catches of non-target animals (bycatch) in fisheries reduces the impact on
a marine community and may help to sustain the fishery in the long term.
Various authors such as Brewer et al. (1996) and Kenneally (1997) have
discussed ways in which the bycatch problem could be addressed. Various
devices to reduce bycatch have been developed. These include exclusion
devices designed to exclude larger animals (e.g., dugongs), avoidance
mechanisms (e.g., raising a trawl slightly off the bottom), and filtering
using a targeted mesh size. The last two approaches are particularly
pertinent to invertebrates. Roosenburg and Green (2000) discuss the use of
a bycatch reduction device on crab pots.
have been relatively few studies on the invertebrate component of bycatch
(see Section 6.10.1). Assessment of the bycatch (as well as target
species) would be a convenient way of determining ecosystem changes over
time and could be used as a management tool.
matter what avoidance techniques are used, bycatch of non-targeted
invertebrates will still be an issue. Typically, once caught the mortality
of the animals in the bycatch is very high to total, even when returned to
the sea quickly.