How to determine the likely indirect food-web consequences of a newly introduced non-native species: A worked example


Pinnegar, JK, Tomczak, TM, Link, JS.


Ecological Modelling 272 (2014) 379– 387


• It is difficult to predict food-web consequences resulting from arrival of a new non-native species.

• We explore implications using a novel suite of complimentary ecosystem modelling tools.

Fistularia commersonii is reported as the fastest spreading lessepsian fish migrant ever recorded.

• We used the Rank Proportion Algorithm (RPA) to predict the diet composition of this species.

• An Ecopath with Ecosim (EwE) model was used to simulate consequences for commercial fisheries.

Assessing food-web consequences of non-native species

In this paper the researchers demonstrate, through a worked case-study, that it is possible to make an assessment of the indirect food-web consequences that might occur as a result of the arrival of a hither-to not observed non-native species.

They also explore implications for commercial fisheries catches, through the application of a suite of complimentary ecosystem modelling tools.

Fistularia commersonii is a lessepsian migrant (introduced via the Suez Canal) that was first recorded in the Mediterranean in January 2000. It has since spread throughout the basin and has been described as ‘the fastest and farthest spreading lessepsian fish migrant ever recorded’.

Predicting diet composition using algorithm-models

The researchers have predicted the theoretical diet composition of F. commersonii in the Bay of Calvi, Corsica based on potential prey abundances, as well as morphological and behavioural characteristics of both the prey and this novel predator.

The ‘predicted’ diet composition of F. commersonii derived from the RPA analysis (Rank Pro-portion Algorithm (RPA) model) was then used as input to an Ecopath with Ecosim (EwE) model.

This model was used to simulate possible consequences of introducing this invasive species, assuming different rates of expansion of F. commersonii populations in the region.

Increases in fish catches

Increases in the F. commersonii population resulted in a marked decline in certain prey types (notably planktivorous fish, Mullus surmuletus and Symphodus tinca).

By contrast, seabirds and piscivorous fish were suggested as possible beneficiaries, although this depended heavily on model and scenario assumptions.

Overall fisheries catches were projected to increase, and this reflected an anticipated ‘bottom up’ increase in piscivorous fish that are the main target of the commercial fishery in the Bay of Calvi region.

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Published January 2014

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