What is the environment in which fish larvae find themselves and how does cod see that environment

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• What is the environment in which fish larvae find
  themselves and how does cod see that
  environment?
• Are the feeding strategies of larvae sufficiently
  different among species so as to result in
  different rates of increase in feeding success?
• How does the feeding environment vary on the
  scale relevant to a larva?
• What can the larvae tell us about how they
  perceive their environment?

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• What is the environment in which fish larvae find
  themselves and how does cod see that
  environment?
• Are the feeding strategies of larvae sufficiently
  different among species so as to result in
  different rates of increase in feeding success?
• How does the feeding environment vary on the
  scale relevant to a larva?
• What can the larvae tell us about how they
  perceive their environment?

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• What is the environment in which fish larvae find
  themselves and how does cod see that
  environment?
• Are the feeding strategies of larvae sufficiently
  different among species so as to result in
  different rates of increase in feeding success?
• How does the feeding environment vary on the
  scale relevant to a larva?
• What can the larvae tell us about how they
  perceive their environment?

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• What is the environment in which fish larvae find
  themselves and how does cod see that
  environment?
• Are the feeding strategies of larvae sufficiently
  different among species so as to result in
  different rates of increase in feeding success?
• How does the feeding environment vary on the
  scale relevant to a larva?
• What can the larvae tell us about how they
  perceive their environment?

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Transects sampled with mini-OPC (optical plankton
counter) Towed-body undulating between
5-70m Distance covered per cycle 1.2
km Towing speed 9.5 kn (4.9 m s-1) Horizontal
resolution 5m Vertical resolution 0.5m
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• Over range of mean (seasonal) concentrations
• Similar patterns of changes in prey density at
  small spatial scales
• Autocorrelation
• Similar large scale patterns (horizontal) across
  productive season
• Largest differences across seasonal are in
  vertical plane microlayer patchiness

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• What is the environment in which fish larvae find
  themselves and how does cod see that
  environment?
• Are the feeding strategies of larvae sufficiently
  different among species so as to result in
  different rates of increase in feeding success?
• How does the feeding environment vary on the
  scale relevant to a larva?
• What can the larvae tell us about how they
  perceive their environment?

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Number of prey per stomach is well described by a
Poisson distribution Significantly better fit
than either negative binomial or gamma
distributions Applies to all prey species (and
does so for all other species as well)
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• A simple model of feeding
• Nprey P(En )P(AE) P(CA) 1
• Encounters modelled as
• ? ? R2 Aprey (u2 v2)0.5 2
• P(En ) (?n / n!) e - ? 3
• If we know
• Density of prey in field (Aprey) (e.g., from
  plankton nets)
• Mean number of prey in stomach (?)
• ? / Aprey ? R2 (u2 v2)0.5P(AE) P(CA)
  K 4
• ? / Aprey Effective volume swept K
• K can be estimated as f(Ll, Ptaxa, Pl)

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Gadus morhua Nlarva 121
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• Distribution of prey per stomach well described
  by Poisson distribution
• Depends of larval length, prey type (and possible
  size/stage)
• Simplification of foraging model coupled with
  estimates of mean prey density
• Results in estimate of effective volume swept
  f(Ll,Ptaxa)
• Can these parameter estimates provide predictions
  of feeding patterns across systems?