Assessment of stocking effectiveness for Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua) in rivers and impoundments of south-eastern Australia

Abstract

Stock enhancement is a management tool used for fishery recovery worldwide, yet the success of many stocking programs remains unquantified. Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua) are important Australian recreational target species that have experienced widespread decline. Stocking of these species has been undertaken for decades, with limited assessment of effectiveness. A batch marking and recapture approach was applied to assess stocked Murray cod and golden perch survival, contributions to wild fisheries, and condition in rivers and impoundments. Stocked fish were marked with calcein. Marked fish were detected during surveys undertaken 3 years and 10 months from initial marking, and it is probable that marks will persist beyond this time. The proportion of calcein marked fish in the population sub-sample whose age was equal to, or less than, the number of years since release, varied by 7–94% for Murray cod, and 9–98% for golden perch. Higher proportions of marked fish were found in impoundments than rivers. Marked Murray cod had significantly steeper length–weight relationships (i.e. higher weight at a given length) to unmarked fish. Our results show that application of methods for discriminating stocked and wild fish provides critical information for the development of adaptive, location-specific stocking strategies.

Recovery from a fish kill in a semi‐arid Australian river: Can stocking augment natural recruitment processes?

“…in press; Forbes et al . in press; this study) indicate that stocking of golden perch and Murray cod into riverine habitats where natural recruitment levels are high can be of limited benefit. Although it is worthwhile noting that current stocking evaluation practices only focus on the survival of stocked individuals, and do not encompass the multigenerational effects or benefits of stocking.…”

“…in press; Forbes et al . in press), the findings are suggestive of a limited benefit of stocking when natural levels of recruitment are high. This is consistent with the recommendations of Kitada and Kishino (), whereby marine stock enhancement through hatchery releases should target local populations where limited recruitment is occurring for any benefit to be realized.…”

“…Similarly, Forbes et al . (in press) identified that stocking contributed little to riverine populations of both golden perch and Murray cod, but substantially to reservoir populations. The results of these studies highlight the variability in stocking effectiveness, and the subsequent importance of stocking evaluations for effective fishery management to inform harvest rates and recovery trajectories (e.g.…”

Efficacy of fluorescent calcein mark retention and identification in endangered Colorado pikeminnow Ptychocheilus lucius

“…However, this may require in situ discrimination between hatchery‐reared and wild fish (Crook et al, ; Koehn et al, ). In instances where hatcheries produce a large number of young fish for stocking, the small size, fragile nature and high mortality rates of these young fish can limit the suite of available and practical marking tools to track individuals for extended periods post‐release (Forbes et al, ; Hammer & Blankenship, ; Sandford, Castillo, & Hung, ; Skalski, Buchanan, & Griswold, ). To overcome this challenge, managers have used chemical batch‐marking techniques that strive to have minimal effects on the well‐being of fish while providing the opportunity to monitor cohorts post‐stocking.…”

Development of a Calcein Marking Technique for Juvenile Mulloway Argyrosomus japonicus to Be Used in Stock Enhancement Programs

“…Calcein marks are known to be retained over extended periods in freshwater fishes; for example, recaptured Golden Perch Macquaria ambigua still show visible marks on internal structures after 3.5 years (Forbes et al 2016). Captive studies have revealed similar results (Mohler 2003;Negus and Tureson 2004); however, the strength and characteristics of these marks can vary among species (Cameron et al 2011).…”