is of course a huge problem, since invasive species alter habitats, compete with native species and cost millions of dollars to control. Sweden has a long coast line, and the regions along the west-coast and east-coast facing the Baltic Sea are very different. Invasive species in these regions face different environments, and might spread due to different constraints. We are in need of regional knowledge of the ecological processes and patterns that non-native species are involved in, if we are to manage them successfully.

The goal of our project is to give Swedish authourities and the global research community knowledge on how two important ecological processes contribute to the containment of invasive species in the marine environment. These two processes are [1] top down-control through predation; and [2] nische space limitation as a consequence of high biodiversity. If these two precoseess do limit the spread of invasice species, healthy populations of predatory fish, as well as thriving, biodiverse fish communities can function as bio-control of non-native species that risk becoming invasive. Conserving the predatory fish and high biodiversity areas would in this case offer added benefit to the resilience of our aquatic environments. These studies are therefore beneficial for understanding what conservation measures and strategies are the most effective and sustainable.

Do predatory fish on the west-coast eat round gobies? - Top down control through predation
Many species of gobies are popular prey for cod, and in the Baltic Sea, it is well known that cod eat the abundant round gobies. But what about the population in the Gothenburg archipelago? Cod are frequent visitors in the Gothenburg habour where round gobies are common. However, nothing is known about the interactions between these two species, and whether or not west-coast cod has learnt to eat round gobies. Other predatory fish, such as eel, might also be important predators that can keep the invasive round gobies in check.

Our goal is to determine how common round goby is as a prey for cod in the Gothenburg archipelago by sampling residual goby DNA in the feces of the cod! By looking for evidence of predation in a non-invasive way, we can save the lives of the cod that have learnt to prey on gobies, and let them continue their presumptive control of the goby population. This is especially important since cod are visual predators that hunt in groups as juveniles, when they can also learn from eachother! Similar proicesses have been observed among groupers feeding on invasive lionfish in the Carribbean.

Photo: Leon Green

The round goby (Neogobius melanostomus, sv: Svartmunnad smörbult) is the first invasive fish found in the Swedish marine environment. The species grows to about 25 cm, is bottom-associated and feeds on a wide range of small invertebrates, small fishes, and fish eggs and larvae. Life-span is a maximum of six years, and sexual maturity is commonly reached after two. The spawning takes place in the males nest, commonly under a rock. After spawning the male stays and protects the eggs until they hatch. The round goby is abundant in the Baltic Sea, but at the Swedish west-coast, the species is, so far, locally restricted to the Gothenburg harbour, parts of the Gothenburg archipelago and the northern coast towards Marstrand. 

Can other fish species limit the spread of the round gobies? - Nische limitation as a consequence of high biodiversity
Fish interact with eachother all the time! And the more species of fish there are, the more potential conflicts appear, as access to feeding and nesting sites become limited. With increased biodiversity, nisch space for novel species become limited. The ecological theory behind this phenomenon is old, but it is severely understudied in marine environments, and especially in fish communities.

We want to understand if this theory also apply to the round gobies. Do areas with fewer fish species have more round gobies? And how do these patterns change with time and other abiotic factors? We are studying this by monitoring the fish community and the precense of round gobies across many sites along the Swedish west-coast. Monitoring is done through under water video recording and identification analysis. An online citicen science identification project is on it’s way (in the mean time, check out the predecessor The Koster Seafloor Observatory). This project is also aligning with the school project “Alien species” (sv: Främmande arter) where students in primary and junior high school learn about invasive species and the issues these cause in the environment.

The project aligns research within the Gothenburg Global Biodiversity Centre (GGBC), Centre for Marine Evolutionary Biology (CeMEB) and the Centre for Sea and Society.

The project is financed by the Swedish Environmental Protection Agency together with the research council Formas. The Swedish Agency for Marine and Water Management as well as the Swedish Transport Administration are also contributing stakeholders in the national focus on combating invasive species (link in Swedish).

Here you can read more about the work against invasive species undertaken by the Swedish Environmental Protection Agency (in Swedish).

Here you can read more about the work against invasive species undertaken by the Swedish Agency for Marine and Water Management (in Swedish).

You can report sightings of round gobies on this site (in Swedish) or on this (also in Swedish).