Download understanding the trophic ecology of small pelagic fish

To eat, to be eaten, and a lot of questions: understanding the
trophic ecology of small pelagic fish
Susana Garrido
Portuguese Sea and Atmosphere Institute, Portugal. E-mail: [email protected]
Small pelagic fish are typically abundant in the highly productive regions of the world’s
oceans where they are thought to control the variability of these ecosystems by exerting
top-down control on their plankton prey and bottom-up control on their predators.
Whereas some recent studies suggest that at least some of these ecosystems are more
stable and diverse than initially thought, the importance of small pelagic fish in
mediating energy transfer from plankton to higher trophic levels is indisputable. This
talk will describe trophodynamically-mediated processes that influence small pelagic
fish dynamics, from the indirect effect of spawner body condition on the quantity and
quality of reproductive products, to the direct impact of food availability on larval
survival. The plasticity and variability of small pelagic fish diets and feeding
behaviours, morphological and behavioural adaptations of populations to prevailing
environmental conditions, competition with co-occurring species, cannibalism and
intraguild predation, and the simple difficulty of properly quantifying both their prey
and their predators in the field make it difficult to assess the impact of environmental
changes on the pelagic foodweb. However, studies using stable isotopic composition,
laboratory experimentation and modelling are presently being carried out for several
(and contrasting) ecosystems, including the Iberia/Canary, Benguela and California
eastern boundary upwelling ecosystems and the Mediterranean Sea, which are
advancing our knowledge of the relationship between environmental variability and
dynamics of small pelagics, and these are briefly described and discussed.