Diet of perch in the Baltic Sea – could the European perch (Perca fluviatilis) be used to combat round goby (Neogobius melanostomus)?
(2021) BION03 20202Degree Projects in Biology
- Abstract
- The round goby, Neogobius melanostomus, is a recent intruder of the Baltic Sea, which presumably arrived via the ballast water of travelling ships. The establishment of self-sustaining populations in this ecosystem has had both negative and positive effects on the native species composition within the area. Competition over resources and shelter, spawning interference, and the predation on native species, for instance, are negative effects N. melanostomus has on native species. This results in a displacement of affected native species to suboptimal environments and, thus, to a reduction of their success of reproduction and abundance. However, N. melanostomus represents a new prey source, which is potentially more available and easily... (More)
- The round goby, Neogobius melanostomus, is a recent intruder of the Baltic Sea, which presumably arrived via the ballast water of travelling ships. The establishment of self-sustaining populations in this ecosystem has had both negative and positive effects on the native species composition within the area. Competition over resources and shelter, spawning interference, and the predation on native species, for instance, are negative effects N. melanostomus has on native species. This results in a displacement of affected native species to suboptimal environments and, thus, to a reduction of their success of reproduction and abundance. However, N. melanostomus represents a new prey source, which is potentially more available and easily accessible for native predators. This might benefit the condition of local piscivorous predators with their survival success and, consequently, serve as an opportunity to combat N. melanostomus in a natural way. Hence, the focus of this project was to investigate the importance of N. melanostomus as a prey species to European perch, Perca fluviatilis, a key species and common predator of this environment, in the archipelago of Karlskrona. For this, the diet of 783 P. fluviatilis individuals from that area were examined through stomach content analysis. Based on the analyses, the Index of Relative Importance (IRI) and its % (IRI%) were calculated for the five most occurring prey categories (N. melanostomus, Gasterosteus aculeatus, Osteichthyes, Crustacea, and Mollusca + Other) to identify their importance as a prey. The analyse showed that N. melanostomus is overall the most consumed and seasonally the most important prey species for P. fluviatilis, predominantly during spring and autumn. To investigate the assumed positive effects of N. melanostomus as prey on the body condition of P. fluviatilis, the Fulton’s Condition Factor (FCF) of individuals that had consumed N. melanostomus was calculated and compared to the FCF of individuals that consumed only other prey. The comparison between these groups showed no significant difference, indicating that there is no direct benefit for P. fluviatilis to consume N. melanostomus regarding their condition. The results obtained showed that N. melanostomus became an important prey species to local P. fluviatilis since its arrival to the archipelago of Karlskrona, but does not exceed other native prey species regarding their effect on the condition of P. fluviatilis when preyed on. Supporting native predators like P. fluviatilis could therefore be a legit method to combat the dominance of N. melanostomus in certain areas, as a greater appearance of predators could result in higher predation pressure and consequently in a lower abundance of this prey species. (Less)
- Popular Abstract
- Diet of perch in the Baltic Sea – could the European perch (Perca fluviatilis) be used to combat round goby (Neogobius melanostomus)?
The round goby is a fish species that, since its invasion in the Baltic Sea in last 30 years, has become a new prey source for native predators, like the European perch. Thus, by analysing the diet of local perch, the importance of round goby as its prey could be calculated and, consequently, an assumption been made if perch is able to combat the round goby in a natural way.
The European perch is a common predator in the Baltic Sea, which feeds on a broad spectrum of prey species. Thus, the arrival of round goby in this ecosystem represented a new prey source for them, which is become more abundant and... (More) - Diet of perch in the Baltic Sea – could the European perch (Perca fluviatilis) be used to combat round goby (Neogobius melanostomus)?
The round goby is a fish species that, since its invasion in the Baltic Sea in last 30 years, has become a new prey source for native predators, like the European perch. Thus, by analysing the diet of local perch, the importance of round goby as its prey could be calculated and, consequently, an assumption been made if perch is able to combat the round goby in a natural way.
The European perch is a common predator in the Baltic Sea, which feeds on a broad spectrum of prey species. Thus, the arrival of round goby in this ecosystem represented a new prey source for them, which is become more abundant and accessible over time. To understand how much the diet of perch shifted towards round goby since, several perch stomachs were monthly analysed over a timespan of three years (June 2018 until May 2021), and their content identified to the lowest taxonomic level.
