Despite the large number of impoundments currently stocked in Queensland for recreational fishing, and the economic benefits resulting from this activity, almost no research has been conducted on developing strategies to maximise survival of stocked fry. Post-stocking surveys and creel surveys have given an indication of whether a given fishery is successful or not, but these surveys have not been designed to test any hypotheses on effective release strategies. To achieve maximum productivity at minimum cost freshwater fish stocking groups require reliable information that will assist them improve stocking procedures. This information will help stocking groups to be more cost effective in their operations by increasing the chances of stocked fish reaching a catchable size. To date impoundment stocking groups have been releasing fry without knowledge of whether different size classes of fry have different probabilities of survival. Similarly it is not known if point of release of stocked fry has any influence on survival rates. Properly conducted experiments which examine the relative survival of different size classes of fry and the influence of different release strategies on survival would be of immense benefit to recreational fishing groups in Queensland and other states. If for example small fry of one species (eg barramundi) were found to survive equally well as larger size classes, then it would make sense for the stocking groups to stock the cheaper smaller size classes. If larger size classes survive well, but smaller size classes have poor survival, then fish stocking groups will have better returns by stocking the more expensive larger size classes of fry. Similarly knowledge of whether point of release has any influence on survival for different stocked species will assist stocking groups to use their time and money efficiently.
It is clear from post-stocking and creel surveys that fry survive and grow better in some impoundments than others. A number of new dams are planned in various parts of Queensland. Knowledge of the environmental characteristics which influence the productivity and carrying capacity of impoundments will also benefit stocking groups by directing their efforts to productive locations or providing advice on actions which may enhance productivity or carrying capacity of impoundments. The current proposed project is a necessary first step to develop efficient stocking protocols and will lead to a follow up experiment/project examining in greater detail the success of stocked fisheries in a up to twenty impoundments. The subsequent project is expected to lead to predictions of the suitability of new impoundments for stocked fisheries and to strategies to improve the fisheries value of impoundments.
This project has provided scientifically validated information on optimal stocking sizes and optimal release strategies for four popular freshwater angling species. We now also have a better understanding of the impacts of different predators and impoundment conditions on stocking success. This information will enable community groups and fisheries managers to determine cost-effective stocking strategies and maximise survival of stocked fish. This information has been summarised in a user-friendly fish stocking manual.
By following this advice, stocking groups can increase survival of stocked fish by more than 10 times (depending on past stocking practices by each group), or ensure that they get the most cost-efficient result in terms of numbers of fish reaching legal size per stocking dollar. A copy of the stocking manual has been sent to every fish stocking group in Queensland, and also to peak angler representative bodies and fisheries management agencies in New South Wales and Victoria. The manual has also been made available in PDF format on the internet. The advice in the stocking manual, and outlined in this report, will lead to improved impoundment fisheries and associated economic benefits in those areas where it is implemented.
Our evaluation of the use of scales as tags has shown that scales do have potential as low-cost batch tags, but there are also limitations. Such tags are likely to be more reliable for fish stocked at larger sizes. Our research has proven the need for verification of scale patterns as tags through use of a secondary tagging system. If researchers recognise the limitations of scales and assess reliability of scales for each new species via secondary tagging, then costly research mistakes can be avoided in the future.
Keywords: Fish stocking, release size, release strategies, stocking strategies, batch tagging, visual implant elastomer (VIE) tag, coded wire tag, impoundment, lake, dam, Australian bass, silver perch, barramundi, golden perch, scale pattern analysis, Australia.
Fish stocking is a valuable and widely used fisheries management tool. If managed well, a fish stocking program can improve the status of declining or threatened fish stocks, restore species diversity to a degraded waterway, and even create a fishery where there was none before. The positive image of thousands of small fish being released into a waterway ensures that fish stocking is equally popular among politicians, fisheries managers and the general community.
This manual provides guidelines to help plan and carry out fish stocking programs in northern and eastern Australian impoundments. It presents an introduction to the main biological and ecological concepts that determine the outcome of stocking programs, and provides community fish stocking groups with a protocol to help ensure the success of their stocking activities.
The information in this document is taken from Fish stocking in impoundments: A best practice manual for eastern and northern Australia; Fisheries Research and Development Corporation Project 1998-221.
The information is based on research carried out in south-east Queensland, but can also be applied to fish stocking in impoundments in other parts of Australia. It should be regarded as general advice to assist groups or individuals in their fish stocking activities.
Although fish stocking has been carried out in northern and eastern Australia for some years now, there are still many unknowns regarding the best methods and approaches required to provide optimum results for anglers and for the environment. This document attempts to shed light on some of these unknowns, but given the highly variable conditions experienced in different regions and impoundments, and the complex interactions that occur between different combinations of fish species, there is a need to tailor stocking approaches to suit particular situations.
Despite these difficulties, it is possible to provide some answers to the questions that are commonly asked by people and organisations involved in fish stocking.