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Could Seals Prevent Cod Recovery in the Baltic Sea?

By Brian R. MacKenzie, Margit Eero and Henn Ojaveer

Abstract

Fish populations are increasingly affected by multiple human and natural impacts including exploitation, eutrophication, habitat alteration and climate change. As a result many collapsed populations may have to recover in ecosystems whose structure and functioning differ from those in which they were formerly productive and supported sustainable fisheries. Here we investigate how a cod (Gadus morhua) population in the Baltic Sea whose biomass was reduced due to a combination of high exploitation and deteriorating environmental conditions might recover and develop in the 21st century in an ecosystem that likely will change due to both the already started recovery of a cod predator, the grey seal Halichoerus grypus, and projected climate impacts. Simulation modelling, assuming increased seal predation, fishing levels consistent with management plan targets and stable salinity, shows that the cod population could reach high levels well above the long-term average. Scenarios with similar seal and fishing levels but with 15% lower salinity suggest that the Baltic will still be able to support a cod population which can sustain a fishery, but biomass and yields will be lower. At present knowledge of cod and seal interactions, seal predation was found to have much lower impact on cod recovery, compared to the effects of exploitation and salinity. These results suggest that dual management objectives (recovery of both seal and cod populations) are realistic but success in achieving these goals will also depend on how climate change affects cod recruitment

Topics: Research Article
Publisher: Public Library of Science
OAI identifier: oai:pubmedcentral.nih.gov:3090395
Provided by: PubMed Central