The following calculation of the Index of Relative Importance (IRI) gave insight on how important round goby (and all other prey groups) were to perch on a monthly, seasonally, and annually basis, and how their importance changed over time. The higher the IRI value was, the more important a species was in the diet of perch. Calculating the Fulton’s Condition Factor (FCF) allowed a comparison between the condition of perch individuals that showed round goby in their diet and individuals that did not. The aim of this was to see if the consumption of round goby affects the condition of perch in any way.
Outcome and conclusion of the analysis.
The results showed that round goby was consumed the most frequently and the most in biomass overall. However, the IRI indicated that there is a seasonal change in importance of round goby during a year. Whilst there was a high importance of round goby as prey species for perch in Spring and Autumn, their IRI dropped in Summer and Winter. The FCF did not show any difference between perch individuals that consumed round goby and individuals that did not. Therefore, there was no correlation between the presence/absence of round goby in the diet of perch and its condition.
Based on the results, I can state that perch, if abundant enough, could successfully reduce the number of round goby in an area, as they were consumed in high number and biomass, if available. Thus, elevated predation through the support of the perch population by fisheries or marine protected areas could result in a natural measure against further spread of round goby and, finally, control its population size.
Master’s Degree Project in Biology/Aquatic Ecology/60 credits 2021
Department of Biology, Lund University
Advisor: Anders Persson
Department of Biology/Aquatic Ecology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9069187
- author
- Arnet, Guillaume
- supervisor
- organization
- course
- BION03 20202
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9069187
- date added to LUP
- 2021-12-16 14:03:07
- date last changed
- 2021-12-16 14:03:07
@misc{9069187,
abstract = {{The round goby, Neogobius melanostomus, is a recent intruder of the Baltic Sea, which presumably arrived via the ballast water of travelling ships. The establishment of self-sustaining populations in this ecosystem has had both negative and positive effects on the native species composition within the area. Competition over resources and shelter, spawning interference, and the predation on native species, for instance, are negative effects N. melanostomus has on native species. This results in a displacement of affected native species to suboptimal environments and, thus, to a reduction of their success of reproduction and abundance. However, N. melanostomus represents a new prey source, which is potentially more available and easily accessible for native predators. This might benefit the condition of local piscivorous predators with their survival success and, consequently, serve as an opportunity to combat N. melanostomus in a natural way. Hence, the focus of this project was to investigate the importance of N. melanostomus as a prey species to European perch, Perca fluviatilis, a key species and common predator of this environment, in the archipelago of Karlskrona. For this, the diet of 783 P. fluviatilis individuals from that area were examined through stomach content analysis. Based on the analyses, the Index of Relative Importance (IRI) and its % (IRI%) were calculated for the five most occurring prey categories (N. melanostomus, Gasterosteus aculeatus, Osteichthyes, Crustacea, and Mollusca + Other) to identify their importance as a prey. The analyse showed that N. melanostomus is overall the most consumed and seasonally the most important prey species for P. fluviatilis, predominantly during spring and autumn. To investigate the assumed positive effects of N. melanostomus as prey on the body condition of P. fluviatilis, the Fulton’s Condition Factor (FCF) of individuals that had consumed N. melanostomus was calculated and compared to the FCF of individuals that consumed only other prey. The comparison between these groups showed no significant difference, indicating that there is no direct benefit for P. fluviatilis to consume N. melanostomus regarding their condition. The results obtained showed that N. melanostomus became an important prey species to local P. fluviatilis since its arrival to the archipelago of Karlskrona, but does not exceed other native prey species regarding their effect on the condition of P. fluviatilis when preyed on. Supporting native predators like P. fluviatilis could therefore be a legit method to combat the dominance of N. melanostomus in certain areas, as a greater appearance of predators could result in higher predation pressure and consequently in a lower abundance of this prey species.}},
author = {{Arnet, Guillaume}},
language = {{eng}},
note = {{Student Paper}},
title = {{Diet of perch in the Baltic Sea – could the European perch (Perca fluviatilis) be used to combat round goby (Neogobius melanostomus)?}},
year = {{2021}},
}