JELLYFISH BLOOMS Jellyfish in ecosystems, online databases, and ecosystem models

There are indications that pelagic cnidarians and ctenophores (‘jellyfish’) have increased in abundance throughout the world, or that outbreaks are more frequent, although much uncertainty surrounds the issue, due to the scarcity of reliable baseline data. Numerous hypotheses have been proposed for the individual increases or outbreaks that are better documented, but direct experimental or manipulative studies at the ecosystem scale cannot be used for testing them. Thus, ecological modeling provides the best alternative to understand the role of jellyfish in large fisheries-based ecosystems; indeed, it is an approach consistent with new ecosystembased fisheries management practices. Here, we provide an overview of online databases available to ecosystem modelers and discuss general aspects and shortcomings of the coverage of jellyfish in these databases. We then provide a summary of how jellyfish have been treated and parameterized by existing ecosystem models (specifically focusing on ‘Ecopath with Ecosim’ as a standard modeling toolset). Despite overall weaknesses in the parameterization of jellyfish in these models, interesting patterns emerge that suggest some systems, especially smaller and more structured ones, may be particularly vulnerable to long-term jellyfish biomass increase. Since jellyfish also feed on the eggs and larvae of commercially important food fish, outbreaks of jellyfish may ultimately imply a reduction in the fish biomass available to fisheries. On the other hand, jellyfish, which have been traditionally fished for human consumption in East and Southeast Asia, are now seen as a potential resource in other parts of the world, where pilot fisheries have emerged. It is also argued here that reduced predation on the benthic and pelagic stages of jellyfish, both a result of fishing, may be a strong contributing factor as well. For marine biologists specializing on jellyfish, this means that their research might become more applied. This Guest editors: K. A. Pitt & J. E. Purcell Jellyfish Blooms: Causes, Consequences, and Recent Advances D. Pauly (&) M. L. Deng Palomares Sea Around Us Project, Fisheries Centre, University of British Columbia, 2202 Main Mall, Vancouver, BC, Canada V6T 1Z4 e-mail: [email protected] M. L. Deng Palomares e-mail: [email protected] W. Graham Dauphin Island Sea Lab and University of South Alabama, 101 Bienville Blvd., Dauphin Island, AL 36528, USA e-mail: [email protected] S. Libralato Istituto Nazionale di Oceanografia e di Geofisica Sperimentale—OGS, Borgo Grotta Gigante 42/c, Sgonico, Trieste 34010, Italy e-mail: [email protected] L. Morissette Institut des Sciences de la Mer de Rimouski, 310, Allée des Ursulines C.P. 3300, Rimouski, QC, Canada G5L 3A1 123 Hydrobiologia (2009) 616:67–85 DOI 10.1007/s10750-008-9583-x