Doctor defence: The dynamics of gastric evacuation in predatory fish - A mechanistic model of gastric evacuation – development and applications in fish and fishery biology

The thesis deals with the work aimed to establish and test a mechanistic gastric evacuation rate (GER) model for predatory fish, and to show its utility as a versatile tool in fish and fishery research.
Together with marine fisheries, predatory fish preying on fish comprises a major structuring force in fish communities and has the potential to exert top-down control on entire ecosystems. Inclusion of species interactions in fish stock assessment and fishery management calls for accurate quantification of the predator food intake and the associated prey mortality.

The food intake is estimated from stomach contents of representatively sampled predators combined with GER of the contents. A high internationally coordinated effort has therefore been invested in stomach sampling and laboratory analyses of stomach contents.

In contrast, research on GER has been sparse and uncoordinated, and predictions of previous GER models disparate. Neither of these models can accurately quantify the current GER regardless of prey composition and feeding rhythm and chronology.

The new, mechanistic model is based on comprehensive experiments on marine predatory fish. Subsequent tests confirm the generic ability of the model to predict the course and rate of evacuation of individual prey in relevant scenarios for predatory fish under natural conditions.

Implementation of the model estimates in stock assessment should significantly improve predictions of predation and mortality rates. The model further facilitates studies on small-scale species interactions and foraging strategies and allows for identification of the assimilative capacity of predatory fish in the wild leading to more realistic descriptions of the relationship between prey abundance and predator food intake in the sea.

The thesis is available in full here

If you wish to be an unofficial opponent, you may sign up at dr.techn.-adm@dtu.dk or announce it at the defence.

The defence will be live streamed here.