Abstract
Millions of fish are currently released in NSW waters to support recreational fisheries. However, due to the challenges of surveying stocked fish, little is known about the likelihood of these fish surviving for any length of time.
In order to survive after stocking, fish need to find shelter and food, avoid predation and explore and occupy appropriate habitat. We have developed a model based on the known life-history of Murray cod and golden perch to predict, from laboratory tests, how likely fish are to survive when released.
We tested Murray cod and golden perch reared in outdoor earth dams in two hatcheries at six different ages ranging from one week to 20 weeks, as well as 20 week-old wild-caught Murray cod, to evaluate their survival behaviour.
Murray cod showed a clear developmental shift towards greater exploration and risk taking at 6 and10 weeks of age, and reduced risk taking at 16 weeks of age. These findings suggest an “exploration” sensitive phase when fish naturally move to find new habitat between 6 and 16 weeks of age. Our findings suggest that plants and boulders are the preferred habitat for juvenile Murray cod. If exploration behaviour is conducive to young fish finding suitable habitat and food, then perhaps the best time to release them, based on experimental findings, is between 6 and 16 weeks of age.
Behaviour of juvenile golden perch showed a typical pattern governed by physical and motor maturation. Development before 6 weeks of age is rapid and mostly linked to physical and motor maturation. After 6 weeks of age, behavioural changes in golden perch are more gradual and steady improvements in predator avoidance and exploration were observed. If predator avoidance and exploration are deemed as important characteristics for the survival of stocked fish, then our laboratory findings suggest that golden perch mostly lack these abilities before 6 weeks of age, and that these abilities gradually improve as fish mature up to 20 weeks of age.
The findings support the use of tests of survival behaviour to inform stocking practices, which can be extended to other native fish species. The main benefit to recreational fishing will be the improved returns, in terms of more surviving fish, for the money invested in re-stocking programs.
In order to survive after stocking, fish need to find shelter and food, avoid predation and explore and occupy appropriate habitat. We have developed a model based on the known life-history of Murray cod and golden perch to predict, from laboratory tests, how likely fish are to survive when released.
We tested Murray cod and golden perch reared in outdoor earth dams in two hatcheries at six different ages ranging from one week to 20 weeks, as well as 20 week-old wild-caught Murray cod, to evaluate their survival behaviour.
Murray cod showed a clear developmental shift towards greater exploration and risk taking at 6 and10 weeks of age, and reduced risk taking at 16 weeks of age. These findings suggest an “exploration” sensitive phase when fish naturally move to find new habitat between 6 and 16 weeks of age. Our findings suggest that plants and boulders are the preferred habitat for juvenile Murray cod. If exploration behaviour is conducive to young fish finding suitable habitat and food, then perhaps the best time to release them, based on experimental findings, is between 6 and 16 weeks of age.
Behaviour of juvenile golden perch showed a typical pattern governed by physical and motor maturation. Development before 6 weeks of age is rapid and mostly linked to physical and motor maturation. After 6 weeks of age, behavioural changes in golden perch are more gradual and steady improvements in predator avoidance and exploration were observed. If predator avoidance and exploration are deemed as important characteristics for the survival of stocked fish, then our laboratory findings suggest that golden perch mostly lack these abilities before 6 weeks of age, and that these abilities gradually improve as fish mature up to 20 weeks of age.
The findings support the use of tests of survival behaviour to inform stocking practices, which can be extended to other native fish species. The main benefit to recreational fishing will be the improved returns, in terms of more surviving fish, for the money invested in re-stocking programs.
| Original language | English |
|---|---|
| Place of Publication | Albury, NSW |
| Publisher | Institute of Land Water and Society |
| Commissioning body | Recreational Fishing Trust |
| Number of pages | 15 |
| Publication status | Published - 2021 |
Publication series
| Name | ILWS Report |
|---|---|
| No. | 153 |