Monitoring fish stockings in Victoria: 2014 native fish surveys
Recreational Fishing Grants Program Research Report
Since the late 1980's the Victorian government has invested considerably in native fish stocking aimed at improving recreational fishing. Since December 2010, three large-scale native fish stocking initiatives involving golden perch and Murray cod, and one major stocking initiative recreational fisher (creel) survey, have been conducted. Building Northern Native Fisheries initiative aimed to stock an extra 670,000 native fish fingerlings into the Campaspe River, Gunbower Creek, Loddon River and Kow Swamp, in addition to the regular allocation of 180,000 native fish. A further 425,000 native fingerlings are expected to be stocked into these waters in 2014. As part of the "Million Murray Cod" Program (MMC), it is expected that Lake Eildon will be stocked with 1,150,000 Murray cod. This program, which is considered to be the largest single-waterway stocking of Murray cod in Australia was funded entirely by recreational fishing license fees at a value of $800,000. Lower Goulburn River enhancement initiative will see 359,500 Murray cod and 527,700 golden perch released over a period of 4 years. The anglers of Nagambie Lakes have been creel surveyed to determine their perception of the native fish fishery and catch.
The broad objective of this project was to address key knowledge gaps in the management of Victorian inland fisheries by answering recognised measures of stocking success including:
- Is there evidence of stocked fish survival?
- What is the percentage contribution from fish stocking to the fish population and fishery?
- Is there a net increase in fish abundance in the fish population and angler catch?
- Is there a net increase in fisher target preference, participation and/or satisfaction from fish stocking?
Golden perch and Murray cod fingerlings marked with calcein were released into the selected waters over four years from 2010/11. In 2014 electro-fishing surveys were conducted to capture fish from the stocked sites. Sampled fish were measured, aged and analysed for the presence of a calcein mark. Results from these surveys were compared with surveys conducted before the stocking events. Between December 2013 and April 2014, anglers fishing at Lake Eildon and the Nagambie Lakes were interviewed to assess catch and satisfaction. These results were compared with surveys conducted during 2010 and 2011.
In waters that were stocked with calcein-marked golden perch, the percent of fish that were stocked ranged from 11% (lower Goulburn R.) to 54% (Campaspe R.) (overall mean 22%). The percent of Murray cod that were stocked ranged from 11% (lower Goulburn R.) to 100% (Campaspe R.) (overall mean 50%).
Based on the proportion of stocked fish amongst sampled fish (as above), the distribution of stocked fish across sites sampled and change in abundance of fish, information on the contribution of stocked fish to wild stocks was provided for the water bodies assessed (see table below).
|Species||Water||Contribution of stocked fish to wild stocks||Comments|
|Golden perch||Campaspe R.||Likely|
Current project supports past studies suggesting that regular stocking is maintaining the golden perch population. Presence of marked fish may be underestimated due to nonmarked fish being released. No appreciable change in electro-fishing CPUE.
The contribution of stocking to the population is uncertain as sample size was too small for assessment and non-marked fish were released. Results were confounded by most marked fish being from the 2013/14 stocking that were captured 3 weeks after release. These fish also inflated the CPUE.
The high percentage of stocked fish present along with an appreciable change in electro-fishing CPUE suggests that golden perch stocking is making a substantial contribution to
|Lower Goulburn R.||Unlikely|
Results suggest that stocking is contributing little to the population, which is more likely being supported by immigration and natural recruitment. Sample size was too small for assessment and marked fish caught at small number of surveyed sites only.
|Murray cod||Campaspe R.||Unlikely|
The sample size was too small to assess the contribution of stockings to the population. Marked fish caught in small number of surveyed sites only. No appreciable change in electro-fishing CPUE.
The contribution of stocking to the population is uncertain as the sample size was too small for assessment and nonmarked fish were released. Electro-fishing CPUE greater
The contribution of stocking to the population is uncertain as sample size too small for assessment and non-marked fish were released. Results confounded as most marked Murray cod caught were thought to be fish that moved from Gunbower Ck to Kow Swamp (released 3 weeks before the survey occurred).
Stocked Murray cod have made a significant contribution to the Murray cod population. Marked fish were caught at all sites surveyed.
No conclusions can be made regarding the contribution of stocking Murray cod to the population as the sample size was small and marked fish were caught in a small number of sites only. Presence of marked fish may be underestimated due to non-marked fish being released.
|Lower Goulburn R.||Likely|
Small numbers of stocked fish were caught which are likely to contribute to the population, along with immigration and natural recruitment. Marked fish caught in a small number of surveyed sites only.
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