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Background:
Townsville City encompasses a diverse range of water bodies. These
include the estuaries of Ross River, Ross Creek and Three-Mile Creek,
the freshwaters of the impounded section of the Ross River, Louisa Creek,
the wetlands of the Town Common, the Lakes Development stages I and II
and a variety of other water bodies. The freshwater areas particularly
have been proven to contain substantial stocks of sport-fish and/or have
the potential to provide substantial areas of nursery ground habitats
for sport-fish.
In order to promote sustainable fishing and sport-fishing in the Townsville
region, it is imperative to understand the biological dynamics occurring
in these systems. Although these impounded and heavily impacted areas
are not necessarily healthy natural systems, they have been proven nevertheless
to be highly productive fisheries and thus need to be researched and managed
appropriately. The primary goal of this project is to understand these
systems biologically in order to maintain this productivity and thus maintain
a constant, relatively healthy fishery, which can be utilised now and
in the future.
AIMS:
- To investigate the fish community dynamics of the stocked impoundments
along the Ross River including: relative species abundance; stocked
fish size and age structure; mortality rates; fish condition; trophic
(food-web) dynamics.
- To investigate the ecology of the artificial wetlands of the Lakes
(Garbutt) and understand the fishery dynamics in order to put in place
measures to prevent fish-kills.
- To investigate the ecology of the Louisa Creek wetland restoration
project.
- To determine potential causes of fish-kills in these systems and
recommend measures to prevent future fatalities.
- To produce conceptual and empirical models of the dynamics of these
systems which may be used as a predictive tool for future management.
PROPOSED RESEARCH
It is planned for the research to address all of these aims. However,
this can only occur over quite a long time frame so depending on funding,
these aims may have to be modified.
- 1: Fish dynamics It is important, particularly in small bodies
of water proven to have a large biomass of fish, e.g. Lakes I and II
and the impounded areas of the Ross River, to understand the dynamics
of the fish populations within these systems. What is needed is:
- a. Sampling to determining the current fish stocks in these systems.
- b. Repeated sampling to gain an understanding of the dynamics
of those fish stocks:
- i. Are numbers and biomass stable or increasing/fluctuating
over time? This information is relevant to how large a stock
can be supported by particular water bodies and what critical
levels of such things as oxygen need to be maintained.
- ii. Are individual fish functioning normally (reproduction,
fish condition, growth rates)?
- iii. Are communities and ecosystems functioning normally
(food chain dynamics, predator-prey abundance, over-crowding
and competition for resources)?
- 2: Ecosystems Status One of the greatest dangers in water bodies
of restricted volume that harbour large biomasses of predatory fishes,
is that predation will sequentially deplete abundant species, leading
to ecosystems change. Such change could result in ecosystem collapse,
which would rebound to devastate predator stocks. Ecosystem change could
be best accomplished by examining the gut contents of fish at regular
intervals.
- 3: Connectivity To what extent are the systems connected to
each other? i.e. How much biological interchange is there between the
systems? The most efficient way to determine the level of biological
connection between these systems is via a directed fish tagging program.
- 4: Detection of Sub-lethal effects of Stress on Fishes Biological
material could be collected in Part 1 (above) that will allow investigation
of sub-lethal effects of stress on the fishes in these systems (i.e.
detectors of poor health before fish start dying). This research is
designed to be beneficial to various stakeholders and community groups
in Townsville concerned with the health of local waterways. The end
result may be the promotion of Townsville as a very accessible recreational
fishery. On a larger scale, this research has implications both in Australia
and world-wide for regulated rivers, stocked impoundments and wetlands
with urban influences.
This project is a co-operative venture between Townsville City Council,
N.Q. Water, the Twin Cities Fish Stocking Group and James Cook University.
Information provided by PhD student, Ann
Penny,
Coastal Ecology Group,
James Cook University
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