Age and growth of Murray Cod, Maccullochella peelii (Perciformes: Percichthyidae), in the Lower Murray-Darling Basin, Australia, from thin-sectioned Otoliths

Abstract

Transverse thin sections (0.5 mm thick) of sagittal otoliths from 290 Murray cod up to 1400 mm in total length and 47.3 kg in weight were used to establish the age and growth of cod in the lower Murray-Darling Basin, including comparisons of recent (1986-91) and past (1949-51) growth rates and growth in different waters. The maximum estimated age was 48 years. Quantitative and qualitative analysis of the seasonal changes in otolith marginal increments showed that annuli in fish of all ages were laid down each spring, and 1 October was assigned as the birthday. The thin-sectioning method was validated by comparing age estimates for 55 Murray cod from Lake Charlegrark (age 0-21 years), which had been validated by using burnt and polished half-otoliths. The new method had an accuracy of 96.4% and it offers major advantages in ease of preparation, reading, and batch-handling of large numbers of otoliths. The precision of the method, estimated as an average error for four readers, was 5.4% (3.0% after ignoring discrepancies in relation to annuli on otolith edges). There was a linear relationship between otolith weight and fish age and an exponential relationship between otolith weight and fish length. Both otolith length and otolith width reached an asymptote at about 15 years, when fish length also approached its maximum. However, otolith thickness continued to increase throughout the life of the fish and, after about 15 years, contributed most to the increase in otolith weight. This confirmed that otoliths continued to grow in thickness and that annuli were laid down throughout life, and that cod could be aged reliably to the maximum age. The annulus pattern is very clear and distinct, and the reading techniques are fully described, including recognition of 'larval' and 'false' rings. Various differences were found in the growth rates, and the length-weight relationships for males and females, for cod caught in 1986-91 and those caught in 1949-51, and various subpopulations are discussed. The von Bertalanffy growth parameters (all individuals combined) were estimated at L∞ = 1202 mm, k=0.108 and t0= -0.832. The availability of a reliable ageing method provides the first opportunity to determine year of birth and thus to examine the age structure of populations and to effectively manage cod populations that have declined in abundance.

Age, growth and non‐flood recruitment of two potamodromous fishes in a large semi‐arid/temperate river system

“…This is not unexpected since Harris (1987) aged Australian bass Macquaria novemaculeata, a similar-sized (L ∞ = 396) percichthyid, up to 22 years, and Anderson et al (1992b) aged Murray cod Maccullochella peelii peelii, a large (L ∞ = 1202 mm) percichthyid, up to 48 years. The longevity of silver perch, at an estimated 27 years, is similar to golden perch.…”

Spawning time and early life history of Murray cod, Maccullochella peelii (Mitchell) in an Australian river

“…Much of our knowledge of the biology of Murray cod has, therefore, relied on investigations carried out under aquaculture-type conditions 2 (Lake 1967a, b;Rowland 1983Rowland , 1988Rowland , 1998. Recent work on life history (Humphries et al 1999(Humphries et al , 2002, habitat use, 3 movement 4 and ageing (Anderson et al 1992;Gooley 1992) in the wild, however, is adding significantly to our knowledge base. Although Murray cod spawn each year -unlike, perhaps golden perch Macquaria ambigua (Richardson) -an inability to locate spawning individuals in the wild has meant that reliable identification of spawning times has been elusive, as have the environmental variables associated with them (although, see Langtry's mainly anecdotal accounts 5 .…”

Environmental conditions and timing for the spawning of Murray cod (Maccullochella peelii peelii) and the endangered trout cod (M. macquariensis) in southeastern Australian rivers

“…Otolith ageing was undertaken for a limited number of larval and post-larval fish in 1993/94 and 1995/96. Otolith ageing of adult Murray cod and other species had previously been undertaken for adult and juvenile fish (Anderson et al, 1992;Gooley, 1992), but not for larvae. A sample of 29 larval Murray cod from site MR2 in 1995/96, 11 larval Murray cod from OR in 1993/94 and nine trout cod larvae from MR2 were aged by the Central Ageing Facility at the then Victorian Institute of Marine Sciences, Queenscliff, Victoria (see Morison et al, 1998).…”