Natural hybridization between Murray cod, Maccullochella peelii peelii (Mitchell) and trout cod, Maccullochella macquariensis (Cuvier) (Percichthyidae) in the Murray River, Australia

Abstract

Hybridization is confirmed between two wild, naturally sympatric populations of Murray cod, Maccullochella peelii peelii, and trout cod, M. macquariensis, from the Murray River, Australia. Electrophoretic comparisons of proteins in muscle and liver tissues from trout cod, Murray cod, an artificially produced hybrid of Murray cod and trout cod, and putative wild hybrids from the Murray River indicated that the last group were first-generation interspecific hybrids. This is the first record of hybridization between naturally occumng populations of these two species. Naturally occurring wild populations of both trout cod and Murray cod are nonetheless genetically distinct and there is no evidence of introgression between the species. These findings have some implications for management policies and practices in relation to both species, and these are discussed.

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

“…Coupled with their similar spawning strategies, this is a likely explanation for the occasional hybridization exhibited between these two species both in the wild (albeit at low frequencies in the Murray River population) and in hatchery conditions (Wajon, unpublished B.Sc. (Hons) thesis; Douglas et al, 1995).…”

Who’s your mama? Riverine hybridisation of threatened freshwater Trout Cod and Murray Cod

“…First generation interspecific hybridization between Murray Cod and Trout Cod has been recorded in impoundments (Harris & Dixon, 1986), hatcheries (Ho et al, 2008) and rarely in wild sympatric populations (Douglas et al, 1995). Fisherman too have reported catching hybrid fish (based on phenotypic characteristics) although not all of these anecdotal records are reliable (Cleaver, 2015) as misidentification of these two cod species was only resolved in 1972 with the formal redescription of Trout Cod (Berra & Weatherley, 1972).…”

“…Hybridization was identified as a major concern for one population of Trout Cod translocated to Cataract Dam, a water reservoir (Harris & Dixon, 1986; Douglas, Gooley & Ingram, 1994). This then resulted in initial stocking site selection criteria in the program excluding sites where Murray Cod were known to be present (Douglas, Gooley & Ingram, 1994).…”

“…Hybridization was identified as a major concern for one population of Trout Cod translocated to Cataract Dam, a water reservoir (Harris & Dixon, 1986; Douglas, Gooley & Ingram, 1994). This then resulted in initial stocking site selection criteria in the program excluding sites where Murray Cod were known to be present (Douglas, Gooley & Ingram, 1994). However, minimal detection of hybrids between Murray Cod and Trout Cod in riverine environments (e.g., Douglas et al, 1995) has meant that site selection criteria has been relaxed in recent years and stocking now regularly occurs where Murray Cod are present.…”

Who’s your mama? Riverine hybridisation of threatened freshwater Trout Cod and Murray Cod

“…30 We detected hybrid Trout Cod-Murray Cod in the Upper Murrumbidgee, recording the first 31 hybrid larvae in the wild. Although hybrid larvae, juveniles and adults have been recorded in 32 hatcheries and impoundments, and hybrid adults have been recorded in rivers previously 33 (Douglas, Gooley & Ingram, 1994;Douglas et al, 1995), this is the first time fertile F1 have 34 been recorded in the wild. The F1 backcrosses with Murray cod have also been found to be 35 fertile.…”