In Moreton Bay and in other
parts of Australia, large areas of seagrass and other
intertidal habitat are dug over to collect yabbies,
bloodworms and other invertebrates. This comprises a
fishery, the products of which are sold to recreational
fishers for bait. Large numbers of recreational
fishers also dig their own bait, increasing the area of
habitat which is damaged. The habitats where the bait
is collected are important nursery areas for commercial
species such as bream, tarwhine, snapper, whiting, garfish,
prawns and crabs. Many of the other invertebrates
which also live in these habitats, and which may be
affected by bait-digging, are important food items for the
commercial fish and crustaceans.
Direct and indirect effects can arise from bait-harvesting
activities in intertidal areas. These can be
summarised as: (i) direct effects on the populations
of the species being exploited (ii) indirect effects on
other species which interact with the exploited species
(e.g. use them as food); (iii) direct effects on
other species in the habitats which are incidentally killed
or injured during harvesting (ie. by-catch); and (iv)
direct and indirect effects due to habitat damage arising
from harvesting.
The objectives of the project are:
1. Assess the ecological impacts of commercial and
recreational harvesting of yabbies and bloodworms on other
components of the ecosystem;
2. Assess the impacts of bait-harvesting activities on the
sustainability of populations of yabbies and bloodworms;
3. Develop a population assessment technique for yabbies
and bloodworms;
4. Determine levels of recruitment of these species and
assess whether harvesting affects recruitment;
5. Obtain estimates of the recreational harvest of these
species.
Linked Projects
Dr Yuri Zharikov: Consequences of commercial baitworm
harvesting on overwintering shorebird populations and their
prey. The components of Mr Zharikov's project which
are directly integrated with the current FRDC proposal
are: (i) an examination of the effects of harvesting
of yabbies on their density, age/size structure and
reproductive cycles; (ii) examination of the effects
of harvesting on other common benthic species which occur
in the same habitats as yabbies; and (iii) an
examination of how harvesting influences shorebird
populations, especially the Eastern Curlew and the
Bar-Tailed Godwit.