Seals and fish-eating birds have increased in the Baltic Sea and there is concern that they compete with fisheries. Using data from around year 2010, we compare consumption of different fish species by seals and birds to the catch in the commercial and recreational fishery. When applicable this is done at the geographical resolution of ICES subdivisions. Predation by birds and mammals likely has limited impact on the populations of the commercially most important species (herring, sprat, and cod). In the central and southern Baltic, seals and birds consume about as much flatfish as is caught by the fishery and competition is possible. Birds and seals consume 2-3 times as much coastal fish as is caught in the fishery. Many of these species are important to the fishery (e.g. perch and whitefish) and competition between wildlife and the fishery is likely, at least locally. Estimated wildlife consumption of pike, sea trout and pikeperch varies among ICES subdivisions and the degree of competition for these species may differ among areas. Competition between wildlife and fisheries need to be addressed in basic ecosystem research, management and conservation. This requires improved quantitative data on wildlife diets, abundances and fish production.

21In wetland ecosystems, birds and fish are important dispersal vectors for plants and 22invertebrates, but the consequences of their interactions as vectors are unknown. Darwin 23 suggested that piscivorous birds carry out secondary dispersal of seeds and invertebrates via 24 predation on fish. We tested this hypothesis in the great cormorant (Phalacrocorax carbo L.). 25Cormorants regurgitate pellets daily, which we collected at seven European locations and 26 examined for intact propagules. One-third of pellets contained at least one intact plant seed, 27 with seeds from 16 families covering a broad range of freshwater, marine and terrestrial 28 habitats. Of 21 plant species, only two have an endozoochory dispersal syndrome, compared 29 to five for water and eight for unassisted dispersal syndromes. One-fifth of the pellets 30 contained at least one intact propagule of aquatic invertebrates from seven taxa. Secondary 31 dispersal by piscivorous birds may be vital to maintain connectivity in meta-populations and 32 between river catchments, and in the movement of plants and invertebrates in response to 33 climate change. Secondary dispersal pathways associated with complex food webs must be 34 studied in detail if we are to understand species movements in a changing world. 35 36

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This paper provides the results from the first meta-analysis to examine the impact of cormorant (Phalacrocoracidae) predation on fish. It is based on a systematic search of literature, covering studies using significance-based hypotheses tests on the relation between fish parameters and cormorant abundance. The results show that extensive research on cormorant diet exists, but few studies use statistical hypotheses testing to examine the effect on fish populations. In total, 603 publications were identified from titles and abstracts, to include the interaction between cormorants and fish.From these, 27 articles tested fish population parameters against cormorant predation, whereof 22 could be included in analyses. The effect size was defined negative in cases when cormorant numbers or presence reduced fish numbers or biomasses, or when individual fish sizes decreased, and vice versa for a positive effect. In a hierarchical dependence model, the combined effect of cormorant predation on fish was negative, but the overall effect was not significant at the 95% confidence level (−0.169, 95% C.L. −0.505 to 0.167, p = .256, df = 5.26). A covariate analysis revealed a difference in predatory effects between fish prey taxa (p = .006, df = 5.73), but no difference in effect sizes between study type, foraging habitat, or response variable measured. The meta-analysis reveals a complex interaction between cormorants and fish, but adds to the consensus on the importance of considering cormorant predatory effects in research, conservation actions, ecosystem-based management, and environmental monitoring.

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