About Fish Populations

Fish populations go up and down naturally but the level of fishing can also change fish populations.

Understanding how much they go up and down and why is a key component of fisheries science.

About Fish Populations

Fisheries Science

Fisheries science endeavours to understand the biology of fish and the state of fish stocks. It draws on a range of disciplines including marine and freshwater biology, oceanography, physics, chemistry and mathematics. One of the main aims of fisheries science is to provide fisheries managers with quality data on which they can make informed decisions about how best to manage fish stocks. Data about fish stocks is collected through surveys and monitoring. Fisheries science work is undertaken by fisheries agencies (both state and commonwealth), government science organisations (e.g. CSIRO and the Australian Antarctic Division etc), universities, non-government organisations and independent research providers.

There are a range of different survey and monitoring tools used to collect data. Fisheries data is split into fishery-dependent data and fishery-independent data. Fishery dependent data is collected directly from a fishery of fisher and includes creel surveys, boat ramp cameras, logbooks, fishery observers and port sampling. Fishery-independent data is collected outside of normal fishing and includes baited remote underwater video surveys, tagging experiments, trawl surveys, dive surveys and experiments.

It’s important to make sure that results from fisheries science research is communicated to stakeholders and the public.  This ensures the data is used to best manage Australia’s fisheries and provide the public with the confidence that the fish they buy comes from sustainable stocks.

More Information

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Northern Territory Department of Industry, Tourism and Trade Fisheries Research
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Western Australian DPIRD Fisheries Science
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South Australian Research and Development Institute (SARDI) Fisheries Science Program
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Institute for Marine and Antarctic Studies Fisheries Research
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Queensland Department of Agriculture and Fisheries Fisheries monitoring
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CSIRO's Fisheries Research
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AFMA's Science and Research
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NSW Department of Primary Industries Fisheries Research
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Victorian Fisheries Authority Fisheries Science

Presentations

Fish Biology

Understanding fish biology is essential to good fisheries management because it gives information about the productivity of a fish stock and informs the most sustainable strategy for managing that stock. Fisheries scientists collect a wide range of information on fish biology that is used in fisheries management. This information includes:

  • Stock structure – the division of local sub-populations of fish that don’t mix or breed with other stocks.
  • Age and growth – these can be estimated using ear bones or other hard parts, or through tagging experiments.
  • Reproduction – including at what age and length fish reach maturity, how many eggs they produce and how that changes with fish size and how, when and where the fish breed.
  • Recruitment – the entry of young fish into the fished component of the stock through growth or movement.  It can be important to understand what effects recruitment levels such as, the number of mature fish in the stock and environmental variables.
  • Mortality – total mortality is the rate that fish are killed both from natural causes (natural mortality from predation, old age, disease) and from fishing (fishing mortality).

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Presentations

Stock Assessment

Stock assessments are undertaken to check that stocks are being fished sustainably, both biologically and economically.  From a biological point of view, stock assessments generally address two questions about a fish stock:

  1. Is the size of the fish stock (for example the biomass) above a level that is considered overfished?
  2. Will the current levels of fishing cause the stock to become overfished?

Stock assessment methods are many and varied and the type of method used largely depends on the amount and type of data available. The amount of data available for a species (or stock) is often related to the value of that stock and the risk posed to it by the fishery. The more quality data available, the more complex the stock assessment can be, and the more confidence you can have in its results.  The results of stock assessments are used in harvest strategies to compare indicators against target reference points (the point you want the fishery to be) and limit reference points (the point at which the risk to the stock is too high).

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Presentations

Directory

Resources and organisations about sustainable fishing.

Glossary

All of the industry lingo explained in one place.

Policies and Legislation

Fishery legislation resources.