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Marine Ecology Progress Series

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MEPS 510:201-213 (2014)  -  DOI:

Digestion times and predation potentials of Pelagia noctiluca eating fish larvae and copepods in the NW Mediterranean Sea

Jennifer E. Purcell1,*, Uxue Tilves2, Verónica L. Fuentes2, Giacomo Milisenda3, Alejandro Olariaga2, Ana Sabatés

1Western Washington University, Shannon Point Marine Center, 1900 Shannon Point Rd, Anacortes, WA 98221, USA
2Institut de Ciències del Mar, CSIC, P. Marítim 37–49, 08003 Barcelona, Spain
3Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, 73100 Lecce, Italy
*Corresponding author:

ABSTRACT: Predation is the principal direct cause of mortality of fish eggs and larvae (ichthyoplankton). Pelagic cnidarians and ctenophores are consumers of ichthyoplankton and zooplankton foods of fish, yet few estimates exist of predation effects in situ. Microscopic analyses of the gastric ‘gut’ contents of gelatinous predators reveal the types and amounts of prey eaten and can be used with digestion time (DT) to estimate feeding rates (prey consumed predator-1 time-1). We measured the DT and recognition time (RT) of prey for Pelagia noctiluca, an abundant jellyfish with increasing blooms in the Mediterranean Sea. DT of fish larvae averaged 2.5 to 3.0 h for P. noctiluca (4-110 mm diameter) and was significantly related to jellyfish and larval sizes. In contrast, DT of fish eggs ranged from 1.2 to 44.8 h for jellyfish ≤22 mm diameter (‘ephyrae’), but DT was not significantly related to ephyra or egg diameter. Approximately half of the eggs ingested were not digested. DT of copepods averaged 4 h. We also measured DT and RT of salps, euphausiids, and miscellaneous zooplankton. Temperature (20-25°C) generally did not significantly affect DT of any prey. Estimated potential predation effects of ephyrae on fish larvae in the Catalan Sea in 1995 showed great variability among 9 stations (0-3.7% consumed h-1). We discuss how sampling methods contributed to variation in predation estimates and offer recommendations to improve accuracy. Our results enable estimation of predation on ichthyoplankton and competition for zooplankton prey, which can have extremely important effects on fish populations globally.

KEY WORDS: Anchovy · Jellyfish · Salp · Fish eggs · Ichthyoplankton · Zooplankton · Competition

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Cite this article as: Purcell JE, Tilves U, Fuentes VL, Milisenda G, Olariaga A, Sabatés A (2014) Digestion times and predation potentials of Pelagia noctiluca eating fish larvae and copepods in the NW Mediterranean Sea. Mar Ecol Prog Ser 510:201-213.

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