Fish Habitat I

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• Fish Habitat I
• Basics Habitat, Niche and Range
• Habitat generalists vs. habitat specialists
• How much do we know about habitats of marine fish
• How can we study fish habitats?
• Three example studies

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Population size
environmental variable 2
Time
environmental variable 3
environmental variable 1
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Two main strategies have evolved by which animals
utilize the environment Habitat generalists are
able to utilize and prosper under variety of
environmental conditions. These fish therefore
often have a wide distributed. Habitat
specialists constraint to specific environmental
conditions which they may utilize more successful
then other species. These fish usually show a
very localized distribution.
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How much do we know about habitats of marine fish?
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To study fish habitats you need to connect the
presence / abundances of a fish species to
particular habitat features or parameters and
this is where it becomes difficult! Mobility
(most fish swim around a lot which makes it
difficult to pinpoint them down to a particular
locality) Dynamic habitats (think of pelagic
fish such as tuna. Parameters important to these
fish species may change continuously over time
such as temperature salinity or even food
availability.
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But fish have basic requirements so maybe if we
start from here we will get somewhere! Basic
requirements what do we need to find out
about Which food (diet)? benthivore
(polychaetes, bivalves), pelagivore (zoop
lankton, fish) What kind of protection? kelp,
Sponges, other emergent epifauna, floating
sea weed What are tolerable and optimal abiotic
parameters temperatures, salinity, depth?
Mates for shoaling or mating will be there if
other requirements are fulfilled
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• These requirements can be investigated by direct
  and indirect methods
• Direct observations with underwater video devices
• Large amounts of data from surveys on various
  spatial scales connecting fish abundance with
  other parameters
• Diet analysis and prey distributions
• appropriate experimental studies offering a
  variety of habitat features to the fish under
  investigation and noting downs the preferred
  choices
• Morphology of the fish might tell us something
  about their preferred habitat

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Example 1 Survey data (Hinz et al. 2003 J Fish
Biol)
SD log10 abundance over 9 years
Mean log10 abundance over 9 years
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P Plaice S Sole L Lemon sole
Depth
B Stations with high consistent abundances S
Stations with medium varying abundances Z
Stations with zero catches
Log10 stones per hour
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Example 2 Dietary and morphological study Piet
GJ, Pfisterer AB, Rijnsdorp AD (1998) On factors
structuring the flatfish assemblage in the
southern North Sea JOURNAL OF SEA RESEARCH 40
143-152
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Example 3 Experimental study Stoner AW, Titgen
RH (2003) Biological structures and bottom type
influence habitat choices made by Alaskan
flatfishes. Journal of Experimental Marine
Biology and Ecology 292 43-59
SH High density sponges SL Low density
sponges BH High density bryozoans BL Low
density bryozoans Sh Bivalve shells SW Seaweed
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Shell and invertebrate bycatch (CPUE)
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Fish Habitat II Essential Fish Habitats new
considerations for fisheries science and
management