Abstract
Marine fish spawns thousands of small eggs and the hatched larvae becomes part of the plankton ecosystem of the open sea. The larva is a vulnerable stage in the life cycle of fishes and already during the initial fisheries research in the early 1900’s it was realized that high and variable mortality in the fish larval stages is the cause of observed fluctuations in the fish stocks. Since this discovery it has been heavily debated to what extent life prospects of larvae depend on biological or physical constraints. However a wide range of interacting factors affects larval life and this should be perceived in a broader ecological context in which both bio-physical conditions and behavioral and evolutionary adaptations are taken into account. In this thesis I present studies providing insight into important life traits of larvae: their feeding, growth, mortality and dispersal/drift, and through cross-cutting comparisons between characteristics of species and their immediate environments I assess commonalities in larval adaptations and linkages between biology and physics. The findings point to a much more advanced behavior and ecological adaptability of larvae than generally believed. In spite of significant differences between investigated larval species in their morphology, development and experienced conditions there are obvious commonalities in their early lives. Strong linkages were apparent between fish larval life and physical characteristics of fronts and other marine interfaces, and observations point to a multitude of closely spaced habitats for fish larvae in the frontal zones. Thus the prospects of larval life, determined by the niche and the appropriate habitat, could be very species-specific and a likely variation in the overlap between niche and habitat would lead to variable mortality of larvae. Analysis of niche and habitat overlap could be a fruitful way to combine insights into biological and physical processes of importance in the fish larval life, and combined with cross-cutting comparisons this provides possibilities for marking out the dominating life-cycle processes of fish.
Info
Thesis Doctoral, 2016
UN SDG Classification
DK Main Research Area
Science/Technology
