Predator and prey: the role of the round goby Neogobius melanostomus in the western Baltic

Figures & data

Figure 1. Sampling stations of cormorant pellets, round gobies and piscivorous fish in the Pomeranian Bay. Numbers indicate the case study number.

Figure 2. Frequency of occurrence of different prey taxa for different length classes, Case Study 2. Numbers in brackets indicate the number of non-empty analysed round goby stomachs.

Table I. Detailed information about investigated round gobies (RG) and respective stomach contents from Case Study 1.

Location	Littoral zone								Oderbank Plateau
	August		October			November			May		November
Depth (m)	∼1.5	∼2.5	∼1.5	∼3.5	∼6	∼1.5	∼3.5	∼6	∼5	∼10	∼5	∼10
RG mean total length (mm)	43.4 (±22.9)	34.6 (±11.1)	39.0 (±13.0)	27.5 (±4.1)	24.3 (±5.4)	37.4 (±6.7)	37.0 (±7.0)	29.3 (±13.2)	128.77 (±32.99)	123.95 (±32.36)	148.73 (±24.49)	136.92 (±25.27)
Total number of RG	156	89	89	10	25	266	3	4	503	19	15	13
Investigated stomachs	19	26	34	9	11	31	3	4	65	19	15	13
Empty stomachs	7	4	3	1	3	8	0	0	13	4	4	0
Prey presence %
Polychaeta	26	19	15	0	9	35	0	25	21	7	0	15
Nereididae	11	4	3	0	0	32	0	25	13	0	0	15
Arthropoda	95	62	88	100	100	84	100	75	44	47	64	38
Amphipoda	26	12	3	0	0	19	0	0	0	0	0	0
Corophium sp.	0	4	0	0	0	6	0	0	0	0	0	0
Gammaridae	5	0	3	0	0	10	0	0	0	0	0	0
Bosmina sp.	0	0	9	0	0	45	0	0	0	0	0	0
Copepoda	21	4	59	33	0	77	67	75	0	0	0	0
Balanidae	0	0	0	0	0	0	0	0	23	20	55	31
Crangon crangon	0	0	0	0	0	0	0	0	0	0	9	15
Palaemon sp.									0	0	0	15
Insecta	21	4	15	0	0	6	33	0	0	0	0	0
Chironomidae	16	0	15	0	0	6	33	0	0	0	0	0
Isopoda	32	8	21	0	0	0	0	0	0	0	0	0
Cyathura carinata	0	0	3	0	0	0	0	0	0	0	0	0
Idotea chelipes	32	0	18	0	0	0	0	0	0	0	0	0
Ostracoda	11	12	44	100	100	29	67	25	0	0	0	0
Mollusca	37	69	21	56	82	0	33	25	98	93	100	100
Bivalvia	26	46	9	0	55	0	33	25	85	80	45	62
Cerastoderma sp.	0	4	0	0	45	0	0	0	27	27	0	31
Limecola balthica	5	0	3	0	9	0	0	0	4	7	0	0
Mya arenaria	11	4	3	0	9	0	0	0	27	0	27	15
Mytilus sp.	11	4	3	0	0	0	0	0	67	73	36	31
Gastropoda	11	35	15	56	64	0	0	0	92	67	82	92
Hydrobiid gastropods	11	31	6	0	0	0	0	0	92	67	82	92
Littorina sp.	0	0	6	44	64	0	0	0
Priapulidae	0	0	0	0	0	0	0	0	12	7	0	0
Halicryptus spinulosus	0	0	0	0	0	0	0	0	12	7	0	0

Prey presence is the percentage of the taxa (per line and column) occurring in non-empty stomachs based on presence/absence analysis.

Figure 3. Diet composition of Perca fluviatilis in black (n = 104) and Sander lucioperca in grey (n = 57) expressed as Index of Relative Importance.

Table II. Information about analysed piscivorous fish species (Case Study 3).

Species	Geographical area	Number	Total number	Non-empty stomachs
Scophthalmus maximus (Linnaeus, 1758)	Pomeranian Bay	8	8	8
Perca fluviatilis Linnaeus, 1758	Pomeranian Bay	91	186	104
	Greifswald Bay	19
	Saaler Bodden & Darss-Zingst Lagoon	44
	Odra estuary	32
Sander lucioperca (Linnaeus, 1758)	Greifswald Bay	28	89	57
	Pomeranian Bay	29
	Odra estuary	32
Gymnocephalus cernuus (Linnaeus, 1758)	Greifswald Bay	3	38	12
	Pomeranian Bay	35

Figure 4. Number of individuals and estimated biomass of round goby as percentage of the total number and biomass of the cormorant pellets for 2010–2015 in Peenemünde (Case Study 4) (Stark 2011; Myts 2012; Winkler et al. 2014). Number of analysed cormorant pellets: 2010 = 263, 2011 = 221, 2012 = 184, 2013 = 164, 2014 = 103, 2015 = 113.

Figure 5. Abundance of fish species in cormorant pellets from 2010 (first appearance of round goby in prey) compared to 2015 (Case Study 4). Data for 2010 modified from Stark (2011). Number of analysed cormorant pellets: 2010 = 263, 2015 = 113.

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