Thomas:

You asked:

> Has anyone a good idea on how sampling data from active gears (beach seine,
> trawls; as fish per haul, fish per m2 or per m3) may be directly compared
> with data from passive gears (gill-nets, traps; fish per fleet per hour,
> fish per hour)?

and said:

> I have got only two replies; in both a reference was mentioned:
>

Hmmmm.  You should have had more of a response than that.  This question
is related to "relative fishing power" whereby different fishing gears
are compared as to their fishing effectivness.  Most fishery management
texts will mention this, particularly those dealing with commercial
fisheries.  These relate effectiveness of different gears so that one
gear can be expressed in terms of another.  This can be done for total
catch or on a species by species basis.

For example: Gillnets catch 30kg per trip of species x and trawls catch
catch 10kg per trip.  Then if we use a gillnet trip as the basis (=1)
then a trawl trip is equal to 0.3 gillnet trips (for that species, and
size etc).

For example, take a look at:

Introduction to tropical fish stock asessment. Sparre and Venema.  1992.
FAO. see p267-271.

also see most stock assessment and similar texts.... look for 'fishing
power' in the index.  This should give you lots of ideas (...not all
good!).

Of course none of this will tell you the _actual_ abundance of the fish.

--
Richard G. Dudley

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