What can size distributions within cohorts tell us about ecological processes in fish larvae?

Arne Johannessen,Knut Wiik Vollset,Erling Otterlei,Øyvind Fiksen,Arild Folkvord,Hans Høie

doi:10.3989/scimar.2009.73s1119

Abstract

size, prey concentrations, and temperature are shown to influence growth rates. We present a method based on cumulative size distributions (Csds) for visualizing variability of sizes within cohorts over time. Analysis of Csds revealed sizeselective mortality and variations among populations in size- and temperature-dependent growth throughout ontogeny. We found that cod larvae consistently exhibit higher growth rates than herring larvae. While cod larvae may have an advantage over herring larvae when food availability is high, herring were more able to survive at low food concentrations than cod. Cod and herring seem to represent two growth strategies: cod larvae are relatively small at hatching and a high growth rate appears to be a prerequisite for success, whereas herring larvae are initially large, but grow more slowly.

Highlights

The larvae of many marine fish species are subject to high and variable mortality and growth rates (McGurk, 1986)
Summary: Marine fish larvae are subject to variable environments, which is probably reflected in their growth and survival rates
Mortality rates are generally high and size-dependent. These mortality rates are usually accompanied by correspondingly high growth rates

Summary

Introduction

The larvae of many marine fish species are subject to high and variable mortality and growth rates (McGurk, 1986). The foraging activity of larvae is likely to elevate the risk of predation due to increased encounters with predators, as well as reduced larval vigilance and evasion ability (Fuiman and Magurran, 1994; Lankford et al, 2001) These trade-offs change during the early life stages as larvae increase in size, sensory function and locomotory performance (Billerbeck et al, 2001; Skajaa et al, 2003). The fact that body mass may multiply a hundred fold during the larval stage without any improvement in the ability to resist starvation suggests a trade-off between storage and growth, where growth rate is more important than starvation resistance This trade-off suggests that predation, which tends to decrease with fish size (McGurk, 1986; Bailey and Houde, 1989), is a driving force in the growth strategies of fish larvae

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