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Citations

  1. (2004). An overview of recent global experience with recovery plans for depleted marine resources and suggested guidelines for recovery planning.
  2. (2010). Approaches to end-to-end ecosystem models.
  3. (2007). Assessment of climate change for the Baltic Sea Basin-the
  4. (2008). Average salinity as an index for environmental forcing on cod recruitment in the Baltic Sea.
  5. (2005). Baltic cod recruitment–the impact of climate variability on key processes.
  6. (2009). Cascading top-down effects of changing ocean predator abundances.
  7. (1996). Causal correlation between recruitment and spawning stock size of central Baltic cod?
  8. (2009). Chair’s report of the workshop on the form of advice (WKFORM).
  9. (2010). Climate-change effects on the Baltic Sea ecosystem: A model study.
  10. (2000). Cod (Gadus morhua callarias L.) cannibalism in the Central Baltic: interannual variability and influence of recruitment abundance and distribution.
  11. (2007). Council regulation (EC) no. 1098/2007 establishing a multi-annual plan for the cod stocks in the Baltic Sea and the fisheries exploiting those stocks, amending Regulation (ECC) no. 2847/93 and repealing Regulation (EC)
  12. (2005). Covariation between grey seal (Halichoerus grypus) abundance and natural mortality of cod (Gadus morhua) in the southern Gulf of St.
  13. (2008). Directive 2008/56/EC of the European Parliament and the Council of 17
  14. (2010). Ecological forecasting under climate change: the case of Baltic cod.
  15. (2002). Ecological hypotheses for a historical reconstruction of upper trophic level biomass in the Baltic Sea and Skagerrak.
  16. (2009). Environmental effects on recruitment and implications for biological reference points of eastern Baltic cod (Gadus morhua).
  17. (2007). Estimation of grey seal (Halichoerus grypus) diet composition in the Baltic Sea.
  18. (2010). Experimental demonstration of population extinction due to a predator-driven Allee effect.
  19. (1975). Feeding habits and commercial damage of seals in the Baltic.
  20. (1994). Fish species interactions in the Baltic Sea.
  21. (2005). Functional and aggregative response of North Sea whiting.
  22. (2009). Green paper: Reform of the Common Fisheries Policy.
  23. (2006). Grey seal diet composition and prey consumption in the North Sea. Final report to Department of Environment, Food and Rural Affairs on project MF0319.
  24. (1999). Ha ¨rko ¨nen TJ
  25. (2007). HELCOM Baltic Sea Action Plan. 102 pp.Helsinki: Helsinki Commission for the Protection of the Baltic Marine Environment (http://www. helcom.fi). Accessed
  26. (2009). Historical baselines for large marine animals.
  27. (2008). Human impact on ancient marine ecosystems: a global perspective. Berkeley and Los Angeles.
  28. (2007). Humaninduced trophic cascades and ecological regime shifts in the Baltic Sea. Ecosys doi:
  29. (2010). ICES Advice-Baltic Sea ecoregion, cod in Subdivisions 25-32.
  30. (2009). Identifying eastern Baltic cod nursery grounds using hydrodynamic modelling: knowledge for the design of Marine Protected Areas.
  31. (2007). Impact of 21st century climate change on the Baltic Sea fish community and fisheries.
  32. (2009). Impending collapse of bluefin tuna in the northeast Atlantic and Mediterranean.
  33. (2004). Ko ¨ster FW
  34. (2010). Making the ecosystem approach operational-Can regime shifts in ecological-and governance systems facilitate the transition?
  35. (1989). Man’s impact on the ecosystem of the Baltic Sea: energy flows today and at the turn of the century.
  36. (2007). Managing Baltic Sea fisheries under contrasting production and predation regimesecosystem model analyses.
  37. (2000). Mo ¨llmann C
  38. (2009). Modelling multi-species interactions in the Barents Sea ecosystem with special emphasis on minke whales and their interactions with cod, herring and capelin.
  39. (2010). Multi-decadal responses of a cod (Gadus morhua) population to human-induced trophic changes, exploitation and climate variability. Ecol Appl (accepted).
  40. (2007). Multidecadal scale variability in the eastern Baltic cod fishery 1550-1860: evidence and causes.
  41. (2008). Predicted extirpation of the dominant demersal fish in a large marine ecosystem: Atlantic cod (Gadus morhua)i nt h e southern
  42. (2010). Quality assessment of state-of-the-art coupled physical-biogeochemical models in hind cast simulations 1970-2005. Report 101/2010:38 pp.Norrko ¨ping,
  43. (1992). Quantitative Fisheries Stock Assessment: Choice, Dynamics and Uncertainty.
  44. (2010). Rebuilding depleted fish stocks: the good, the bad, and, mostly, the ugly.
  45. (2009). Rebuilding global fisheries.
  46. (2008). Reconstructing historical stock development of the eastern Baltic cod (Gadus morhua) before the beginning of intensive exploitation.
  47. (2010). Report of the Baltic fisheries assessment working group (WGBFAS).
  48. (2008). Report of the Baltic Fisheries Assessment Working Group.
  49. (2009). Report of the ICES Baltic fisheries assessment working group.
  50. (2010). Report of the ICES/HELCOM working group on integrated assessments of the Baltic Sea (WGIAB).
  51. (2008). Report of the working group on marine mammal ecology (WGMME).
  52. (2007). Report of the Working Group on Multispecies Assessment Methods.
  53. (2010). Report of the workshop on implementing the ICES Fmsy framework.
  54. (2007). Report of the workshop on limit and target reference points
  55. (2006). Report of the Workshop on the Decline and Recovery of Cod Stocks throughout the North Atlantic, including trophodynamic effects.
  56. (2007). Report of the workshop on the integration of environmental information into fisheries management strategies and advice (WKEFA).
  57. (2009). Role of predation by harp seals Pagophilus groenlandicus in the collapse and nonrecovery of northern
  58. (2009). Seals, cod and forage fish: A comparative exploration of variations in the theme of stock collapse and ecosystem change in four Northwest Atlantic ecosystems.
  59. (2008). State and evolution of the Baltic Sea,
  60. (2010). Stock-based vs. fleet-based evaluation of the multi-annual management plan for the cod stocks in the Baltic Sea.
  61. (2008). Temming A
  62. (1959). The components of predation as revealed by a study of small mammal predation of the European pine sawfly.
  63. (2010). The functional response of a generalist predator. PLoS One 5:
  64. (2009). Trophic cascades promote threshold-like shifts in pelagic marine ecosystems.
  65. (2010). Understanding the diet composition of marine mammals: grey seals (Halichoerus grypus) in the Baltic Sea.
  66. (2006). Wasp-waist populations and marine ecosystem dynamics: Navigating the "predator pit" topographies.
  67. (2010). What can ecology contribute to ecosystem-based management?
  68. (2008). Why fishing magnifies fluctuations in fish abundance.